7909 lines
351 KiB
HTML
7909 lines
351 KiB
HTML
<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<!--[if IE]><meta http-equiv="X-UA-Compatible" content="IE=edge"><![endif]-->
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<meta name="generator" content="Asciidoctor 1.5.0">
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<title>Spring Cloud</title>
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<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Open+Sans:300,300italic,400,400italic,600,600italic|Noto+Serif:400,400italic,700,700italic|Droid+Sans+Mono:400">
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<style>
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/* Asciidoctor default stylesheet | MIT License | http://asciidoctor.org */
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/* Remove the comments around the @import statement below when using this as a custom stylesheet */
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/*@import "https://fonts.googleapis.com/css?family=Open+Sans:300,300italic,400,400italic,600,600italic|Noto+Serif:400,400italic,700,700italic|Droid+Sans+Mono:400";*/
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article,aside,details,figcaption,figure,footer,header,hgroup,main,nav,section,summary{display:block}
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audio,canvas,video{display:inline-block}
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audio:not([controls]){display:none;height:0}
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[hidden],template{display:none}
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script{display:none!important}
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html{font-family:sans-serif;-ms-text-size-adjust:100%;-webkit-text-size-adjust:100%}
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body{margin:0}
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a{background:transparent}
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a:focus{outline:thin dotted}
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a:active,a:hover{outline:0}
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h1{font-size:2em;margin:.67em 0}
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abbr[title]{border-bottom:1px dotted}
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b,strong{font-weight:bold}
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dfn{font-style:italic}
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pre{white-space:pre-wrap}
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small{font-size:80%}
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sup{top:-.5em}
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sub{bottom:-.25em}
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img{border:0}
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svg:not(:root){overflow:hidden}
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figure{margin:0}
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button,input,select,textarea{font-family:inherit;font-size:100%;margin:0}
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button,input{line-height:normal}
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button,select{text-transform:none}
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*,*:before,*:after{-moz-box-sizing:border-box;-webkit-box-sizing:border-box;box-sizing:border-box}
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html,body{font-size:100%}
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body{background:#fff;color:rgba(0,0,0,.8);padding:0;margin:0;font-family:"Noto Serif","DejaVu Serif",serif;font-weight:400;font-style:normal;line-height:1;position:relative;cursor:auto}
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a:hover{cursor:pointer}
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img{-ms-interpolation-mode:bicubic}
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img{display:inline-block;vertical-align:middle}
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textarea{height:auto;min-height:50px}
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select{width:100%}
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a{color:#2156a5;text-decoration:underline;line-height:inherit}
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a:hover,a:focus{color:#1d4b8f}
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a img{border:none}
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small{font-size:60%;line-height:inherit}
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code{font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;font-weight:400;color:rgba(0,0,0,.9)}
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ul.square{list-style-type:square}
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ul.disc{list-style-type:disc}
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dl dt{margin-bottom:.3125em;font-weight:bold}
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dl dd{margin-bottom:1.25em}
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abbr,acronym{text-transform:uppercase;font-size:90%;color:rgba(0,0,0,.8);border-bottom:1px dotted #ddd;cursor:help}
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abbr{text-transform:none}
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h2{font-size:2.3125em}
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h4{font-size:1.4375em}}table{background:#fff;margin-bottom:1.25em;border:solid 1px #dedede}
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table thead,table tfoot{background:#f7f8f7;font-weight:bold}
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table thead tr th,table thead tr td,table tfoot tr th,table tfoot tr td{padding:.5em .625em .625em;font-size:inherit;color:rgba(0,0,0,.8);text-align:left}
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table tr th,table tr td{padding:.5625em .625em;font-size:inherit;color:rgba(0,0,0,.8)}
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table tr.even,table tr.alt,table tr:nth-of-type(even){background:#f8f8f7}
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h1,h2,h3,#toctitle,.sidebarblock>.content>.title,h4,h5,h6{line-height:1.2;word-spacing:-.05em}
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h1 strong,h2 strong,h3 strong,#toctitle strong,.sidebarblock>.content>.title strong,h4 strong,h5 strong,h6 strong{font-weight:400}
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*:not(pre)>code{font-size:.9375em;font-style:normal!important;letter-spacing:0;padding:.1em .5ex;word-spacing:-.15em;background-color:#f7f7f8;-webkit-border-radius:4px;border-radius:4px;line-height:1.45;text-rendering:optimizeSpeed}
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pre,pre>code{line-height:1.45;color:rgba(0,0,0,.9);font-family:"Droid Sans Mono","DejaVu Sans Mono",monospace;font-weight:400;text-rendering:optimizeSpeed}
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.keyseq{color:rgba(51,51,51,.8)}
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kbd{display:inline-block;color:rgba(0,0,0,.8);font-size:.75em;line-height:1.4;background-color:#f7f7f7;border:1px solid #ccc;-webkit-border-radius:3px;border-radius:3px;-webkit-box-shadow:0 1px 0 rgba(0,0,0,.2),0 0 0 .1em white inset;box-shadow:0 1px 0 rgba(0,0,0,.2),0 0 0 .1em #fff inset;margin:-.15em .15em 0 .15em;padding:.2em .6em .2em .5em;vertical-align:middle;white-space:nowrap}
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.keyseq kbd:first-child{margin-left:0}
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.keyseq kbd:last-child{margin-right:0}
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.menuseq,.menu{color:rgba(0,0,0,.8)}
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b.button:before,b.button:after{position:relative;top:-1px;font-weight:400}
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b.button:before{content:"[";padding:0 3px 0 2px}
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b.button:after{content:"]";padding:0 2px 0 3px}
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p a>code:hover{color:rgba(0,0,0,.9)}
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#header,#content,#footnotes,#footer{width:100%;margin-left:auto;margin-right:auto;margin-top:0;margin-bottom:0;max-width:62.5em;*zoom:1;position:relative;padding-left:.9375em;padding-right:.9375em}
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#header:before,#header:after,#content:before,#content:after,#footnotes:before,#footnotes:after,#footer:before,#footer:after{content:" ";display:table}
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#header:after,#content:after,#footnotes:after,#footer:after{clear:both}
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#content{margin-top:1.25em}
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#content:before{content:none}
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#header>h1:first-child{color:rgba(0,0,0,.85);margin-top:2.25rem;margin-bottom:0}
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#header>h1:first-child+#toc{margin-top:8px;border-top:1px solid #ddddd8}
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#header .details span:first-child{margin-left:-.125em}
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#header .details span.email a{color:rgba(0,0,0,.85)}
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#header .details br{display:none}
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#header .details br+span.author:before{content:"\00a0\22c5\00a0";color:rgba(0,0,0,.85)}
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#header .details br+span#revremark:before{content:"\00a0|\00a0"}
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#header #revnumber{text-transform:capitalize}
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#header #revnumber:after{content:"\00a0"}
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#content>h1:first-child:not([class]){color:rgba(0,0,0,.85);border-bottom:1px solid #ddddd8;padding-bottom:8px;margin-top:0;padding-top:1rem;margin-bottom:1.25rem}
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#toc{border-bottom:1px solid #efefed;padding-bottom:.5em}
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#toc>ul{margin-left:.125em}
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#toc ul{font-family:"Open Sans","DejaVu Sans",sans-serif;list-style-type:none}
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#toc a{text-decoration:none}
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#toctitle{color:#7a2518;font-size:1.2em}
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#content #toc>:first-child{margin-top:0}
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#content #toc>:last-child{margin-bottom:0}
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|
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table.tableblock>caption.title{white-space:nowrap;overflow:visible;max-width:0}
|
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table.tableblock #preamble>.sectionbody>.paragraph:first-of-type p{font-size:inherit}
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|
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.admonitionblock>table td.icon{text-align:center;width:80px}
|
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.admonitionblock>table td.icon img{max-width:none}
|
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.admonitionblock>table td.icon .title{font-weight:bold;font-family:"Open Sans","DejaVu Sans",sans-serif;text-transform:uppercase}
|
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.admonitionblock>table td.content{padding-left:1.125em;padding-right:1.25em;border-left:1px solid #ddddd8;color:rgba(0,0,0,.6)}
|
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|
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.exampleblock>.content>:first-child{margin-top:0}
|
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.exampleblock>.content>:last-child{margin-bottom:0}
|
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.sidebarblock{border-style:solid;border-width:1px;border-color:#e0e0dc;margin-bottom:1.25em;padding:1.25em;background:#f8f8f7;-webkit-border-radius:4px;border-radius:4px}
|
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.sidebarblock>:first-child{margin-top:0}
|
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.sidebarblock>:last-child{margin-bottom:0}
|
||
.sidebarblock>.content>.title{color:#7a2518;margin-top:0;text-align:center}
|
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|
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.literalblock pre,.listingblock pre:not(.highlight),.listingblock pre[class="highlight"],.listingblock pre[class^="highlight "],.listingblock pre.CodeRay,.listingblock pre.prettyprint{background:#f7f7f8}
|
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.sidebarblock .literalblock pre,.sidebarblock .listingblock pre:not(.highlight),.sidebarblock .listingblock pre[class="highlight"],.sidebarblock .listingblock pre[class^="highlight "],.sidebarblock .listingblock pre.CodeRay,.sidebarblock .listingblock pre.prettyprint{background:#f2f1f1}
|
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|
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|
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@media only screen and (min-width:768px){.literalblock pre,.literalblock pre[class],.listingblock pre,.listingblock pre[class]{font-size:.90625em}}@media only screen and (min-width:1280px){.literalblock pre,.literalblock pre[class],.listingblock pre,.listingblock pre[class]{font-size:1em}}.literalblock.output pre{color:#f7f7f8;background-color:rgba(0,0,0,.9)}
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</style>
|
||
</head>
|
||
<body class="book toc2 toc-left">
|
||
<div id="header">
|
||
<h1>Spring Cloud</h1>
|
||
<div id="toc" class="toc2">
|
||
<div id="toctitle">Table of Contents</div>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_features">Features</a></li>
|
||
<li><a href="#_cloud_native_applications">Cloud Native Applications</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_spring_cloud_context_application_context_services">Spring Cloud Context: Application Context Services</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_the_bootstrap_application_context">The Bootstrap Application Context</a></li>
|
||
<li><a href="#_application_context_hierarchies">Application Context Hierarchies</a></li>
|
||
<li><a href="#customizing-bootstrap-properties">Changing the Location of Bootstrap Properties</a></li>
|
||
<li><a href="#_customizing_the_bootstrap_configuration">Customizing the Bootstrap Configuration</a></li>
|
||
<li><a href="#customizing-bootstrap-property-sources">Customizing the Bootstrap Property Sources</a></li>
|
||
<li><a href="#_environment_changes">Environment Changes</a></li>
|
||
<li><a href="#_refresh_scope">Refresh Scope</a></li>
|
||
<li><a href="#_encryption_and_decryption">Encryption and Decryption</a></li>
|
||
<li><a href="#_endpoints">Endpoints</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_commons_common_abstractions">Spring Cloud Commons: Common Abstractions</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_spring_resttemplate_as_a_load_balancer_client">Spring RestTemplate as a Load Balancer Client</a></li>
|
||
<li><a href="#_multiple_resttemplate_objects">Multiple RestTemplate objects</a></li>
|
||
<li><a href="#ignore-network-interfaces">Ignore Network Interfaces</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_config">Spring Cloud Config</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_quick_start">Quick Start</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_client_side_usage">Client Side Usage</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_config_server">Spring Cloud Config Server</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_environment_repository">Environment Repository</a></li>
|
||
<li><a href="#_health_indicator">Health Indicator</a></li>
|
||
<li><a href="#_security">Security</a></li>
|
||
<li><a href="#_encryption_and_decryption_2">Encryption and Decryption</a></li>
|
||
<li><a href="#_key_management">Key Management</a></li>
|
||
<li><a href="#_creating_a_key_store_for_testing">Creating a Key Store for Testing</a></li>
|
||
<li><a href="#_using_multiple_keys_and_key_rotation">Using Multiple Keys and Key Rotation</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_serving_plain_text">Serving Plain Text</a></li>
|
||
<li><a href="#_embedding_the_config_server">Embedding the Config Server</a></li>
|
||
<li><a href="#_push_notifications_and_spring_cloud_bus">Push Notifications and Spring Cloud Bus</a></li>
|
||
<li><a href="#_spring_cloud_config_client">Spring Cloud Config Client</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#config-first-bootstrap">Config First Bootstrap</a></li>
|
||
<li><a href="#eureka-first-bootstrap">Eureka First Bootstrap</a></li>
|
||
<li><a href="#config-client-fail-fast">Config Client Fail Fast</a></li>
|
||
<li><a href="#config-client-retry">Config Client Retry</a></li>
|
||
<li><a href="#_locating_remote_configuration_resources">Locating Remote Configuration Resources</a></li>
|
||
<li><a href="#_security_2">Security</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_netflix">Spring Cloud Netflix</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_service_discovery_eureka_clients">Service Discovery: Eureka Clients</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_registering_with_eureka">Registering with Eureka</a></li>
|
||
<li><a href="#_status_page_and_health_indicator">Status Page and Health Indicator</a></li>
|
||
<li><a href="#_registering_a_secure_application">Registering a Secure Application</a></li>
|
||
<li><a href="#_eureka_s_health_checks">Eureka’s Health Checks</a></li>
|
||
<li><a href="#_eureka_metadata_for_instances_and_clients">Eureka Metadata for Instances and Clients</a></li>
|
||
<li><a href="#_using_the_eurekaclient">Using the EurekaClient</a></li>
|
||
<li><a href="#_alternatives_to_the_native_netflix_eurekaclient">Alternatives to the native Netflix EurekaClient</a></li>
|
||
<li><a href="#_why_is_it_so_slow_to_register_a_service">Why is it so Slow to Register a Service?</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#spring-cloud-eureka-server">Service Discovery: Eureka Server</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_high_availability_zones_and_regions">High Availability, Zones and Regions</a></li>
|
||
<li><a href="#_standalone_mode">Standalone Mode</a></li>
|
||
<li><a href="#_peer_awareness">Peer Awareness</a></li>
|
||
<li><a href="#_prefer_ip_address">Prefer IP Address</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_circuit_breaker_hystrix_clients">Circuit Breaker: Hystrix Clients</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_propagating_the_security_context_or_using_spring_scopes">Propagating the Security Context or using Spring Scopes</a></li>
|
||
<li><a href="#_health_indicator_2">Health Indicator</a></li>
|
||
<li><a href="#_hystrix_metrics_stream">Hystrix Metrics Stream</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_circuit_breaker_hystrix_dashboard">Circuit Breaker: Hystrix Dashboard</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_turbine">Turbine</a></li>
|
||
<li><a href="#_turbine_amqp">Turbine AMQP</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_customizing_the_amqp_connectionfactory">Customizing the AMQP ConnectionFactory</a></li>
|
||
<li><a href="#spring-cloud-ribbon">Client Side Load Balancer: Ribbon</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_customizing_the_ribbon_client">Customizing the Ribbon Client</a></li>
|
||
<li><a href="#_using_ribbon_with_eureka">Using Ribbon with Eureka</a></li>
|
||
<li><a href="#spring-cloud-ribbon-without-eureka">Example: How to Use Ribbon Without Eureka</a></li>
|
||
<li><a href="#_example_disable_eureka_use_in_ribbon">Example: Disable Eureka use in Ribbon</a></li>
|
||
<li><a href="#_using_the_ribbon_api_directly">Using the Ribbon API Directly</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#spring-cloud-feign">Declarative REST Client: Feign</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#spring-cloud-feign-overriding-defaults">Overriding Feign Defaults</a></li>
|
||
<li><a href="#spring-cloud-feign-hystrix">Feign Hystrix Support</a></li>
|
||
<li><a href="#spring-cloud-feign-hystrix-fallback">Feign Hystrix Fallbacks</a></li>
|
||
<li><a href="#spring-cloud-feign-inheritance">Feign Inheritance Support</a></li>
|
||
<li><a href="#_feign_request_response_compression">Feign request/response compression</a></li>
|
||
<li><a href="#_feign_logging">Feign logging</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_external_configuration_archaius">External Configuration: Archaius</a></li>
|
||
<li><a href="#_router_and_filter_zuul">Router and Filter: Zuul</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#netflix-zuul-reverse-proxy">Embedded Zuul Reverse Proxy</a></li>
|
||
<li><a href="#_strangulation_patterns_and_local_forwards">Strangulation Patterns and Local Forwards</a></li>
|
||
<li><a href="#_uploading_files_through_zuul">Uploading Files through Zuul</a></li>
|
||
<li><a href="#_plain_embedded_zuul">Plain Embedded Zuul</a></li>
|
||
<li><a href="#_disable_zuul_filters">Disable Zuul Filters</a></li>
|
||
<li><a href="#_polyglot_support_with_sidecar">Polyglot support with Sidecar</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_metrics_spectator_servo_and_atlas">Metrics: Spectator, Servo, and Atlas</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_dimensional_vs_hierarchical_metrics">Dimensional vs. Hierarchical Metrics</a></li>
|
||
<li><a href="#_default_metrics_collection">Default Metrics Collection</a></li>
|
||
<li><a href="#_metrics_collection_spectator">Metrics Collection: Spectator</a></li>
|
||
<li><a href="#_metrics_collection_servo">Metrics Collection: Servo</a></li>
|
||
<li><a href="#_metrics_backend_atlas">Metrics Backend: Atlas</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_stream">Spring Cloud Stream</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#spring-cloud-stream-overview">Spring Cloud Stream Overview</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_introducing_spring_cloud_stream">Introducing Spring Cloud Stream</a></li>
|
||
<li><a href="#_binder_selection">Binder Selection</a></li>
|
||
<li><a href="#_managed_vs_standalone">Managed vs Standalone</a></li>
|
||
<li><a href="#_binder_spi">Binder SPI</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_task">Spring Cloud Task</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#getting-started">Getting started</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#getting-started-introducing-spring-cloud-task">Introducing Spring Cloud Task</a></li>
|
||
<li><a href="#getting-started-system-requirements">System Requirements</a></li>
|
||
<li><a href="#getting-started-developing-first-task">Developing your first Spring Cloud Task application</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#features">Features</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#features-lifecycle">The lifecycle of a Spring Cloud Task</a></li>
|
||
<li><a href="#features-configuration">Configuration</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_bus">Spring Cloud Bus</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_quick_start_2">Quick Start</a></li>
|
||
<li><a href="#_addressing_an_instance">Addressing an Instance</a></li>
|
||
<li><a href="#_addressing_all_instances_of_a_service">Addressing all instances of a service</a></li>
|
||
<li><a href="#_application_context_id_must_be_unique">Application Context ID must be unique</a></li>
|
||
<li><a href="#_customizing_the_message_broker">Customizing the Message Broker</a></li>
|
||
<li><a href="#_tracing_bus_events">Tracing Bus Events</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_sleuth">Spring Cloud Sleuth</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_spring_cloud_sleuth_2">Spring Cloud Sleuth</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_terminology">Terminology</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_features_2">Features</a></li>
|
||
<li><a href="#_sampling">Sampling</a></li>
|
||
<li><a href="#_instrumentation">Instrumentation</a></li>
|
||
<li><a href="#_span_data_as_messages">Span Data as Messages</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_zipkin_consumer">Zipkin Consumer</a></li>
|
||
<li><a href="#_custom_consumer">Custom Consumer</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_consul">Spring Cloud Consul</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#spring-cloud-consul-install">Install Consul</a></li>
|
||
<li><a href="#spring-cloud-consul-agent">Consul Agent</a></li>
|
||
<li><a href="#spring-cloud-consul-discovery">Service Discovery with Consul</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_registering_with_consul">Registering with Consul</a></li>
|
||
<li><a href="#_http_health_check">HTTP Health Check</a></li>
|
||
<li><a href="#_using_the_discoveryclient">Using the DiscoveryClient</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#spring-cloud-consul-config">Distributed Configuration with Consul</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_how_to_activate">How to activate</a></li>
|
||
<li><a href="#_customizing">Customizing</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#spring-cloud-consul-config-format">YAML or Properties with Config</a></li>
|
||
<li><a href="#spring-cloud-consul-retry">Consul Retry</a></li>
|
||
<li><a href="#spring-cloud-consul-bus">Spring Cloud Bus with Consul</a></li>
|
||
<li><a href="#spring-cloud-consul-hystrix">Circuit Breaker with Hystrix</a></li>
|
||
<li><a href="#spring-cloud-consul-turbine">Hystrix metrics aggregation with Turbine and Consul</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_zookeeper">Spring Cloud Zookeeper</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#spring-cloud-zookeeper-install">Install Zookeeper</a></li>
|
||
<li><a href="#spring-cloud-zookeeper-discovery">Service Discovery with Zookeeper</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_how_to_activate_2">How to activate</a></li>
|
||
<li><a href="#_registering_with_zookeeper">Registering with Zookeeper</a></li>
|
||
<li><a href="#_using_the_discoveryclient_2">Using the DiscoveryClient</a></li>
|
||
<li><a href="#spring-cloud-zookeeper-dependencies">Using the Zookeeper Dependencies</a></li>
|
||
<li><a href="#_how_to_activate_zookeeper_dependencies">How to activate Zookeeper Dependencies</a></li>
|
||
<li><a href="#_setting_up_zookeeper_dependencies">Setting up Zookeeper Dependencies</a></li>
|
||
<li><a href="#_stubs">Stubs</a></li>
|
||
<li><a href="#_configuring_spring_cloud_zookeeper_dependencies">Configuring Spring Cloud Zookeeper Dependencies</a></li>
|
||
<li><a href="#spring-cloud-zookeeper-dependency-watcher">Spring Cloud Zookeeper Dependency Watcher</a></li>
|
||
<li><a href="#_how_to_activate_3">How to activate</a></li>
|
||
<li><a href="#_registering_a_listener">Registering a listener</a></li>
|
||
<li><a href="#_presence_checker">Presence Checker</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#spring-cloud-zookeeper-config">Distributed Configuration with Zookeeper</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_how_to_activate_4">How to activate</a></li>
|
||
<li><a href="#_customizing_2">Customizing</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_boot_cloud_cli">Spring Boot Cloud CLI</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_installation">Installation</a></li>
|
||
<li><a href="#_writing_groovy_scripts_and_running_applications">Writing Groovy Scripts and Running Applications</a></li>
|
||
<li><a href="#_encryption_and_decryption_3">Encryption and Decryption</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_security">Spring Cloud Security</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_quickstart">Quickstart</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_oauth2_single_sign_on">OAuth2 Single Sign On</a></li>
|
||
<li><a href="#_oauth2_protected_resource">OAuth2 Protected Resource</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_more_detail">More Detail</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_single_sign_on">Single Sign On</a></li>
|
||
<li><a href="#_token_relay">Token Relay</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_configuring_authentication_downstream_of_a_zuul_proxy">Configuring Authentication Downstream of a Zuul Proxy</a></li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_for_cloud_foundry">Spring Cloud for Cloud Foundry</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_quickstart_2">Quickstart</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#_single_sign_on_2">Single Sign On</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</li>
|
||
<li><a href="#_spring_cloud_cluster">Spring Cloud Cluster</a>
|
||
<ul class="sectlevel1">
|
||
<li><a href="#_leader_election">Leader Election</a>
|
||
<ul class="sectlevel2">
|
||
<li><a href="#spring-cloud-cluster-leaderelection-zookeeper">Zookeeper</a></li>
|
||
<li><a href="#spring-cloud-cluster-leaderelection-hazelcast">Hazelcast</a></li>
|
||
<li><a href="#spring-cloud-cluster-leaderelection-etcd">Etcd</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
<div id="content">
|
||
<div id="preamble">
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud provides tools for developers to quickly build some of
|
||
the common patterns in distributed systems (e.g. configuration
|
||
management, service discovery, circuit breakers, intelligent routing,
|
||
micro-proxy, control bus, one-time tokens, global locks, leadership
|
||
election, distributed sessions, cluster state). Coordination of
|
||
distributed systems leads to boiler plate patterns, and using Spring
|
||
Cloud developers can quickly stand up services and applications that
|
||
implement those patterns. They will work well in any distributed
|
||
environment, including the developer’s own laptop, bare metal data
|
||
centres, and managed platforms such as Cloud Foundry.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_features">Features</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud focuses on providing good out of box experience for typical use cases
|
||
and extensibility mechanism to cover others.</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>Distributed/versioned configuration</p>
|
||
</li>
|
||
<li>
|
||
<p>Service registration and discovery</p>
|
||
</li>
|
||
<li>
|
||
<p>Routing</p>
|
||
</li>
|
||
<li>
|
||
<p>Service-to-service calls</p>
|
||
</li>
|
||
<li>
|
||
<p>Load balancing</p>
|
||
</li>
|
||
<li>
|
||
<p>Circuit Breakers</p>
|
||
</li>
|
||
<li>
|
||
<p>Global locks</p>
|
||
</li>
|
||
<li>
|
||
<p>Leadership election and cluster state</p>
|
||
</li>
|
||
<li>
|
||
<p>Distributed messaging</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_cloud_native_applications" class="sect0">Cloud Native Applications</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
<div class="paragraph">
|
||
<p><a href="http://pivotal.io/platform-as-a-service/migrating-to-cloud-native-application-architectures-ebook">Cloud Native</a> is a style of application development that encourages easy adoption of best practices in the areas of continuous delivery and value-driven development. A related discipline is that of building <a href="http://12factor.net/">12-factor Apps</a> in which development practices are aligned with delivery and operations goals, for instance by using declarative programming and management and monitoring. Spring Cloud facilitates these styles of development in a number of specific ways and the starting point is a set of features that all components in a distributed system either need or need easy access to when required.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Many of those features are covered by <a href="http://projects.spring.io/spring-boot">Spring Boot</a>, which we build on in Spring Cloud. Some more are delivered by Spring Cloud as two libraries: Spring Cloud Context and Spring Cloud Commons. Spring Cloud Context provides utilities and special services for the <code>ApplicationContext</code> of a Spring Cloud application (bootstrap context, encryption, refresh scope and environment endpoints). Spring Cloud Commons is a set of abstractions and common classes used in different Spring Cloud implementations (eg. Spring Cloud Netflix vs. Spring Cloud Consul).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you are getting an exception due to "Illegal key size" and you are using Sun’s JDK, you need to install the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files. See the following links for more information:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><a href="http://www.oracle.com/technetwork/java/javase/downloads/jce-6-download-429243.html">Java 6 JCE</a></p>
|
||
</li>
|
||
<li>
|
||
<p><a href="http://www.oracle.com/technetwork/java/javase/downloads/jce-7-download-432124.html">Java 7 JCE</a></p>
|
||
</li>
|
||
<li>
|
||
<p><a href="http://www.oracle.com/technetwork/java/javase/downloads/jce8-download-2133166.html">Java 8 JCE</a></p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Extract files into JDK/jre/lib/security folder (whichever version of JRE/JDK x64/x86 you are using).</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
Spring Cloud is released under the non-restrictive Apache 2.0 license. If you would like to contribute to this section of the documentation or if you find an error, please find the source code and issue trackers in the project at {githubmaster}/docs/src/main/asciidoc[github].
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_spring_cloud_context_application_context_services">Spring Cloud Context: Application Context Services</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Spring Boot has an opinionated view of how to build an application
|
||
with Spring: for instance it has conventional locations for common
|
||
configuration file, and endpoints for common management and monitoring
|
||
tasks. Spring Cloud builds on top of that and adds a few features that
|
||
probably all components in a system would use or occasionally need.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_the_bootstrap_application_context">The Bootstrap Application Context</h3>
|
||
<div class="paragraph">
|
||
<p>A Spring Cloud application operates by creating a "bootstrap"
|
||
context, which is a parent context for the main application. Out of
|
||
the box it is responsible for loading configuration properties from
|
||
the external sources, and also decrypting properties in the local
|
||
external configuration files. The two contexts share an <code>Environment</code>
|
||
which is the source of external properties for any Spring
|
||
application. Bootstrap properties are added with high precedence, so
|
||
they cannot be overridden by local configuration.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The bootstrap context uses a different convention for locating
|
||
external configuration than the main application context, so instead
|
||
of <code>application.yml</code> (or <code>.properties</code>) you use <code>bootstrap.yml</code>,
|
||
keeping the external configuration for bootstrap and main context
|
||
nicely separate. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">bootstrap.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
application:
|
||
name: foo
|
||
cloud:
|
||
config:
|
||
uri: ${SPRING_CONFIG_URI:http://localhost:8888}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>It is a good idea to set the <code>spring.application.name</code> (in
|
||
<code>bootstrap.yml</code> or <code>application.yml</code>) if your application needs any
|
||
application-specific configuration from the server.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can disable the bootstrap process completely by setting
|
||
<code>spring.cloud.bootstrap.enabled=false</code> (e.g. in System properties).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_application_context_hierarchies">Application Context Hierarchies</h3>
|
||
<div class="paragraph">
|
||
<p>If you build an application context from <code>SpringApplication</code> or
|
||
<code>SpringApplicationBuilder</code>, then the Bootstrap context is added as a
|
||
parent to that context. It is a feature of Spring that child contexts
|
||
inherit property sources and profiles from their parent, so the "main"
|
||
application context will contain additional property sources, compared
|
||
to building the same context without Spring Cloud Config. The
|
||
additional property sources are:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>"bootstrap": an optional <code>CompositePropertySource</code> appears with high
|
||
priority if any <code>PropertySourceLocators</code> are found in the Bootstrap
|
||
context, and they have non-empty properties. An example would be
|
||
properties from the Spring Cloud Config Server. See
|
||
<a href="#customizing-bootstrap-property-sources">below</a> for instructions
|
||
on how to customize the contents of this property source.</p>
|
||
</li>
|
||
<li>
|
||
<p>"applicationConfig: [classpath:bootstrap.yml]" (and friends if
|
||
Spring profiles are active). If you have a <code>bootstrap.yml</code> (or
|
||
properties) then those properties are used to configure the Bootstrap
|
||
context, and then they get added to the child context when its parent
|
||
is set. They have lower precedence than the <code>application.yml</code> (or
|
||
properties) and any other property sources that are added to the child
|
||
as a normal part of the process of creating a Spring Boot
|
||
application. See <a href="#customizing-bootstrap-properties">below</a> for
|
||
instructions on how to customize the contents of these property
|
||
sources.</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Because of the ordering rules of property sources the "bootstrap"
|
||
entries take precedence, but note that these do not contain any data
|
||
from <code>bootstrap.yml</code>, which has very low precedence, but can be used
|
||
to set defaults.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can extend the context hierarchy by simply setting the parent
|
||
context of any <code>ApplicationContext</code> you create, e.g. using its own
|
||
interface, or with the <code>SpringApplicationBuilder</code> convenience methods
|
||
(<code>parent()</code>, <code>child()</code> and <code>sibling()</code>). The bootstrap context will be
|
||
the parent of the most senior ancestor that you create yourself.
|
||
Every context in the hierarchy will have its own "bootstrap" property
|
||
source (possibly empty) to avoid promoting values inadvertently from
|
||
parents down to their descendants. Every context in the hierarchy can
|
||
also (in principle) have a different <code>spring.application.name</code> and
|
||
hence a different remote property source if there is a Config
|
||
Server. Normal Spring application context behaviour rules apply to
|
||
property resolution: properties from a child context override those in
|
||
the parent, by name and also by property source name (if the child has
|
||
a property source with the same name as the parent, the one from the
|
||
parent is not included in the child).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Note that the <code>SpringApplicationBuilder</code> allows you to share an
|
||
<code>Environment</code> amongst the whole hierarchy, but that is not the
|
||
default. Thus, sibling contexts in particular do not need to have the
|
||
same profiles or property sources, even though they will share common
|
||
things with their parent.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="customizing-bootstrap-properties">Changing the Location of Bootstrap Properties</h3>
|
||
<div class="paragraph">
|
||
<p>The <code>bootstrap.yml</code> (or <code>.properties</code>) location can be specified using
|
||
<code>spring.cloud.bootstrap.name</code> (default "bootstrap") or
|
||
<code>spring.cloud.bootstrap.location</code> (default empty), e.g. in System
|
||
properties. Those properties behave like the <code>spring.config.*</code>
|
||
variants with the same name, in fact they are used to set up the
|
||
bootstrap <code>ApplicationContext</code> by setting those properties in its
|
||
<code>Environment</code>. If there is an active profile (from
|
||
<code>spring.profiles.active</code> or through the <code>Environment</code> API in the
|
||
context you are building) then properties in that profile will be
|
||
loaded as well, just like in a regular Spring Boot app, e.g. from
|
||
<code>bootstrap-development.properties</code> for a "development" profile.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_customizing_the_bootstrap_configuration">Customizing the Bootstrap Configuration</h3>
|
||
<div class="paragraph">
|
||
<p>The bootstrap context can be trained to do anything you like by adding
|
||
entries to <code>/META-INF/spring.factories</code> under the key
|
||
<code>org.springframework.cloud.bootstrap.BootstrapConfiguration</code>. This is
|
||
a comma-separated list of Spring <code>@Configuration</code> classes which will
|
||
be used to create the context. Any beans that you want to be available
|
||
to the main application context for autowiring can be created here,
|
||
and also there is a special contract for <code>@Beans</code> of type
|
||
<code>ApplicationContextInitializer</code>. Classes can be marked with an <code>@Order</code>
|
||
if you want to control the startup sequence (the default order is
|
||
"last").</p>
|
||
</div>
|
||
<div class="admonitionblock warning">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Warning</div>
|
||
</td>
|
||
<td class="content">
|
||
Be careful when adding custom <code>BootstrapConfiguration</code> that the
|
||
classes you add are not <code>@ComponentScanned</code> by mistake into your
|
||
"main" application context, where they might not be needed.
|
||
Use a separate package name for boot configuration classes that is
|
||
not already covered by your <code>@ComponentScan</code> or <code>@SpringBootApplication</code>
|
||
annotated configuration classes.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The bootstrap process ends by injecting initializers into the main
|
||
<code>SpringApplication</code> instance (i.e. the normal Spring Boot startup
|
||
sequence, whether it is running as a standalone app or deployed in an
|
||
application server). First a bootstrap context is created from the
|
||
classes found in <code>spring.factories</code> and then all <code>@Beans</code> of type
|
||
<code>ApplicationContextInitializer</code> are added to the main
|
||
<code>SpringApplication</code> before it is started.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="customizing-bootstrap-property-sources">Customizing the Bootstrap Property Sources</h3>
|
||
<div class="paragraph">
|
||
<p>The default property source for external configuration added by the
|
||
bootstrap process is the Config Server, but you can add additional
|
||
sources by adding beans of type <code>PropertySourceLocator</code> to the
|
||
bootstrap context (via <code>spring.factories</code>). You could use this to
|
||
insert additional properties from a different server, or from a
|
||
database, for instance.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>As an example, consider the following trivial custom locator:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
|
||
public class CustomPropertySourceLocator implements PropertySourceLocator {
|
||
|
||
@Override
|
||
public PropertySource<?> locate(Environment environment) {
|
||
return new MapPropertySource("customProperty",
|
||
Collections.<String, Object>singletonMap("property.from.sample.custom.source", "worked as intended"));
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>Environment</code> that is passed in is the one for the
|
||
<code>ApplicationContext</code> about to be created, i.e. the one that we are
|
||
supplying additional property sources for. It will already have its
|
||
normal Spring Boot-provided property sources, so you can use those to
|
||
locate a property source specific to this <code>Environment</code> (e.g. by
|
||
keying it on the <code>spring.application.name</code>, as is done in the default
|
||
Config Server property source locator).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you create a jar with this class in it and then add a
|
||
<code>META-INF/spring.factories</code> containing:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>org.springframework.cloud.bootstrap.BootstrapConfiguration=sample.custom.CustomPropertySourceLocator</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>then the "customProperty" <code>PropertySource</code> will show up in any
|
||
application that includes that jar on its classpath.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_environment_changes">Environment Changes</h3>
|
||
<div class="paragraph">
|
||
<p>The application will listen for an <code>EnvironmentChangedEvent</code> and react
|
||
to the change in a couple of standard ways (additional
|
||
<code>ApplicationListeners</code> can be added as <code>@Beans</code> by the user in the
|
||
normal way). When an <code>EnvironmentChangedEvent</code> is observed it will
|
||
have a list of key values that have changed, and the application will
|
||
use those to:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>Re-bind any <code>@ConfigurationProperties</code> beans in the context</p>
|
||
</li>
|
||
<li>
|
||
<p>Set the logger levels for any properties in <code>logging.level.*</code></p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Note that the Config Client does not by default poll for changes in
|
||
the <code>Environment</code>, and generally we would not recommend that approach
|
||
for detecting changes (although you could set it up with a
|
||
<code>@Scheduled</code> annotation). If you have a scaled-out client application
|
||
then it is better to broadcast the <code>EnvironmentChangedEvent</code> to all
|
||
the instances instead of having them polling for changes (e.g. using
|
||
the <a href="https://github.com/spring-cloud/spring-cloud-bus">Spring Cloud
|
||
Bus</a>).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>EnvironmentChangedEvent</code> covers a large class of refresh use
|
||
cases, as long as you can actually make a change to the <code>Environment</code>
|
||
and publish the event (those APIs are public and part of core
|
||
Spring). You can verify the changes are bound to
|
||
<code>@ConfigurationProperties</code> beans by visiting the <code>/configprops</code>
|
||
endpoint (normal Spring Boot Actuator feature). For instance a
|
||
<code>DataSource</code> can have its <code>maxPoolSize</code> changed at runtime (the
|
||
default <code>DataSource</code> created by Spring Boot is an
|
||
<code>@ConfigurationProperties</code> bean) and grow capacity
|
||
dynamically. Re-binding <code>@ConfigurationProperties</code> does not cover
|
||
another large class of use cases, where you need more control over the
|
||
refresh, and where you need a change to be atomic over the whole
|
||
<code>ApplicationContext</code>. To address those concerns we have
|
||
<code>@RefreshScope</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_refresh_scope">Refresh Scope</h3>
|
||
<div class="paragraph">
|
||
<p>A Spring <code>@Bean</code> that is marked as <code>@RefreshScope</code> will get special
|
||
treatment when there is a configuration change. This addresses the
|
||
problem of stateful beans that only get their configuration injected
|
||
when they are initialized. For instance if a <code>DataSource</code> has open
|
||
connections when the database URL is changed via the <code>Environment</code>, we
|
||
probably want the holders of those connections to be able to complete
|
||
what they are doing. Then the next time someone borrows a connection
|
||
from the pool he gets one with the new URL.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Refresh scope beans are lazy proxies that initialize when they are
|
||
used (i.e. when a method is called), and the scope acts as a cache of
|
||
initialized values. To force a bean to re-initialize on the next
|
||
method call you just need to invalidate its cache entry.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>RefreshScope</code> is a bean in the context and it has a public method
|
||
<code>refreshAll()</code> to refresh all beans in the scope by clearing the
|
||
target cache. There is also a <code>refresh(String)</code> method to refresh an
|
||
individual bean by name. This functionality is exposed in the
|
||
<code>/refresh</code> endpoint (over HTTP or JMX).</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
<code>@RefreshScope</code> works (technically) on an <code>@Configuration</code>
|
||
class, but it might lead to surprising behaviour: e.g. it does <strong>not</strong>
|
||
mean that all the <code>@Beans</code> defined in that class are themselves
|
||
<code>@RefreshScope</code>. Specifically, anything that depends on those beans
|
||
cannot rely on them being updated when a refresh is initiated, unless
|
||
it is itself in <code>@RefreshScope</code> (in which it will be rebuilt on a
|
||
refresh and its dependencies re-injected, at which point they will be
|
||
re-initialized from the refreshed <code>@Configuration</code>).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_encryption_and_decryption">Encryption and Decryption</h3>
|
||
<div class="paragraph">
|
||
<p>The Config Client has an <code>Environment</code> pre-processor for decrypting
|
||
property values locally. It follows the same rules as the Config
|
||
Server, and has the same external configuration via <code>encrypt.*</code>. Thus
|
||
you can use encrypted values in the form <code>{cipher}*</code> and as long as
|
||
there is a valid key then they will be decrypted before the main
|
||
application context gets the <code>Environment</code>. To use the encryption
|
||
features in a client you need to include Spring Security RSA in your
|
||
classpath (Maven co-ordinates
|
||
"org.springframework.security:spring-security-rsa") and you also need
|
||
the full strength JCE extensions in your JVM.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you are getting an exception due to "Illegal key size" and you are using Sun’s JDK, you need to install the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files. See the following links for more information:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><a href="http://www.oracle.com/technetwork/java/javase/downloads/jce-6-download-429243.html">Java 6 JCE</a></p>
|
||
</li>
|
||
<li>
|
||
<p><a href="http://www.oracle.com/technetwork/java/javase/downloads/jce-7-download-432124.html">Java 7 JCE</a></p>
|
||
</li>
|
||
<li>
|
||
<p><a href="http://www.oracle.com/technetwork/java/javase/downloads/jce8-download-2133166.html">Java 8 JCE</a></p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Extract files into JDK/jre/lib/security folder (whichever version of JRE/JDK x64/x86 you are using).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_endpoints">Endpoints</h3>
|
||
<div class="paragraph">
|
||
<p>For a Spring Boot Actuator application there are some additional management endpoints:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>POST to <code>/env</code> to update the <code>Environment</code> and rebind <code>@ConfigurationProperties</code> and log levels</p>
|
||
</li>
|
||
<li>
|
||
<p><code>/refresh</code> for re-loading the boot strap context and refreshing the <code>@RefreshScope</code> beans</p>
|
||
</li>
|
||
<li>
|
||
<p><code>/restart</code> for closing the <code>ApplicationContext</code> and restarting it (disabled by default)</p>
|
||
</li>
|
||
<li>
|
||
<p><code>/pause</code> and <code>/resume</code> for calling the <code>Lifecycle</code> methods (<code>stop()</code> and <code>start()</code> on the <code>ApplicationContext</code>)</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_spring_cloud_commons_common_abstractions">Spring Cloud Commons: Common Abstractions</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Patterns such as service discovery, load balancing and circuit breakers lend themselves to a common abstraction layer that can be consumed by all Spring Cloud clients, independent of the implementation (e.g. discovery via Eureka or Consul).</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_spring_resttemplate_as_a_load_balancer_client">Spring RestTemplate as a Load Balancer Client</h3>
|
||
<div class="paragraph">
|
||
<p>You can use Ribbon indirectly via an autoconfigured <code>RestTemplate</code>
|
||
when RestTemplate is on the classpath and a <code>LoadBalancerClient</code> bean is defined):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">public class MyClass {
|
||
@Autowired
|
||
private RestTemplate restTemplate;
|
||
|
||
public String doOtherStuff() {
|
||
String results = restTemplate.getForObject("http://stores/stores", String.class);
|
||
return results;
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The URI needs to use a virtual host name (ie. service name, not a host name).
|
||
The Ribbon client is used to create a full physical address. See
|
||
<a href="https://github.com/spring-cloud/spring-cloud-netflix/blob/master/spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/ribbon/RibbonAutoConfiguration.java">RibbonAutoConfiguration</a>
|
||
for details of how the <code>RestTemplate</code> is set up.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_multiple_resttemplate_objects">Multiple RestTemplate objects</h3>
|
||
<div class="paragraph">
|
||
<p>If you want a <code>RestTemplate</code> that is not load balanced, create a <code>RestTemplate</code>
|
||
bean and inject it as normal. To access the load balanced <code>RestTemplate use
|
||
the provided `@LoadBalanced</code> <code>Qualifier</code>:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">public class MyClass {
|
||
@Autowired
|
||
private RestTemplate restTemplate;
|
||
|
||
@Autowired
|
||
@LoadBalanced
|
||
private RestTemplate loadBalanced;
|
||
|
||
public String doOtherStuff() {
|
||
return loadBalanced.getForObject("http://stores/stores", String.class);
|
||
}
|
||
|
||
public String doStuff() {
|
||
return restTemplate.getForObject("http://example.com", String.class);
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="ignore-network-interfaces">Ignore Network Interfaces</h3>
|
||
<div class="paragraph">
|
||
<p>Sometimes it is useful to ignore certain named network interfaces so they can be excluded from Service Discovery registration (eg. running in a Docker container). A list of regular expressions can be set that will cause the desired network interfaces to be ignored. The following configuration will ignore the "docker0" interface and all interfaces that start with "veth".</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
cloud:
|
||
inetutils:
|
||
ignoredInterfaces:
|
||
- docker0
|
||
- veth.*</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_config" class="sect0">Spring Cloud Config</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
Spring Cloud Config provides server and client-side support for externalized configuration in a distributed system. With the Config Server you have a central place to manage external properties for applications across all environments. The concepts on both client and server map identically to the Spring <code>Environment</code> and <code>PropertySource</code> abstractions, so they fit very well with Spring applications, but can be used with any application running in any language. As an application moves through the deployment pipeline from dev to test and into production you can manage the configuration between those environments and be certain that applications have everything they need to run when they migrate. The default implementation of the server storage backend uses git so it easily supports labelled versions of configuration environments, as well as being accessible to a wide range of tooling for managing the content. It is easy to add alternative implementations and plug them in with Spring configuration.
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_quick_start">Quick Start</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Start the server:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ cd spring-cloud-config-server
|
||
$ mvn spring-boot:run</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The server is a Spring Boot application so you can run it from your
|
||
IDE instead if you prefer (the main class is
|
||
<code>ConfigServerApplication</code>). Then try it out a client:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ curl localhost:8888/foo/development
|
||
{"name":"development","label":"master","propertySources":[
|
||
{"name":"https://github.com/scratches/config-repo/foo-development.properties","source":{"bar":"spam"}},
|
||
{"name":"https://github.com/scratches/config-repo/foo.properties","source":{"foo":"bar"}}
|
||
]}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The default strategy for locating property sources is to clone a git
|
||
repository (at <code>spring.cloud.config.server.git.uri</code>) and use it to
|
||
initialize a mini <code>SpringApplication</code>. The mini-application’s
|
||
<code>Environment</code> is used to enumerate property sources and publish them
|
||
via a JSON endpoint.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The HTTP service has resources in the form:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>/{application}/{profile}[/{label}]
|
||
/{application}-{profile}.yml
|
||
/{label}/{application}-{profile}.yml
|
||
/{application}-{profile}.properties
|
||
/{label}/{application}-{profile}.properties</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>where the "application" is injected as the <code>spring.config.name</code> in the
|
||
<code>SpringApplication</code> (i.e. what is normally "application" in a regular
|
||
Spring Boot app), "profile" is an active profile (or comma-separated
|
||
list of properties), and "label" is an optional git label (defaults to
|
||
"master".)</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The YAML and properties forms are coalesced into a single
|
||
map, even if the origin of the values (reflected in the
|
||
"propertySources" of the "standard" form) has multiple sources.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Config Server pulls configuration for remote clients
|
||
from a git repository (which must be provided):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
git:
|
||
uri: https://github.com/spring-cloud-samples/config-repo</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_client_side_usage">Client Side Usage</h3>
|
||
<div class="paragraph">
|
||
<p>To use these features in an application, just build it as a Spring
|
||
Boot application that depends on spring-cloud-config-client (e.g. see
|
||
the test cases for the config-client, or the sample app). The most
|
||
convenient way to add the dependency is via a Spring Boot starter
|
||
<code>org.springframework.cloud:spring-cloud-starter-config</code>. There is also a
|
||
parent pom and BOM (<code>spring-cloud-starter-parent</code>) for Maven users and a
|
||
Spring IO version management properties file for Gradle and Spring CLI
|
||
users. Example Maven configuration:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">pom.xml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-xml" data-lang="xml"><parent>
|
||
<groupId>org.springframework.boot</groupId>
|
||
<artifactId>spring-boot-starter-parent</artifactId>
|
||
<version>1.2.3.RELEASE</version>
|
||
<relativePath /> <!-- lookup parent from repository -->
|
||
</parent>
|
||
|
||
<dependencyManagement>
|
||
<dependencies>
|
||
<dependency>
|
||
<groupId>org.springframework.cloud</groupId>
|
||
<artifactId>spring-cloud-starter-parent</artifactId>
|
||
<version>1.0.1.RELEASE</version>
|
||
<type>pom</type>
|
||
<scope>import</scope>
|
||
</dependency>
|
||
</dependencies>
|
||
</dependencyManagement>
|
||
|
||
<dependencies>
|
||
<dependency>
|
||
<groupId>org.springframework.cloud</groupId>
|
||
<artifactId>spring-cloud-starter-config</artifactId>
|
||
</dependency>
|
||
<dependency>
|
||
<groupId>org.springframework.boot</groupId>
|
||
<artifactId>spring-boot-starter-test</artifactId>
|
||
<scope>test</scope>
|
||
</dependency>
|
||
</dependencies>
|
||
|
||
<build>
|
||
<plugins>
|
||
<plugin>
|
||
<groupId>org.springframework.boot</groupId>
|
||
<artifactId>spring-boot-maven-plugin</artifactId>
|
||
</plugin>
|
||
</plugins>
|
||
</build>
|
||
|
||
<!-- repositories also needed for snapshots and milestones --></code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Then you can create a standard Spring Boot application, like this simple HTTP server:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>@SpringBootApplication
|
||
@RestController
|
||
public class Application {
|
||
|
||
@RequestMapping("/")
|
||
public String home() {
|
||
return "Hello World!";
|
||
}
|
||
|
||
public static void main(String[] args) {
|
||
SpringApplication.run(Application.class, args);
|
||
}
|
||
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>When it runs it will pick up the external configuration from the
|
||
default local config server on port 8888 if it is running. To modify
|
||
the startup behaviour you can change the location of the config server
|
||
using <code>bootstrap.properties</code> (like <code>application.properties</code> but for
|
||
the bootstrap phase of an application context), e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>spring.cloud.config.uri: http://myconfigserver.com</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The bootstrap properties will show up in the <code>/env</code> endpoint as a
|
||
high-priority property source, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ curl localhost:8080/env
|
||
{
|
||
"profiles":[],
|
||
"configService:https://github.com/spring-cloud-samples/config-repo/bar.properties":{"foo":"bar"},
|
||
"servletContextInitParams":{},
|
||
"systemProperties":{...},
|
||
...
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>(a property source called "configService:<URL of remote
|
||
repository>/<file name>" contains the property "foo" with value
|
||
"bar" and is highest priority).</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
the URL in the property source name is the git repository not
|
||
the config server URL.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_spring_cloud_config_server">Spring Cloud Config Server</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>The Server provides an HTTP, resource-based API for external
|
||
configuration (name-value pairs, or equivalent YAML content). The
|
||
server is easily embeddable in a Spring Boot application using the
|
||
<code>@EnableConfigServer</code> annotation. So this app is a config server:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">ConfigServer.java</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@SpringBootApplication
|
||
@EnableConfigServer
|
||
public class ConfigServer {
|
||
public static void main(String[] args) {
|
||
SpringApplication.run(ConfigServer.class, args);
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Like all Spring Boot apps it runs on port 8080 by default, but you
|
||
can switch it to the conventional port 8888 in various ways. The
|
||
easiest, which also sets a default configuration repository,
|
||
is by launching it with <code>spring.config.name=configserver</code> (there
|
||
is a <code>configserver.yml</code> in the Config Server jar). Another is
|
||
to use your own <code>application.properties</code>, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.properties</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-properties" data-lang="properties">server.port: 8888
|
||
spring.cloud.config.server.git.uri: file://${user.home}/config-repo</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>where <code>${user.home}/config-repo</code> is a git repository containing
|
||
YAML and properties files.</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
in Windows you need an extra "/" in the file URL if it is
|
||
absolute with a drive prefix, e.g. <code><a href="file:///${user.home}/config-repo" class="bare">file:///${user.home}/config-repo</a></code>.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
<div class="paragraph">
|
||
<p>Here’s a recipe for creating the git repository in the example
|
||
above:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ cd $HOME
|
||
$ mkdir config-repo
|
||
$ cd config-repo
|
||
$ git init .
|
||
$ echo info.foo: bar > application.properties
|
||
$ git add -A .
|
||
$ git commit -m "Add application.properties"</pre>
|
||
</div>
|
||
</div>
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="admonitionblock warning">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Warning</div>
|
||
</td>
|
||
<td class="content">
|
||
using the local filesystem for your git repository is
|
||
intended for testing only. Use a server to host your
|
||
configuration repositories in production.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_environment_repository">Environment Repository</h3>
|
||
<div class="paragraph">
|
||
<p>Where do you want to store the configuration data for the Config
|
||
Server? The strategy that governs this behaviour is the
|
||
<code>EnvironmentRepository</code>, serving <code>Environment</code> objects. This
|
||
<code>Environment</code> is a shallow copy of the domain from the Spring
|
||
<code>Environment</code> (including <code>propertySources</code> as the main feature). The
|
||
<code>Environment</code> resources are parametrized by three variables:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>{application}</code> maps to "spring.application.name" on the client side;</p>
|
||
</li>
|
||
<li>
|
||
<p><code>{profile}</code> maps to "spring.active.profiles" on the client (comma separated list); and</p>
|
||
</li>
|
||
<li>
|
||
<p><code>{label}</code> which is a server side feature labelling a "versioned" set of config files.</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Repository implementations generally behave just like a Spring Boot
|
||
application loading configuration files from a "spring.config.name"
|
||
equal to the <code>{application}</code> parameter, and "spring.profiles.active"
|
||
equal to the <code>{profiles}</code> parameter. Precedence rules for profiles are
|
||
also the same as in a regular Boot application: active profiles take
|
||
precedence over defaults, and if there are multiple profiles the last
|
||
one wins (like adding entries to a <code>Map</code>).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Example: a client application has this bootstrap configuration:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">bootstrap.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
application:
|
||
name: foo
|
||
profiles:
|
||
active: dev,mysql</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>(as usual with a Spring Boot application, these properties could also
|
||
be set as environment variables or command line arguments).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If the repository is file-based, the server will create an
|
||
<code>Environment</code> from <code>application.yml</code> (shared between all clients), and
|
||
<code>foo.yml</code> (with <code>foo.yml</code> taking precedence). If the YAML files have
|
||
documents inside them that point to Spring profiles, those are applied
|
||
with higher precendence (in order of the profiles listed), and if
|
||
there are profile-specific YAML (or properties) files these are also
|
||
applied with higher precedence than the defaults. Higher precendence
|
||
translates to a <code>PropertySource</code> listed earlier in the
|
||
<code>Environment</code>. (These are the same rules as apply in a standalone
|
||
Spring Boot application.)</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_git_backend">Git Backend</h4>
|
||
<div class="paragraph">
|
||
<p>The default implementation of <code>EnvironmentRepository</code> uses a Git
|
||
backend, which is very convenient for managing upgrades and physical
|
||
environments, and also for auditing changes. To change the location of
|
||
the repository you can set the "spring.cloud.config.server.git.uri"
|
||
configuration property in the Config Server (e.g. in
|
||
<code>application.yml</code>). If you set it with a <code>file:</code> prefix it should work
|
||
from a local repository so you can get started quickly and easily
|
||
without a server, but in that case the server operates directly on the
|
||
local repository without cloning it (it doesn’t matter if it’s not
|
||
bare because the Config Server never makes changes to the "remote"
|
||
repository). To scale the Config Server up and make it highly
|
||
available, you would need to have all instances of the server pointing
|
||
to the same repository, so only a shared file system would work. Even
|
||
in that case it is better to use the <code>ssh:</code> protocol for a shared
|
||
filesystem repository, so that the server can clone it and use a local
|
||
working copy as a cache.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This repository implementation maps the <code>{label}</code> parameter of the
|
||
HTTP resource to a git label (commit id, branch name or tag). If the
|
||
git branch or tag name contains a slash ("/") then the label in the
|
||
HTTP URL should be specified with the special string "(_)" instead (to
|
||
avoid ambiguity with other URL paths). Be careful with the brackets in
|
||
the URL if you are using a command line client like curl (e.g. escape
|
||
them from the shell with quotes '').</p>
|
||
</div>
|
||
<div class="sect4">
|
||
<h5 id="_placeholders_in_git_uri">Placeholders in Git URI</h5>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Config Server supports a git repository URL with
|
||
placeholders for the <code>{application}</code> and <code>{profile}</code> (and <code>{label}</code> if
|
||
you need it, but remember that the label is applied as a git label
|
||
anyway). So you can easily support a "one repo per application" policy
|
||
using (for example):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
git:
|
||
uri: https://github.com/myorg/{application}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>or a "one repo per profile" policy using a similar pattern but with
|
||
<code>{profile}</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect4">
|
||
<h5 id="_pattern_matching_and_multiple_repositories">Pattern Matching and Multiple Repositories</h5>
|
||
<div class="paragraph">
|
||
<p>There is also support for more complex requirements with pattern
|
||
matching on the application and profile name. The pattern format is a
|
||
comma-separated list of <code>{application}/{profile}</code> names with wildcards
|
||
(where a pattern beginning with a wildcard may need to be
|
||
quoted). Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
git:
|
||
uri: https://github.com/spring-cloud-samples/config-repo
|
||
repos:
|
||
simple: https://github.com/simple/config-repo
|
||
special:
|
||
pattern: special*/dev*,*special*/dev*
|
||
uri: https://github.com/special/config-repo
|
||
local:
|
||
pattern: local*
|
||
uri: file:/home/configsvc/config-repo</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If <code>{application}/{profile}</code> does not match any of the patterns, it
|
||
will use the default uri defined under
|
||
"spring.cloud.config.server.git.uri". In the above example, for the
|
||
"simple" repository, the pattern is <code>simple/*</code> (i.e. it only matches
|
||
one application named "simple" in all profiles). The "local"
|
||
repository matches all application names beginning with "local" in all
|
||
profiles (the <code>/*</code> suffix is added automatically to any pattern that
|
||
doesn’t have a profile matcher).</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
the "one-liner" short cut used in the "simple" example above can
|
||
only be used if the only property to be set is the URI. If you need to
|
||
set anything else (credentials, pattern, etc.) you need to use the full
|
||
form.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>pattern</code> property in the repo is actually an array, so you can
|
||
use a YAML array (or <code>[0]</code>, <code>[1]</code>, etc. suffixes in properties files)
|
||
to bind to multiple patterns. You may need to do this if you are going
|
||
to run apps with multiple profiles. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
git:
|
||
uri: https://github.com/spring-cloud-samples/config-repo
|
||
repos:
|
||
development:
|
||
pattern:
|
||
- */development
|
||
- */staging
|
||
uri: https://github.com/development/config-repo
|
||
staging:
|
||
pattern:
|
||
- */qa
|
||
- */production
|
||
uri: https://github.com/staging/config-repo</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
Spring Cloud will guess that a pattern containing a profile that
|
||
doesn’t end in <code>*</code> implies that you actually want to match a list of
|
||
profiles starting with this pattern (so <code>*/staging</code> is a shortcut for
|
||
<code>["*/staging", "*/staging,*"]</code>). This is common where you need to run
|
||
apps in the "development" profile locally but also the "cloud" profile
|
||
remotely, for instance.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Every repository can also optionally store config files in
|
||
sub-directories, and patterns to search for those directories can be
|
||
specified as <code>searchPaths</code>. For example at the top level:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
git:
|
||
uri: https://github.com/spring-cloud-samples/config-repo
|
||
searchPaths: foo,bar*</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this example the server searches for config files in the top level
|
||
and in the "foo/" sub-directory and also any sub-directory whose name
|
||
begins with "bar".</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>By default the server clones remote repositories when configuration
|
||
is first requested. The server can be configured to clone the repositories
|
||
at startup. For example at the top level:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
git:
|
||
uri: https://git/common/config-repo.git
|
||
repos:
|
||
team-a:
|
||
pattern: team-a-*
|
||
cloneOnStart: true
|
||
uri: http://git/team-a/config-repo.git
|
||
team-b:
|
||
pattern: team-b-*
|
||
cloneOnStart: false
|
||
uri: http://git/team-b/config-repo.git
|
||
team-c:
|
||
pattern: team-c-*
|
||
uri: http://git/team-a/config-repo.git</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this example the server clones team-a’s config-repo on startup before it
|
||
accepts any requests. All other repositories will not be cloned until
|
||
configuration from the repository is requested.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To use HTTP basic authentication on the remote repository add the
|
||
"username" and "password" properties separately (not in the URL),
|
||
e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
git:
|
||
uri: https://github.com/spring-cloud-samples/config-repo
|
||
username: trolley
|
||
password: strongpassword</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you don’t use HTTPS and user credentials, SSH should also work out
|
||
of the box when you store keys in the default directories (<code>~/.ssh</code>)
|
||
and the uri points to an SSH location,
|
||
e.g. "<a href="mailto:git@github.com">git@github.com</a>:configuration/cloud-configuration". The
|
||
repository is accessed using JGit, so any documentation you find on
|
||
that should be applicable. HTTPS proxy settings can be set in
|
||
<code>~/.git/config</code> or in the same way as for any other JVM process via
|
||
system properties (<code>-Dhttps.proxyHost</code> and <code>-Dhttps.proxyPort</code>).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect4">
|
||
<h5 id="_placeholders_in_git_search_paths">Placeholders in Git Search Paths</h5>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Config Server also supports a search path with
|
||
placeholders for the <code>{application}</code> and <code>{profile}</code> (and <code>{label}</code> if
|
||
you need it). Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
git:
|
||
uri: https://github.com/spring-cloud-samples/config-repo
|
||
searchPaths: {application}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>searches the repository for files in the same name as the directory
|
||
(as well as the top level). Wildcards are also valid in a search
|
||
path with placeholders (any matching directory is included in the
|
||
search).</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_file_system_backend">File System Backend</h4>
|
||
<div class="paragraph">
|
||
<p>There is also a "native" profile in the Config Server that doesn’t use
|
||
Git, but just loads the config files from the local classpath or file
|
||
system (any static URL you want to point to with
|
||
"spring.cloud.config.server.native.searchLocations"). To use the
|
||
native profile just launch the Config Server with
|
||
"spring.profiles.active=native".</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
Remember to use the <code>file:</code> prefix for file resources (the
|
||
default without a prefix is usually the classpath). Just as with any
|
||
Spring Boot configuration you can embed <code>${}</code>-style environment
|
||
placeholders, but remember that absolute paths in Windows require an
|
||
extra "/", e.g. <code><a href="file:///${user.home}/config-repo" class="bare">file:///${user.home}/config-repo</a></code>
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="admonitionblock warning">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Warning</div>
|
||
</td>
|
||
<td class="content">
|
||
The default value of the <code>searchLocations</code> is identical to a
|
||
local Spring Boot application (so <code>[classpath:/, classpath:/config,
|
||
file:./, file:./config]</code>). This does not expose the
|
||
<code>application.properties</code> from the server to all clients because any
|
||
property sources present in the server are removed before being sent
|
||
to the client.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
A filesystem backend is great for getting started quickly and
|
||
for testing. To use it in production you need to be sure that the
|
||
file system is reliable, and shared across all instances of the
|
||
Config Server.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The search locations can contain placeholders for <code>{application}</code>,
|
||
<code>{profile}</code> and <code>{label}</code>. In this way you can segregate the
|
||
directories in the path, and choose a strategy that makes sense for
|
||
you (e.g. sub-directory per application, or sub-directory per
|
||
profile).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you don’t use placeholders in the search locations, this repository
|
||
also appends the <code>{label}</code> parameter of the HTTP resource to a suffix
|
||
on the search path, so properties files are loaded from each search
|
||
location <strong>and</strong> a subdirectory with the same name as the label (the
|
||
labelled properties take precedence in the Spring Environment). Thus
|
||
the default behaviour with no placeholders is the same as adding a
|
||
search location ending with <code>/{label}/. For example `file:/tmp/config</code>
|
||
is the same as <code>file:/tmp/config,file:/tmp/config/{label}</code></p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_sharing_configiration_with_all_applications">Sharing Configiration With All Applications</h4>
|
||
<div class="paragraph">
|
||
<p>With file-based (i.e. git, svn and native) repositories, resources
|
||
with file names in <code>application*</code> are shared between all client
|
||
applications (so <code>application.properties</code>, <code>application.yml</code>,
|
||
<code>application-*.properties</code> etc.). You can use resources with these
|
||
file names to configure global defaults and have them overridden by
|
||
application-specific files as necessary.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The #_property_overrides[property overrides] feature can also be used
|
||
for setting global defaults, and with placeholders applications are
|
||
allowed to override them locally.</p>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
With the "native" profile (local file system backend) it is
|
||
recommended that you use an explicit search location that isn’t part
|
||
of the server’s own configuration. Otherwise the <code>application*</code>
|
||
resources in the default search locations are removed because they are
|
||
part of the server.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_property_overrides">Property Overrides</h4>
|
||
<div class="paragraph">
|
||
<p>The Config Server has an "overrides" feature that allows the operator
|
||
to provide configuration properties to all applications that cannot be
|
||
accidentally changed by the application using the normal Spring Boot
|
||
hooks. To declare overrides just add a map of name-value pairs to
|
||
<code>spring.cloud.config.server.overrides</code>. For example</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
overrides:
|
||
foo: bar</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>will cause all applications that are config clients to read <code>foo=bar</code>
|
||
independent of their own configuration. (Of course an application can
|
||
use the data in the Config Server in any way it likes, so overrides
|
||
are not enforceable, but they do provide useful default behaviour if
|
||
they are Spring Cloud Config clients.)</p>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
Normal, Spring environment placeholders with "${}" can be escaped
|
||
(and resolved on the client) by using backslash ("\") to escape the
|
||
"$" or the "{", e.g. <code>\${app.foo:bar}</code> resolves to "bar" unless the
|
||
app provides its own "app.foo". Note that in YAML you don’t need to
|
||
escape the backslash itself, but in properties files you do, when you
|
||
configure the overrides on the server.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can change the priority of all overrides in the client to be more
|
||
like default values, allowing applications to supply their own values
|
||
in environment variables or System properties, by setting the flag `</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_health_indicator">Health Indicator</h3>
|
||
<div class="paragraph">
|
||
<p>Config Server comes with a Health Indicator that checks if the configured
|
||
<code>EnvironmentRepository</code> is working. By default it asks the <code>EnvironmentRepository</code>
|
||
for an application named <code>app</code>, the <code>default</code> profile and the default
|
||
label provided by the <code>EnvironmentRepository</code> implementation.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can configure the Health Indicator to check more applications
|
||
along with custom profiles and custom labels, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
server:
|
||
health:
|
||
repositories:
|
||
myservice:
|
||
label: mylabel
|
||
myservice-dev:
|
||
name: myservice
|
||
profiles: development</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can disable the Health Indicator by setting <code>spring.cloud.config.server.health.enabled=false</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_security">Security</h3>
|
||
<div class="paragraph">
|
||
<p>You are free to secure your Config Server in any way that makes sense
|
||
to you (from physical network security to OAuth2 bearer
|
||
tokens), and Spring Security and Spring Boot make it easy to do pretty
|
||
much anything.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To use the default Spring Boot configured HTTP Basic security, just
|
||
include Spring Security on the classpath (e.g. through
|
||
<code>spring-boot-starter-security</code>). The default is a username of "user"
|
||
and a randomly generated password, which isn’t going to be very useful
|
||
in practice, so we recommend you configure the password (via
|
||
<code>security.user.password</code>) and encrypt it (see below for instructions
|
||
on how to do that).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_encryption_and_decryption_2">Encryption and Decryption</h3>
|
||
<div class="admonitionblock important">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Important</div>
|
||
</td>
|
||
<td class="content">
|
||
<strong>Prerequisites:</strong> to use the encryption and decryption features
|
||
you need the full-strength JCE installed in your JVM (it’s not there by default).
|
||
You can download the "Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files"
|
||
from Oracle, and follow instructions for installation (essentially replace the 2 policy files
|
||
in the JRE lib/security directory with the ones that you downloaded).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If the remote property sources contain encrypted content (values
|
||
starting with <code>{cipher}</code>) they will be decrypted before sending to
|
||
clients over HTTP. The main advantage of this set up is that the
|
||
property values don’t have to be in plain text when they are "at rest"
|
||
(e.g. in a git repository). If a value cannot be decrypted it is
|
||
removed from the property source and an additional property is added
|
||
with the same key, but prefixed with "invalid." and a value that means
|
||
"not applicable" (usually "<n/a>"). This is largely to prevent cipher
|
||
text being used as a password and accidentally leaking.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you are setting up a remote config repository for config client
|
||
applications it might contain an <code>application.yml</code> like this, for
|
||
instance:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
datasource:
|
||
username: dbuser
|
||
password: '{cipher}FKSAJDFGYOS8F7GLHAKERGFHLSAJ'</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Encrypted values in a .properties file must not be wrapped in quotes, otherwise the value will not be decrypted:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.properties</div>
|
||
<div class="content">
|
||
<pre>spring.datasource.username: dbuser
|
||
spring.datasource.password: {cipher}FKSAJDFGYOS8F7GLHAKERGFHLSAJ</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can safely push this plain text to a shared git repository and the
|
||
secret password is protected.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The server also exposes <code>/encrypt</code> and <code>/decrypt</code> endpoints (on the
|
||
assumption that these will be secured and only accessed by authorized
|
||
agents). If you are editing a remote config file you can use the Config Server
|
||
to encrypt values by POSTing to the <code>/encrypt</code> endpoint, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ curl localhost:8888/encrypt -d mysecret
|
||
682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The inverse operation is also available via <code>/decrypt</code> (provided the server is
|
||
configured with a symmetric key or a full key pair):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ curl localhost:8888/decrypt -d 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda
|
||
mysecret</pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
If you are testing like this with curl, then use
|
||
<code>--data-urlencode</code> (instead of <code>-d</code>) or set an explicit <code>Content-Type:
|
||
text/plain</code> to make sure curl encodes the data correctly when there
|
||
are special characters ('+' is particularly tricky).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Take the encrypted value and add the <code>{cipher}</code> prefix before you put
|
||
it in the YAML or properties file, and before you commit and push it
|
||
to a remote, potentially insecure store.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>/encrypt</code> and <code>/decrypt</code> endpoints also both accept paths of the
|
||
form <code>/*/{name}/{profiles}</code> which can be used to control cryptography
|
||
per application (name) and profile when clients call into the main
|
||
Environment resource.</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
to control the cryptography in this granular way you must also
|
||
provide a <code>@Bean</code> of type <code>TextEncryptorLocator</code> that creates a
|
||
different encryptor per name and profiles. The one that is provided
|
||
by default does not do this (so all encryptions use the same key).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>spring</code> command line client (with Spring Cloud CLI extensions
|
||
installed) can also be used to encrypt and decrypt, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ spring encrypt mysecret --key foo
|
||
682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda
|
||
$ spring decrypt --key foo 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda
|
||
mysecret</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To use a key in a file (e.g. an RSA public key for encryption) prepend
|
||
the key value with "@" and provide the file path, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ spring encrypt mysecret --key @${HOME}/.ssh/id_rsa.pub
|
||
AQAjPgt3eFZQXwt8tsHAVv/QHiY5sI2dRcR+...</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The key argument is mandatory (despite having a <code>--</code> prefix).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_key_management">Key Management</h3>
|
||
<div class="paragraph">
|
||
<p>The Config Server can use a symmetric (shared) key or an asymmetric
|
||
one (RSA key pair). The asymmetric choice is superior in terms of
|
||
security, but it is often more convenient to use a symmetric key since
|
||
it is just a single property value to configure.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To configure a symmetric key you just need to set <code>encrypt.key</code> to a
|
||
secret String (or use an enviroment variable <code>ENCRYPT_KEY</code> to keep it
|
||
out of plain text configuration files).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To configure an asymmetric key you can either set the key as a
|
||
PEM-encoded text value (in <code>encrypt.key</code>), or via a keystore (e.g. as
|
||
created by the <code>keytool</code> utility that comes with the JDK). The
|
||
keystore properties are <code>encrypt.keyStore.*</code> with <code>*</code> equal to</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>location</code> (a <code>Resource</code> location),</p>
|
||
</li>
|
||
<li>
|
||
<p><code>password</code> (to unlock the keystore) and</p>
|
||
</li>
|
||
<li>
|
||
<p><code>alias</code> (to identify which key in the store is to be
|
||
used).</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The encryption is done with the public key, and a private key is
|
||
needed for decryption. Thus in principle you can configure only the
|
||
public key in the server if you only want to do encryption (and are
|
||
prepared to decrypt the values yourself locally with the private
|
||
key). In practice you might not want to do that because it spreads the
|
||
key management process around all the clients, instead of
|
||
concentrating it in the server. On the other hand it’s a useful option
|
||
if your config server really is relatively insecure and only a
|
||
handful of clients need the encrypted properties.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_creating_a_key_store_for_testing">Creating a Key Store for Testing</h3>
|
||
<div class="paragraph">
|
||
<p>To create a keystore for testing you can do something like this:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ keytool -genkeypair -alias mytestkey -keyalg RSA \
|
||
-dname "CN=Web Server,OU=Unit,O=Organization,L=City,S=State,C=US" \
|
||
-keypass changeme -keystore server.jks -storepass letmein</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Put the <code>server.jks</code> file in the classpath (for instance) and then in
|
||
your <code>application.yml</code> for the Config Server:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">encrypt:
|
||
keyStore:
|
||
location: classpath:/server.jks
|
||
password: letmein
|
||
alias: mytestkey
|
||
secret: changeme</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_using_multiple_keys_and_key_rotation">Using Multiple Keys and Key Rotation</h3>
|
||
<div class="paragraph">
|
||
<p>In addition to the <code>{cipher}</code> prefix in encrypted property values, the
|
||
Config Server looks for <code>{name:value}</code> prefixes (zero or many) before
|
||
the start of the (Base64 encoded) cipher text. The keys are passed to
|
||
a <code>TextEncryptorLocator</code> which can do whatever logic it needs to
|
||
locate a <code>TextEncryptor</code> for the cipher. If you have configured a
|
||
keystore (<code>encrypt.keystore.location</code>) the default locator will look
|
||
for keys in the store with aliases as supplied by the "key" prefix,
|
||
i.e. with a cipher text like this:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">foo:
|
||
bar: `{cipher}{key:testkey}...`</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>the locator will look for a key named "testkey". A secret can also be
|
||
supplied via a <code>{secret:…​}</code> value in the prefix, but if it is not
|
||
the default is to use the keystore password (which is what you get
|
||
when you build a keytore and don’t specify a secret). If you <strong>do</strong>
|
||
supply a secret it is recommended that you also encrypt the secrets
|
||
using a custom <code>SecretLocator</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Key rotation is hardly ever necessary on cryptographic grounds if the
|
||
keys are only being used to encrypt a few bytes of configuration data
|
||
(i.e. they are not being used elsewhere), but occasionally you might
|
||
need to change the keys if there is a security breach for instance. In
|
||
that case all the clients would need to change their source config
|
||
files (e.g. in git) and use a new <code>{key:…​}</code> prefix in all the
|
||
ciphers, checking beforehand of course that the key alias is available
|
||
in the Config Server keystore.</p>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
the <code>{name:value}</code> prefixes can also be added to plaintext posted
|
||
to the <code>/encrypt</code> endpoint, if you want to let the Config Server
|
||
handle all encryption as well as decryption.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_serving_plain_text">Serving Plain Text</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Instead of using the <code>Environment</code> abstraction (or one of the
|
||
alternative representations of it in YAML or properties format) your
|
||
applications might need generic plain text configuration files,
|
||
tailored to their environment. The Config Server provides these
|
||
through an additional endpoint at <code>/{name}/{profile}/{label}/{path}</code>
|
||
where "name", "profile" and "label" have the same meaning as the
|
||
regular environment endpoint, but "path" is a file name
|
||
(e.g. <code>log.xml</code>). The source files for this endpoint are located in
|
||
the same way as for the environment endpoints: the same search path is
|
||
used as for properties or YAML files, but instead of aggregating all
|
||
matching resources, only the first one to match is returned.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>After a resource is located, placeholders in the normal format
|
||
(<code>${…​}</code>) are resolved using the effective <code>Environment</code> for the
|
||
application name, profile and label supplied. In this way the resource
|
||
endpoint is tightly integrated with the environment
|
||
endpoints. Example, if you have this layout for a GIT (or SVN)
|
||
repository:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>application.yml
|
||
nginx.conf</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>where <code>nginx.conf</code> looks like this:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>server {
|
||
listen 80;
|
||
server_name ${nginx.server.name};
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>and <code>application.yml</code> like this:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">nginx:
|
||
server:
|
||
name: example.com
|
||
---
|
||
spring:
|
||
profiles: development
|
||
nginx:
|
||
server:
|
||
name: develop.com</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>then the <code>/foo/default/master/nginx.conf</code> resource looks like this:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>server {
|
||
listen 80;
|
||
server_name example.com;
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>and <code>/foo/development/master/nginx.conf</code> like this:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>server {
|
||
listen 80;
|
||
server_name develop.com;
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
just like the source files for environment configuration, the
|
||
"profile" is used to resolve the file name, so if you want a
|
||
profile-specific file then <code>/*/development/*/logback.xml</code> will be
|
||
resolved by a file called <code>logback-development.xml</code> (in preference
|
||
to <code>logback.xml</code>).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_embedding_the_config_server">Embedding the Config Server</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>The Config Server runs best as a standalone application, but if you
|
||
need to you can embed it in another application. Just use the
|
||
<code>@EnableConfigServer</code> annotation. An optional property that can be
|
||
useful in this case is <code>spring.cloud.config.server.bootstrap</code> which is
|
||
a flag to indicate that the server should configure itself from its
|
||
own remote repository. The flag is off by default because it can delay
|
||
startup, but when embedded in another application it makes sense to
|
||
initialize the same way as any other application.</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
It should be obvious, but remember that if you use the bootstrap
|
||
flag the config server will need to have its name and repository URI
|
||
configured in <code>bootstrap.yml</code>.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To change the location of the server endpoints you can (optionally)
|
||
set <code>spring.cloud.config.server.prefix</code>, e.g. "/config", to serve the
|
||
resources under a prefix. The prefix should start but not end with a
|
||
"/". It is applied to the <code>@RequestMappings</code> in the Config Server
|
||
(i.e. underneath the Spring Boot prefixes <code>server.servletPath</code> and
|
||
<code>server.contextPath</code>).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you want to read the configuration for an application directly from
|
||
the backend repository (instead of from the config server) that’s
|
||
basically an embedded config server with no endpoints. You can switch
|
||
off the endpoints entirely if you don’t use the <code>@EnableConfigServer</code>
|
||
annotation (just set <code>spring.cloud.config.server.bootstrap=true</code>).</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_push_notifications_and_spring_cloud_bus">Push Notifications and Spring Cloud Bus</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Many source code repository providers (like Github, Gitlab or Bitbucket
|
||
for instance) will notify you of changes in a repository through a
|
||
webhook. You can configure the webhook via the provider’s user
|
||
interface as a URL and a set of events in which you are
|
||
interested. For instance
|
||
<a href="https://developer.github.com/v3/activity/events/types/#pushevent">Github</a>
|
||
will POST to the webhook with a JSON body containing a list of
|
||
commits, and a header "X-Github-Event" equal to "push". If you add a
|
||
dependency on the <code>spring-cloud-config-monitor</code> library and activate
|
||
the Spring Cloud Bus in your Config Server, then a "/monitor" endpoint
|
||
is enabled.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>When the webhook is activated the Config Server will send a
|
||
<code>RefreshRemoteApplicationEvent</code> targeted at the applications it thinks
|
||
might have changed. The change detection can be strategized, but by
|
||
default it just looks for changes in files that match the application
|
||
name (e.g. "foo.properties" is targeted at the "foo" application, and
|
||
"application.properties" is targeted at all applications). The strategy
|
||
if you want to override the behaviour is <code>PropertyPathNotificationExtractor</code>
|
||
which accepts the request headers and body as parameters and returns a list
|
||
of file paths that changed.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The default configuration works out of the box with Github, Gitlab or
|
||
Bitbucket. In addition to the JSON notifications from Github, Gitlab
|
||
or Bitbucket you can trigger a change notification by POSTing to
|
||
"/monitor" with a form-encoded body parameters <code>path={name}</code>. This will
|
||
broadcast to applications matching the "{name}" pattern (can contain
|
||
wildcards).</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
the <code>RefreshRemoteApplicationEvent</code> will only be transmitted if
|
||
the <code>spring-cloud-bus</code> is activated in the Config Server and in the
|
||
client application.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
the default configuration also detects filesystem changes in
|
||
local git repositories (the webhook is not used in that case but as
|
||
soon as you edit a config file a refresh will be broadcast).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_spring_cloud_config_client">Spring Cloud Config Client</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>A Spring Boot application can take immediate advantage of the Spring
|
||
Config Server (or other external property sources provided by the
|
||
application developer), and it will also pick up some additional
|
||
useful features related to <code>Environment</code> change events.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="config-first-bootstrap">Config First Bootstrap</h3>
|
||
<div class="paragraph">
|
||
<p>This is the default behaviour for any application which has the Spring
|
||
Cloud Config Client on the classpath. When a config client starts up
|
||
it binds to the Config Server (via the bootstrap configuration
|
||
property <code>spring.cloud.config.uri</code>) and initializes Spring
|
||
<code>Environment</code> with remote property sources.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The net result of this is that all client apps that want to consume
|
||
the Config Server need a <code>bootstrap.yml</code> (or an environment variable)
|
||
with the server address in <code>spring.cloud.config.uri</code> (defaults to
|
||
"http://localhost:8888").</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="eureka-first-bootstrap">Eureka First Bootstrap</h3>
|
||
<div class="paragraph">
|
||
<p>If you are using Spring Cloud Netflix and Eureka Service Discovery,
|
||
then you can have the Config Server register with Eureka if you want
|
||
to, but in the default "Config First" mode, clients won’t be able to
|
||
take advantage of the registration.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you prefer to use Eureka to locate the Config Server, you can do
|
||
that by setting <code>spring.cloud.config.discovery.enabled=true</code> (default
|
||
"false"). The net result of that is that client apps all need a
|
||
<code>bootstrap.yml</code> (or an environment variable) with the Eureka server
|
||
address, e.g. in <code>eureka.client.serviceUrl.defaultZone</code>. The price
|
||
for using this option is an extra network round trip on start up to
|
||
locate the service registration. The benefit is that the Config Server
|
||
can change its co-ordinates, as long as Eureka is a fixed point. The
|
||
default service id is "CONFIGSERVER" but you can change that on the
|
||
client with <code>spring.cloud.config.discovery.serviceId</code> (and on the server
|
||
in the usual way for a service, e.g. by setting <code>spring.application.name</code>).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The discovery client implementations all support some kind of metadata
|
||
map (e.g. for Eureka we have <code>eureka.instance.metadataMap</code>). Some
|
||
additional properties of the Config Server may need to be configured
|
||
in its service registration metadata so that clients can connect
|
||
correctly. If the Config Server is secured with HTTP Basic you can
|
||
configure the credentials as "username" and "password". And if the
|
||
Config Server has a context path you can set "configPath". Example,
|
||
for a Config Server that is a Eureka client:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">bootstrap.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">eureka:
|
||
instance:
|
||
...
|
||
metadataMap:
|
||
username: osufhalskjrtl
|
||
password: lviuhlszvaorhvlo5847
|
||
configPath: /config</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="config-client-fail-fast">Config Client Fail Fast</h3>
|
||
<div class="paragraph">
|
||
<p>In some cases, it may be desirable to fail startup of a service if
|
||
it cannot connect to the Config Server. If this is the desired
|
||
behavior, set the bootstrap configuration property
|
||
<code>spring.cloud.config.failFast=true</code> and the client will halt with
|
||
an Exception.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="config-client-retry">Config Client Retry</h3>
|
||
<div class="paragraph">
|
||
<p>If you expect that the config server may occasionally be unavailable when
|
||
your app starts, you can ask it to keep trying after a failure. First you need
|
||
to set <code>spring.cloud.config.failFast=true</code>, and then you need to add
|
||
<code>spring-retry</code> and <code>spring-boot-starter-aop</code> to your classpath. The default
|
||
behaviour is to retry 6 times with an initial backoff interval of 1000ms and an
|
||
exponential multiplier of 1.1 for subsequent backoffs. You can configure these
|
||
properties (and others) using <code>spring.cloud.config.retry.*</code> configuration properties.</p>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
To take full control of the retry add a <code>@Bean</code> of type
|
||
<code>RetryOperationsInterceptor</code> with id "configServerRetryInterceptor". Spring
|
||
Retry has a <code>RetryInterceptorBuilder</code> that makes it easy to create one.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_locating_remote_configuration_resources">Locating Remote Configuration Resources</h3>
|
||
<div class="paragraph">
|
||
<p>The Config Service serves property sources from <code>/{name}/{profile}/{label}</code>, where the default bindings in the client app are</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>"name" = <code>${spring.application.name}</code></p>
|
||
</li>
|
||
<li>
|
||
<p>"profile" = <code>${spring.profiles.active}</code> (actually <code>Environment.getActiveProfiles()</code>)</p>
|
||
</li>
|
||
<li>
|
||
<p>"label" = "master"</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>All of them can be overridden by setting <code>spring.cloud.config.*</code>
|
||
(where <code>*</code> is "name", "profile" or "label"). The "label" is useful for
|
||
rolling back to previous versions of configuration; with the default
|
||
Config Server implementation it can be a git label, branch name or
|
||
commit id. Label can also be provided as a comma-separated list, in
|
||
which case the items in the list are tried on-by-one until one succeeds.
|
||
This can be useful when working on a feature branch, for instance,
|
||
when you might want to align the config label with your branch, but
|
||
make it optional (e.g. <code>spring.cloud.config.label=myfeature,develop</code>).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_security_2">Security</h3>
|
||
<div class="paragraph">
|
||
<p>If you use HTTP Basic security on the server then clients just need to
|
||
know the password (and username if it isn’t the default). You can do
|
||
that via the config server URI, or via separate username and password
|
||
properties, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">bootstrap.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
uri: https://user:secret@myconfig.mycompany.com</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>or</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">bootstrap.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
uri: https://myconfig.mycompany.com
|
||
username: user
|
||
password: secret</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>spring.cloud.config.password</code> and <code>spring.cloud.config.username</code>
|
||
values override anything that is provided in the URI.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you deploy your apps on Cloud Foundry then the best way to provide
|
||
the password is through service credentials, e.g. in the URI, since
|
||
then it doesn’t even need to be in a config file. An example which
|
||
works locally and for a user-provided service on Cloud Foundry named
|
||
"configserver":</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">bootstrap.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
cloud:
|
||
config:
|
||
uri: ${vcap.services.configserver.credentials.uri:http://user:password@localhost:8888}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you use another form of security you might need to provide a
|
||
<code>RestTemplate</code> to the <code>ConfigServicePropertySourceLocator</code> (e.g. by
|
||
grabbing it in the bootstrap context and injecting one).</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_netflix" class="sect0">Spring Cloud Netflix</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
This project provides Netflix OSS integrations for Spring Boot apps through autoconfiguration
|
||
and binding to the Spring Environment and other Spring programming model idioms. With a few
|
||
simple annotations you can quickly enable and configure the common patterns inside your
|
||
application and build large distributed systems with battle-tested Netflix components. The
|
||
patterns provided include Service Discovery (Eureka), Circuit Breaker (Hystrix),
|
||
Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon).
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_service_discovery_eureka_clients">Service Discovery: Eureka Clients</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Service Discovery is one of the key tenets of a microservice based architecture. Trying to hand configure each client or some form of convention can be very difficult to do and can be very brittle. Eureka is the Netflix Service Discovery Server and Client. The server can be configured and deployed to be highly available, with each server replicating state about the registered services to the others.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_registering_with_eureka">Registering with Eureka</h3>
|
||
<div class="paragraph">
|
||
<p>When a client registers with Eureka, it provides meta-data about itself
|
||
such as host and port, health indicator URL, home page etc. Eureka
|
||
receives heartbeat messages from each instance belonging to a service.
|
||
If the heartbeat fails over a configurable timetable, the instance is
|
||
normally removed from the registry.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Example eureka client:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
|
||
@ComponentScan
|
||
@EnableAutoConfiguration
|
||
@EnableEurekaClient
|
||
@RestController
|
||
public class Application {
|
||
|
||
@RequestMapping("/")
|
||
public String home() {
|
||
return "Hello world";
|
||
}
|
||
|
||
public static void main(String[] args) {
|
||
new SpringApplicationBuilder(Application.class).web(true).run(args);
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>(i.e. utterly normal Spring Boot app). In this example we use
|
||
<code>@EnableEurekaClient</code> explicitly, but with only Eureka available you
|
||
could also use <code>@EnableDiscoveryClient</code>. Configuration is required to
|
||
locate the Eureka server. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>eureka:
|
||
client:
|
||
serviceUrl:
|
||
defaultZone: http://localhost:8761/eureka/</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>where "defaultZone" is a magic string fallback value that provides the
|
||
service URL for any client that doesn’t express a preference
|
||
(i.e. it’s a useful default).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The default application name (service ID), virtual host and non-secure
|
||
port, taken from the <code>Environment</code>, are <code>${spring.application.name}</code>,
|
||
<code>${spring.application.name}</code> and <code>${server.port}</code> respectively.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><code>@EnableEurekaClient</code> makes the app into both a Eureka "instance"
|
||
(i.e. it registers itself) and a "client" (i.e. it can query the
|
||
registry to locate other services). The instance behaviour is driven
|
||
by <code>eureka.instance.*</code> configuration keys, but the defaults will be
|
||
fine if you ensure that your application has a
|
||
<code>spring.application.name</code> (this is the default for the Eureka service
|
||
ID, or VIP).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>See <a href="http://github.com/{github-repo}/tree/{github-tag}/spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/eureka/EurekaInstanceConfigBean.java">EurekaInstanceConfigBean</a> and <a href="http://github.com/{github-repo}/tree/{github-tag}/spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/eureka/EurekaClientConfigBean.java">EurekaClientConfigBean</a> for more details of the configurable options.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_status_page_and_health_indicator">Status Page and Health Indicator</h3>
|
||
<div class="paragraph">
|
||
<p>The status page and health indicators for a Eureka instance default to
|
||
"/info" and "/health" respectively, which are the default locations of
|
||
useful endpoints in a Spring Boot Actuator application. You need to
|
||
change these, even for an Actuator application if you use a
|
||
non-default context path or servlet path
|
||
(e.g. <code>server.servletPath=/foo</code>) or management endpoint path
|
||
(e.g. <code>management.contextPath=/admin</code>). Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>eureka:
|
||
instance:
|
||
statusPageUrlPath: ${management.context-path}/info
|
||
healthCheckUrlPath: ${management.context-path}/health</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>These links show up in the metadata that is consumed by clients, and
|
||
used in some scenarios to decide whether to send requests to your
|
||
application, so it’s helpful if they are accurate.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_registering_a_secure_application">Registering a Secure Application</h3>
|
||
<div class="paragraph">
|
||
<p>If your app wants to be contacted over HTTPS you can set two flags in
|
||
the <code>EurekaInstanceConfig</code>, <em>viz</em>
|
||
<code>eureka.instance.[nonSecurePortEnabled,securePortEnabled]=[false,true]</code>
|
||
respectively. This will make Eureka publish instance information
|
||
showing an explicit preference for secure communication. The Spring
|
||
Cloud <code>DiscoveryClient</code> will always return an <code><a href="https://…​" class="bare">https://…​</a>;</code> URI for a
|
||
service configured this way, and the Eureka (native) instance
|
||
information will have a secure health check URL.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Because of the way
|
||
Eureka works internally, it will still publish a non-secure URL for
|
||
status and home page unless you also override those explicitly.
|
||
You can use placeholders to configure the eureka instance urls,
|
||
e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>eureka:
|
||
instance:
|
||
statusPageUrl: https://${eureka.hostname}/info
|
||
healthCheckUrl: https://${eureka.hostname}/health
|
||
homePageUrl: https://${eureka.hostname}/</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>(Note that <code>${eureka.hostname}</code> is a native placeholder only available
|
||
in later versions of Eureka. You could achieve the same thing with
|
||
Spring placeholders as well, e.g. using <code>${eureka.instance.hostName}</code>.)</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
If your app is running behind a proxy, and the SSL termination
|
||
is in the proxy (e.g. if you run in Cloud Foundry or other platforms
|
||
as a service) then you will need to ensure that the proxy "forwarded"
|
||
headers are intercepted and handled by the application. An embedded
|
||
Tomcat container in a Spring Boot app does this automatically if it
|
||
has explicit configuration for the 'X-Forwarded-\*` headers. A sign
|
||
that you got this wrong will be that the links rendered by your app to
|
||
itself will be wrong (the wrong host, port or protocol).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_eureka_s_health_checks">Eureka’s Health Checks</h3>
|
||
<div class="paragraph">
|
||
<p>By default, Eureka uses the client heartbeat to determine if a client is up.
|
||
Unless specified otherwise the Discovery Client will not propagate the
|
||
current health check status of the application per the Spring Boot Actuator. Which means
|
||
that after successful registration Eureka will always announce that the
|
||
application is in 'UP' state. This behaviour can be altered by enabling
|
||
Eureka health checks, which results in propagating application status
|
||
to Eureka. As a consequence every other application won’t be sending
|
||
traffic to application in state other then 'UP'.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>eureka:
|
||
client:
|
||
healthcheck:
|
||
enabled: true</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you require more control over the health checks, you may consider
|
||
implementing your own <code>com.netflix.appinfo.HealthCheckHandler</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_eureka_metadata_for_instances_and_clients">Eureka Metadata for Instances and Clients</h3>
|
||
<div class="paragraph">
|
||
<p>It’s worth spending a bit of time understanding how the Eureka metadata works, so you can use it in a way that makes sense in your platform. There is standard metadata for things like hostname, IP address, port numbers, status page and health check. These are published in the service registry and used by clients to contact the services in a straightforward way. Additional metadata can be added to the instance registration in the <code>eureka.instance.metadataMap</code>, and this will be accessible in the remote clients, but in general will not change the behaviour of the client, unless it is made aware of the meaning of the metadata. There are a couple of special cases described below where Spring Cloud already assigns meaning to the metadata map.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_using_eureka_on_cloudfoundry">Using Eureka on Cloudfoundry</h4>
|
||
<div class="paragraph">
|
||
<p>Cloudfoundry has a global router so that all instances of the same app have the same hostname (it’s the same in other PaaS solutions with a similar architecture). This isn’t necessarily a barrier to using Eureka, but if you use the router (recommended, or even mandatory depending on the way your platform was set up), you need to explicitly set the hostname and port numbers (secure or non-secure) so that they use the router. You might also want to use instance metadata so you can distinguish between the instances on the client (e.g. in a custom load balancer). By default, the <code>eureka.instance.instanceId</code> is <code>vcap.application.instance_id</code>. For example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>eureka:
|
||
instance:
|
||
hostname: ${vcap.application.uris[0]}
|
||
nonSecurePort: 80</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Depending on the way the security rules are set up in your Cloudfoundry instance, you might be able to register and use the IP address of the host VM for direct service-to-service calls. This feature is not (yet) available on Pivotal Web Services (<a href="https://run.pivotal.io">PWS</a>).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_using_eureka_on_aws">Using Eureka on AWS</h4>
|
||
<div class="paragraph">
|
||
<p>If the application is planned to be deployed to an AWS cloud, then the Eureka instance will have to be configured to be Amazon aware and this can be done by customizing the <a href="http://github.com/{github-repo}/tree/{github-tag}/spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/eureka/EurekaInstanceConfigBean.java">EurekaInstanceConfigBean</a> the following way:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Bean
|
||
@Profile("!default")
|
||
public EurekaInstanceConfigBean eurekaInstanceConfig() {
|
||
EurekaInstanceConfigBean b = new EurekaInstanceConfigBean();
|
||
AmazonInfo info = AmazonInfo.Builder.newBuilder().autoBuild("eureka");
|
||
b.setDataCenterInfo(info);
|
||
return b;
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_changing_the_eureka_instance_id">Changing the Eureka Instance ID</h4>
|
||
<div class="paragraph">
|
||
<p>A vanilla Netflix Eureka instance is registered with an ID that is equal to its host name (i.e. only one service per host). Spring Cloud Eureka provides a sensible default that looks like this: <code>${spring.cloud.client.hostname}:${spring.application.name}:${spring.application.instance_id:${server.port}}}</code>. For example <code>myhost:myappname:8080</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Using Spring Cloud you can override this by providing a unique identifier in <code>eureka.instance.instanceId</code>. For example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>eureka:
|
||
instance:
|
||
instanceId: ${spring.application.name}:${spring.application.instance_id:${random.value}}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>With this metadata, and multiple service instances deployed on
|
||
localhost, the random value will kick in there to make the instance
|
||
unique. In Cloudfoundry the <code>spring.application.instance_id</code> will be
|
||
populated automatically in a Spring Boot Actuator application, so the
|
||
random value will not be needed.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_using_the_eurekaclient">Using the EurekaClient</h3>
|
||
<div class="paragraph">
|
||
<p>Once you have an app that is <code>@EnableDiscoveryClient</code> (or <code>@EnableEurekaClient</code>) you can use it to
|
||
discover service instances from the <a href="#spring-cloud-eureka-server">Eureka Server</a>. One way to do that is to use the native
|
||
<code>com.netflix.discovery.EurekaClient</code> (as opposed to the Spring
|
||
Cloud <code>DiscoveryClient</code>), e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>@Autowired
|
||
private EurekaClient discoveryClient;
|
||
|
||
public String serviceUrl() {
|
||
InstanceInfo instance = discoveryClient.getNextServerFromEureka("STORES", false);
|
||
return instance.getHomePageUrl();
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
<div class="paragraph">
|
||
<p>Don’t use the <code>EurekaClient</code> in <code>@PostConstruct</code> method or in a
|
||
<code>@Scheduled</code> method (or anywhere where the <code>ApplicationContext</code> might
|
||
not be started yet). It is initialized in a <code>SmartLifecycle</code> (with
|
||
<code>phase=0</code>) so the earliest you can rely on it being available is in
|
||
another <code>SmartLifecycle</code> with higher phase.</p>
|
||
</div>
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_alternatives_to_the_native_netflix_eurekaclient">Alternatives to the native Netflix EurekaClient</h3>
|
||
<div class="paragraph">
|
||
<p>You don’t have to use the raw Netflix <code>EurekaClient</code> and usually it
|
||
is more convenient to use it behind a wrapper of some sort. Spring
|
||
Cloud has support for <a href="#spring-cloud-feign">Feign</a> (a REST client
|
||
builder) and also <a href="#spring-cloud-ribbon">Spring <code>RestTemplate</code></a> using
|
||
the logical Eureka service identifiers (VIPs) instead of physical
|
||
URLs. To configure Ribbon with a fixed list of physical servers you
|
||
can simply set <code><client>.ribbon.listOfServers</code> to a comma-separated
|
||
list of physical addresses (or hostnames), where <code><client></code> is the ID
|
||
of the client.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can also use the <code>org.springframework.cloud.client.discovery.DiscoveryClient</code>
|
||
which provides a simple API for discovery clients that is not specific
|
||
to Netflix, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>@Autowired
|
||
private DiscoveryClient discoveryClient;
|
||
|
||
public String serviceUrl() {
|
||
List<ServiceInstance> list = client.getInstances("STORES");
|
||
if (list != null && list.size() > 0 ) {
|
||
return list.get(0).getUri();
|
||
}
|
||
return null;
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_why_is_it_so_slow_to_register_a_service">Why is it so Slow to Register a Service?</h3>
|
||
<div class="paragraph">
|
||
<p>Being an instance also involves a periodic heartbeat to the registry
|
||
(via the client’s <code>serviceUrl</code>) with default duration 30 seconds. A
|
||
service is not available for discovery by clients until the instance,
|
||
the server and the client all have the same metadata in their local
|
||
cache (so it could take 3 hearbeats). You can change the period using
|
||
<code>eureka.instance.leaseRenewalIntervalInSeconds</code> and this will speed up
|
||
the process of getting clients connected to other services. In
|
||
production it’s probably better to stick with the default because
|
||
there are some computations internally in the server that make
|
||
assumptions about the lease renewal period.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-eureka-server">Service Discovery: Eureka Server</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Example eureka server (e.g. using spring-cloud-starter-eureka-server to set up the classpath):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@SpringBootApplication
|
||
@EnableEurekaServer
|
||
public class Application {
|
||
|
||
public static void main(String[] args) {
|
||
new SpringApplicationBuilder(Application.class).web(true).run(args);
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The server has a home page with a UI, and HTTP API endpoints per the
|
||
normal Eureka functionality under <code>/eureka/*</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Eureka background reading: see <a href="https://github.com/cfregly/fluxcapacitor/wiki/NetflixOSS-FAQ#eureka-service-discovery-load-balancer">flux capacitor</a> and <a href="https://groups.google.com/forum/?fromgroups#!topic/eureka_netflix/g3p2r7gHnN0">google group discussion</a>.</p>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
<div class="paragraph">
|
||
<p>Due to Gradle’s dependency resolution rules and the lack of a parent bom feature, simply depending on spring-cloud-starter-eureka-server can cause failures on application startup. To remedy this the Spring dependency management plugin must be added and the Spring cloud starter parent bom must be imported like so:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">build.gradle</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">buildscript {
|
||
dependencies {
|
||
classpath "io.spring.gradle:dependency-management-plugin:0.4.0.RELEASE"
|
||
}
|
||
}
|
||
|
||
apply plugin: "io.spring.dependency-management"
|
||
|
||
dependencyManagement {
|
||
imports {
|
||
mavenBom 'org.springframework.cloud:spring-cloud-starter-parent:1.0.0.RELEASE'
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_high_availability_zones_and_regions">High Availability, Zones and Regions</h3>
|
||
<div class="paragraph">
|
||
<p>The Eureka server does not have a backend store, but the service
|
||
instances in the registry all have to send heartbeats to keep their
|
||
registrations up to date (so this can be done in memory). Clients also
|
||
have an in-memory cache of eureka registrations (so they don’t have to
|
||
go to the registry for every single request to a service).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>By default every Eureka server is also a Eureka client and requires
|
||
(at least one) service URL to locate a peer. If you don’t provide it
|
||
the service will run and work, but it will shower your logs with a lot
|
||
of noise about not being able to register with the peer.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>See also <a href="#spring-cloud-ribbon">below for details of Ribbon
|
||
support</a> on the client side for Zones and Regions.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_standalone_mode">Standalone Mode</h3>
|
||
<div class="paragraph">
|
||
<p>The combination of the two caches (client and server) and the
|
||
heartbeats make a standalone Eureka server fairly resilient to
|
||
failure, as long as there is some sort of monitor or elastic runtime
|
||
keeping it alive (e.g. Cloud Foundry). In standalone mode, you might
|
||
prefer to switch off the client side behaviour, so it doesn’t keep
|
||
trying and failing to reach its peers. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml (Standalone Eureka Server)</div>
|
||
<div class="content">
|
||
<pre>server:
|
||
port: 8761
|
||
|
||
eureka:
|
||
instance:
|
||
hostname: localhost
|
||
client:
|
||
registerWithEureka: false
|
||
fetchRegistry: false
|
||
serviceUrl:
|
||
defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Notice that the <code>serviceUrl</code> is pointing to the same host as the local
|
||
instance.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_peer_awareness">Peer Awareness</h3>
|
||
<div class="paragraph">
|
||
<p>Eureka can be made even more resilient and available by running
|
||
multiple instances and asking them to register with each other. In
|
||
fact, this is the default behaviour, so all you need to do to make it
|
||
work is add a valid <code>serviceUrl</code> to a peer, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml (Two Peer Aware Eureka Servers)</div>
|
||
<div class="content">
|
||
<pre>---
|
||
spring:
|
||
profiles: peer1
|
||
eureka:
|
||
instance:
|
||
hostname: peer1
|
||
client:
|
||
serviceUrl:
|
||
defaultZone: http://peer2/eureka/
|
||
|
||
---
|
||
spring:
|
||
profiles: peer2
|
||
eureka:
|
||
instance:
|
||
hostname: peer2
|
||
client:
|
||
serviceUrl:
|
||
defaultZone: http://peer1/eureka/</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this example we have a YAML file that can be used to run the same
|
||
server on 2 hosts (peer1 and peer2), by running it in different
|
||
Spring profiles. You could use this configuration to test the peer
|
||
awareness on a single host (there’s not much value in doing that in
|
||
production) by manipulating <code>/etc/hosts</code> to resolve the host names. In
|
||
fact, the <code>eureka.instance.hostname</code> is not needed if you are running
|
||
on a machine that knows its own hostname (it is looked up using
|
||
<code>java.net.InetAddress</code> by default).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can add multiple peers to a system, and as long as they are all
|
||
connected to each other by at least one edge, they will synchronize
|
||
the registrations amongst themselves. If the peers are physically
|
||
separated (inside a data centre or between multiple data centres) then
|
||
the system can in principle survive split-brain type failures.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_prefer_ip_address">Prefer IP Address</h3>
|
||
<div class="paragraph">
|
||
<p>In some cases, it is preferable for Eureka to advertise the IP Adresses
|
||
of services rather than the hostname. Set <code>eureka.instance.preferIpAddress</code>
|
||
to <code>true</code> and when the application registers with eureka, it will use its
|
||
IP Address rather than its hostname.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_circuit_breaker_hystrix_clients">Circuit Breaker: Hystrix Clients</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Netflix has created a library called <a href="https://github.com/Netflix/Hystrix">Hystrix</a> that implements the <a href="http://martinfowler.com/bliki/CircuitBreaker.html">circuit breaker pattern</a>. In a microservice architecture it is common to have multiple layers of service calls.</p>
|
||
</div>
|
||
<div class="imageblock">
|
||
<div class="content">
|
||
<img src="images/HystrixGraph.png" alt="HystrixGraph">
|
||
</div>
|
||
<div class="title">Figure 1. Microservice Graph</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>A service failure in the lower level of services can cause cascading failure all the way up to the user. When calls to a particular service reach a certain threshold (20 failures in 5 seconds is the default in Hystrix), the circuit opens and the call is not made. In cases of error and an open circuit a fallback can be provided by the developer.</p>
|
||
</div>
|
||
<div class="imageblock">
|
||
<div class="content">
|
||
<img src="images/HystrixFallback.png" alt="HystrixFallback">
|
||
</div>
|
||
<div class="title">Figure 2. Hystrix fallback prevents cascading failures</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Having an open circuit stops cascading failures and allows overwhelmed or failing services time to heal. The fallback can be another Hystrix protected call, static data or a sane empty value. Fallbacks may be chained so the first fallback makes some other business call which in turn falls back to static data.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Example boot app:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>@SpringBootApplication
|
||
@EnableCircuitBreaker
|
||
public class Application {
|
||
|
||
public static void main(String[] args) {
|
||
new SpringApplicationBuilder(Application.class).web(true).run(args);
|
||
}
|
||
|
||
}
|
||
|
||
@Component
|
||
public class StoreIntegration {
|
||
|
||
@HystrixCommand(fallbackMethod = "defaultStores")
|
||
public Object getStores(Map<String, Object> parameters) {
|
||
//do stuff that might fail
|
||
}
|
||
|
||
public Object defaultStores(Map<String, Object> parameters) {
|
||
return /* something useful */;
|
||
}
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>@HystrixCommand</code> is provided by a Netflix contrib library called
|
||
<a href="https://github.com/Netflix/Hystrix/tree/master/hystrix-contrib/hystrix-javanica">"javanica"</a>.
|
||
Spring Cloud automatically wraps Spring beans with that
|
||
annotation in a proxy that is connected to the Hystrix circuit
|
||
breaker. The circuit breaker calculates when to open and close the
|
||
circuit, and what to do in case of a failure.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To configure the <code>@HystrixCommand</code> you can use the <code>commandProperties</code>
|
||
attribute with a list of <code>@HystrixProperty</code> annotations. See
|
||
<a href="https://github.com/Netflix/Hystrix/tree/master/hystrix-contrib/hystrix-javanica#configuration">here</a>
|
||
for more details. See the <a href="https://github.com/Netflix/Hystrix/wiki/Configuration">Hystrix wiki</a>
|
||
for details on the properties available.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_propagating_the_security_context_or_using_spring_scopes">Propagating the Security Context or using Spring Scopes</h3>
|
||
<div class="paragraph">
|
||
<p>If you want some thread local context to propagate into a <code>@HystrixCommand</code> the default declaration will not work because it executes the command in a thread pool (in case of timeouts). You can switch Hystrix to use the same thread as the caller using some configuration, or directly in the annotation, by asking it to use a different "Isolation Strategy". For example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@HystrixCommand(fallbackMethod = "stubMyService",
|
||
commandProperties = {
|
||
@HystrixProperty(name="execution.isolation.strategy", value="SEMAPHORE")
|
||
}
|
||
)
|
||
...</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The same thing applies if you are using <code>@SessionScope</code> or <code>@RequestScope</code>. You will know when you need to do this because of a runtime exception that says it can’t find the scoped context.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_health_indicator_2">Health Indicator</h3>
|
||
<div class="paragraph">
|
||
<p>The state of the connected circuit breakers are also exposed in the
|
||
<code>/health</code> endpoint of the calling application.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-json" data-lang="json">{
|
||
"hystrix": {
|
||
"openCircuitBreakers": [
|
||
"StoreIntegration::getStoresByLocationLink"
|
||
],
|
||
"status": "CIRCUIT_OPEN"
|
||
},
|
||
"status": "UP"
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_hystrix_metrics_stream">Hystrix Metrics Stream</h3>
|
||
<div class="paragraph">
|
||
<p>To enable the Hystrix metrics stream include a dependency on <code>spring-boot-starter-actuator</code>. This will expose the <code>/hystrix.stream</code> as a management endpoint.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-xml" data-lang="xml"> <dependency>
|
||
<groupId>org.springframework.boot</groupId>
|
||
<artifactId>spring-boot-starter-actuator</artifactId>
|
||
</dependency></code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_circuit_breaker_hystrix_dashboard">Circuit Breaker: Hystrix Dashboard</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>One of the main benefits of Hystrix is the set of metrics it gathers about each HystrixCommand. The Hystrix Dashboard displays the health of each circuit breaker in an efficient manner.</p>
|
||
</div>
|
||
<div class="imageblock">
|
||
<div class="content">
|
||
<img src="images/Hystrix.png" alt="Hystrix">
|
||
</div>
|
||
<div class="title">Figure 3. Hystrix Dashboard</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To run the Hystrix Dashboard annotate your Spring Boot main class with <code>@EnableHystrixDashboard</code>. You then visit <code>/hystrix</code> and point the dashboard to an individual instances <code>/hystrix.stream</code> endpoint in a Hystrix client application.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_turbine">Turbine</h3>
|
||
<div class="paragraph">
|
||
<p>Looking at an individual instances Hystrix data is not very useful in terms of the overall health of the system. <a href="https://github.com/Netflix/Turbine">Turbine</a> is an application that aggregates all of the relevant <code>/hystrix.stream</code> endpoints into a combined <code>/turbine.stream</code> for use in the Hystrix Dashboard. Individual instances are located via Eureka. Running Turbine is as simple as annotating your main class with the <code>@EnableTurbine</code> annotation (e.g. using spring-cloud-starter-turbine to set up the classpath). All of the documented configuration properties from <a href="https://github.com/Netflix/Turbine/wiki/Configuration-(1.x)">the Turbine 1 wiki</a> apply. The only difference is that the <code>turbine.instanceUrlSuffix</code> does not need the port prepended as this is handled automatically unless <code>turbine.instanceInsertPort=false</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The configuration key <code>turbine.appConfig</code> is a list of eureka serviceIds that turbine will use to lookup instances. The turbine stream is then used in the Hystrix dashboard using a url that looks like: <code><a href="http://my.turbine.sever:8080/turbine.stream?cluster=<CLUSTERNAME>" class="bare">http://my.turbine.sever:8080/turbine.stream?cluster=<CLUSTERNAME></a>;</code> (the cluster parameter can be omitted if the name is "default"). The <code>cluster</code> parameter must match an entry in <code>turbine.aggregator.clusterConfig</code>. Values returned from eureka are uppercase, thus we expect this example to work if there is an app registered with Eureka called "customers":</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>turbine:
|
||
aggregator:
|
||
clusterConfig: CUSTOMERS
|
||
appConfig: customers</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>clusterName</code> can be customized by a SPEL expression in <code>turbine.clusterNameExpression</code> with root an instance of <code>InstanceInfo</code>. The default value is <code>appName</code>, which means that the Eureka serviceId ends up as the cluster key (i.e. the <code>InstanceInfo</code> for customers has an <code>appName</code> of "CUSTOMERS"). A different example would be <code>turbine.clusterNameExpression=aSGName</code>, which would get the cluster name from the AWS ASG name. Another example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>turbine:
|
||
aggregator:
|
||
clusterConfig: SYSTEM,USER
|
||
appConfig: customers,stores,ui,admin
|
||
clusterNameExpression: metadata['cluster']</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this case, the cluster name from 4 services is pulled from their metadata map, and is expected to have values that include "SYSTEM" and "USER".</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To use the "default" cluster for all apps you need a string literal expression (with single quotes):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>turbine:
|
||
appConfig: customers,stores
|
||
clusterNameExpression: 'default'</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud provides a <code>spring-cloud-starter-turbine</code> that has all the dependencies you need to get a Turbine server running. Just create a Spring Boot application and annotate it with <code>@EnableTurbine</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_turbine_amqp">Turbine AMQP</h3>
|
||
<div class="paragraph">
|
||
<p>In some environments (e.g. in a PaaS setting), the classic Turbine model of pulling metrics from all the distributed Hystrix commands doesn’t work. In that case you might want to have your Hystrix commands push metrics to Turbine, and Spring Cloud enables that with AMQP messaging. All you need to do on the client is add a dependency to <code>spring-cloud-netflix-hystrix-amqp</code> and make sure there is a Rabbit broker available (see Spring Boot documentation for details on how to configure the client credentials, but it should work out of the box for a local broker or in Cloud Foundry).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>On the server side Just create a Spring Boot application and annotate it with <code>@EnableTurbineAmqp</code> and by default it will come up on port 8989 (point your Hystrix dashboard to that port, any path). You can customize the port using either <code>server.port</code> or <code>turbine.amqp.port</code>. If you have <code>spring-boot-starter-web</code> and <code>spring-boot-starter-actuator</code> on the classpath as well, then you can open up the Actuator endpoints on a separate port (with Tomcat by default) by providing a <code>management.port</code> which is different.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can then point the Hystrix Dashboard to the Turbine AMQP Server instead of individual Hystrix streams. If Turbine AMQP is running on port 8989 on myhost, then put <code><a href="http://myhost:8989" class="bare">http://myhost:8989</a></code> in the stream input field in the Hystrix Dashboard. Circuits will be prefixed by their respective serviceId, followed by a dot, then the circuit name.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud provides a <code>spring-cloud-starter-turbine-amqp</code> that has all the dependencies you need to get a Turbine AMQP server running. You need Java 8 to run the app because it is Netty-based.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_customizing_the_amqp_connectionfactory">Customizing the AMQP ConnectionFactory</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>If you are using AMQP there needs to be a <code>ConnectionFactory</code> (from
|
||
Spring Rabbit) in the application context. If there is a single
|
||
<code>ConnectionFactory</code> it will be used, or if there is a one qualified as
|
||
<code>@HystrixConnectionFactory</code> (on the client) and
|
||
<code>@TurbineConnectionFactory</code> (on the server) it will be preferred over
|
||
others, otherwise the <code>@Primary</code> one will be used. If there are
|
||
multiple unqualified connection factories there will be an error.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Note that Spring Boot (as of 1.2.2) creates a <code>ConnectionFactory</code> that
|
||
is <em>not</em> <code>@Primary</code>, so if you want to use one connection factory for
|
||
the bus and another for business messages, you need to create both,
|
||
and annotate them <code>@*ConnectionFactory</code> and <code>@Primary</code> respectively.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-ribbon">Client Side Load Balancer: Ribbon</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Ribbon is a client side load balancer which gives you a lot of control
|
||
over the behaviour of HTTP and TCP clients. Feign already uses Ribbon,
|
||
so if you are using <code>@FeignClient</code> then this section also applies.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>A central concept in Ribbon is that of the named client. Each load
|
||
balancer is part of an ensemble of components that work together to
|
||
contact a remote server on demand, and the ensemble has a name that
|
||
you give it as an application developer (e.g. using the <code>@FeignClient</code>
|
||
annotation). Spring Cloud creates a new ensemble as an
|
||
<code>ApplicationContext</code> on demand for each named client using
|
||
<code>RibbonClientConfiguration</code>. This contains (amongst other things) an
|
||
<code>ILoadBalancer</code>, a <code>RestClient</code>, and a <code>ServerListFilter</code>.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_customizing_the_ribbon_client">Customizing the Ribbon Client</h3>
|
||
<div class="paragraph">
|
||
<p>You can configure some bits of a Ribbon client using external
|
||
properties in <code><client>.ribbon.*</code>, which is no different than using
|
||
the Netflix APIs natively, except that you can use Spring Boot
|
||
configuration files. The native options can
|
||
be inspected as static fields in <code>CommonClientConfigKey</code> (part of
|
||
ribbon-core).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud also lets you take full control of the client by
|
||
declaring additional configuration (on top of the
|
||
<code>RibbonClientConfiguration</code>) using <code>@RibbonClient</code>. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
|
||
@RibbonClient(name = "foo", configuration = FooConfiguration.class)
|
||
public class TestConfiguration {
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this case the client is composed from the components already in
|
||
<code>RibbonClientConfiguration</code> together with any in <code>FooConfiguration</code>
|
||
(where the latter generally will override the former).</p>
|
||
</div>
|
||
<div class="admonitionblock warning">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Warning</div>
|
||
</td>
|
||
<td class="content">
|
||
The <code>FooConfiguration</code> has to be <code>@Configuration</code> but take
|
||
care that it is not in a <code>@ComponentScan</code> for the main application
|
||
context, otherwise it will be shared by all the <code>@RibbonClients</code>. If
|
||
you use <code>@ComponentScan</code> (or <code>@SpringBootApplication</code>) you need to
|
||
take steps to avoid it being included (for instance put it in a
|
||
separate, non-overlapping package, or specify the packages to scan
|
||
explicitly in the <code>@ComponentScan</code>).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Netflix provides the following beans by default for ribbon
|
||
(<code>BeanType</code> beanName: <code>ClassName</code>):</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>IClientConfig</code> ribbonClientConfig: <code>DefaultClientConfigImpl</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>IRule</code> ribbonRule: <code>ZoneAvoidanceRule</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>IPing</code> ribbonPing: <code>NoOpPing</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>ServerList<Server></code> ribbonServerList: <code>ConfigurationBasedServerList</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>ServerListFilter<Server></code> ribbonServerListFilter: <code>ZonePreferenceServerListFilter</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>ILoadBalancer</code> ribbonLoadBalancer: <code>ZoneAwareLoadBalancer</code></p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Creating a bean of one of those type and placing it in a <code>@RibbonClient</code>
|
||
configuration (such as <code>FooConfiguration</code> above) allows you to override each
|
||
one of the beans described. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
|
||
public class FooConfiguration {
|
||
@Bean
|
||
public IPing ribbonPing(IClientConfig config) {
|
||
return new PingUrl();
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This replaces the <code>NoOpPing</code> with <code>PingUrl</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_using_ribbon_with_eureka">Using Ribbon with Eureka</h3>
|
||
<div class="paragraph">
|
||
<p>When Eureka is used in conjunction with Ribbon the <code>ribbonServerList</code>
|
||
is overridden with an extension of <code>DiscoveryEnabledNIWSServerList</code>
|
||
which populates the list of servers from Eureka. It also replaces the
|
||
<code>IPing</code> interface with <code>NIWSDiscoveryPing</code> which delegates to Eureka
|
||
to determine if a server is up. The <code>ServerList</code> that is installed by
|
||
default is a <code>DomainExtractingServerList</code> and the purpose of this is
|
||
to make physical metadata available to the load balancer without using
|
||
AWS AMI metadata (which is what Netflix relies on). By default the
|
||
server list will be constructed with "zone" information as provided in
|
||
the instance metadata (so on the client set
|
||
<code>eureka.instance.metadataMap.zone</code>), and if that is missing it can use
|
||
the domain name from the server hostname as a proxy for zone (if the
|
||
flag <code>approximateZoneFromHostname</code> is set). Once the zone information is
|
||
available it can be used in a <code>ServerListFilter</code> (by default it will
|
||
be used to locate a server in the same zone as the client because the
|
||
default is a <code>ZonePreferenceServerListFilter</code>).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-ribbon-without-eureka">Example: How to Use Ribbon Without Eureka</h3>
|
||
<div class="paragraph">
|
||
<p>Eureka is a convenient way to abstract the discovery of remote servers
|
||
so you don’t have to hard code their URLs in clients, but if you
|
||
prefer not to use it, Ribbon and Feign are still quite
|
||
amenable. Suppose you have declared a <code>@RibbonClient</code> for "stores",
|
||
and Eureka is not in use (and not even on the classpath). The Ribbon
|
||
client defaults to a configured server list, and you can supply the
|
||
configuration like this</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>stores:
|
||
ribbon:
|
||
listOfServers: example.com,google.com</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_example_disable_eureka_use_in_ribbon">Example: Disable Eureka use in Ribbon</h3>
|
||
<div class="paragraph">
|
||
<p>Setting the property <code>ribbon.eureka.enabled = false</code> will explicitly
|
||
disable the use of Eureka in Ribbon.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>ribbon:
|
||
eureka:
|
||
enabled: false</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_using_the_ribbon_api_directly">Using the Ribbon API Directly</h3>
|
||
<div class="paragraph">
|
||
<p>You can also use the <code>LoadBalancerClient</code> directly. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">public class MyClass {
|
||
@Autowired
|
||
private LoadBalancerClient loadBalancer;
|
||
|
||
public void doStuff() {
|
||
ServiceInstance instance = loadBalancer.choose("stores");
|
||
URI storesUri = URI.create(String.format("http://%s:%s", instance.getHost(), instance.getPort()));
|
||
// ... do something with the URI
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-feign">Declarative REST Client: Feign</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p><a href="https://github.com/Netflix/feign">Feign</a> is a declarative web service client. It makes writing web service clients easier. To use Feign create an interface and annotate it. It has pluggable annotation support including Feign annotations and JAX-RS annotations. Feign also supports pluggable encoders and decoders. Spring Cloud adds support for Spring MVC annotations and for using the same <code>HttpMessageConverters</code> used by default in Spring Web. Spring Cloud integrates Ribbon and Eureka to provide a load balanced http client when using Feign.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Example spring boot app</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
|
||
@ComponentScan
|
||
@EnableAutoConfiguration
|
||
@EnableEurekaClient
|
||
@EnableFeignClients
|
||
public class Application {
|
||
|
||
public static void main(String[] args) {
|
||
SpringApplication.run(Application.class, args);
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">StoreClient.java</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@FeignClient("stores")
|
||
public interface StoreClient {
|
||
@RequestMapping(method = RequestMethod.GET, value = "/stores")
|
||
List<Store> getStores();
|
||
|
||
@RequestMapping(method = RequestMethod.POST, value = "/stores/{storeId}", consumes = "application/json")
|
||
Store update(@PathVariable("storeId") Long storeId, Store store);
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In the <code>@FeignClient</code> annotation the String value ("stores" above) is
|
||
an arbitrary client name, which is used to create a Ribbon load
|
||
balancer (see <a href="#spring-cloud-ribbon">below for details of Ribbon
|
||
support</a>). You can also specify a URL using the <code>url</code> attribute
|
||
(absolute value or just a hostname).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The Ribbon client above will want to discover the physical addresses
|
||
for the "stores" service. If your application is a Eureka client then
|
||
it will resolve the service in the Eureka service registry. If you
|
||
don’t want to use Eureka, you can simply configure a list of servers
|
||
in your external configuration (see
|
||
<a href="#spring-cloud-ribbon-without-eureka">above for example</a>).</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-feign-overriding-defaults">Overriding Feign Defaults</h3>
|
||
<div class="paragraph">
|
||
<p>A central concept in Spring Cloud’s Feign support is that of the named client. Each feign client is part of an ensemble of components that work together to contact a remote server on demand, and the ensemble has a name that you give it as an application developer using the <code>@FeignClient</code> annotation. Spring Cloud creates a new ensemble as an
|
||
<code>ApplicationContext</code> on demand for each named client using <code>FeignClientsConfiguration</code>. This contains (amongst other things) an <code>feign.Decoder</code>, a <code>feign.Encoder</code>, and a <code>feign.Contract</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud lets you take full control of the feign client by declaring additional configuration (on top of the <code>FeignClientsConfiguration</code>) using <code>@FeignClient</code>. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@FeignClient(name = "stores", configuration = FooConfiguration.class)
|
||
public interface StoreClient {
|
||
//..
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this case the client is composed from the components already in <code>FeignClientsConfiguration</code> together with any in <code>FooConfiguration</code> (where the latter will override the former).</p>
|
||
</div>
|
||
<div class="admonitionblock warning">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Warning</div>
|
||
</td>
|
||
<td class="content">
|
||
The <code>FooConfiguration</code> has to be <code>@Configuration</code> but take care that it is not in a <code>@ComponentScan</code> for the main application context, otherwise it will be used for every <code>@FeignClient</code>. If you use <code>@ComponentScan</code> (or <code>@SpringBootApplication</code>) you need to take steps to avoid it being included (for instance put it in a separate, non-overlapping package, or specify the packages to scan explicitly in the <code>@ComponentScan</code>).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
The <code>serviceId</code> attribute is now deprecated in favor of the <code>name</code> attribute.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="admonitionblock warning">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Warning</div>
|
||
</td>
|
||
<td class="content">
|
||
Previously, using the <code>url</code> attribute, did not require the <code>name</code> attribute. Using <code>name</code> is now required.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Placeholders are supported in the <code>name</code> and <code>url</code> attributes.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@FeignClient(name = "${feign.name}", url = "${feign.url}")
|
||
public interface StoreClient {
|
||
//..
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Netflix provides the following beans by default for feign (<code>BeanType</code> beanName: <code>ClassName</code>):</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>Decoder</code> feignDecoder: <code>ResponseEntityDecoder</code> (which wraps a <code>SpringDecoder</code>)</p>
|
||
</li>
|
||
<li>
|
||
<p><code>Encoder</code> feignEncoder: <code>SpringEncoder</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>Logger</code> feignLogger: <code>Slf4jLogger</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>Contract</code> feignContract: <code>SpringMvcContract</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>Feign.Builder</code> feignBuilder: <code>HystrixFeign.Builder</code></p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Netflix <em>does not</em> provide the following beans by default for feign, but still looks up beans of these types from the application context to create the feign client:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>Logger.Level</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>Retryer</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>ErrorDecoder</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>Request.Options</code></p>
|
||
</li>
|
||
<li>
|
||
<p><code>Collection<RequestInterceptor></code></p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Creating a bean of one of those type and placing it in a <code>@FeignClient</code> configuration (such as <code>FooConfiguration</code> above) allows you to override each one of the beans described. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
|
||
public class FooConfiguration {
|
||
@Bean
|
||
public Contract feignContractg() {
|
||
return new feign.Contract.Default();
|
||
}
|
||
|
||
@Bean
|
||
public BasicAuthRequestInterceptor basicAuthRequestInterceptor() {
|
||
return new BasicAuthRequestInterceptor("user", "password");
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This replaces the <code>SpringMvcContract</code> with <code>feign.Contract.Default</code> and adds a <code>RequestInterceptor</code> to the collection of <code>RequestInterceptor</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Default configurations can be specified in the <code>@EnableFeignClients</code> attribute <code>defaultConfiguration</code> in a similar manner as described above. The difference is that this configuration will apply to <em>all</em> feign clients.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-feign-hystrix">Feign Hystrix Support</h3>
|
||
<div class="paragraph">
|
||
<p>If Hystrix is on the classpath, by default Feign will wrap all methods with a circuit breaker. Returning a <code>com.netflix.hystrix.HystrixCommand</code> is also available. This lets you use reactive patterns (with a call to <code>.toObservable()</code> or <code>.observe()</code> or asynchronous use (with a call to <code>.queue()</code>).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To disable Hystrix support for Feign, set <code>feign.hystrix.enabled=false</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To disable Hystrix support on a per-client basis create a vanilla <code>Feign.Builder</code> with the "prototype" scope, e.g.:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
|
||
public class FooConfiguration {
|
||
@Bean
|
||
@Scope("prototype")
|
||
public Feign.Builder feignBuilder() {
|
||
return Feign.builder();
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-feign-hystrix-fallback">Feign Hystrix Fallbacks</h3>
|
||
<div class="paragraph">
|
||
<p>Hystrix supports the notion of a fallback: a default code path that is executed when they circuit is open or there is an error. To enable fallbacks for a given <code>@FeignClient</code> set the <code>fallback</code> attribute to the class name that implements the fallback.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@FeignClient(name = "hello", fallback = HystrixClientFallback.class)
|
||
protected interface HystrixClient {
|
||
@RequestMapping(method = RequestMethod.GET, value = "/hello")
|
||
Hello iFailSometimes();
|
||
}
|
||
|
||
static class HystrixClientFallback implements HystrixClient {
|
||
@Override
|
||
public Hello iFailSometimes() {
|
||
return new Hello("fallback");
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock warning">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Warning</div>
|
||
</td>
|
||
<td class="content">
|
||
There is a limitation with the implementation of fallbacks in Feign and how Hystrix fallbacks work. Fallbacks are currently not supported for methods that return <code>com.netflix.hystrix.HystrixCommand</code> and <code>rx.Observable</code>.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-feign-inheritance">Feign Inheritance Support</h3>
|
||
<div class="paragraph">
|
||
<p>Feign supports boilerplate apis via single-inheritance interfaces.
|
||
This allows grouping common operations into convenient base interfaces.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">UserService.java</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">public interface UserService {
|
||
|
||
@RequestMapping(method = RequestMethod.GET, value ="/users/{id}")
|
||
User getUser(@PathVariable("id") long id);
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">UserResource.java</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@RestController
|
||
public class UserResource implements UserService {
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">UserClient.java</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">package project.user;
|
||
|
||
@FeignClient("users")
|
||
public interface UserClient extends UserService {
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
It is generally not advisable to share an interface between a
|
||
server and a client. It introduces tight coupling, and also actually
|
||
doesn’t work with Spring MVC in its current form (method parameter
|
||
mapping is not inherited).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_feign_request_response_compression">Feign request/response compression</h3>
|
||
<div class="paragraph">
|
||
<p>You may consider enabling the request or response GZIP compression for your
|
||
Feign requests. You can do this by enabling one of the properties:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">feign.compression.request.enabled=true
|
||
feign.compression.response.enabled=true</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Feign request compression gives you settings similar to what you may set for your web server:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">feign.compression.request.enabled=true
|
||
feign.compression.request.mime-types=text/xml,application/xml,application/json
|
||
feign.compression.request.min-request-size=2048</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>These properties allow you to be selective about the compressed media types and minimum request threshold length.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_feign_logging">Feign logging</h3>
|
||
<div class="paragraph">
|
||
<p>A logger is created for each Feign client created. By default the name of the logger is the full class name of the interface used to create the Feign client. Feign logging only responds to the <code>DEBUG</code> level.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">logging.level.project.user.UserClient: DEBUG</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>Logger.Level</code> object that you may configure per client, tells Feign how much to log. Choices are:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>NONE</code>, No logging (<strong>DEFAULT</strong>).</p>
|
||
</li>
|
||
<li>
|
||
<p><code>BASIC</code>, Log only the request method and URL and the response status code and execution time.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>HEADERS</code>, Log the basic information along with request and response headers.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>FULL</code>, Log the headers, body, and metadata for both requests and responses.</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>For example, the following would set the <code>Logger.Level</code> to <code>FULL</code>:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
|
||
public class FooConfiguration {
|
||
@Bean
|
||
Logger.Level feignLoggerLevel() {
|
||
return Logger.Level.FULL;
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_external_configuration_archaius">External Configuration: Archaius</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p><a href="https://github.com/Netflix/archaius">Archaius</a> is the Netflix client side configuration library. It is the library used by all of the Netflix OSS components for configuration. Archaius is an extension of the <a href="http://commons.apache.org/proper/commons-configuration">Apache Commons Configuration</a> project. It allows updates to configuration by either polling a source for changes or for a source to push changes to the client. Archaius uses Dynamic<Type>Property classes as handles to properties.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">Archaius Example</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">class ArchaiusTest {
|
||
DynamicStringProperty myprop = DynamicPropertyFactory
|
||
.getInstance()
|
||
.getStringProperty("my.prop");
|
||
|
||
void doSomething() {
|
||
OtherClass.someMethod(myprop.get());
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Archaius has its own set of configuration files and loading priorities. Spring applications should generally not use Archaius directly, but the need to configure the Netflix tools natively remains. Spring Cloud has a Spring Environment Bridge so Archaius can read properties from the Spring Environment. This allows Spring Boot projects to use the normal configuration toolchain, while allowing them to configure the Netflix tools, for the most part, as documented.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_router_and_filter_zuul">Router and Filter: Zuul</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Routing in an integral part of a microservice architecture. For example, <code>/</code> may be mapped to your web application, <code>/api/users</code> is mapped to the user service and <code>/api/shop</code> is mapped to the shop service. <a href="https://github.com/Netflix/zuul">Zuul</a> is a JVM based router and server side load balancer by Netflix.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><a href="http://www.slideshare.net/MikeyCohen1/edge-architecture-ieee-international-conference-on-cloud-engineering-32240146/27">Netflix uses Zuul</a> for the following:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>Authentication</p>
|
||
</li>
|
||
<li>
|
||
<p>Insights</p>
|
||
</li>
|
||
<li>
|
||
<p>Stress Testing</p>
|
||
</li>
|
||
<li>
|
||
<p>Canary Testing</p>
|
||
</li>
|
||
<li>
|
||
<p>Dynamic Routing</p>
|
||
</li>
|
||
<li>
|
||
<p>Service Migration</p>
|
||
</li>
|
||
<li>
|
||
<p>Load Shedding</p>
|
||
</li>
|
||
<li>
|
||
<p>Security</p>
|
||
</li>
|
||
<li>
|
||
<p>Static Response handling</p>
|
||
</li>
|
||
<li>
|
||
<p>Active/Active traffic management</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Zuul’s rule engine allows rules and filters to be written in essentially any JVM language, with built in support for Java and Groovy.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="netflix-zuul-reverse-proxy">Embedded Zuul Reverse Proxy</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud has created an embedded Zuul proxy to ease the
|
||
development of a very common use case where a UI application wants to
|
||
proxy calls to one or more back end services. This feature is useful
|
||
for a user interface to proxy to the backend services it requires,
|
||
avoiding the need to manage CORS and authentication concerns
|
||
independently for all the backends.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To enable it, annotate a Spring Boot main class with
|
||
<code>@EnableZuulProxy</code>, and this forwards local calls to the appropriate
|
||
service. By convention, a service with the Eureka ID "users", will
|
||
receive requests from the proxy located at <code>/users</code> (with the prefix
|
||
stripped). The proxy uses Ribbon to locate an instance to forward to
|
||
via Eureka, and all requests are executed in a hystrix command, so
|
||
failures will show up in Hystrix metrics, and once the circuit is open
|
||
the proxy will not try to contact the service.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To skip having a service automatically added, set
|
||
<code>zuul.ignored-services</code> to a list of service id patterns. If a service
|
||
matches a pattern that is ignored, but also included in the explicitly
|
||
configured routes map, then it will be unignored. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml"> zuul:
|
||
ignoredServices: '*'
|
||
routes:
|
||
users: /myusers/**</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this example, all services are ignored <strong>except</strong> "users".</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To augment or change
|
||
the proxy routes, you can add external configuration like the
|
||
following:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml"> zuul:
|
||
routes:
|
||
users: /myusers/**</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This means that http calls to "/myusers" get forwarded to the "users"
|
||
service (for example "/myusers/101" is forwarded to "/101").</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To get more fine-grained control over a route you can specify the path
|
||
and the serviceId independently:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml"> zuul:
|
||
routes:
|
||
users:
|
||
path: /myusers/**
|
||
serviceId: users_service</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This means that http calls to "/myusers" get forwarded to the
|
||
"users_service" service. The route has to have a "path" which can be
|
||
specified as an ant-style pattern, so "/myusers/*" only matches one
|
||
level, but "/myusers/{asterisk}{asterisk}" matches hierarchically.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The location of the backend can be specified as either a "serviceId"
|
||
(for a Eureka service) or a "url" (for a physical location), e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml"> zuul:
|
||
routes:
|
||
users:
|
||
path: /myusers/**
|
||
url: http://example.com/users_service</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>These simple url-routes doesn’t get executed as HystrixCommand nor can you loadbalance multiple url with Ribbon.
|
||
To achieve this specify a service-route and configure a Ribbon client for the
|
||
serviceId (this currently requires disabling Eureka support in Ribbon:
|
||
see <a href="#spring-cloud-ribbon-without-eureka">above for more information</a>), e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">zuul:
|
||
routes:
|
||
users:
|
||
path: /myusers/**
|
||
serviceId: users
|
||
|
||
ribbon:
|
||
eureka:
|
||
enabled: false
|
||
|
||
users:
|
||
ribbon:
|
||
listOfServers: example.com,google.com</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can provide convention between serviceId and routes using
|
||
regexmapper. It uses regular expression named group to extract
|
||
variables from serviceId and inject them into a route pattern.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">ApplicationConfiguration.java</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Bean
|
||
public PatternServiceRouteMapper serviceRouteMapper() {
|
||
return new PatternServiceRouteMapper(
|
||
"(?<name>^.+)-(?<version>v.+$)",
|
||
"${version}/${name}");
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This means that a serviceId "myusers-v1" will be mapped to route
|
||
"/v1/myusers/{asterisk}{asterisk}". Any regular expression is accepted but all named
|
||
group must be present in both servicePattern and routePattern. If
|
||
servicePattern do not match a serviceId, the default behavior is
|
||
used. In exemple above, a serviceId "myusers" will be mapped to route
|
||
"/myusers/{asterisk}{asterisk}" (no version detected) These feature is disable by
|
||
default and is only applied to discovered services.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To add a prefix to all mappings, set <code>zuul.prefix</code> to a value, such as
|
||
<code>/api</code>. The proxy prefix is stripped from the request before the
|
||
request is forwarded by default (switch this behaviour off with
|
||
<code>zuul.stripPrefix=false</code>). You can also switch off the stripping of
|
||
the service-specific prefix from individual routes, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml"> zuul:
|
||
routes:
|
||
users:
|
||
path: /myusers/**
|
||
stripPrefix: false</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this example requests to "/myusers/101" will be forwarded to "/myusers/101" on the "users" service.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>zuul.routes</code> entries actually bind to an object of type <code>ProxyRouteLocator</code>. If you
|
||
look at the properties of that object you will see that it also has a "retryable" flag.
|
||
Set that flag to "true" to have the Ribbon client automatically retry failed requests
|
||
(and if you need to you can modify the parameters of the retry operations using
|
||
the Ribbon client configuration).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>X-Forwarded-Host</code> header is added to the forwarded requests by
|
||
default. To turn it off set <code>zuul.addProxyHeaders = false</code>. The
|
||
prefix path is stripped by default, and the request to the backend
|
||
picks up a header "X-Forwarded-Prefix" ("/myusers" in the examples
|
||
above).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>An application with the <code>@EnableZuulProxy</code> could act as a standalone
|
||
server if you set a default route ("/"), for example <code>zuul.route.home:
|
||
/</code> would route all traffic (i.e. "/{asterisk}{asterisk}") to the "home" service.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If more fine-grained ignoring is needed, you can specify specific patterns to ignore.
|
||
These patterns are being evaluated at the start of the route location process, which
|
||
means prefixes should be included in the pattern to warrant a match. Ignored patterns
|
||
span all services and supersede any other route specification.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml"> zuul:
|
||
ignoredPatterns: /**/admin/**
|
||
routes:
|
||
users: /myusers/**</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This means that all calls such as "/myusers/101" will be forwarded to "/101" on the "users" service.
|
||
But calls including "/admin/" will not resolve.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_strangulation_patterns_and_local_forwards">Strangulation Patterns and Local Forwards</h3>
|
||
<div class="paragraph">
|
||
<p>A common pattern when migrating an existing application or API is to
|
||
"strangle" old endpoints, slowly replacing them with different
|
||
implementations. The Zuul proxy is a useful tool for this because you
|
||
can use it to handle all traffic from clients of the old endpoints,
|
||
but redirect some of the requests to new ones.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Example configuration:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml"> zuul:
|
||
routes:
|
||
first:
|
||
path: /first/**
|
||
url: http://first.example.com
|
||
second:
|
||
path: /second/**
|
||
url: forward:/second
|
||
third:
|
||
path: /third/**
|
||
url: forward:/3rd
|
||
legacy:
|
||
path: /**
|
||
url: http://legacy.example.com</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this example we are strangling the "legacy" app which is mapped to
|
||
all requests that do not match one of the other patterns. Paths in
|
||
<code>/first/{asterisk}{asterisk}</code> have been extracted into a new service with an external
|
||
URL. And paths in <code>/second/{asterisk}{asterisk}</code> are forwared so they can be handled
|
||
locally, e.g. with a normal Spring <code>@RequestMapping</code>. Paths in
|
||
<code>/third/{asterisk}{asterisk}</code> are also forwarded, but with a different prefix
|
||
(i.e. <code>/third/foo</code> is forwarded to <code>/3rd/foo</code>).</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
The ignored pattterns aren’t completely ignored, they just
|
||
aren’t handled by the proxy (so they are also effectively forwarded
|
||
locally).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_uploading_files_through_zuul">Uploading Files through Zuul</h3>
|
||
<div class="paragraph">
|
||
<p>If you <code>@EnableZuulProxy</code> you can use the proxy paths to
|
||
upload files and it should just work as long as the files
|
||
are small. For large files there is an alternative path
|
||
which bypasses the Spring <code>DispatcherServlet</code> (to
|
||
avoid multipart processing) in "/zuul/*". I.e. if
|
||
<code>zuul.routes.customers=/customers/{asterisk}{asterisk}</code> then you can
|
||
POST large files to "/zuul/customers/*". The servlet
|
||
path is externalized via <code>zuul.servletPath</code>. Extremely
|
||
large files will also require elevated timeout settings
|
||
if the proxy route takes you through a Ribbon load
|
||
balancer, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds: 60000
|
||
ribbon:
|
||
ConnectTimeout: 3000
|
||
ReadTimeout: 60000</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Note that for streaming to work with large files, you need to use chunked encoding in the request (which some browsers
|
||
do not do by default). E.g. on the command line:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ curl -v -H "Transfer-Encoding: chunked" \
|
||
-F "file=@mylarge.iso" localhost:9999/zuul/simple/file</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_plain_embedded_zuul">Plain Embedded Zuul</h3>
|
||
<div class="paragraph">
|
||
<p>You can also run a Zuul server without the proxying, or switch on parts of the proxying platform selectively, if you
|
||
use <code>@EnableZuulServer</code> (instead of <code>@EnableZuulProxy</code>). Any beans that you add to the application of type <code>ZuulFilter</code>
|
||
will be installed automatically, as they are with <code>@EnableZuulProxy</code>, but without any of the proxy filters being added
|
||
automatically.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this case the routes into the Zuul server are still specified by
|
||
configuring "zuul.routes.*", but there is no service
|
||
discovery and no proxying, so the "serviceId" and "url" settings are
|
||
ignored. For example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml"> zuul:
|
||
routes:
|
||
api: /api/**</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>maps all paths in "/api/{asterisk}{asterisk}" to the Zuul filter chain.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_disable_zuul_filters">Disable Zuul Filters</h3>
|
||
<div class="paragraph">
|
||
<p>Zuul for Spring Cloud comes with a number of <code>ZuulFilter</code> beans enabled by default
|
||
in both proxy and server mode. See <a href="https://github.com/spring-cloud/spring-cloud-netflix/tree/master/spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters">the zuul filters package</a> for the
|
||
possible filters that are enabled. If you want to disable one, simply set
|
||
<code>zuul.<SimpleClassName>.<filterType>.disable=true</code>. By convention, the package after
|
||
<code>filters</code> is the Zuul filter type. For example to disable
|
||
<code>org.springframework.cloud.netflix.zuul.filters.post.SendResponseFilter</code> set
|
||
<code>zuul.SendResponseFilter.post.disable=true</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_polyglot_support_with_sidecar">Polyglot support with Sidecar</h3>
|
||
<div class="paragraph">
|
||
<p>Do you have non-jvm languages you want to take advantage of Eureka, Ribbon and
|
||
Config Server? The Spring Cloud Netflix Sidecar was inspired by
|
||
<a href="https://github.com/Netflix/Prana">Netflix Prana</a>. It includes a simple http api
|
||
to get all of the instances (ie host and port) for a given service. You can
|
||
also proxy service calls through an embedded Zuul proxy which gets its route
|
||
entries from Eureka. The Spring Cloud Config Server can be accessed directly
|
||
via host lookup or through the Zuul Proxy. The non-jvm app should implement
|
||
a health check so the Sidecar can report to eureka if the app is up or down.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To enable the Sidecar, create a Spring Boot application with <code>@EnableSidecar</code>.
|
||
This annotation includes <code>@EnableCircuitBreaker</code>, <code>@EnableDiscoveryClient</code>,
|
||
and <code>@EnableZuulProxy</code>. Run the resulting application on the same host as the
|
||
non-jvm application.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To configure the side car add <code>sidecar.port</code> and <code>sidecar.health-uri</code> to <code>application.yml</code>.
|
||
The <code>sidecar.port</code> property is the port the non-jvm app is listening on. This
|
||
is so the Sidecar can properly register the app with Eureka. The <code>sidecar.health-uri</code>
|
||
is a uri accessible on the non-jvm app that mimicks a Spring Boot health
|
||
indicator. It should return a json document like the following:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">health-uri-document</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-json" data-lang="json">{
|
||
"status":"UP"
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Here is an example application.yml for a Sidecar application:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">server:
|
||
port: 5678
|
||
spring:
|
||
application:
|
||
name: sidecar
|
||
|
||
sidecar:
|
||
port: 8000
|
||
health-uri: http://localhost:8000/health.json</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The api for the <code>DiscoveryClient.getInstances()</code> method is <code>/hosts/{serviceId}</code>.
|
||
Here is an example response for <code>/hosts/customers</code> that returns two instances on
|
||
different hosts. This api is accessible to the non-jvm app (if the sidecar is
|
||
on port 5678) at <code><a href="http://localhost:5678/hosts/{serviceId}" class="bare">http://localhost:5678/hosts/{serviceId}</a></code>.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">/hosts/customers</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-json" data-lang="json">[
|
||
{
|
||
"host": "myhost",
|
||
"port": 9000,
|
||
"uri": "http://myhost:9000",
|
||
"serviceId": "CUSTOMERS",
|
||
"secure": false
|
||
},
|
||
{
|
||
"host": "myhost2",
|
||
"port": 9000,
|
||
"uri": "http://myhost2:9000",
|
||
"serviceId": "CUSTOMERS",
|
||
"secure": false
|
||
}
|
||
]</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The Zuul proxy automatically adds routes for each service known in eureka to
|
||
<code>/<serviceId></code>, so the customers service is available at <code>/customers</code>. The
|
||
Non-jvm app can access the customer service via <code><a href="http://localhost:5678/customers" class="bare">http://localhost:5678/customers</a></code>
|
||
(assuming the sidecar is listening on port 5678).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If the Config Server is registered with Eureka, non-jvm application can access
|
||
it via the Zuul proxy. If the serviceId of the ConfigServer is <code>configserver</code>
|
||
and the Sidecar is on port 5678, then it can be accessed at
|
||
<a href="http://localhost:5678/configserver" class="bare">http://localhost:5678/configserver</a></p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Non-jvm app can take advantage of the Config Server’s ability to return YAML
|
||
documents. For example, a call to <a href="http://sidecar.local.spring.io:5678/configserver/default-master.yml" class="bare">http://sidecar.local.spring.io:5678/configserver/default-master.yml</a>
|
||
might result in a YAML document like the following</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">eureka:
|
||
client:
|
||
serviceUrl:
|
||
defaultZone: http://localhost:8761/eureka/
|
||
password: password
|
||
info:
|
||
description: Spring Cloud Samples
|
||
url: https://github.com/spring-cloud-samples</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_metrics_spectator_servo_and_atlas">Metrics: Spectator, Servo, and Atlas</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>When used together, Spectator/Servo and Atlas provide a near real-time operational insight platform.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spectator and Servo are Netflix’s metrics collection libraries. Atlas is a Netflix metrics backend to manage dimensional time series data.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Servo served Netflix for several years and is still usable, but is gradually being phased out in favor of Spectator, which is only designed to work with Java 8. Spring Cloud Netflix provides support for both, but Java 8 based applications are encouraged to use Spectator.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_dimensional_vs_hierarchical_metrics">Dimensional vs. Hierarchical Metrics</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Boot Actuator metrics are hierarchical and metrics are separated only by name. These names often follow a naming convention that embeds key/value attribute pairs (dimensions) into the name separated by periods. Consider the following metrics for two endpoints, root and star-star:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-json" data-lang="json">{
|
||
"counter.status.200.root": 20,
|
||
"counter.status.400.root": 3,
|
||
"counter.status.200.star-star": 5,
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The first metric gives us a normalized count of successful requests against the root endpoint per unit of time. But what if the system had 20 endpoints and you want to get a count of successful requests against all the endpoints? Some hierarchical metrics backends would allow you to specify a wild card such as <code>counter.status.200.<strong></code> that would read all 20 metrics and aggregate the results. Alternatively, you could provide a <code>HandlerInterceptorAdapter</code> that intercepts and records a metric like <code>counter.status.200.all</code> for all successful requests irrespective of the endpoint, but now you must write 20+1 different metrics. Similarly if you want to know the total number of successful requests for all endpoints in the service, you could specify a wild card such as <code>counter.status.2</strong>.*</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Even in the presence of wildcarding support on a hierarchical metrics backend, naming consistency can be difficult. Specifically the position of these tags in the name string can slip with time, breaking queries. For example, suppose we add an additional dimension to the hierarchical metrics above for HTTP method. Then <code>counter.status.200.root</code> becomes <code>counter.status.200.method.get.root</code>, etc. Our <code>counter.status.200.*</code> suddenly no longer has the same semantic meaning. Furthermore, if the new dimension is not applied uniformly across the codebase, certain queries may become impossible. This can quickly get out of hand.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Netflix metrics are tagged (a.k.a. dimensional). Each metric has a name, but this single named metric can contain multiple statistics and 'tag' key/value pairs that allows more querying flexibility. In fact, the statistics themselves are recorded in a special tag.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Recorded with Netflix Servo or Spectator, a timer for the root endpoint described above contains 4 statistics per status code, where the count statistic is identical to Spring Boot Actuator’s counter. In the event that we have encountered an HTTP 200 and 400 thus far, there will be 8 available data points:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-json" data-lang="json">{
|
||
"root(status=200,stastic=count)": 20,
|
||
"root(status=200,stastic=max)": 0.7265630630000001,
|
||
"root(status=200,stastic=totalOfSquares)": 0.04759702862580789,
|
||
"root(status=200,stastic=totalTime)": 0.2093076914666667,
|
||
"root(status=400,stastic=count)": 1,
|
||
"root(status=400,stastic=max)": 0,
|
||
"root(status=400,stastic=totalOfSquares)": 0,
|
||
"root(status=400,stastic=totalTime)": 0,
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_default_metrics_collection">Default Metrics Collection</h3>
|
||
<div class="paragraph">
|
||
<p>Without any additional dependencies or configuration, a Spring Cloud based service will autoconfigure a Servo <code>MonitorRegistry</code> and begin collecting metrics on every Spring MVC request. By default, a Servo timer with the name <code>rest</code> will be recorded for each MVC request which is tagged with:</p>
|
||
</div>
|
||
<div class="olist arabic">
|
||
<ol class="arabic">
|
||
<li>
|
||
<p>HTTP method</p>
|
||
</li>
|
||
<li>
|
||
<p>HTTP status (e.g. 200, 400, 500)</p>
|
||
</li>
|
||
<li>
|
||
<p>URI (or "root" if the URI is empty), sanitized for Atlas</p>
|
||
</li>
|
||
<li>
|
||
<p>The exception class name, if the request handler threw an exception</p>
|
||
</li>
|
||
<li>
|
||
<p>The caller, if a request header with a key matching <code>netflix.metrics.rest.callerHeader</code> is set on the request. There is no default key for <code>netflix.metrics.rest.callerHeader</code>. You must add it to your application properties if you wish to collect caller information.</p>
|
||
</li>
|
||
</ol>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Set the <code>netflix.metrics.rest.metricName</code> property to change the name of the metric from <code>rest</code> to a name you provide.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If Spring AOP is enabled and <code>org.aspectj:aspectjweaver</code> is present on your runtime classpath, Spring Cloud will also collect metrics on every client call made with <code>RestTemplate</code>. A Servo timer with the name of <code>restclient</code> will be recorded for each MVC request which is tagged with:</p>
|
||
</div>
|
||
<div class="olist arabic">
|
||
<ol class="arabic">
|
||
<li>
|
||
<p>HTTP method</p>
|
||
</li>
|
||
<li>
|
||
<p>HTTP status (e.g. 200, 400, 500), "CLIENT_ERROR" if the response returned null, or "IO_ERROR" if an <code>IOException</code> occurred during the execution of the <code>RestTemplate</code> method</p>
|
||
</li>
|
||
<li>
|
||
<p>URI, sanitized for Atlas</p>
|
||
</li>
|
||
<li>
|
||
<p>Client name</p>
|
||
</li>
|
||
</ol>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_metrics_collection_spectator">Metrics Collection: Spectator</h3>
|
||
<div class="paragraph">
|
||
<p>To enable Spectator metrics, include a dependency on <code>spring-boot-starter-spectator</code>:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-xml" data-lang="xml"> <dependency>
|
||
<groupId>org.springframework.cloud</groupId>
|
||
<artifactId>spring-cloud-starter-spectator</artifactId>
|
||
</dependency></code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In Spectator parlance, a meter is a named, typed, and tagged configuration and a metric represents the value of a given meter at a point in time. Spectator meters are created and controlled by a registry, which currently has several different implementations. Spectator provides 4 meter types: counter, timer, gauge, and distribution summary.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Spectator integration configures an injectable <code>com.netflix.spectator.api.Registry</code> instance for you. Specifically, it configures a <code>ServoRegistry</code> instance in order to unify the collection of REST metrics and the exporting of metrics to the Atlas backend under a single Servo API. Practically, this means that your code may use a mixture of Servo monitors and Spectator meters and both will be scooped up by Spring Boot Actuator <code>MetricReader</code> instances and both will be shipped to the Atlas backend.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_spectator_counter">Spectator Counter</h4>
|
||
<div class="paragraph">
|
||
<p>A counter is used to measure the rate at which some event is occurring.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">// create a counter with a name and a set of tags
|
||
Counter counter = registry.counter("counterName", "tagKey1", "tagValue1", ...);
|
||
counter.increment(); // increment when an event occurs
|
||
counter.increment(10); // increment by a discrete amount</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The counter records a single time-normalized statistic.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_spectator_timer">Spectator Timer</h4>
|
||
<div class="paragraph">
|
||
<p>A timer is used to measure how long some event is taking. Spring Cloud automatically records timers for Spring MVC requests and conditionally <code>RestTemplate</code> requests, which can later be used to create dashboards for request related metrics like latency:</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<div class="title">Request Latency</div>
|
||
<p>image::RequestLatency.png []</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">// create a timer with a name and a set of tags
|
||
Timer timer = registry.timer("timerName", "tagKey1", "tagValue1", ...);
|
||
|
||
// execute an operation and time it at the same time
|
||
T result = timer.record(() -> fooReturnsT());
|
||
|
||
// alternatively, if you must manually record the time
|
||
Long start = System.nanoTime();
|
||
T result = fooReturnsT();
|
||
timer.record(System.nanoTime() - start, TimeUnit.NANOSECONDS);</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The timer simultaneously records 4 statistics: count, max, totalOfSquares, and totalTime. The count statistic will always match the single normalized value provided by a counter if you had called <code>increment()</code> once on the counter for each time you recorded a timing, so it is rarely necessary to count and time separately for a single operation.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>For <a href="https://github.com/Netflix/spectator/wiki/Timer-Usage#longtasktimer">long running operations</a>, Spectator provides a special <code>LongTaskTimer</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_spectator_gauge">Spectator Gauge</h4>
|
||
<div class="paragraph">
|
||
<p>Gauges are used to determine some current value like the size of a queue or number of threads in a running state. Since gauges are sampled, they provide no information about how these values fluctuate between samples.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The normal use of a gauge involves registering the gauge once in initialization with an id, a reference to the object to be sampled, and a function to get or compute a numeric value based on the object. The reference to the object is passed in separately and the Spectator registry will keep a weak reference to the object. If the object is garbage collected, then Spectator will automatically drop the registration. See <a href="https://github.com/Netflix/spectator/wiki/Gauge-Usage#using-lambda">the note</a> in Spectator’s documentation about potential memory leaks if this API is misused.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">// the registry will automatically sample this gauge periodically
|
||
registry.gauge("gaugeName", pool, Pool::numberOfRunningThreads);
|
||
|
||
// manually sample a value in code at periodic intervals -- last resort!
|
||
registry.gauge("gaugeName", Arrays.asList("tagKey1", "tagValue1", ...), 1000);</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_spectator_distribution_summaries">Spectator Distribution Summaries</h4>
|
||
<div class="paragraph">
|
||
<p>A distribution summary is used to track the distribution of events. It is similar to a timer, but more general in that the size does not have to be a period of time. For example, a distribution summary could be used to measure the payload sizes of requests hitting a server.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">// the registry will automatically sample this gauge periodically
|
||
DistributionSummary ds = registry.distributionSummary("dsName", "tagKey1", "tagValue1", ...);
|
||
ds.record(request.sizeInBytes());</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_metrics_collection_servo">Metrics Collection: Servo</h3>
|
||
<div class="admonitionblock warning">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Warning</div>
|
||
</td>
|
||
<td class="content">
|
||
If your code is compiled on Java 8, please use Spectator instead of Servo as Spectator is destined to replace Servo entirely in the long term.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In Servo parlance, a monitor is a named, typed, and tagged configuration and a metric represents the value of a given monitor at a point in time. Servo monitors are logically equivalent to Spectator meters. Servo monitors are created and controlled by a <code>MonitorRegistry</code>. In spite of the above warning, Servo does have a <a href="https://github.com/Netflix/servo/wiki/Getting-Started">wider array</a> of monitor options than Spectator has meters.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud integration configures an injectable <code>com.netflix.servo.MonitorRegistry</code> instance for you. Once you have created the appropriate <code>Monitor</code> type in Servo, the process of recording data is wholly similar to Spectator.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_creating_servo_monitors">Creating Servo Monitors</h4>
|
||
<div class="paragraph">
|
||
<p>If you are using the Servo <code>MonitorRegistry</code> instance provided by Spring Cloud (specifically, an instance of <code>DefaultMonitorRegistry</code>), Servo provides convenience classes for retrieving <a href="https://github.com/Netflix/spectator/wiki/Servo-Comparison#dynamiccounter">counters</a> and <a href="https://github.com/Netflix/spectator/wiki/Servo-Comparison#dynamictimer">timers</a>. These convenience classes ensure that only one <code>Monitor</code> is registered for each unique combination of name and tags.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To manually create a Monitor type in Servo, especially for the more exotic monitor types for which convenience methods are not provided, instantiate the appropriate type by providing a <code>MonitorConfig</code> instance:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">MonitorConfig config = MonitorConfig.builder("timerName").withTag("tagKey1", "tagValue1").build();
|
||
|
||
// somewhere we should cache this Monitor by MonitorConfig
|
||
Timer timer = new BasicTimer(config);
|
||
monitorRegistry.register(timer);</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_metrics_backend_atlas">Metrics Backend: Atlas</h3>
|
||
<div class="paragraph">
|
||
<p>Atlas was developed by Netflix to manage dimensional time series data for near real-time operational insight. Atlas features in-memory data storage, allowing it to gather and report very large numbers of metrics, very quickly.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Atlas captures operational intelligence. Whereas business intelligence is data gathered for analyzing trends over time, operational intelligence provides a picture of what is currently happening within a system.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud provides a <code>spring-cloud-starter-atlas</code> that has all the dependencies you need. Then just annotate your Spring Boot application with <code>@EnableAtlas</code> and provide a location for your running Atlas server with the <code>netflix.atlas.uri</code> property.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_global_tags">Global tags</h4>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud enables you to add tags to every metric sent to the Atlas backend. Global tags can be used to separate metrics by application name, environment, region, etc.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Each bean implementing <code>AtlasTagProvider</code> will contribute to the global tag list:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Bean
|
||
AtlasTagProvider atlasCommonTags(
|
||
@Value("${spring.application.name}") String appName) {
|
||
return () -> Collections.singletonMap("app", appName);
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_using_atlas">Using Atlas</h4>
|
||
<div class="paragraph">
|
||
<p>To bootstrap a in-memory standalone Atlas instance:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-bash" data-lang="bash">$ curl -LO https://github.com/Netflix/atlas/releases/download/v1.4.2/atlas-1.4.2-standalone.jar
|
||
$ java -jar atlas-1.4.2-standalone.jar</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
An Atlas standalone node running on an r3.2xlarge (61GB RAM) can handle roughly 2 million metrics per minute for a given 6 hour window.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Once running and you have collected a handful of metrics, verify that your setup is correct by listing tags on the Atlas server:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-bash" data-lang="bash">$ curl http://ATLAS/api/v1/tags</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
After executing several requests against your service, you can gather some very basic information on the request latency of every request by pasting the following url in your browser: <code><a href="http://ATLAS/api/v1/graph?q=name,rest,:eq,:avg" class="bare">http://ATLAS/api/v1/graph?q=name,rest,:eq,:avg</a></code>
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The Atlas wiki contains a <a href="https://github.com/Netflix/atlas/wiki/Single-Line">compilation of sample queries</a> for various scenarios.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Make sure to check out the <a href="https://github.com/Netflix/atlas/wiki/Alerting-Philosophy">alerting philosophy</a> and docs on using <a href="https://github.com/Netflix/atlas/wiki/DES">double exponential smoothing</a> to generate dynamic alert thresholds.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_stream" class="sect0">Spring Cloud Stream</h1>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-stream-overview">Spring Cloud Stream Overview</h2>
|
||
<div class="sectionbody">
|
||
|
||
<div class="sect2">
|
||
<h3 id="_introducing_spring_cloud_stream">Introducing Spring Cloud Stream</h3>
|
||
<div class="paragraph">
|
||
<p>The Spring Cloud Stream project allows a user to develop and run messaging microservices using Spring Integration.
|
||
Just add <code>@EnableBinding</code> and run your app as a Spring Boot app (single application context).
|
||
Spring Cloud Stream applications connect to the physical broker through bindings, which link Spring Integration
|
||
channels to physical broker destinations, for either input (consumer bindings) or output (producer bindings).
|
||
The creation of the bindings, and therefore their broker-specific implementation is handled by a binder, which is
|
||
another important abstraction of Spring Cloud Stream. Binders abstract out the broker-specific implementation details.
|
||
In order to connect to a specific type of broker (e.g. Rabbit or Kafka) you just need to have the relevant binder
|
||
implementation on the classpath.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Here’s a sample source app (output channel only):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@SpringBootApplication
|
||
public class StreamApplication {
|
||
|
||
public static void main(String[] args) {
|
||
SpringApplication.run(StreamApplication.class, args);
|
||
}
|
||
}
|
||
|
||
@EnableBinding(Source.class)
|
||
public class TimerSource {
|
||
|
||
@Value("${format}")
|
||
private String format;
|
||
|
||
@Bean
|
||
@InboundChannelAdapter(value = Source.OUTPUT, poller = @Poller(fixedDelay = "${fixedDelay}", maxMessagesPerPoll = "1"))
|
||
public MessageSource<String> timerMessageSource() {
|
||
return () -> new GenericMessage<>(new SimpleDateFormat(format).format(new Date()));
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><code>@EnableBinding</code> is parameterized by one or more interfaces (in this case a single <code>Source</code> interface), which declares
|
||
input and/or output channels. The interfaces <code>Source</code>, <code>Sink</code> and <code>Processor</code> are provided off the shelf, but you can
|
||
define others. Here’s the definition of <code>Source</code>:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">public interface Source {
|
||
String OUTPUT = "output";
|
||
|
||
@Output(Source.OUTPUT)
|
||
MessageChannel output();
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>@Output</code> annotation is used to identify output channels (messages leaving the app), and <code>@Input</code> is used to
|
||
identify input channels (messages entering the app). It is optionally parameterized by a channel name - if the name is
|
||
not provided the method name is used instead. An implementation of the interface is created for you and can be used in
|
||
the application context by autowiring it, e.g. into a test case:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@RunWith(SpringJUnit4ClassRunner.class)
|
||
@SpringApplicationConfiguration(classes = StreamApplication.class)
|
||
@WebAppConfiguration
|
||
@DirtiesContext
|
||
public class StreamApplicationTests {
|
||
|
||
@Autowired
|
||
private Source source
|
||
|
||
@Test
|
||
public void contextLoads() {
|
||
assertNotNull(this.source.output());
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
In this case there is only one <code>Source</code> in the application context so there is no need to qualify it when it is
|
||
autowired. If there is ambiguity, e.g. if you are composing one application from some others, you can use the
|
||
<code>@Bindings</code> qualifier to inject a specific channel set. The <code>@Bindings</code> qualifier takes a parameter which is the class
|
||
that carries the <code>@EnableBinding</code> annotation (in this case the <code>TimerSource</code>).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_multiple_input_or_output_channels">Multiple Input or Output Channels</h4>
|
||
<div class="paragraph">
|
||
<p>A stream app can have multiple input or output channels defined as <code>@Input</code> and <code>@Output</code> methods in an interface.
|
||
Instead of just one channel named "input" or "output", you can add multiple <code>MessageChannel</code> methods annotated with
|
||
<code>@Input</code> or <code>@Output</code>, and their names will be converted to external destination names on the broker. It is common to
|
||
specify the channel names at runtime in order to have multiple applications communicate over well known destination
|
||
names. Channel names can be specified as properties that consist of the channel names prefixed with
|
||
<code>spring.cloud.stream.bindings</code> (e.g. <code>spring.cloud.stream.bindings.input</code> or <code>spring.cloud.stream.bindings.output</code>).
|
||
These properties can be specified though environment variables, the application YAML file, or any of the other
|
||
mechanisms supported by Spring Boot.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>For example, you can have two <code>MessageChannels</code> called "default" and "tap" in an application with
|
||
<code>spring.cloud.stream.bindings.default.destination=foo</code> and <code>spring.cloud.stream.bindings.tap.destination=bar</code>,
|
||
and the result is 2 bindings to an external broker with destinations called "foo" and "bar".</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_inter_app_communication">Inter-app Communication</h4>
|
||
<div class="paragraph">
|
||
<p>While Spring Cloud Stream makes it easy for individual boot apps to connect to messaging systems, the typical scenario
|
||
for Spring Cloud Stream is the creation of multi-app pipelines, where microservice apps are sending data to each other.
|
||
This can be achieved by correlating the input and output destinations of adjacent apps, as in the following example.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Supposing that the design calls for the <code>time-source</code> app to send data to the <code>log-sink</code> app, we will use a
|
||
common destination named <code>ticktock</code> for bindings within both apps. <code>time-source</code> will set
|
||
<code>spring.cloud.stream.bindings.output.destination=ticktock</code>, and <code>log-sink</code> will set
|
||
<code>spring.cloud.stream.bindings.input.destination=ticktock</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_consumer_group_support">Consumer Group Support</h4>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Stream is a library focusing on building message-driven microservices, and more specifically stream
|
||
processing applications. In such scenarios, communication between different logical applications follows a
|
||
publish-subscribe pattern, with data being broadcast through a shared topic, but at the same time, it is important to
|
||
be able to scale up by creating multiple instances of a given application, which are in a competing consumer
|
||
relationship with each other.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Stream models this behavior through the concept of a consumer group, which is similar to the notion of
|
||
consumer groups in Kafka. Each consumer binding can specify a group name such as
|
||
<code>spring.cloud.stream.bindings.input.group=foo</code> (the actual name of the binding may vary). Each consumer group bound to
|
||
a given destination will receive a copy of the published data, but within the group, only one application will receive
|
||
each specific message.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If no consumer group is specified for a given binding, then the binding is treated as if belonging to an anonymous,
|
||
independent, single-member consumer group. Otherwise said, if no consumer group is specified for a binding, it will be
|
||
in a publish-subscribe relationship with any other consumer groups.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In general, it is preferable to always specify a consumer group when binding an application to a given destination.
|
||
When scaling up a Spring Cloud Stream application, a consumer group must be specified for each of its input bindings,
|
||
in order to prevent its instances from receiving duplicate messages (unless that behavior is desired, which is a less
|
||
common use case).</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
This feature has been introduced since version 1.0.0.M4.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_instance_index_and_instance_count">Instance Index and Instance Count</h4>
|
||
<div class="paragraph">
|
||
<p>When scaling up Spring Cloud Stream applications, each instance can receive information about how many other instances
|
||
of the same application exist and what its own instance index is. This is done through the
|
||
<code>spring.cloud.stream.instanceCount</code> and <code>spring.cloud.stream.instanceIndex</code> properties. For example, if there are 3
|
||
instances of the HDFS sink application, all three will have <code>spring.cloud.stream.instanceCount</code> set to 3, and the
|
||
applications will have <code>spring.cloud.stream.instanceIndex</code> set to 0, 1 and 2, respectively. When Spring Cloud Stream
|
||
applications are deployed via Spring Cloud Data Flow, these properties are configured automatically, but when Spring
|
||
Cloud Stream applications are launched independently, these properties must be set correctly. By default
|
||
<code>spring.cloud.stream.instanceCount</code> is 1, and <code>spring.cloud.stream.instanceIndex</code> is 0.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Setting up the two properties correctly on scale up scenarios is important for addressing partitioning behavior in
|
||
general (see below), and they are always required by certain types of binders (e.g. the Kafka binder) in order to
|
||
ensure that data is split correctly across multiple consumer instances.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_advanced_binding_properties">Advanced Binding Properties</h4>
|
||
<div class="paragraph">
|
||
<p>The input and output destination names are the primary properties to set in order to have Spring Cloud Stream
|
||
applications communicate with each other as their channels are bound to an external message broker automatically.
|
||
However, there are a number of scenarios where it is required to configure other attributes besides the destination
|
||
name. This is done using the following naming scheme:
|
||
<code>spring.cloud.stream.bindings.<channelName>.<attributeName>=<attributeValue></code>. The <code>destination</code> attribute is one such
|
||
example: <code>spring.cloud.stream.bindings.input.destination=foo</code>. A shorthand equivalent can be used as follows:
|
||
<code>spring.cloud.stream.bindings.input=foo</code>, but that shorthand can only be used only when there are no other attributes
|
||
to set on the binding. In other words,
|
||
<code>spring.cloud.stream.bindings.input.destination=foo</code>,<code>spring.cloud.stream.bindings.input.partitioned=true</code> is a valid
|
||
setup, whereas <code>spring.cloud.stream.bindings.input=foo</code>,<code>spring.cloud.stream.bindings.input.partitioned=true</code> is not.</p>
|
||
</div>
|
||
<div class="sect4">
|
||
<h5 id="_partitioning">Partitioning</h5>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Stream provides support for partitioning data between multiple instances of a given application. In a
|
||
partitioned scenario, one or more producer apps will send data to one or more consumer apps, ensuring that data with
|
||
common characteristics is processed by the same consumer instance. The physical communication medium (i.e. the broker
|
||
topic or queue) is viewed as structured into multiple partitions. Regardless of whether the broker type is naturally
|
||
partitioned (e.g. Kafka) or not (e.g. Rabbit), Spring Cloud Stream provides a common abstraction for implementing
|
||
partitioned processing use cases in a uniform fashion.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Setting up a partitioned processing scenario requires configuring both the data producing and the data consuming end.</p>
|
||
</div>
|
||
<div class="sect5">
|
||
<h6 id="_configuring_output_bindings_for_partitioning">Configuring Output Bindings for Partitioning</h6>
|
||
<div class="paragraph">
|
||
<p>An output binding is configured to send partitioned data, by setting one and only one of its <code>partitionKeyExpression</code>
|
||
or <code>partitionKeyExtractorClass</code> properties, as well as its <code>partitionCount</code> property. For example, setting
|
||
<code>spring.cloud.stream.bindings.output.partitionKeyExpression=payload.id</code>,<code>spring.cloud.stream.bindings.output.partitionCount=5</code>
|
||
is a valid and typical configuration.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Based on this configuration, the data will be sent to the target partition using the following logic. A partition key’s
|
||
value is calculated for each message sent to a partitioned output channel based on the <code>partitionKeyExpression</code>. The
|
||
<code>partitionKeyExpression</code> is a SpEL expression that is evaluated against the outbound message for extracting the
|
||
partitioning key. If a SpEL expression is not sufficient for your needs, you can instead calculate the partition key
|
||
value by setting the property <code>partitionKeyExtractorClass</code>. This class must implement the interface
|
||
<code>org.springframework.cloud.stream.binder.PartitionKeyExtractorStrategy</code>. While, in general, the SpEL expression should
|
||
suffice, more complex cases may use the custom implementation strategy.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Once the message key is calculated, the partition selection process will determine the target partition as a value
|
||
between <code>0</code> and <code>partitionCount - 1</code>. The default calculation, applicable in most scenarios is based on the formula
|
||
<code>key.hashCode() % partitionCount</code>. This can be customized on the binding, either by setting a SpEL expression to be
|
||
evaluated against the key via the <code>partitionSelectorExpression</code> property, or by setting a
|
||
<code>org.springframework.cloud.stream.binder.PartitionSelectorStrategy</code> implementation via the <code>partitionSelectorClass</code>
|
||
property.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Additional properties can be configured for more advanced scenarios, as described in the following section.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect5">
|
||
<h6 id="_configuring_input_bindings_for_partitioning">Configuring Input Bindings for Partitioning</h6>
|
||
<div class="paragraph">
|
||
<p>An input binding is configured to receive partitioned data by setting its <code>partitioned</code> property, as well as the
|
||
instance index and instance count properties on the app itself, as follows:
|
||
<code>spring.cloud.stream.bindings.input.partitioned=true</code>,<code>spring.cloud.stream.instanceIndex=3</code>,<code>spring.cloud.stream.instanceCount=5</code>.
|
||
The instance count value represents the total number of app instances between which the data needs to be partitioned,
|
||
whereas instance index must be a unique value across the multiple instances, between <code>0</code> and <code>instanceCount - 1</code>. The
|
||
instance index helps each app instance to identify the unique partition (or in the case of Kafka, the partition set)
|
||
from which it receives data. It is important that both values are set correctly in order to ensure that all the data is
|
||
consumed, and that the app instances receive mutually exclusive datasets.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>While setting up multiple instances for partitioned data processing may be complex in the standalone case, Spring Cloud
|
||
Data Flow can simplify the process significantly, by populating both the input and output values correctly, as well as
|
||
relying on the runtime infrastructure to provide information about the instance index and instance count.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_binder_selection">Binder Selection</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Stream relies on implementations of the Binder SPI to perform the task of connecting channels to message
|
||
brokers. Each Binder implementation typically connects to one type of messaging system. Spring Cloud Stream provides
|
||
out of the box binders for Kafka, RabbitMQ and Redis.</p>
|
||
</div>
|
||
<div class="sect5">
|
||
<h6 id="_classpath_detection">Classpath Detection</h6>
|
||
<div class="paragraph">
|
||
<p>By default, Spring Cloud Stream relies on Spring Boot’s auto-configuration to configure the binding process. If a
|
||
single binder implementation is found on the classpath, Spring Cloud Stream will use it automatically. So, for example,
|
||
a Spring Cloud Stream project that aims to bind only to RabbitMQ can simply add the following dependency:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-xml" data-lang="xml"><dependency>
|
||
<groupId>org.springframework.cloud</groupId>
|
||
<artifactId>spring-cloud-stream-binder-rabbit</artifactId>
|
||
</dependency></code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect5">
|
||
<h6 id="_multiple_binders_on_the_classpath">Multiple Binders on the Classpath</h6>
|
||
<div class="paragraph">
|
||
<p>When multiple binders are present on the classpath, the application must indicate which binder is to be used for each
|
||
channel binding. Each binder configuration contains a <code>META-INF/spring.binders</code>, which is a simple properties file:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code>rabbit:\
|
||
org.springframework.cloud.stream.binder.rabbit.config.RabbitServiceAutoConfiguration</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Similar files exist for the other binder implementations (i.e. Kafka and Redis), and it is expected that custom binder
|
||
implementations will provide them, too. The key represents an identifying name for the binder implementation, whereas
|
||
the value is a comma-separated list of configuration classes that contain one and only one bean definition of the type
|
||
<code>org.springframework.cloud.stream.binder.Binder</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Selecting the binder can be done globally by either using the <code>spring.cloud.stream.defaultBinder</code> property, e.g.
|
||
<code>spring.cloud.stream.defaultBinder=rabbit</code>, or by individually configuring them on each channel binding.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>For instance, a processor app that reads from Kafka and writes to Rabbit can specify the following configuration:
|
||
<code>spring.cloud.stream.bindings.input.binder=kafka</code>,<code>spring.cloud.stream.bindings.output.binder=rabbit</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect5">
|
||
<h6 id="_connecting_to_multiple_systems">Connecting to Multiple Systems</h6>
|
||
<div class="paragraph">
|
||
<p>By default, binders share the Spring Boot auto-configuration of the application and create one instance of each binder
|
||
found on the classpath. In scenarios where an application should connect to more than one broker of the same type,
|
||
Spring Cloud Stream allows you to specify multiple binder configurations, with different environment settings. Please
|
||
note that turning on explicit binder configuration will disable the default binder configuration process altogether, so
|
||
all the binders in use must be included in the configuration.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>For example, this is the typical configuration for a processor that connects to two RabbitMQ broker instances:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yml" data-lang="yml">spring:
|
||
cloud:
|
||
stream:
|
||
bindings:
|
||
input:
|
||
destination: foo
|
||
binder: rabbit1
|
||
output:
|
||
destination: bar
|
||
binder: rabbit2
|
||
binders:
|
||
rabbit1:
|
||
type: rabbit
|
||
environment:
|
||
spring:
|
||
rabbitmq:
|
||
host: <host1>
|
||
rabbit2:
|
||
type: rabbit
|
||
environment:
|
||
spring:
|
||
rabbitmq:
|
||
host: <host2></code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_managed_vs_standalone">Managed vs Standalone</h3>
|
||
<div class="paragraph">
|
||
<p>Code using the Spring Cloud Stream library can be deployed as a standalone application or be used as a Spring Cloud
|
||
Data Flow module. In standalone mode, your application will run happily as a service or in any PaaS (Cloud Foundry,
|
||
Heroku, Azure, etc.). Spring Cloud Data Flow helps orchestrate the communication between instances, so the aspects of
|
||
configuration that deal with application interconnection will be configured transparently.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_fat_jar">Fat JAR</h4>
|
||
<div class="paragraph">
|
||
<p>You can run in standalone mode from your IDE for testing. To run in production you can create an executable (or "fat")
|
||
JAR using the standard Spring Boot tooling provided for Maven or Gradle.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_health_indicator_3">Health Indicator</h4>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Stream provides a health indicator for the binders, registered under the name of <code>binders</code>. It can be
|
||
enabled or disabled using the <code>management.health.binders.enabled</code> property.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_binder_spi">Binder SPI</h3>
|
||
<div class="paragraph">
|
||
<p>As described above, Spring Cloud Stream provides a binder abstraction for connecting to physical destinations. This
|
||
section will provide more information about the main concepts behind the Binder SPI, its main components, as well as
|
||
details specific to different implementations.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_producers_and_consumers">Producers and Consumers</h4>
|
||
<div class="imageblock">
|
||
<div class="content">
|
||
<img src="images/producers-consumers.png" alt="producers consumers" width="300">
|
||
</div>
|
||
<div class="title">Figure 4. Producers and Consumers</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>A producer is any component that sends messages to a channel. That channel can be bound to an external message broker
|
||
via a <code>Binder</code> implementation for that broker. When invoking the <code>bindProducer</code> method, the first parameter is the name
|
||
of the destination within that broker. The second parameter is the local channel instance to which the producer will be
|
||
sending messages, and the third parameter contains properties to be used within the adapter that is created for that
|
||
channel, such as a partition key expression.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>A consumer is any component that receives messages from a channel. As with the producer, the consumer’s channel can be
|
||
bound to an external message broker, and the first parameter for the <code>bindConsumer</code> method is the destination name.
|
||
However, on the consumer side, a second parameter provides the name of a logical group of consumers. Each group
|
||
represented by consumer bindings for a given destination will receive a copy of each message that a producer sends to
|
||
that destination (i.e. pub/sub semantics). If there are multiple consumer instances bound using the same group name,
|
||
then messages will be load balanced across those consumer instances so that each message sent by a producer would only
|
||
be consumed by a single consumer instance within each group (i.e. queue semantics).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_kafka_binder">Kafka Binder</h4>
|
||
<div class="imageblock">
|
||
<div class="content">
|
||
<img src="images/kafka-binder.png" alt="kafka binder" width="300">
|
||
</div>
|
||
<div class="title">Figure 5. Kafka Binder</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The Kafka Binder implementation maps the destination to a Kafka topic, and the consumer group maps directly to the same
|
||
Kafka concept. Spring Cloud Stream does not use the high level consumer, but implements a similar concept for the
|
||
simple consumer.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_rabbitmq_binder">RabbitMQ Binder</h4>
|
||
<div class="imageblock">
|
||
<div class="content">
|
||
<img src="images/rabbit-binder.png" alt="rabbit binder" width="300">
|
||
</div>
|
||
<div class="title">Figure 6. RabbitMQ Binder</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The RabbitMQ Binder implementation maps the destination to a <code>TopicExchange</code>, and for each consumer group, a <code>Queue</code>
|
||
will be bound to that <code>TopicExchange</code>. Each consumer instance that binds will trigger creation of a corresponding
|
||
RabbitMQ <code>Consumer</code> instance for its group’s <code>Queue</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_redis_binder">Redis Binder</h4>
|
||
<div class="imageblock">
|
||
<div class="content">
|
||
<img src="images/redis-binder.png" alt="redis binder" width="300">
|
||
</div>
|
||
<div class="title">Figure 7. Redis Binder</div>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
we recommend only using the Redis Binder for development
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The Redis Binder creates a <code>LIST</code> (which performs the role of a queue) for each consumer group. A consumer binding will
|
||
trigger <code>BRPOP</code> operations on its group’s <code>LIST</code>. A producer binding will consult a <code>ZSET</code> to determine what groups
|
||
currently have active consumers, and then for each message being sent, an <code>LPUSH</code> operation will be executed on each of
|
||
those group’s <code>LISTs</code>.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_task" class="sect0">Spring Cloud Task</h1>
|
||
<div class="sect1">
|
||
<h2 id="getting-started">Getting started</h2>
|
||
<div class="sectionbody">
|
||
<div id="partintro" class="openblock">
|
||
<div class="content">
|
||
<div class="paragraph">
|
||
<p>If you’re just getting started with Spring Cloud Task, this is the section
|
||
for you! Here we answer the basic “what?”, “how?” and “why?” questions. You’ll
|
||
find a gentle introduction to Spring Cloud Task. We’ll then build our first Spring Cloud
|
||
Task application, discussing some core principles as we go.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="getting-started-introducing-spring-cloud-task">Introducing Spring Cloud Task</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Task makes it easy to create short lived microservices. We provide
|
||
capabilities that allow short lived JVM processes to be executed on demand in a production
|
||
environment.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="getting-started-system-requirements">System Requirements</h3>
|
||
<div class="paragraph">
|
||
<p>You need Java installed (Java 7 or better, we recommend Java 8) and to build you need to have Maven installed as well.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_database_requirements">Database Requirements</h4>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Task uses a relational database to store the results of an executed task.
|
||
While you can begin developing a task without a database (the status of the task is logged
|
||
as part of the task repository’s updates), for production environments, you’ll want to
|
||
utilize a supported database. Below is a list of the ones currently supported:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>H2</p>
|
||
</li>
|
||
<li>
|
||
<p>HSQLDB</p>
|
||
</li>
|
||
<li>
|
||
<p>MySql</p>
|
||
</li>
|
||
<li>
|
||
<p>Oracle</p>
|
||
</li>
|
||
<li>
|
||
<p>Postgres</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="getting-started-developing-first-task">Developing your first Spring Cloud Task application</h3>
|
||
<div class="paragraph">
|
||
<p>A good place to start is with a simple "Hello World!" application so we’ll create the
|
||
Spring Cloud Task equivalent to highlight the features of the framework. We’ll use Apache
|
||
Maven as a build tool for this project since most IDEs have good support for it.</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
The spring.io web site contains many “Getting Started” guides that use Spring Boot.
|
||
If you’re looking to solve a specific problem; check there first. You can shortcut the
|
||
steps below by going to start.spring.io and creating a new project. This will
|
||
automatically generate a new project structure so that you can start coding right the way.
|
||
Check the documentation for more details.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Before we begin, open a terminal to check that you have valid versions of Java and Maven
|
||
installed.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code>$ java -version
|
||
java version "1.8.0_31"
|
||
Java(TM) SE Runtime Environment (build 1.8.0_31-b13)
|
||
Java HotSpot(TM) 64-Bit Server VM (build 25.31-b07, mixed mode)</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code>$ mvn -v
|
||
Apache Maven 3.2.3 (33f8c3e1027c3ddde99d3cdebad2656a31e8fdf4; 2014-08-11T15:58:10-05:00)
|
||
Maven home: /usr/local/Cellar/maven/3.2.3/libexec
|
||
Java version: 1.8.0_31, vendor: Oracle Corporation</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
This sample needs to be created in its own folder. Subsequent instructions assume
|
||
you have created a suitable folder and that it is your "current directory".
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="getting-started-creating-the-pom">Creating the POM</h4>
|
||
<div class="paragraph">
|
||
<p>We need to start by creating a Maven <code>pom.xml</code> file. The <code>pom.xml</code> is the recipe that
|
||
will be used to build your project. Open your favorite text editor and add the following:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre><?xml version="1.0" encoding="UTF-8"?>
|
||
<project xmlns="http://maven.apache.org/POM/4.0.0"
|
||
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
||
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
|
||
|
||
<modelVersion>4.0.0</modelVersion>
|
||
|
||
<groupId>com.example</groupId>
|
||
<artifactId>myproject</artifactId>
|
||
<packaging>jar</packaging>
|
||
<version>0.0.1-SNAPSHOT</version>
|
||
|
||
<parent>
|
||
<groupId>org.springframework.boot</groupId>
|
||
<artifactId>spring-boot-starter-parent</artifactId>
|
||
<version>1.3.2.RELEASE</version>
|
||
</parent>
|
||
|
||
<properties>
|
||
<start-class>com.example.SampleTask</start-class>
|
||
</properties>
|
||
|
||
<dependencies>
|
||
<dependency>
|
||
<groupId>org.springframework.boot</groupId>
|
||
<artifactId>spring-boot-starter</artifactId>
|
||
</dependency>
|
||
</dependencies>
|
||
|
||
<build>
|
||
<plugins>
|
||
<plugin>
|
||
<groupId>org.springframework.boot</groupId>
|
||
<artifactId>spring-boot-maven-plugin</artifactId>
|
||
</plugin>
|
||
</plugins>
|
||
</build>
|
||
</project></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This should give you a working build. You can test it out by running <code>mvn package</code> (you
|
||
can ignore the "jar will be empty - no content was marked for inclusion!" warning for
|
||
now).</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
At this point you could import the project into an IDE (most modern Java IDE’s
|
||
include built-in support for Maven). For simplicity we will continue to use a plain text
|
||
editor for this example.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="getting-started-adding-classpath-dependencies">Adding classpath dependencies</h4>
|
||
<div class="paragraph">
|
||
<p>A Spring Cloud Task is made up of a Spring Boot application that is expected to end. In
|
||
our POM above, we created the shell of a Spring Boot application from a dependency
|
||
perspective by setting our parent to use the <code>spring-boot-starter-parent</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spring Boot provides a number of additional "Starter POMs". Some of which are appropriate
|
||
for use within tasks (<code>spring-boot-starter-batch</code>, <code>spring-boot-starter-jdbc</code>, etc) and
|
||
some may not be ('spring-boot-starter-web` is probably not going to be used in a task).
|
||
The indicator of if a starter makes sense or not comes down to if the resulting
|
||
application will end (batch based applications typically end, the
|
||
<code>spring-boot-starter-web</code> dependency bootstraps a servlet container which probably wont').</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>For this example, we’ll only need to add a single additional dependency, the one for
|
||
Spring Cloud Task itself:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-xml" data-lang="xml"> <dependency>
|
||
<groupId>org.springframework.cloud</groupId>
|
||
<artifactId>spring-cloud-task-core</artifactId>
|
||
<version>1.0.0.BUILD-SNAPSHOT</version>
|
||
</dependency></code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="getting-started-writing-the-code">Writing the code</h4>
|
||
<div class="paragraph">
|
||
<p>To finish our application, we need to create a single Java file. Maven will compile the
|
||
sources from <code>src/main/java</code> by default so you need to create that folder structure. Then
|
||
add a file named <code>src/main/java/com/example/SampleTask.java</code>:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">package com.example;
|
||
|
||
import org.springframework.boot.*;
|
||
import org.springframework.boot.autoconfigure.SpringBootApplication;
|
||
import org.springframework.cloud.task.configuration.EnableTask;
|
||
import org.springframework.context.annotation.Bean;
|
||
|
||
@SpringBootApplication
|
||
@EnableTask
|
||
public class SampleTask {
|
||
|
||
@Bean
|
||
public CommandLineRunner commandLineRunner() {
|
||
return new HelloWorldCommandLineRunner();
|
||
}
|
||
|
||
public static void main(String[] args) {
|
||
SpringApplication.run(SampleTask.class, args);
|
||
}
|
||
|
||
public static class HelloWorldCommandLineRunner implements CommandLineRunner {
|
||
|
||
@Override
|
||
public void run(String... strings) throws Exception {
|
||
System.out.println("Hello World!");
|
||
}
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>While it may not look like much, quite a bit is going on. To read more about the Spring
|
||
Boot specifics, take a look at their reference documentation here:
|
||
<a href="http://docs.spring.io/spring-boot/docs/current/reference/html/">http://docs.spring.io/spring-boot/docs/current/reference/html/</a></p>
|
||
</div>
|
||
<div class="sect4">
|
||
<h5 id="getting-started-at-task">The @EnableTask annotation</h5>
|
||
<div class="paragraph">
|
||
<p>The first non boot annotation in our example is the <code>@EnableTask</code> annotation. This class
|
||
level annotation tells Spring Cloud Task to bootstrap it’s functionality. This occurs by
|
||
importing an additional configuration class, <code>SimpleTaskConfiguration</code> by default. This
|
||
additional configuration registers the <code>TaskRepository</code> and the infrastructure for its
|
||
use.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Out of the box, the <code>TaskRepository</code> will use an in memory <code>Map</code> to record the results
|
||
of a task. Obviously this isn’t a practical solution for a production environment since
|
||
the <code>Map</code> goes away once the task ends. However, for a quick getting started
|
||
experience we use this as a default as well as echoing to the logs what is being updated
|
||
in that repository. Later in this documentation we’ll cover how to customize the
|
||
configuration of the pieces provided by Spring Cloud Task.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>When our sample application is run, Spring Boot will launch our
|
||
<code>HelloWorldCommandLineRunner</code> outputting our "Hello World!" message to standard out. The
|
||
<code>TaskLifecyceListener</code> will record the start of the task and the end of the task in the
|
||
repository.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect4">
|
||
<h5 id="getting-started-main-method">The main method</h5>
|
||
<div class="paragraph">
|
||
<p>The main method serves as the entry point to any java application. Our main method
|
||
delegates to Spring Boot’s <code>SpringApplication</code> class. You can read more about it in the
|
||
Spring Boot documentation.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect4">
|
||
<h5 id="getting-started-clr">The CommandLineRunner</h5>
|
||
<div class="paragraph">
|
||
<p>In Spring, there are many ways to bootstrap an application’s logic. Spring Boot provides
|
||
a convenient method of doing so in an organized manor via their <code>*Runner</code> interfaces
|
||
(<code>CommandLineRunner</code> or <code>ApplicationRunner</code>). A well behaved task will bootstrap any
|
||
logic via one of these two runners.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The lifecycle of a task is considered from before the <code>*Runner#run</code> methods are executed
|
||
to once they are all complete. Spring Boot allows an application to use multiple
|
||
<code>*Runner</code> implementation and Spring Cloud Task doesn’t attempt to impede on this convention.</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
Any processing bootstrapped from mechanisms other than a <code>CommandLineRunner</code> or
|
||
<code>ApplicationRunner</code> (using <code>InitializingBean#afterPropertiesSet</code> for example) will not be
|
||
recorded by Spring Cloud Task.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="getting-started-running-the-example">Running the example</h4>
|
||
<div class="paragraph">
|
||
<p>At this point, your application should work. Since this application is Spring Boot based,
|
||
we can run it from the command line via the command <code>$ mvn spring-boot:run</code> from the root
|
||
of our applicaiton:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code>$ mvn clean spring-boot:run
|
||
....... . . .
|
||
....... . . . (Maven log output here)
|
||
....... . . .
|
||
|
||
|
||
. ____ _ __ _ _
|
||
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
|
||
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
|
||
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
|
||
' |____| .__|_| |_|_| |_\__, | / / / /
|
||
=========|_|==============|___/=/_/_/_/
|
||
:: Spring Boot :: (v1.3.2.RELEASE)
|
||
|
||
2016-01-25 11:08:10.183 INFO 12943 --- [ main] com.example.SampleTask : Starting SampleTask on Michaels-MacBook-Pro-2.local with PID 12943 (/Users/mminella/Documents/IntelliJWorkspace/spring-cloud-task-example/target/classes started by mminella in /Users/mminella/Documents/IntelliJWorkspace/spring-cloud-task-example)
|
||
2016-01-25 11:08:10.185 INFO 12943 --- [ main] com.example.SampleTask : No active profile set, falling back to default profiles: default
|
||
2016-01-25 11:08:10.226 INFO 12943 --- [ main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@2a2c3676: startup date [Mon Jan 25 11:08:10 CST 2016]; root of context hierarchy
|
||
2016-01-25 11:08:11.051 INFO 12943 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
|
||
2016-01-25 11:08:11.065 INFO 12943 --- [ main] o.s.c.t.r.support.SimpleTaskRepository : Creating: TaskExecution{executionId=0, externalExecutionID='null', exitCode=0, taskName='application', startTime=Mon Jan 25 11:08:11 CST 2016, endTime=null, statusCode='null', exitMessage='null', parameters=[]}
|
||
Hello World!
|
||
2016-01-25 11:08:11.071 INFO 12943 --- [ main] com.example.SampleTask : Started SampleTask in 1.095 seconds (JVM running for 3.826)
|
||
2016-01-25 11:08:11.220 INFO 12943 --- [ Thread-1] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@2a2c3676: startup date [Mon Jan 25 11:08:10 CST 2016]; root of context hierarchy
|
||
2016-01-25 11:08:11.222 INFO 12943 --- [ Thread-1] o.s.c.t.r.support.SimpleTaskRepository : Updating: TaskExecution{executionId=0, externalExecutionID='null', exitCode=0, taskName='application', startTime=Mon Jan 25 11:08:11 CST 2016, endTime=Mon Jan 25 11:08:11 CST 2016, statusCode='null', exitMessage='null', parameters=[]}
|
||
2016-01-25 11:08:11.222 INFO 12943 --- [ Thread-1] o.s.j.e.a.AnnotationMBeanExporter : Unregistering JMX-exposed beans on shutdown</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you notice, there are three lines of interest in the above output:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>SimpleTaskRepository</code> logged out the creation of the entry in the <code>TaskRepository</code>.</p>
|
||
</li>
|
||
<li>
|
||
<p>The execution of our <code>CommandLineRunner</code>, demonstrated by the "Helo World!" output.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>SimpleTaskREpository</code> logging the completion of the task in the <code>TaskRepository</code>.</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="features">Features</h2>
|
||
<div class="sectionbody">
|
||
<div id="partintro" class="openblock">
|
||
<div class="content">
|
||
<div class="paragraph">
|
||
<p>This section goes into more detail about Spring Cloud Task. How to use it, how to
|
||
configure it, as well as the appropriate extension points are all covered in this section.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="features-lifecycle">The lifecycle of a Spring Cloud Task</h3>
|
||
<div class="paragraph">
|
||
<p>In most cases, the modern cloud environment is designed around the execution of processes
|
||
that are not expected to end. If they do, they are typically restarted. While most
|
||
platforms do have some method to execute a process that isn’t restarted when it ends, the
|
||
results of that execution are typically not maintained in a consumable way. Spring Cloud
|
||
Task brings the ability to execute short lived processes in an environment and record the
|
||
results. This allows for a microservices architecture around short lived processes as
|
||
well as longer running services.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>While this functionality is useful in a cloud environment, the same issues can arise in a
|
||
traditional deployment model as well. When executing Spring Boot applications via a
|
||
scheduler like cron, it can be useful to be able to monitor the results of the application
|
||
after it’s completion.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>A Spring Cloud Task takes the approach that a Spring Boot application can have a start and an
|
||
end and still be successful. Batch applications are just one example of where short lived
|
||
processes can be helpful. Spring Cloud Task records lifecycle events of a given task.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The lifecycle consists of a single task execution. This is a physical execution of a
|
||
Spring Boot application configured to be a task (annotated with the <code>@EnableTask</code>
|
||
annotation).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>At the beginning of a task, an entry in the <code>TaskRepository</code> is created recording the
|
||
start event. This event is triggered via the <code>ContextRefreshEvent</code> being triggered by
|
||
Spring Framework.</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
As Spring Cloud Task is expected to consist of a single application context. If
|
||
multiple application contexts are used (parent/child relationships for example), the first
|
||
<code>ContextRefreshEvent</code> that is published by Spring will be recorded as the start of the
|
||
task.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
The recording of a task will only occur upon the successful bootstrapping of an
|
||
<code>ApplicationContext</code>. If the context fails to bootstrap at all, the task’s execution will
|
||
not be recorded.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Upon completion of all of the <code>*Runner#run</code> calls from Spring Boot or the failure of an
|
||
<code>ApplicationContext</code> (indicated via a <code>ApplicationFailedEvent</code>), the task execution is
|
||
updated in the repository with the results.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="features-task-execution-details">The TaskExecution</h4>
|
||
<div class="paragraph">
|
||
<p>The information stored in the <code>TaskRepository</code> is modeled in the <code>TaskExecution</code> class and
|
||
consists of the following information:</p>
|
||
</div>
|
||
<table class="tableblock frame-all grid-all spread">
|
||
<colgroup>
|
||
<col style="width: 50%;">
|
||
<col style="width: 50%;">
|
||
</colgroup>
|
||
<thead>
|
||
<tr>
|
||
<th class="tableblock halign-left valign-top">Field</th>
|
||
<th class="tableblock halign-left valign-top">Description</th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>executionid</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">The unique id for the task’s execution.</p></td>
|
||
</tr>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>exitCode</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">The exit code generated from an <code>ExitCodeExceptionMapper</code> implementation. If there is no
|
||
exit code generated, but an <code>ApplicationFailedEvent</code> is thrown, 1 is set. Otherwise, it’s
|
||
assumed to be 0.</p></td>
|
||
</tr>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>taskName</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">The name for the task as determined by the configured <code>TaskNameResolver</code>.</p></td>
|
||
</tr>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>starTime</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">The time the task was started as indicated by the <code>ContextRefreshEvent</code>.</p></td>
|
||
</tr>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>endTime</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">The time the task was completed as indicated by the <code>ContextClosedEvent</code>.</p></td>
|
||
</tr>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>exitMessage</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">Any information available at the time of exit. If an exception is the cause of the end
|
||
of the task (as indicated via an <code>ApplicationFailedEvent</code>), the stack trace for that
|
||
exception will be stored here.</p></td>
|
||
</tr>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>parameters</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">A <code>List</code> of the string parameters as they were passed into the executable boot
|
||
application.</p></td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="features-lifecycle-exit-codes">Mapping Exit Codes</h4>
|
||
<div class="paragraph">
|
||
<p>When a task completes, it will want to return an exit code to the OS. If we take a look
|
||
at our original example, we can see that we are not controlling that aspect of our
|
||
application. So if an exception is thrown, the JVM will return a code that may or may not
|
||
be of any use to you in the debugging of that.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>As such, Spring Boot provides an interface, <code>ExitCodeExceptionMapper</code> that allows you to
|
||
map uncaught exceptions to exit codes. This allows you to be able to indicate at that
|
||
level what went wrong. Also, by mapping exit codes in this manor, Spring Cloud Task will
|
||
record the exit code returned.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="features-configuration">Configuration</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Task provides an out of the box configuration as defined in the
|
||
<code>DefaultTaskConfigurer</code> and <code>SimpleTaskConfiguration</code>. This section will walk through
|
||
the defaults as well as how to customize Spring Cloud Task for your needs</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="features-data-source">DataSource</h4>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Task utilizes a datasource for storing the results of task executions. By
|
||
default, we provide an in memory instance of H2 to provide a simple method of
|
||
bootstrapping development. However, in a production environment, you’ll want to configure
|
||
your own <code>DataSource</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If your application utilizes only a single <code>DataSource</code> and that will serve as both your
|
||
business schema as well as the task repository, all you need to do is provide any
|
||
<code>DataSource</code> (via Spring Boot’s configuration conventions is the easiest way). This will
|
||
be automatically used by Spring Cloud Task for the repository.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If your application utilizes more than one <code>DataSource</code>, you’ll need to configure the
|
||
task repository with the appropriate <code>DataSource</code>. This customization can be done via an
|
||
implementation of the <code>TaskConfigurer</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="features-task-configurer">TaskConfigurer</h4>
|
||
<div class="paragraph">
|
||
<p>The <code>TaskConfigurer</code> is a strategy interface allowing for users to customize the way
|
||
components of Spring Cloud Task are configured. By default, we provide the
|
||
<code>DefaultTaskConfigurer</code> that provides logical defaults (<code>Map</code> based in memory components
|
||
useful for development if no <code>DataSource</code> is provided and JDBC based components if there
|
||
is a <code>DataSource</code> available.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>TaskConfigurer</code> allows the configuration of three main components:</p>
|
||
</div>
|
||
<table class="tableblock frame-all grid-all spread">
|
||
<colgroup>
|
||
<col style="width: 33%;">
|
||
<col style="width: 33%;">
|
||
<col style="width: 33%;">
|
||
</colgroup>
|
||
<thead>
|
||
<tr>
|
||
<th class="tableblock halign-left valign-top">Component</th>
|
||
<th class="tableblock halign-left valign-top">Description</th>
|
||
<th class="tableblock halign-left valign-top">Default (provided by <code>DefaultTaskConfigurer</code>)</th>
|
||
</tr>
|
||
</thead>
|
||
<tbody>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>TaskRepository</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">The implementation of the <code>TaskRepository</code> to be used.</p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>SimpleTaskRepository</code></p></td>
|
||
</tr>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>TaskExplorer</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">The implementation of the <code>TaskExplorer</code> (a component for read only access to the task
|
||
repository) to be used.</p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>SimpleTaskExplorer</code></p></td>
|
||
</tr>
|
||
<tr>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>PlatformTransactionManager</code></p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock">A transaction manager to be used when executing updates for tasks.</p></td>
|
||
<td class="tableblock halign-left valign-top"><p class="tableblock"><code>DataSourceTransactionManager</code> if a <code>DataSource</code> is used,
|
||
<code>ResourcelessTransactionManager</code> if it is not.</p></td>
|
||
</tr>
|
||
</tbody>
|
||
</table>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="features-task-name">Task Name</h4>
|
||
<div class="paragraph">
|
||
<p>In most cases, the name of the task will be the application name as configured via Spring
|
||
Boot. However, there are some cases, where you may want to map the run of a task to a
|
||
different name. Spring Data Flow is an example of this (where you want the task to be run
|
||
with the name of the task definition). Because of this, we offer the ability to customize
|
||
how the task is named via the <code>TaskNameResolver</code> interface.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>By default, Spring Cloud Task provides the <code>SimpleTaskNameResolver</code> which will use the
|
||
following options (in order of precedence):</p>
|
||
</div>
|
||
<div class="olist arabic">
|
||
<ol class="arabic">
|
||
<li>
|
||
<p>A Spring Boot property (configured any of the ways Spring Boot allows)
|
||
<code>spring.cloud.task.name</code>.</p>
|
||
</li>
|
||
<li>
|
||
<p>The application name as resolved using Spring Boot’s rules (obtained via
|
||
<code>ApplicationContext#getId</code>).</p>
|
||
</li>
|
||
</ol>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_bus" class="sect0">Spring Cloud Bus</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Bus links nodes of a distributed system with a lightweight message broker. This can then be used to broadcast state changes (e.g. configuration changes) or other management instructions. A key idea is that the Bus is like a distributed Actuator for a Spring Boot application that is scaled out, but it can also be used as a communication channel between apps. The only implementation currently is with an AMQP broker as the transport, but the same basic feature set (and some more depending on the transport) is on the roadmap for other transports.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><a href="https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/contributing-docs.adoc" class="bare">https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/contributing-docs.adoc</a></p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_quick_start_2">Quick Start</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Bus works by adding Spring Boot autconfiguration if it detects itself on the classpath. All you need to do to enable the bus is to add <code>spring-cloud-starter-bus-amqp</code> to your dependency management and Spring Cloud takes care of the rest. Make sure RabbitMQ is available and configured to provide a <code>ConnectionFactory</code>: running on localhost you shouldn’t have to do anything, but if you are running remotely use Spring Cloud Connectors, or Spring Boot conventions to define the broker credentials, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
rabbitmq:
|
||
host: mybroker.com
|
||
port: 5672
|
||
username: user
|
||
password: secret</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The bus currently supports sending messages to all nodes listening or all nodes for a particular service (as defined by Eureka). More selector criteria will be added in the future (ie. only service X nodes in data center Y, etc…​). The http endpoints are under the <code>/bus/*</code> actuator namespace. There are currently two implemented. The first, <code>/bus/env</code>, sends key/values pairs to update each nodes Spring Environment. The second, <code>/bus/refresh</code>, will reload each application’s configuration, just as if they had all been pinged on their <code>/refresh</code> endpoint.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_addressing_an_instance">Addressing an Instance</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>The HTTP endpoints accept a "destination" parameter, e.g. "/bus/refresh?destination=customers:9000", where the destination is an <code>ApplicationContext</code> ID. If the ID is owned by an instance on the Bus then it will process the message and all other instances will ignore it. Spring Boot sets the ID for you in the <code>ContextIdApplicationContextInitializer</code> to a combination of the <code>spring.application.name</code>, active profiles and <code>server.port</code> by default.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_addressing_all_instances_of_a_service">Addressing all instances of a service</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>The "destination" parameter is used in a Spring <code>PathMatcher</code> (with the path separator as a colon <code>:</code>) to determine if an instance will process the message. Using the example from above, "/bus/refresh?destination=customers:**" will target all instances of the "customers" service regardless of the profiles and ports set as the <code>ApplicationContext</code> ID.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_application_context_id_must_be_unique">Application Context ID must be unique</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>The bus tries to eliminate processing an event twice, once from the original <code>ApplicationEvent</code> and once from the queue. To do this, it checks the sending application context id againts the current application context id. If multiple instances of a service have the same application context id, events will not be processed. Running on a local machine, each service will be on a different port and that will be part of the application context id. Cloud Foundry supplies an index to differentiate. To ensure that the application context id is the unique, set <code>spring.application.index</code> to something unique for each instance of a service. For example, in lattice, set <code>spring.application.index=${INSTANCE_INDEX}</code> in application.properties (or bootstrap.properties if using configserver).</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_customizing_the_message_broker">Customizing the Message Broker</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Bus uses
|
||
<a href="https://cloud.spring.io/spring-cloud-stream">Spring Cloud Stream</a> to
|
||
broadcast the messages so to get messages to flow you only need to
|
||
include the binder implementation of your choice in the
|
||
classpath. There are convenient starters specifically for the bus with
|
||
AMQP, Kafka and Redis
|
||
(<code>spring-cloud-starter-bus-[amqp,kafka,redis]</code>). Generally speaking
|
||
Spring Cloud Stream relies on Spring Boot autoconfiguration
|
||
conventions for configuring middleware, so for instance the AMQP
|
||
broker address can be changed with <code>spring.rabbitmq.*</code>
|
||
configuration properties. Spring Cloud Bus has a handful of native
|
||
configuration properties in <code>spring.cloud.bus.*</code>
|
||
(e.g. <code>spring.cloud.bus.destination</code> is the name of the topic to use
|
||
the the externall middleware). Normally the defaults will suffice.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To lean more about how to customize the message broker settings
|
||
consult the Spring Cloud Stream documentation.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_tracing_bus_events">Tracing Bus Events</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Bus events (subclasses of <code>RemoteApplicationEvent</code>) can be traced by
|
||
setting <code>spring.cloud.bus.trace.enabled=true</code>. If you do this then the
|
||
Spring Boot <code>TraceRepository</code> (if it is present) will show each event
|
||
sent and all the acks from each service instance. Example (from the
|
||
<code>/trace</code> endpoint):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-json" data-lang="json">{
|
||
"timestamp": "2015-11-26T10:24:44.411+0000",
|
||
"info": {
|
||
"signal": "spring.cloud.bus.ack",
|
||
"type": "RefreshRemoteApplicationEvent",
|
||
"id": "c4d374b7-58ea-4928-a312-31984def293b",
|
||
"origin": "stores:8081",
|
||
"destination": "*:**"
|
||
}
|
||
},
|
||
{
|
||
"timestamp": "2015-11-26T10:24:41.864+0000",
|
||
"info": {
|
||
"signal": "spring.cloud.bus.sent",
|
||
"type": "RefreshRemoteApplicationEvent",
|
||
"id": "c4d374b7-58ea-4928-a312-31984def293b",
|
||
"origin": "customers:9000",
|
||
"destination": "*:**"
|
||
}
|
||
},
|
||
{
|
||
"timestamp": "2015-11-26T10:24:41.862+0000",
|
||
"info": {
|
||
"signal": "spring.cloud.bus.ack",
|
||
"type": "RefreshRemoteApplicationEvent",
|
||
"id": "c4d374b7-58ea-4928-a312-31984def293b",
|
||
"origin": "customers:9000",
|
||
"destination": "*:**"
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This trace shows that a <code>RefreshRemoteApplicationEvent</code> was sent from
|
||
<code>customers:9000</code>, broadcast to all services, and it was received
|
||
(acked) by <code>customers:9000</code> and <code>stores:8081</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To handle the ack signals yourself you could add an <code>@EventListener</code>
|
||
for the <code>AckRemoteAppplicationEvent</code> and <code>SentApplicationEvent</code> types
|
||
to your app (and enable tracing). Or you could tap into the
|
||
<code>TraceRepository</code> and mine the data from there.</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
Any Bus application can trace acks, but sometimes it will be
|
||
useful to do this in a central service that can do more complex
|
||
queries on the data. Or forward it to a specialized tracing service.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_sleuth" class="sect0">Spring Cloud Sleuth</h1>
|
||
<div class="sect1">
|
||
<h2 id="_spring_cloud_sleuth_2">Spring Cloud Sleuth</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Sleuth implements a distributed tracing solution for <a href="http://cloud.spring.io">Spring Cloud</a>.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_terminology">Terminology</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Sleuth borrows <a href="http://research.google.com/pubs/pub36356.html">Dapper’s</a> terminology.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><strong>Span:</strong> The basic unit of work. For example, sending an RPC is a new span, as is sending a response to an RPC. Span’s are identified by a unique 64-bit ID for the span and another 64-bit ID for the trace the span is a part of. Spans also have other data, such as descriptions, timestamped events, key-value annotations (tags), the ID of the span that caused them, and process ID’s (normally IP address).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spans are started and stopped, and they keep track of their timing information. Once you create a span, you must stop it at some point in the future.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><strong>Trace:</strong> A set of spans forming a tree-like structure. For example, if you are running a distributed big-data store, a trace might be formed by a put request.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_features_2">Features</h2>
|
||
<div class="sectionbody">
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>Adds trace and span ids to the Slf4J MDC, so you can extract all the logs from a given trace or span in a log aggregator. Example logs:</p>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>2016-02-02 15:30:57.902 INFO [bar,6bfd228dc00d216b,6bfd228dc00d216b,false] 23030 --- [nio-8081-exec-3] ...
|
||
2016-02-02 15:30:58.372 ERROR [bar,6bfd228dc00d216b,6bfd228dc00d216b,false] 23030 --- [nio-8081-exec-3] ...
|
||
2016-02-02 15:31:01.936 INFO [bar,46ab0d418373cbc9,46ab0d418373cbc9,false] 23030 --- [nio-8081-exec-4] ...</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>(notice the <code>[appname,traceId,spanId,exportable]</code> entries from the MDC).</p>
|
||
</div>
|
||
</li>
|
||
<li>
|
||
<p>Optionally log span data in JSON format for harvesting in a log aggregator (set <code>spring.sleuth.log.json.enabled=true</code>).</p>
|
||
</li>
|
||
<li>
|
||
<p>Provides an abstraction over common distributed tracing data models: traces, spans (forming a DAG), annotations, key-value annotations. Loosely based on HTrace, but Zipkin (Dapper) compatible.</p>
|
||
</li>
|
||
<li>
|
||
<p>Instruments common ingress and egress points from Spring applications (servlet filter, rest template, scheduled actions, message channels, zuul filters, feign client).</p>
|
||
</li>
|
||
<li>
|
||
<p>If <code>spring-cloud-sleuth-zipkin</code> then the app will generate and collect Zipkin-compatible traces (using Brave). By default it sends them via HTTP to a Zipkin server on localhost (port 9411). Configure the location of the service using <code>spring.zipkin.[host,port]</code>.</p>
|
||
</li>
|
||
<li>
|
||
<p>If <code>spring-cloud-sleuth-stream</code> then the app will generate and collect traces via Spring Cloud Stream. Your app automatically becomes a producer of tracer messages that are sent over your broker of choice (e.g. RabbitMQ, Apache Kafka, Redis).</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If using Zipkin or Stream, configure the percentage of spans exported using <code>spring.sleuth.sampler.percentage</code> (default 0.1, i.e. 10%).</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_sampling">Sampling</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>In distributed tracing the data volumes can be very high so sampling
|
||
can be important (you usually don’t need to export all spans to get a
|
||
good picture of what is happening). Spring Cloud Sleuth has a
|
||
<code>Sampler</code> strategy that you can implement to take control of the
|
||
sampling algorithm. Samplers do not stop span (correlation) ids from
|
||
being generated, but they do prevent the tags and events being
|
||
attached and exported. By default you get a strategy that continues to
|
||
trace if a span is already active, but new ones are always marked as
|
||
non-exportable. If all your apps run with this sampler you will see
|
||
traces in logs, but not in any remote store. For testing the default
|
||
is often enough, and it probably is all you need if you are only using
|
||
the logs (e.g. with an ELK aggregator). If you are exporting span data
|
||
to Zipkin or Spring Cloud Stream, there is also an <code>AlwaysSampler</code>
|
||
that exports everything and a <code>PercentageBasedSampler</code> that samples a
|
||
fixed fraction of spans.</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
the <code>PercentageBasedSampler</code> is the default if you are using
|
||
<code>spring-cloud-sleuth-zipkin</code> or <code>spring-cloud-sleuth-stream</code>. You can
|
||
configure the exports using <code>spring.sleuth.sampler.percentage</code>.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>A sampler can be installed just by creating a bean definition, e.g:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Bean
|
||
public Sampler<?> defaultSampler() {
|
||
return new AlwaysSampler();
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_instrumentation">Instrumentation</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Sleuth instruments all your Spring application
|
||
automatically, so you shouldn’t have to do anything to activate
|
||
it. The instrumentation is added using a variety of technologies
|
||
according to the stack that is available, e.g. for a servlet web
|
||
application we use a <code>Filter</code>, and for Spring Integration we use
|
||
<code>ChannelInterceptors</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can customize the keys used in span tags. To limit the volume of
|
||
span data, by default an HTTP request will be tagged only with a
|
||
handful of metadata like the status code, host and URL. You can add
|
||
request headers by configuring <code>spring.sleuth.keys.http.headers</code> (a
|
||
list of header names).</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
Remember that tags are only collected and exported if there is a
|
||
<code>Sampler</code> that allows it (by default there is not, so there is no
|
||
danger of accidentally collecting too much data without configuring
|
||
something).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_span_data_as_messages">Span Data as Messages</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>You can accumulate and send span data over
|
||
<a href="http://cloud.spring.io/spring-cloud-stream">Spring Cloud Stream</a> by
|
||
including the <code>spring-cloud-sleuth-stream</code> jar as a dependency, and
|
||
adding a Channel Binder implementation
|
||
(e.g. <code>spring-cloud-starter-stream-rabbit</code> for RabbitMQ or
|
||
<code>spring-cloud-starter-stream-kafka</code> for Kafka). This will
|
||
automatically turn your app into a producer of messages with payload
|
||
type <code>Spans</code>.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_zipkin_consumer">Zipkin Consumer</h3>
|
||
<div class="paragraph">
|
||
<p>There is a special convenience annotation for setting up a message consumer
|
||
for the Span data and pushing it into a Zipkin <code>SpanStore</code>. This application</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@SpringBootApplication
|
||
@EnableZipkinStreamServer
|
||
public class Consumer {
|
||
public static void main(String[] args) {
|
||
SpringApplication.run(Consumer.class, args);
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>will listen for the Span data on whatever transport you provide via a
|
||
Spring Cloud Stream <code>Binder</code> (e.g. include
|
||
<code>spring-cloud-starter-stream-rabbit</code> for RabbitMQ, and similar
|
||
starters exist for Redis and Kafka). The app will also be a
|
||
<a href="https://github.com/openzipkin/zipkin-java">Zipkin query server</a>, so you
|
||
can point a standard Zipkin UI at it (e.g. run the consumer app on
|
||
port 9411 if you want the query server on the same host and the
|
||
default configuration).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The deafult <code>SpanStore</code> is in-memory (good for demos and getting
|
||
started quickly). For a more robust solution you can add MySQL and
|
||
<code>spring-boot-starter-jdbc</code> to your classpath and enable the JDBC
|
||
<code>SpanStore</code> via configuration, e.g.:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
rabbitmq:
|
||
host: ${RABBIT_HOST:localhost}
|
||
datasource:
|
||
schema: classpath:/mysql.sql
|
||
url: jdbc:mysql://${MYSQL_HOST:localhost}/test
|
||
username: root
|
||
password: root
|
||
# Switch this on to create the schema on startup:
|
||
initialize: true
|
||
continueOnError: true
|
||
sleuth:
|
||
enabled: false
|
||
zipkin:
|
||
store:
|
||
type: mysql</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
The <code>@EnableZipkinStreamServer</code> is also annotated with
|
||
<code>@EnableZipkinServer</code> so the process will also expose the standard
|
||
Zipkin server endpoints for collecting spans over HTTP, and for
|
||
querying in the Zipkin Web UI.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_custom_consumer">Custom Consumer</h3>
|
||
<div class="paragraph">
|
||
<p>A custom consumer can also easily be implemented using
|
||
<code>spring-cloud-sleuth-stream</code> and binding to the <code>SleuthSink</code>. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@EnableBinding(SleuthSink.class)
|
||
@SpringBootApplication(exclude = SleuthStreamAutoConfiguration.class)
|
||
@MessageEndpoint
|
||
public class Consumer {
|
||
|
||
@ServiceActivator(inputChannel = SleuthSink.INPUT)
|
||
public void sink(Spans input) throws Exception {
|
||
// ... process spans
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
the sample consumer application above explicitly excludes
|
||
<code>SleuthStreamAutoConfiguration</code> so it doesn’t send messages to itself,
|
||
but this is optional (you might actually want to trace requests into
|
||
the consumer app).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_consul" class="sect0">Spring Cloud Consul</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
This project provides Consul integrations for Spring Boot apps through autoconfiguration
|
||
and binding to the Spring Environment and other Spring programming model idioms. With a few
|
||
simple annotations you can quickly enable and configure the common patterns inside your
|
||
application and build large distributed systems with Consul based components. The
|
||
patterns provided include Service Discovery, Control Bus and Configuration.
|
||
Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon), Circuit Breaker
|
||
(Hystrix) are provided by integration with Spring Cloud Netflix.
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-consul-install">Install Consul</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Please see the <a href="https://www.consul.io/intro/getting-started/install.html">installation documentation</a> for instructions on how to install Consul.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-consul-agent">Consul Agent</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>A Consul Agent client must be available to all Spring Cloud Consul applications. By default, the Agent client is expected to be at <code>localhost:8500</code>. See the <a href="https://consul.io/docs/agent/basics.html">Agent documentation</a> for specifics on how to start an Agent client and how to connect to a cluster of Consul Agent Servers. For development, after you have installed consul, you may start a Consul Agent using the following command:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>./src/main/bash/local_run_consul.sh</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This will start an agent in server mode on port 8500, with the ui available at <a href="http://localhost:8500" class="bare">http://localhost:8500</a></p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-consul-discovery">Service Discovery with Consul</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Service Discovery is one of the key tenets of a microservice based architecture. Trying to hand configure each client or some form of convention can be very difficult to do and can be very brittle. Consul provides Service Discovery services via an <a href="https://www.consul.io/docs/agent/http.html">HTTP API</a> and <a href="https://www.consul.io/docs/agent/dns.html">DNS</a>. Spring Cloud Consul leverages the HTTP API for service registration and discovery. This does not prevent non-Spring Cloud applications from leveraging the DNS interface. Consul Agents servers are run in a <a href="https://www.consul.io/docs/internals/architecture.html">cluster</a> that communicates via a <a href="https://www.consul.io/docs/internals/gossip.html">gossip protocol</a> and uses the <a href="https://www.consul.io/docs/internals/consensus.html">Raft consensus protocol</a>.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_registering_with_consul">Registering with Consul</h3>
|
||
<div class="paragraph">
|
||
<p>When a client registers with Consul, it provides meta-data about itself such as host and port, id, name and tags. An HTTP <a href="https://www.consul.io/docs/agent/checks.html">Check</a> is created by default that Consul hits the <code>/health</code> endpoint every 10 seconds. If the health check fails, the service instance is marked as critical.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Example Consul client:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@SpringBootApplication
|
||
@EnableDiscoveryClient
|
||
@RestController
|
||
public class Application {
|
||
|
||
@RequestMapping("/")
|
||
public String home() {
|
||
return "Hello world";
|
||
}
|
||
|
||
public static void main(String[] args) {
|
||
new SpringApplicationBuilder(Application.class).web(true).run(args);
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>(i.e. utterly normal Spring Boot app). If the Consul client is located somewhere other than <code>localhost:8500</code>, the configuration is required to locate the client. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
cloud:
|
||
consul:
|
||
host: localhost
|
||
port: 8500</pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock caution">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Caution</div>
|
||
</td>
|
||
<td class="content">
|
||
If you use <a href="#spring-cloud-consul-config">Spring Cloud Consul Config</a>, the above values will need to be placed in <code>bootstrap.yml</code> instead of <code>application.yml</code>.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The default service name, instance id and port, taken from the <code>Environment</code>, are <code>${spring.application.name}</code>, the Spring Context ID and <code>${server.port}</code> respectively.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><code>@EnableDiscoveryClient</code> make the app into both a Consul "service" (i.e. it registers itself) and a "client" (i.e. it can query Consul to locate other services).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_http_health_check">HTTP Health Check</h3>
|
||
<div class="paragraph">
|
||
<p>The health check for a Consul instance defaults to "/health", which is the default locations of a useful endpoint in a Spring Boot Actuator application. You need to change these, even for an Actuator application if you use a non-default context path or servlet path (e.g. <code>server.servletPath=/foo</code>) or management endpoint path (e.g. <code>management.contextPath=/admin</code>). The interval that Consul uses to check the health endpoint may also be configured. "10s" and "1m" represent 10 seconds and 1 minute respectively. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
cloud:
|
||
consul:
|
||
discovery:
|
||
healthCheckPath: ${management.contextPath}/health
|
||
healthCheckInterval: 15s</pre>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_making_the_consul_instance_id_unique">Making the Consul Instance ID Unique</h4>
|
||
<div class="paragraph">
|
||
<p>By default a consul instance is registered with an ID that is equal to its Spring Application Context ID. By default, the Spring Application Context ID is <code>${spring.application.name}:comma,separated,profiles:${server.port}</code>. For most cases, this will allow multiple instances of one service to run on one machine. If further uniqueness is required, Using Spring Cloud you can override this by providing a unique identifier in <code>spring.cloud.consul.discovery.instanceId</code>. For example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
cloud:
|
||
consul:
|
||
discovery:
|
||
instanceId: ${spring.application.name}:${spring.application.instance_id:${random.value}}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>With this metadata, and multiple service instances deployed on localhost, the random value will kick in there to make the instance unique. In Cloudfoundry the <code>spring.application.instance_id</code> will be populated automatically in a Spring Boot Actuator application, so the random value will not be needed.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_using_the_discoveryclient">Using the DiscoveryClient</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud has support for <a href="https://github.com/spring-cloud/spring-cloud-netflix/blob/master/docs/src/main/asciidoc/spring-cloud-netflix.adoc#spring-cloud-feign">Feign</a> (a REST client builder) and also <a href="https://github.com/spring-cloud/spring-cloud-netflix/blob/master/docs/src/main/asciidoc/spring-cloud-netflix.adoc#spring-cloud-ribbon">Spring <code>RestTemplate</code></a> using the logical service names instead of physical URLs.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can also use the <code>org.springframework.cloud.client.discovery.DiscoveryClient</code> which provides a simple API for discovery clients that is not specific to Netflix, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>@Autowired
|
||
private DiscoveryClient discoveryClient;
|
||
|
||
public String serviceUrl() {
|
||
List<ServiceInstance> list = client.getInstances("STORES");
|
||
if (list != null && list.size() > 0 ) {
|
||
return list.get(0).getUri();
|
||
}
|
||
return null;
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-consul-config">Distributed Configuration with Consul</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Consul provides a <a href="https://consul.io/docs/agent/http/kv.html">Key/Value Store</a> for storing configuration and other metadata. Spring Cloud Consul Config is an alternative to the <a href="https://github.com/spring-cloud/spring-cloud-config">Config Server and Client</a>. Configuration is loaded into the Spring Environment during the special "bootstrap" phase. Configuration is stored in the <code>/config</code> folder by default. Multiple <code>PropertySource</code> instances are created based on the application’s name and the active profiles that mimicks the Spring Cloud Config order of resolving properties. For example, an application with the name "testApp" and with the "dev" profile will have the following property sources created:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>config/testApp,dev/
|
||
config/testApp/
|
||
config/application,dev/
|
||
config/application/</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The most specific property source is at the top, with the least specific at the bottom. Properties is the <code>config/application</code> folder are applicable to all applications using consul for configuration. Properties in the <code>config/testApp</code> folder are only available to the instances of the service named "testApp".</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Configuration is currently read on startup of the application. Sending a HTTP POST to <code>/refresh</code> will cause the configuration to be reloaded. Watching the key value store (which Consul supports) is not currently possible, but will be a future addition to this project.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_how_to_activate">How to activate</h3>
|
||
<div class="paragraph">
|
||
<p>Including a dependency on <code>org.springframework.cloud:spring-cloud-consul-config</code> will enable auto-configuration that will setup Spring Cloud Consul Config.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_customizing">Customizing</h3>
|
||
<div class="paragraph">
|
||
<p>Consul Config may be customized using the following properties:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">bootstrap.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
cloud:
|
||
consul:
|
||
config:
|
||
enabled: true
|
||
prefix: configuration
|
||
defaultContext: apps
|
||
profileSeparator: '::'</pre>
|
||
</div>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>enabled</code> setting this value to "false" disables Consul Config</p>
|
||
</li>
|
||
<li>
|
||
<p><code>prefix</code> sets the base folder for configuration values</p>
|
||
</li>
|
||
<li>
|
||
<p><code>defaultContext</code> sets the folder name used by all applications</p>
|
||
</li>
|
||
<li>
|
||
<p><code>profileSeparator</code> sets the value of the separator used to separate the profile name in property sources with profiles</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-consul-config-format">YAML or Properties with Config</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>It may be more convenient to store a blob of properties in YAML or Properties format as opposed to individual key/value pairs. Set the <code>spring.cloud.consul.config.format</code> property to <code>YAML</code> or <code>PROPERTIES</code>. For example to use YAML:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">bootstrap.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
cloud:
|
||
consul:
|
||
config:
|
||
format: YAML</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>YAML must be set in the appropriate <code>data</code> key in consul. Using the defaults above the keys would look like:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>config/testApp,dev/data
|
||
config/testApp/data
|
||
config/application,dev/data
|
||
config/application/data</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You could store a YAML document in any of the keys listed above.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can change the data key using <code>spring.cloud.consul.config.data-key</code>.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-consul-retry">Consul Retry</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>If you expect that the consul agent may occasionally be unavailable when
|
||
your app starts, you can ask it to keep trying after a failure. You need to add
|
||
<code>spring-retry</code> and <code>spring-boot-starter-aop</code> to your classpath. The default
|
||
behaviour is to retry 6 times with an initial backoff interval of 1000ms and an
|
||
exponential multiplier of 1.1 for subsequent backoffs. You can configure these
|
||
properties (and others) using <code>spring.cloud.consul.retry.*</code> configuration properties.
|
||
This works with both Spring Cloud Consul Config and Discovery registration.</p>
|
||
</div>
|
||
<div class="admonitionblock tip">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Tip</div>
|
||
</td>
|
||
<td class="content">
|
||
To take full control of the retry add a <code>@Bean</code> of type
|
||
<code>RetryOperationsInterceptor</code> with id "consulRetryInterceptor". Spring
|
||
Retry has a <code>RetryInterceptorBuilder</code> that makes it easy to create one.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-consul-bus">Spring Cloud Bus with Consul</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>TODO: document Spring Cloud Consul Bus</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-consul-hystrix">Circuit Breaker with Hystrix</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Applications can use the Hystrix Circuit Breaker provided by the Spring Cloud Netflix project by including this starter in the projects pom.xml: <code>spring-cloud-starter-hystrix</code>. Hystrix doesn’t depend on the Netflix Discovery Client. The <code>@EnableHystrix</code> annotation should be placed on a configuration class (usually the main class). Then methods can be annotated with <code>@HystrixCommand</code> to be protected by a circuit breaker. See <a href="http://projects.spring.io/spring-cloud/spring-cloud.html#_circuit_breaker_hystrix_clients">the documentation</a> for more details.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-consul-turbine">Hystrix metrics aggregation with Turbine and Consul</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Turbine (provided by the Spring Cloud Netflix project), aggregates multiple instances Hystrix metrics streams, so the dashboard can display an aggregate view. Turbine uses the <code>DiscoveryClient</code> interface to lookup relevant instances. To use Turbine with Spring Cloud Consul, configure the Turbine application in a manner similar to the following examples:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">pom.xml</div>
|
||
<div class="content">
|
||
<pre><dependency>
|
||
<groupId>org.springframework.cloud</groupId>
|
||
<artifactId>spring-cloud-netflix-turbine</artifactId>
|
||
</dependency>
|
||
<dependency>
|
||
<groupId>org.springframework.cloud</groupId>
|
||
<artifactId>spring-cloud-starter-consul-discovery</artifactId>
|
||
</dependency></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Notice that the Turbine dependency is not a starter. The turbine starter includes support for Netflix Eureka.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>spring.application.name: turbine
|
||
applications: consulhystrixclient
|
||
turbine:
|
||
aggregator:
|
||
clusterConfig: ${applications}
|
||
appConfig: ${applications}</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>clusterConfig</code> and <code>appConfig</code> sections must match, so it’s useful to put the comma-separated list of service ID’s into a separate configuration property.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">Turbine.java</div>
|
||
<div class="content">
|
||
<pre>@EnableTurbine
|
||
@EnableDiscoveryClient
|
||
@SpringBootApplication
|
||
public class Turbine {
|
||
public static void main(String[] args) {
|
||
SpringApplication.run(DemoturbinecommonsApplication.class, args);
|
||
}
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_zookeeper" class="sect0">Spring Cloud Zookeeper</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
This project provides Zookeeper integrations for Spring Boot apps through autoconfiguration
|
||
and binding to the Spring Environment and other Spring programming model idioms. With a few
|
||
simple annotations you can quickly enable and configure the common patterns inside your
|
||
application and build large distributed systems with Zookeeper based components. The
|
||
patterns provided include Service Discovery and Configuration.
|
||
Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon), Circuit Breaker
|
||
(Hystrix) are provided by integration with Spring Cloud Netflix.
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-zookeeper-install">Install Zookeeper</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Please see the <a href="http://zookeeper.apache.org/doc/current/zookeeperStarted.html">installation documentation</a> for instructions on how to install Zookeeper.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-zookeeper-discovery">Service Discovery with Zookeeper</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Service Discovery is one of the key tenets of a microservice based architecture. Trying to hand configure each client or some form of convention can be very difficult to do and can be very brittle. <a href="http://curator.apache.org">Curator</a>(A java library for Zookeeper) provides Service Discovery services via <a href="http://curator.apache.org/curator-x-discovery/">Service Discovery Extension</a>. Spring Cloud Zookeeper leverages this extension for service registration and discovery.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_how_to_activate_2">How to activate</h3>
|
||
<div class="paragraph">
|
||
<p>Including a dependency on <code>org.springframework.cloud:spring-cloud-starter-zookeeper-discovery</code> will enable auto-configuration that will setup Spring Cloud Zookeeper Discovery.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_registering_with_zookeeper">Registering with Zookeeper</h3>
|
||
<div class="paragraph">
|
||
<p>When a client registers with Zookeeper, it provides meta-data about itself such as host and port, id and name.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Example Zookeeper client:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@SpringBootApplication
|
||
@EnableDiscoveryClient
|
||
@RestController
|
||
public class Application {
|
||
|
||
@RequestMapping("/")
|
||
public String home() {
|
||
return "Hello world";
|
||
}
|
||
|
||
public static void main(String[] args) {
|
||
new SpringApplicationBuilder(Application.class).web(true).run(args);
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>(i.e. utterly normal Spring Boot app). If Zookeeper is located somewhere other than <code>localhost:2181</code>, the configuration is required to locate the server. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
cloud:
|
||
zookeeper:
|
||
connect-string: localhost:2181</pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock caution">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Caution</div>
|
||
</td>
|
||
<td class="content">
|
||
If you use <a href="#spring-cloud-zookeeper-config">Spring Cloud Zookeeper Config</a>, the above values will need to be placed in <code>bootstrap.yml</code> instead of <code>application.yml</code>.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The default service name, instance id and port, taken from the <code>Environment</code>, are <code>${spring.application.name}</code>, the Spring Context ID and <code>${server.port}</code> respectively.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><code>@EnableDiscoveryClient</code> makes the app into both a Zookeeper "service" (i.e. it registers itself) and a "client" (i.e. it can query Zookeeper to locate other services).</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_using_the_discoveryclient_2">Using the DiscoveryClient</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud has support for <a href="https://github.com/spring-cloud/spring-cloud-netflix/blob/master/docs/src/main/asciidoc/spring-cloud-netflix.adoc#spring-cloud-feign">Feign</a> (a REST client builder) and also <a href="https://github.com/spring-cloud/spring-cloud-netflix/blob/master/docs/src/main/asciidoc/spring-cloud-netflix.adoc#spring-cloud-ribbon">Spring <code>RestTemplate</code></a> using the logical service names instead of physical URLs.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can also use the <code>org.springframework.cloud.client.discovery.DiscoveryClient</code> which provides a simple API for discovery clients that is not specific to Netflix, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>@Autowired
|
||
private DiscoveryClient discoveryClient;
|
||
|
||
public String serviceUrl() {
|
||
List<ServiceInstance> list = discoveryClient.getInstances("STORES");
|
||
if (list != null && list.size() > 0 ) {
|
||
return list.get(0).getUri().toString();
|
||
}
|
||
return null;
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-zookeeper-dependencies">Using the Zookeeper Dependencies</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Zookeeper gives you a possibility to provide dependencies of your application as properties. As dependencies you can understand other applications that are registered
|
||
in Zookeeper and which you would like to call via <a href="https://github.com/spring-cloud/spring-cloud-netflix/blob/master/docs/src/main/asciidoc/spring-cloud-netflix.adoc#spring-cloud-feign">Feign</a> (a REST client builder)
|
||
and also <a href="https://github.com/spring-cloud/spring-cloud-netflix/blob/master/docs/src/main/asciidoc/spring-cloud-netflix.adoc#spring-cloud-ribbon">Spring <code>RestTemplate</code></a>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can also benefit from the Zookeeper Dependency Watchers functionality that lets you control and monitor what is the state of your dependencies and decide what to do with that.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_how_to_activate_zookeeper_dependencies">How to activate Zookeeper Dependencies</h3>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>Including a dependency on <code>org.springframework.cloud:spring-cloud-starter-zookeeper-discovery</code> will enable auto-configuration that will setup Spring Cloud Zookeeper Dependencies.</p>
|
||
</li>
|
||
<li>
|
||
<p>In addition to that you have to set the property <code>spring.cloud.zookeeper.dependencies.enabled</code> to true (defaults to <code>true</code> if not set explicitly).</p>
|
||
</li>
|
||
<li>
|
||
<p>You have to have the <code>spring.cloud.zookeeper.dependencies</code> section properly set up - check the subsequent section for more details.</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_setting_up_zookeeper_dependencies">Setting up Zookeeper Dependencies</h3>
|
||
<div class="paragraph">
|
||
<p>Let’s take a closer look at an example of dependencies representation:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre>spring.application.name: yourServiceName
|
||
spring.cloud.zookeeper:
|
||
dependencies:
|
||
newsletter:
|
||
path: /path/where/newsletter/has/registered/in/zookeeper
|
||
loadBalancerType: ROUND_ROBIN
|
||
contentTypeTemplate: application/vnd.newsletter.$version+json
|
||
version: v1
|
||
headers:
|
||
header1:
|
||
- value1
|
||
header2:
|
||
- value2
|
||
required: false
|
||
stubs: org.springframework:foo:stubs
|
||
mailing:
|
||
path: /path/where/mailing/has/registered/in/zookeeper
|
||
loadBalancerType: ROUND_ROBIN
|
||
contentTypeTemplate: application/vnd.mailing.$version+json
|
||
version: v1
|
||
required: true</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Let’s now go through each part of the dependency one by one. The root property name is <code>spring.cloud.zookeeper.dependencies</code>.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_aliases">Aliases</h4>
|
||
<div class="paragraph">
|
||
<p>Below the root property you have to represent each dependency has by an alias due to the constraints of Ribbon (the application id has to be placed in the URL
|
||
thus you can’t pass any complex path like /foo/bar/name). The alias will be the name that you will use instead of serviceId for <code>DiscoveryClient</code>, <code>Feign</code> or <code>RestTemplate</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In the aforementioned examples the aliases are <code>newsletter</code> and <code>mailing</code>. Example of Feign usage with <code>newsletter</code> would be:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>@FeignClient("newsletter")
|
||
public interface NewsletterService {
|
||
@RequestMapping(method = RequestMethod.GET, value = "/newsletter")
|
||
String getNewsletters();
|
||
}</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_path">Path</h4>
|
||
<div class="paragraph">
|
||
<p>Represented by <code>path</code> yaml property.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Path is the path under which the dependency is registered under Zookeeper. Like presented before Ribbon operates on URLs thus this path is not compliant with its requirement.
|
||
That is why Spring Cloud Zookeeper maps the alias to the proper path.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_load_balancer_type">Load balancer type</h4>
|
||
<div class="paragraph">
|
||
<p>Represented by <code>loadBalancerType</code> yaml property.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you know what kind of load balancing strategy has to be applied when calling this particular dependency then you can provide it in the yaml file and it will be automatically applied.
|
||
You can choose one of the following load balancing strategies</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>STICKY - once chosen the instance will always be called</p>
|
||
</li>
|
||
<li>
|
||
<p>RANDOM - picks an instance randomly</p>
|
||
</li>
|
||
<li>
|
||
<p>ROUND_ROBIN - iterates over instances over and over again</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_content_type_template_and_version">Content-Type template and version</h4>
|
||
<div class="paragraph">
|
||
<p>Represented by <code>contentTypeTemplate</code> and <code>version</code> yaml property.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you version your api via the <code>Content-Type</code> header then you don’t want to add this header to each of your requests. Also if you want to call a new version of the API you don’t want to
|
||
roam around your code to bump up the API version. That’s why you can provide a <code>contentTypeTemplate</code> with a special <code>$version</code> placeholder. That placeholder will be filled by the value of the
|
||
<code>version</code> yaml property. Let’s take a look at an example.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Having the following <code>contentTypeTemplate</code>:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>application/vnd.newsletter.$version+json</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>and the following <code>version</code>:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>v1</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Will result in setting up of a <code>Content-Type</code> header for each request:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>application/vnd.newsletter.v1+json</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_default_headers">Default headers</h4>
|
||
<div class="paragraph">
|
||
<p>Represented by <code>headers</code> map in yaml</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Sometimes each call to a dependency requires setting up of some default headers. In order not to do that in code you can set them up in the yaml file.
|
||
Having the following <code>headers</code> section:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>headers:
|
||
Accept:
|
||
- text/html
|
||
- application/xhtml+xml
|
||
Cache-Control:
|
||
- no-cache</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Results in adding the <code>Accept</code> and <code>Cache-Control</code> headers with appropriate list of values in your HTTP request.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_obligatory_dependencies">Obligatory dependencies</h4>
|
||
<div class="paragraph">
|
||
<p>Represented by <code>required</code> property in yaml</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If one of your dependencies is required to be up and running when your application is booting then it’s enough to set up the <code>required: true</code> property in the yaml file.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If your application can’t localize the required dependency during boot time it will throw an exception and the Spring Context will fail to set up.
|
||
In other words your application won’t be able to start if the required dependency is not registered in Zookeeper.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can read more about Spring Cloud Zookeeper Presence Checker in the following sections.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_stubs">Stubs</h3>
|
||
<div class="paragraph">
|
||
<p>You can provide a colon separated path to the JAR containing stubs of the dependency. Example</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code>stubs: org.springframework:foo:stubs</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>means that for a particular dependencies can be found under:</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>groupId: <code>org.springframework</code></p>
|
||
</li>
|
||
<li>
|
||
<p>artifactId: <code>foo</code></p>
|
||
</li>
|
||
<li>
|
||
<p>classifier: <code>stubs</code> - this is the default value</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This is actually equal to</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code>stubs: org.springframework:foo</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>since <code>stubs</code> is the default classifier.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_configuring_spring_cloud_zookeeper_dependencies">Configuring Spring Cloud Zookeeper Dependencies</h3>
|
||
<div class="paragraph">
|
||
<p>There is a bunch of properties that you can set to enable / disable parts of Zookeeper Dependencies functionalities.</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>spring.cloud.zookeeper.dependencies</code> - if you don’t set this property you won’t benefit from Zookeeper Dependencies</p>
|
||
</li>
|
||
<li>
|
||
<p><code>spring.cloud.zookeeper.dependencies.ribbon.enabled</code> (enabled by default) - Ribbon requires explicit global configuration or a particular one for a dependency. By turning on this property
|
||
runtime load balancing strategy resolution is possible and you can profit from the <code>loadBalancerType</code> section of the Zookeeper Dependencies. The configuration that needs this property
|
||
has an implementation of <code>LoadBalancerClient</code> that delegates to the <code>ILoadBalancer</code> presented in the next bullet</p>
|
||
</li>
|
||
<li>
|
||
<p><code>spring.cloud.zookeeper.dependencies.ribbon.loadbalancer</code> (enabled by default) - thanks to this property the custom <code>ILoadBalancer</code> knows that the part of the URI passed to Ribbon might
|
||
actually be the alias that has to be resolved to a proper path in Zookeeper. Without this property you won’t be able to register applications under nested paths.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>spring.cloud.zookeeper.dependencies.headers.enabled</code> (enabled by default) - this property registers such a <code>RibbonClient</code> that automatically will append appropriate headers and content
|
||
types with version as presented in the Dependency configuration. Without this setting of those two parameters will not be operational.</p>
|
||
</li>
|
||
<li>
|
||
<p><code>spring.cloud.zookeeper.dependencies.resttemplate.enabled</code> (enabled by default) - when enabled will modify the request headers of <code>@LoadBalanced</code> annotated <code>RestTemplate</code> so that it passes
|
||
headers and content type with version set in Dependency configuration. Wihtout this setting of those two parameters will not be operational.</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-zookeeper-dependency-watcher">Spring Cloud Zookeeper Dependency Watcher</h3>
|
||
<div class="paragraph">
|
||
<p>The Dependency Watcher mechanism allows you to register listeners to your dependencies. The functionality is in fact an implementation of the <code>Observator</code> pattern. When a dependency changes
|
||
its state (UP or DOWN) then some custom logic can be applied.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_how_to_activate_3">How to activate</h3>
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Zookeeper Dependencies functionality needs to be enabled to profit from Dependency Watcher mechanism.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_registering_a_listener">Registering a listener</h3>
|
||
<div class="paragraph">
|
||
<p>In order to register a listener you have to implement an interface <code>org.springframework.cloud.zookeeper.discovery.watcher.DependencyWatcherListener</code> and register it as a bean.
|
||
The interface gives you one method:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre> /**
|
||
* Method executed upon state change of a dependency
|
||
*
|
||
* @param dependencyName - alias from microservice configuration {@see ZookeeperDependencies}
|
||
* @param newState
|
||
*/
|
||
void stateChanged(String dependencyName, DependencyState newState);</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you want to register a listener for a particular dependency then the <code>dependencyName</code> would be the discriminator for your concrete implementation. <code>newState</code> will provide you with information
|
||
whether your dependency has changed to <code>CONNECTED</code> or <code>DISCONNECTED</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_presence_checker">Presence Checker</h3>
|
||
<div class="paragraph">
|
||
<p>Bound with Dependency Watcher is the functionality called Presence Checker. It allows you to provide custom behaviour upon booting of your application to react accordingly to the state
|
||
of your dependencies.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The default implementation of the abstract <code>org.springframework.cloud.zookeeper.discovery.watcher.presence.DependencyPresenceOnStartupVerifier</code> class is the
|
||
<code>org.springframework.cloud.zookeeper.discovery.watcher.presence.DefaultDependencyPresenceOnStartupVerifier</code> which works in the following way.</p>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p>If the dependency is marked us <code>required</code> and it’s not in Zookeeper then upon booting your application will throw an exception and shutdown</p>
|
||
</li>
|
||
<li>
|
||
<p>If dependency is not <code>required</code> the <code>org.springframework.cloud.zookeeper.discovery.watcher.presence.LogMissingDependencyChecker</code> will log that application is missing at <code>WARN</code> level</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The functionality can be overriden since the <code>DefaultDependencyPresenceOnStartupVerifier</code> is registered only when there is no bean of <code>DependencyPresenceOnStartupVerifier</code>.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="spring-cloud-zookeeper-config">Distributed Configuration with Zookeeper</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Zookeeper provides a <a href="http://zookeeper.apache.org/doc/current/zookeeperOver.html#sc_dataModelNameSpace">hierarchical namespace</a> that allows clients to store arbitrary data, such as configuration data. Spring Cloud Zookeeper Config is an alternative to the <a href="https://github.com/spring-cloud/spring-cloud-config">Config Server and Client</a>. Configuration is loaded into the Spring Environment during the special "bootstrap" phase. Configuration is stored in the <code>/config</code> namespace by default. Multiple <code>PropertySource</code> instances are created based on the application’s name and the active profiles that mimicks the Spring Cloud Config order of resolving properties. For example, an application with the name "testApp" and with the "dev" profile will have the following property sources created:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>config/testApp,dev
|
||
config/testApp
|
||
config/application,dev
|
||
config/application</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The most specific property source is at the top, with the least specific at the bottom. Properties is the <code>config/application</code> namespace are applicable to all applications using zookeeper for configuration. Properties in the <code>config/testApp</code> namespace are only available to the instances of the service named "testApp".</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Configuration is currently read on startup of the application. Sending a HTTP POST to <code>/refresh</code> will cause the configuration to be reloaded. Watching the configuration namespace (which Zookeeper supports) is not currently implemented, but will be a future addition to this project.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_how_to_activate_4">How to activate</h3>
|
||
<div class="paragraph">
|
||
<p>Including a dependency on <code>org.springframework.cloud:spring-cloud-starter-zookeeper-config</code> will enable auto-configuration that will setup Spring Cloud Zookeeper Config.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_customizing_2">Customizing</h3>
|
||
<div class="paragraph">
|
||
<p>Zookeeper Config may be customized using the following properties:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">bootstrap.yml</div>
|
||
<div class="content">
|
||
<pre>spring:
|
||
cloud:
|
||
zookeeper:
|
||
config:
|
||
enabled: true
|
||
root: configuration
|
||
defaultContext: apps
|
||
profileSeparator: '::'</pre>
|
||
</div>
|
||
</div>
|
||
<div class="ulist">
|
||
<ul>
|
||
<li>
|
||
<p><code>enabled</code> setting this value to "false" disables Zookeeper Config</p>
|
||
</li>
|
||
<li>
|
||
<p><code>root</code> sets the base namespace for configuration values</p>
|
||
</li>
|
||
<li>
|
||
<p><code>defaultContext</code> sets the name used by all applications</p>
|
||
</li>
|
||
<li>
|
||
<p><code>profileSeparator</code> sets the value of the separator used to separate the profile name in property sources with profiles</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_boot_cloud_cli" class="sect0">Spring Boot Cloud CLI</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
<div class="paragraph">
|
||
<p>Spring Boot CLI provides <a href="http://projects.spring.io/spring-boot">Spring Boot</a> command line features for
|
||
<a href="https://github.com/spring-cloud">Spring Cloud</a>. You can write Groovy scripts to run Spring Cloud component applications
|
||
(e.g. <code>@EnableEurekaServer</code>). You can also easily do things like encryption and decryption to support Spring Cloud
|
||
Config clients with secret configuration values.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><a href="https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/contributing-docs.adoc" class="bare">https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/contributing-docs.adoc</a></p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_installation">Installation</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>To install, make
|
||
sure you have
|
||
<a href="https://github.com/spring-projects/spring-boot">Spring Boot CLI</a>
|
||
(1.3.0 or better):</p>
|
||
</div>
|
||
<div class="literalblock">
|
||
<div class="content">
|
||
<pre>$ spring version
|
||
Spring CLI v1.3.2.RELEASE</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>E.g. for SDKMan users</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code>$ sdk install springboot 1.3.2.RELEASE
|
||
$ sdk use springboot 1.3.2.RELEASE</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>and install the Spring Cloud plugin:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code>$ mvn install
|
||
$ spring install org.springframework.cloud:spring-cloud-cli:1.1.0.BUILD-SNAPSHOT</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="admonitionblock important">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Important</div>
|
||
</td>
|
||
<td class="content">
|
||
<strong>Prerequisites:</strong> to use the encryption and decryption features
|
||
you need the full-strength JCE installed in your JVM (it’s not there by default).
|
||
You can download the "Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files"
|
||
from Oracle, and follow instructions for installation (essentially replace the 2 policy files
|
||
in the JRE lib/security directory with the ones that you downloaded).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_writing_groovy_scripts_and_running_applications">Writing Groovy Scripts and Running Applications</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud CLI has support for most of the Spring Cloud declarative
|
||
features, such as the <code>@Enable*</code> class of annotations. For example,
|
||
here is a fully functional Eureka server</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">app.groovy</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-groovy" data-lang="groovy">@EnableEurekaServer
|
||
class Eureka {}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>which you can run from the command line like this</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ spring run app.groovy</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To include additional dependencies, often it suffices just to add the
|
||
appropriate feature-enabling annotation, e.g. <code>@EnableConfigServer</code>,
|
||
<code>@EnableOAuth2Sso</code> or <code>@EnableEurekaClient</code>. To manually include a
|
||
dependency you can use a <code>@Grab</code> with the special "Spring Boot" short
|
||
style artifact co-ordinates, i.e. with just the artifact ID (no need
|
||
for group or version information), e.g. to set up a client app to
|
||
listen on AMQP for management events from the Spring CLoud Bus:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">app.groovy</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-groovy" data-lang="groovy">@Grab('spring-cloud-starter-bus-amqp')
|
||
@RestController
|
||
class Service {
|
||
@RequestMapping('/')
|
||
def home() { [message: 'Hello'] }
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_encryption_and_decryption_3">Encryption and Decryption</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>The Spring Cloud CLI comes with an "encrypt" and a "decrypt"
|
||
command. Both accept arguments in the same form with a key specified
|
||
as a mandatory "--key", e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ spring encrypt mysecret --key foo
|
||
682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda
|
||
$ spring decrypt --key foo 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda
|
||
mysecret</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To use a key in a file (e.g. an RSA public key for encyption) prepend
|
||
the key value with "@" and provide the file path, e.g.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ spring encrypt mysecret --key @${HOME}/.ssh/id_rsa.pub
|
||
AQAjPgt3eFZQXwt8tsHAVv/QHiY5sI2dRcR+...</pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_security" class="sect0">Spring Cloud Security</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud Security offers a set of primitives for building secure
|
||
applications and services with minimum fuss. A declarative model which
|
||
can be heavily configured externally (or centrally) lends itself to
|
||
the implementation of large systems of co-operating, remote components,
|
||
usually with a central indentity management service. It is also extremely
|
||
easy to use in a service platform like Cloud Foundry. Building on
|
||
Spring Boot and Spring Security OAuth2 we can quickly create systems that
|
||
implement common patterns like single sign on, token relay and token
|
||
exchange.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p><a href="https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/contributing-docs.adoc" class="bare">https://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/docs/src/main/asciidoc/contributing-docs.adoc</a></p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_quickstart">Quickstart</h2>
|
||
<div class="sectionbody">
|
||
<div class="sect2">
|
||
<h3 id="_oauth2_single_sign_on">OAuth2 Single Sign On</h3>
|
||
<div class="paragraph">
|
||
<p>Here’s a Spring Cloud "Hello World" app with HTTP Basic
|
||
authentication and a single user account:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">app.groovy</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Grab('spring-boot-starter-security')
|
||
@Controller
|
||
class Application {
|
||
|
||
@RequestMapping('/')
|
||
String home() {
|
||
'Hello World'
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can run it with <code>spring run app.groovy</code> and watch the logs for the password (username is "user"). So far this is just the default for a Spring Boot app.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Here’s a Spring Cloud app with OAuth2 SSO:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">app.groovy</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Controller
|
||
@EnableOAuth2Sso
|
||
class Application {
|
||
|
||
@RequestMapping('/')
|
||
String home() {
|
||
'Hello World'
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Spot the difference? This app will actually behave exactly the same as
|
||
the previous one, because it doesn’t know it’s OAuth2 credentals
|
||
yet.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>You can register an app in github quite easily, so try that if you
|
||
want a production app on your own domain. If you are happy to test on
|
||
localhost:8080, then set up these properties in your application
|
||
configuration:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
oauth2:
|
||
client:
|
||
clientId: bd1c0a783ccdd1c9b9e4
|
||
clientSecret: 1a9030fbca47a5b2c28e92f19050bb77824b5ad1
|
||
accessTokenUri: https://github.com/login/oauth/access_token
|
||
userAuthorizationUri: https://github.com/login/oauth/authorize
|
||
clientAuthenticationScheme: form
|
||
resource:
|
||
userInfoUri: https://api.github.com/user
|
||
preferTokenInfo: false</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>run the app above and it will redirect to github for authorization. If
|
||
you are already signed into github you won’t even notice that it has
|
||
authenticated. These credentials will only work if your app is
|
||
running on port 8080.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>To limit the scope that the client asks for when it obtains an access token
|
||
you can set <code>spring.oauth2.client.scope</code> (comma separated or an array in YAML). By
|
||
default the scope is empty and it is up to to Authorization Server to
|
||
decide what the defaults should be, usually depending on the settings in
|
||
the client registration that it holds.</p>
|
||
</div>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
The examples above are all Groovy scripts. If you want to write the
|
||
same code in Java (or Groovy) you need to add Spring Security OAuth2
|
||
to the classpath (e.g. see the
|
||
<a href="https://github.com/spring-cloud-samples/sso">sample here</a>).
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_oauth2_protected_resource">OAuth2 Protected Resource</h3>
|
||
<div class="paragraph">
|
||
<p>You want to protect an API resource with an OAuth2 token? Here’s a
|
||
simple example (paired with the client above):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">app.groovy</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Grab('spring-cloud-starter-security')
|
||
@RestController
|
||
@EnableResourceServer
|
||
class Application {
|
||
|
||
@RequestMapping('/')
|
||
def home() {
|
||
[message: 'Hello World']
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>and</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">spring:
|
||
oauth2:
|
||
resource:
|
||
userInfoUri: https://api.github.com/user
|
||
preferTokenInfo: false</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_more_detail">More Detail</h2>
|
||
<div class="sectionbody">
|
||
<div class="sect2">
|
||
<h3 id="_single_sign_on">Single Sign On</h3>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
All of the OAuth2 SSO and resource server features moved to Spring Boot
|
||
in version 1.3. You can find documentation in the
|
||
<a href="http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/">Spring Boot user guide</a>.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_token_relay">Token Relay</h3>
|
||
<div class="paragraph">
|
||
<p>A Token Relay is where an OAuth2 consumer acts as a Client and
|
||
forwards the incoming token to outgoing resource requests. The
|
||
consumer can be a pure Client (like an SSO application) or a Resource
|
||
Server.</p>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_client_token_relay">Client Token Relay</h4>
|
||
<div class="paragraph">
|
||
<p>If your app has a
|
||
<a href="http://cloud.spring.io/spring-cloud.html#netflix-zuul-reverse-proxy">Spring
|
||
Cloud Zuul</a> embedded reverse proxy (using <code>@EnableZuulProxy</code>) then you
|
||
can ask it to forward OAuth2 access tokens downstream to the services
|
||
it is proxying. Thus the SSO app above can be enhanced simply like this:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">app.groovy</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Controller
|
||
@EnableOAuth2Sso
|
||
@EnableZuulProxy
|
||
class Application {
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>and it will (in addition to loggin the user in and grabbing a token)
|
||
pass the authentication token downstream to the <code>/proxy/*</code>
|
||
services. If those services are implemented with
|
||
<code>@EnableOAuth2Resource</code> then they will get a valid token in the
|
||
correct header.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>How does it work? The <code>@EnableOAuth2Sso</code> annotation pulls in
|
||
<code>spring-cloud-starter-security</code> (which you could do manually in a
|
||
traditional app), and that in turn triggers some autoconfiguration for
|
||
a <code>ZuulFilter</code>, which itself is activated because Zuul is on the
|
||
classpath (via <code>@EnableZuulProxy</code>). The
|
||
{github}/tree/master/src/main/java/org/springframework/cloud/security/oauth2/proxy/OAuth2TokenRelayFilter.java[filter]
|
||
just extracts an access token from the currently authenticated user,
|
||
and puts it in a request header for the downstream requests.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect3">
|
||
<h4 id="_resource_server_token_relay">Resource Server Token Relay</h4>
|
||
<div class="paragraph">
|
||
<p>If your app has <code>@EnableOAuth2Resource</code> and also is a Client (i.e. it
|
||
has a <code>spring.oauth2.client.clientId</code>, even if it doesn’t use it),
|
||
then the <code>OAuth2RestOperations</code> that is provided for <code>@Autowired</code>
|
||
users by Spring Cloud (it is declared as <code>@Primary</code>) will also forward
|
||
tokens. If you don’t want to forward tokens (and that is a valid
|
||
choice, since you might want to act as yourself, rather than the
|
||
client that sent you the token), then you only need to create your own
|
||
<code>OAuth2RestOperations</code> instead of autowiring the default one. Here’s
|
||
a basic example showing the use of the autowired rest template ("foo.com"
|
||
is a Resource Server accepting the same tokens as the surrounding app):</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">MyController.java</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Autowired
|
||
private OAuth2RestOperations restTemplate;
|
||
|
||
@RequestMapping("/relay")
|
||
public String relay() {
|
||
ResponseEntity<String> response =
|
||
restTemplate.getForEntity("https://foo.com/bar", String.class);
|
||
return "Success! (" + response.getBody() + ")";
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_configuring_authentication_downstream_of_a_zuul_proxy">Configuring Authentication Downstream of a Zuul Proxy</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>You can control the authorization behaviour downstream of an
|
||
<code>@EnableZuulProxy</code> through the <code>proxy.auth.*</code> settings. Example:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">application.yml</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-yaml" data-lang="yaml">proxy:
|
||
auth:
|
||
routes:
|
||
customers: oauth2
|
||
stores: passthru
|
||
recommendations: none</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>In this example the "customers" service gets an OAuth2 token relay,
|
||
the "stores" service gets a passthrough (the authorization header is
|
||
just passed downstream), and the "recommendations" service has its
|
||
authorization header removed. The default behaviour is to do a token
|
||
relay if there is a token available, and passthru otherwise.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>See
|
||
{github}/tree/master/src/main/java/org/springframework/cloud/security/oauth2/proxy/ProxyAuthenticationProperties[
|
||
ProxyAuthenticationProperties] for full details.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_for_cloud_foundry" class="sect0">Spring Cloud for Cloud Foundry</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
<div class="paragraph">
|
||
<p>Spring Cloud for Cloudfoundry makes it easy to run
|
||
<a href="https://github.com/spring-cloud">Spring Cloud</a> apps in
|
||
<a href="https://github.com/cloudfoundry">Cloud Foundry</a> (the Platform as a
|
||
Service). Cloud Foundry has the notion of a "service", which is
|
||
middlware that you "bind" to an app, essentially providing it with an
|
||
environment variable containing credentials (e.g. the location and
|
||
username to use for the service).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>spring-cloud-cloudfoundry-web</code> project provides basic support for
|
||
some enhanced features of webapps in Cloud Foundry: binding
|
||
automatically to single-sign-on services and optionally enabling
|
||
sticky routing for discovery.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The <code>spring-cloud-cloudfoundry-discovery</code> project provides an
|
||
implementation of Spring Cloud Commons <code>DiscoveryClient</code> so you can
|
||
<code>@EnableDiscoveryClient</code> and provide your credentials as
|
||
<code>spring.cloud.cloudfoundry.discovery.[email,password]</code> and then you
|
||
can use the <code>DiscoveryClient</code> directly or via a <code>LoadBalancerClient</code>
|
||
(also <code>*.url</code> if you are not connecting to [Pivotal Web
|
||
Services](<a href="https://run.pivotal.io)" class="bare">https://run.pivotal.io)</a>).</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>The first time you use it the discovery client might be slow owing to
|
||
the fact that it has to get an access token from Cloud Foundry.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_quickstart_2">Quickstart</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Here’s a Spring Cloud app with Cloud Foundry discovery:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="title">app.groovy</div>
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Grab('org.springframework.cloud:spring-cloud-cloudfoundry')
|
||
@RestController
|
||
@EnableDiscoveryClient
|
||
class Application {
|
||
|
||
@Autowired
|
||
DiscoveryClient client
|
||
|
||
@RequestMapping('/')
|
||
String home() {
|
||
'Hello from ' + client.getLocalServiceInstance()
|
||
}
|
||
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you run it without any service bindings:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre>$ spring jar app.jar app.groovy
|
||
$ cf push -p app.jar</pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>It will show its app name in the home page.</p>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="_single_sign_on_2">Single Sign On</h3>
|
||
<div class="admonitionblock note">
|
||
<table>
|
||
<tr>
|
||
<td class="icon">
|
||
<div class="title">Note</div>
|
||
</td>
|
||
<td class="content">
|
||
All of the OAuth2 SSO and resource server features moved to Spring Boot
|
||
in version 1.3. You can find documentation in the
|
||
<a href="http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/">Spring Boot user guide</a>.
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>This project provides automatic binding from CloudFoundry service
|
||
credentials to the Spring Boot features. If you have a CloudFoundry
|
||
service called "sso", for instance, with credentials containing
|
||
"client_id", "client_secret" and "auth_domain", it will bind
|
||
automatically to the Spring OAuth2 client that you enable with
|
||
<code>@EnableOAuth2Sso</code> (from Spring Boot). The name of the service can be
|
||
parameterized using <code>spring.oauth2.sso.serviceId</code>.</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<h1 id="_spring_cloud_cluster" class="sect0">Spring Cloud Cluster</h1>
|
||
<div class="openblock partintro">
|
||
<div class="content">
|
||
Spring Cloud Cluster offers a set of primitives for building "cluster"
|
||
features into a distributed system. Example are leadership election,
|
||
consistent storage of cluster state, global locks and one-time tokens.
|
||
</div>
|
||
</div>
|
||
<div class="sect1">
|
||
<h2 id="_leader_election">Leader Election</h2>
|
||
<div class="sectionbody">
|
||
<div class="paragraph">
|
||
<p>Leader election allows application to work together with other
|
||
applications to coordinate a cluster leadership via a third party system.
|
||
Currently we provide integrations with <code>zookeeper</code>, <code>hazelcast</code> and <code>etcd</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>From user perspective election is working via interfaces
|
||
<code>org.springframework.cloud.cluster.leader.Candidate</code> and
|
||
<code>org.springframework.cloud.cluster.leader.Context</code>. <code>Candidate</code>
|
||
contains access to leadership’s <code>role</code> and <code>id</code> and also have methods
|
||
<code>onGranted</code> and <code>onRevoked</code>. These callback methods are useful if
|
||
default <code>Candidate</code> implementation is changed.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Leader election is auto-configured if <code>spring-cloud-cluster-autoconfigure</code>
|
||
and either <code>spring-cloud-cluster-hazelcast</code>, <code>spring-cloud-cluster-zookeeper</code>
|
||
or <code>spring-cloud-cluster-etcd</code> jars are found from a classpath. In
|
||
case where both jars are found leader election is created using both
|
||
systems. See sections <a href="#spring-cloud-cluster-leaderelection-zookeeper">Zookeeper</a>,
|
||
<a href="#spring-cloud-cluster-leaderelection-hazelcast">Hazelcast</a> and
|
||
<a href="#spring-cloud-cluster-leaderelection-etcd">Etcd</a> for more
|
||
information about a created beans.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Default <code>Candidate</code> created from auto-configuration is
|
||
<code>org.springframework.cloud.cluster.leader.DefaultCandidate</code> which
|
||
currently only logs granted and revoked events.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If there’s a need for disable all leader related auto-configuration,
|
||
a <code>spring.cloud.cluster.leader.enabled</code> can be set to false which
|
||
then allows to do manual configuration even if the jars an on a
|
||
classpath. Properties <code>spring.cloud.cluster.leader.id</code> and
|
||
<code>spring.cloud.cluster.leader.role</code> can be used to set default
|
||
identifier and role.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>If you are interested to simple get notification of granted and
|
||
revoked events one option is to attach event listener into spring
|
||
application context. Events <code>OnGrantedEvent</code> and <code>OnRevokedEvent</code> are
|
||
sent as spring event objects.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Simply create your own event listener class:</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">class MyEventListener implements ApplicationListener<AbstractLeaderEvent> {
|
||
|
||
@Override
|
||
public void onApplicationEvent(AbstractLeaderEvent event) {
|
||
// do something with OnGrantedEvent or OnRevokedEvent
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>and then create it as a bean.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">@Configuration
|
||
static class Config {
|
||
@Bean
|
||
public MyEventListener myEventListener() {
|
||
return new MyEventListener();
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>For simply log events you can also use a utility class
|
||
<code>LoggingListener</code> which allows easy configuration.</p>
|
||
</div>
|
||
<div class="listingblock">
|
||
<div class="content">
|
||
<pre class="highlight"><code class="language-java" data-lang="java">import org.springframework.cloud.cluster.leader.event.LoggingListener;
|
||
|
||
@Configuration
|
||
static class Config {
|
||
@Bean
|
||
public LoggingListener loggingListener() {
|
||
return new LoggingListener("info");
|
||
}
|
||
}</code></pre>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-cluster-leaderelection-zookeeper">Zookeeper</h3>
|
||
<div class="paragraph">
|
||
<p><code>Candidate</code> implementation for zookeeper is created with a bean name
|
||
<code>zookeeperLeaderCandidate</code> which can be used to override the one
|
||
created during auto-configuration.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Zookeeper based election can be explicitly disabled using property
|
||
<code>spring.cloud.cluster.zookeeper.leader.enabled</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Other propertys <code>spring.cloud.cluster.zookeeper.namespace</code> and
|
||
<code>spring.cloud.cluster.zookeeper.connect</code> can be used to set the
|
||
zookeeper base namespace path and connect string.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-cluster-leaderelection-hazelcast">Hazelcast</h3>
|
||
<div class="paragraph">
|
||
<p><code>Candidate</code> implementation for zookeeper is created with a bean name
|
||
<code>hazelcastLeaderCandidate</code> which can be used to override the one
|
||
created during auto-configuration.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Hazelcast based election can be explicitly disabled using property
|
||
<code>spring.cloud.cluster.hazelcast.leader.enabled</code>. If you want to provide xml
|
||
based configuration for Hazelcast instance use property
|
||
<code>spring.cloud.cluster.hazelcast.config-location</code> to tell location of a
|
||
Hazelcast xml configuration file. <code>config-location</code> is a normal spring
|
||
<code>Resource</code>.</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2">
|
||
<h3 id="spring-cloud-cluster-leaderelection-etcd">Etcd</h3>
|
||
<div class="paragraph">
|
||
<p><code>Candidate</code> implementation for etcd is created with a bean name
|
||
<code>etcdLeaderCandidate</code> which can be used to override the one
|
||
created during auto-configuration.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Etcd based election can be explicitly disabled using property
|
||
<code>spring.cloud.cluster.etcd.leader.enabled</code>.</p>
|
||
</div>
|
||
<div class="paragraph">
|
||
<p>Multiple etcd cluster uris can be specified using property
|
||
<code>spring.cloud.cluster.etcd.connect</code></p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div id="footer">
|
||
<div id="footer-text">
|
||
Last updated 2016-02-12 16:34:20 UTC
|
||
</div>
|
||
</div>
|
||
</body>
|
||
</html> |