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<title>Spring Cloud Consul</title><link rel="stylesheet" type="text/css" href="css/manual-singlepage.css"><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div lang="en" class="book"><div class="titlepage"><div><div><h1 class="title"><a name="d0e3"></a>Spring Cloud Consul</h1></div></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="preface"><a href="#d0e9"></a></span></dt><dt><span class="chapter"><a href="#spring-cloud-consul-install">1. Install Consul</a></span></dt><dt><span class="chapter"><a href="#spring-cloud-consul-agent">2. Consul Agent</a></span></dt><dt><span class="chapter"><a href="#spring-cloud-consul-discovery">3. Service Discovery with Consul</a></span></dt><dd><dl><dt><span class="section"><a href="#_how_to_activate">3.1. How to activate</a></span></dt><dt><span class="section"><a href="#_registering_with_consul">3.2. Registering with Consul</a></span></dt><dt><span class="section"><a href="#_http_health_check">3.3. HTTP Health Check</a></span></dt><dd><dl><dt><span class="section"><a href="#_metadata_and_consul_tags">3.3.1. Metadata and Consul tags</a></span></dt><dt><span class="section"><a href="#_making_the_consul_instance_id_unique">3.3.2. Making the Consul Instance ID Unique</a></span></dt></dl></dd><dt><span class="section"><a href="#_looking_up_services">3.4. Looking up services</a></span></dt><dd><dl><dt><span class="section"><a href="#_using_ribbon">3.4.1. Using Ribbon</a></span></dt><dt><span class="section"><a href="#_using_the_discoveryclient">3.4.2. Using the DiscoveryClient</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#spring-cloud-consul-config">4. Distributed Configuration with Consul</a></span></dt><dd><dl><dt><span class="section"><a href="#_how_to_activate_2">4.1. How to activate</a></span></dt><dt><span class="section"><a href="#_customizing">4.2. Customizing</a></span></dt><dt><span class="section"><a href="#spring-cloud-consul-config-watch">4.3. Config Watch</a></span></dt><dt><span class="section"><a href="#spring-cloud-consul-config-format">4.4. YAML or Properties with Config</a></span></dt><dt><span class="section"><a href="#spring-cloud-consul-config-git2consul">4.5. git2consul with Config</a></span></dt><dt><span class="section"><a href="#spring-cloud-consul-failfast">4.6. Fail Fast</a></span></dt></dl></dd><dt><span class="chapter"><a href="#spring-cloud-consul-retry">5. Consul Retry</a></span></dt><dt><span class="chapter"><a href="#spring-cloud-consul-bus">6. Spring Cloud Bus with Consul</a></span></dt><dd><dl><dt><span class="section"><a href="#_how_to_activate_3">6.1. How to activate</a></span></dt></dl></dd><dt><span class="chapter"><a href="#spring-cloud-consul-hystrix">7. Circuit Breaker with Hystrix</a></span></dt><dt><span class="chapter"><a href="#spring-cloud-consul-turbine">8. Hystrix metrics aggregation with Turbine and Consul</a></span></dt></dl></div><div class="preface"><div class="titlepage"><div><div><h1 class="title"><a name="d0e9" href="#d0e9"></a></h1></div></div></div><p><span class="strong"><strong>2.0.0.RC2</strong></span></p><p>This project provides Consul integrations for Spring Boot apps through autoconfiguration
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and binding to the Spring Environment and other Spring programming model idioms. With a few
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simple annotations you can quickly enable and configure the common patterns inside your
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application and build large distributed systems with Consul based components. The
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patterns provided include Service Discovery, Control Bus and Configuration.
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Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon), Circuit Breaker
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(Hystrix) are provided by integration with Spring Cloud Netflix.</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-install" href="#spring-cloud-consul-install"></a>1. Install Consul</h1></div></div></div><p>Please see the <a class="link" href="https://www.consul.io/intro/getting-started/install.html" target="_top">installation documentation</a> for instructions on how to install Consul.</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-agent" href="#spring-cloud-consul-agent"></a>2. Consul Agent</h1></div></div></div><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 class="literal">localhost:8500</code>. See the <a class="link" href="https://consul.io/docs/agent/basics.html" target="_top">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><pre class="screen">./src/main/bash/local_run_consul.sh</pre><p>This will start an agent in server mode on port 8500, with the ui available at <a class="link" href="http://localhost:8500" target="_top">http://localhost:8500</a></p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-discovery" href="#spring-cloud-consul-discovery"></a>3. Service Discovery with Consul</h1></div></div></div><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 class="link" href="https://www.consul.io/docs/agent/http.html" target="_top">HTTP API</a> and <a class="link" href="https://www.consul.io/docs/agent/dns.html" target="_top">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 class="link" href="https://www.consul.io/docs/internals/architecture.html" target="_top">cluster</a> that communicates via a <a class="link" href="https://www.consul.io/docs/internals/gossip.html" target="_top">gossip protocol</a> and uses the <a class="link" href="https://www.consul.io/docs/internals/consensus.html" target="_top">Raft consensus protocol</a>.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_how_to_activate" href="#_how_to_activate"></a>3.1 How to activate</h2></div></div></div><p>To activate Consul Service Discovery use the starter with group <code class="literal">org.springframework.cloud</code> and artifact id <code class="literal">spring-cloud-starter-consul-discovery</code>. See the <a class="link" href="http://projects.spring.io/spring-cloud/" target="_top">Spring Cloud Project page</a> for details on setting up your build system with the current Spring Cloud Release Train.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_registering_with_consul" href="#_registering_with_consul"></a>3.2 Registering with Consul</h2></div></div></div><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 class="link" href="https://www.consul.io/docs/agent/checks.html" target="_top">Check</a> is created by default that Consul hits the <code class="literal">/health</code> endpoint every 10 seconds. If the health check fails, the service instance is marked as critical.</p><p>Example Consul client:</p><pre class="programlisting"><em><span class="hl-annotation" style="color: gray">@SpringBootApplication</span></em>
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<em><span class="hl-annotation" style="color: gray">@RestController</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span> Application {
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<em><span class="hl-annotation" style="color: gray">@RequestMapping("/")</span></em>
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> String home() {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">return</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-string">"Hello world"</span>;
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}
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">public</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">static</span> <span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">void</span> main(String[] args) {
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<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">new</span> SpringApplicationBuilder(Application.<span xmlns:d="http://docbook.org/ns/docbook" class="hl-keyword">class</span>).web(true).run(args);
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}
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}</pre><p>(i.e. utterly normal Spring Boot app). If the Consul client is located somewhere other than <code class="literal">localhost:8500</code>, the configuration is required to locate the client. Example:</p><p><b>application.yml. </b>
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</p><pre class="screen">spring:
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cloud:
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consul:
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host: localhost
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port: 8500</pre><p>
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</p><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Caution"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="images/caution.png"></td><th align="left">Caution</th></tr><tr><td align="left" valign="top"><p>If you use <a class="link" href="#spring-cloud-consul-config" title="4. Distributed Configuration with Consul">Spring Cloud Consul Config</a>, the above values will need to be placed in <code class="literal">bootstrap.yml</code> instead of <code class="literal">application.yml</code>.</p></td></tr></table></div><p>The default service name, instance id and port, taken from the <code class="literal">Environment</code>, are <code class="literal">${spring.application.name}</code>, the Spring Context ID and <code class="literal">${server.port}</code> respectively.</p><p>To disable the Consul Discovery Client you can set <code class="literal">spring.cloud.consul.discovery.enabled</code> to <code class="literal">false</code>.</p><p>To disable the service registration you can set <code class="literal">spring.cloud.consul.discovery.register</code> to <code class="literal">false</code>.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_http_health_check" href="#_http_health_check"></a>3.3 HTTP Health Check</h2></div></div></div><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 class="literal">server.servletPath=/foo</code>) or management endpoint path (e.g. <code class="literal">management.server.servlet.context-path=/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><p><b>application.yml. </b>
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</p><pre class="screen">spring:
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cloud:
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consul:
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discovery:
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healthCheckPath: ${management.server.servlet.context-path}/health
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healthCheckInterval: 15s</pre><p>
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</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_metadata_and_consul_tags" href="#_metadata_and_consul_tags"></a>3.3.1 Metadata and Consul tags</h3></div></div></div><p>Consul does not yet support metadata on services. Spring Cloud’s <code class="literal">ServiceInstance</code> has a <code class="literal">Map<String, String> metadata</code> field. Spring Cloud Consul uses Consul tags to approximate metadata until Consul officially supports metadata. Tags with the form <code class="literal">key=value</code> will be split and used as a <code class="literal">Map</code> key and value respectively. Tags without the equal <code class="literal">=</code> sign, will be used as both the key and value.</p><p><b>application.yml. </b>
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</p><pre class="screen">spring:
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cloud:
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consul:
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discovery:
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tags: foo=bar, baz</pre><p>
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</p><p>The above configuration will result in a map with <code class="literal">foo→bar</code> and <code class="literal">baz→baz</code>.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_making_the_consul_instance_id_unique" href="#_making_the_consul_instance_id_unique"></a>3.3.2 Making the Consul Instance ID Unique</h3></div></div></div><p>By default a consul instance is registered with an ID that is equal to its Spring Application Context ID. By default, the Spring Application Context ID is <code class="literal">${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 class="literal">spring.cloud.consul.discovery.instanceId</code>. For example:</p><p><b>application.yml. </b>
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</p><pre class="screen">spring:
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cloud:
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consul:
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discovery:
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instanceId: ${spring.application.name}:${vcap.application.instance_id:${spring.application.instance_id:${random.value}}}</pre><p>
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</p><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 class="literal">vcap.application.instance_id</code> will be populated automatically in a Spring Boot application, so the random value will not be needed.</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_looking_up_services" href="#_looking_up_services"></a>3.4 Looking up services</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_using_ribbon" href="#_using_ribbon"></a>3.4.1 Using Ribbon</h3></div></div></div><p>Spring Cloud has support for <a class="link" href="https://github.com/spring-cloud/spring-cloud-netflix/blob/master/docs/src/main/asciidoc/spring-cloud-netflix.adoc#spring-cloud-feign" target="_top">Feign</a> (a REST client builder) and also <a class="link" href="https://github.com/spring-cloud/spring-cloud-netflix/blob/master/docs/src/main/asciidoc/spring-cloud-netflix.adoc#spring-cloud-ribbon" target="_top">Spring <code class="literal">RestTemplate</code></a>
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for looking up services using the logical service names/ids instead of physical URLs. Both Feign and the discovery-aware RestTemplate utilize <a class="link" href="http://cloud.spring.io/spring-cloud-netflix/single/spring-cloud-netflix.html#spring-cloud-ribbon" target="_top">Ribbon</a> for client-side load balancing.</p><p>If you want to access service STORES using the RestTemplate simply declare:</p><pre class="screen">@LoadBalanced
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@Bean
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public RestTemplate loadbalancedRestTemplate() {
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new RestTemplate();
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}</pre><p>and use it like this (notice how we use the STORES service name/id from Consul instead of a fully qualified domainname):</p><pre class="screen">@Autowired
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RestTemplate restTemplate;
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public String getFirstProduct() {
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return this.restTemplate.getForObject("https://STORES/products/1", String.class);
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}</pre><p>If you have Consul clusters in multiple datacenters and you want to access a service in another datacenter a service name/id alone is not enough. In that case
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you use property <code class="literal">spring.cloud.consul.discovery.datacenters.STORES=dc-west</code> where <code class="literal">STORES</code> is the service name/id and <code class="literal">dc-west</code> is the datacenter
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where the STORES service lives.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_using_the_discoveryclient" href="#_using_the_discoveryclient"></a>3.4.2 Using the DiscoveryClient</h3></div></div></div><p>You can also use the <code class="literal">org.springframework.cloud.client.discovery.DiscoveryClient</code> which provides a simple API for discovery clients that is not specific to Netflix, e.g.</p><pre class="screen">@Autowired
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private DiscoveryClient discoveryClient;
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public String serviceUrl() {
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List<ServiceInstance> list = discoveryClient.getInstances("STORES");
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if (list != null && list.size() > 0 ) {
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return list.get(0).getUri();
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}
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return null;
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}</pre></div></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-config" href="#spring-cloud-consul-config"></a>4. Distributed Configuration with Consul</h1></div></div></div><p>Consul provides a <a class="link" href="https://consul.io/docs/agent/http/kv.html" target="_top">Key/Value Store</a> for storing configuration and other metadata. Spring Cloud Consul Config is an alternative to the <a class="link" href="https://github.com/spring-cloud/spring-cloud-config" target="_top">Config Server and Client</a>. Configuration is loaded into the Spring Environment during the special "bootstrap" phase. Configuration is stored in the <code class="literal">/config</code> folder by default. Multiple <code class="literal">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><pre class="screen">config/testApp,dev/
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config/testApp/
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config/application,dev/
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config/application/</pre><p>The most specific property source is at the top, with the least specific at the bottom. Properties in the <code class="literal">config/application</code> folder are applicable to all applications using consul for configuration. Properties in the <code class="literal">config/testApp</code> folder are only available to the instances of the service named "testApp".</p><p>Configuration is currently read on startup of the application. Sending a HTTP POST to <code class="literal">/refresh</code> will cause the configuration to be reloaded. <a class="xref" href="#spring-cloud-consul-config-watch" title="4.3 Config Watch">Section 4.3, “Config Watch”</a> will also automatically detect changes and reload the application context.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_how_to_activate_2" href="#_how_to_activate_2"></a>4.1 How to activate</h2></div></div></div><p>To get started with Consul Configuration use the starter with group <code class="literal">org.springframework.cloud</code> and artifact id <code class="literal">spring-cloud-starter-consul-config</code>. See the <a class="link" href="http://projects.spring.io/spring-cloud/" target="_top">Spring Cloud Project page</a> for details on setting up your build system with the current Spring Cloud Release Train.</p><p>This will enable auto-configuration that will setup Spring Cloud Consul Config.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_customizing" href="#_customizing"></a>4.2 Customizing</h2></div></div></div><p>Consul Config may be customized using the following properties:</p><p><b>bootstrap.yml. </b>
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</p><pre class="screen">spring:
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cloud:
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consul:
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config:
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enabled: true
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prefix: configuration
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defaultContext: apps
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profileSeparator: '::'</pre><p>
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</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><code class="literal">enabled</code> setting this value to "false" disables Consul Config</li><li class="listitem"><code class="literal">prefix</code> sets the base folder for configuration values</li><li class="listitem"><code class="literal">defaultContext</code> sets the folder name used by all applications</li><li class="listitem"><code class="literal">profileSeparator</code> sets the value of the separator used to separate the profile name in property sources with profiles</li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="spring-cloud-consul-config-watch" href="#spring-cloud-consul-config-watch"></a>4.3 Config Watch</h2></div></div></div><p>The Consul Config Watch takes advantage of the ability of consul to <a class="link" href="https://www.consul.io/docs/agent/watches.html#keyprefix" target="_top">watch a key prefix</a>. The Config Watch makes a blocking Consul HTTP API call to determine if any relevant configuration data has changed for the current application. If there is new configuration data a Refresh Event is published. This is equivalent to calling the <code class="literal">/refresh</code> actuator endpoint.</p><p>To change the frequency of when the Config Watch is called change <code class="literal">spring.cloud.consul.config.watch.delay</code>. The default value is 1000, which is in milliseconds.</p><p>To disable the Config Watch set <code class="literal">spring.cloud.consul.config.watch.enabled=false</code>.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="spring-cloud-consul-config-format" href="#spring-cloud-consul-config-format"></a>4.4 YAML or Properties with Config</h2></div></div></div><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 class="literal">spring.cloud.consul.config.format</code> property to <code class="literal">YAML</code> or <code class="literal">PROPERTIES</code>. For example to use YAML:</p><p><b>bootstrap.yml. </b>
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</p><pre class="screen">spring:
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cloud:
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consul:
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config:
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format: YAML</pre><p>
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</p><p>YAML must be set in the appropriate <code class="literal">data</code> key in consul. Using the defaults above the keys would look like:</p><pre class="screen">config/testApp,dev/data
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config/testApp/data
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config/application,dev/data
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config/application/data</pre><p>You could store a YAML document in any of the keys listed above.</p><p>You can change the data key using <code class="literal">spring.cloud.consul.config.data-key</code>.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="spring-cloud-consul-config-git2consul" href="#spring-cloud-consul-config-git2consul"></a>4.5 git2consul with Config</h2></div></div></div><p>git2consul is a Consul community project that loads files from a git repository to individual keys into Consul. By default the names of the keys are names of the files. YAML and Properties files are supported with file extensions of <code class="literal">.yml</code> and <code class="literal">.properties</code> respectively. Set the <code class="literal">spring.cloud.consul.config.format</code> property to <code class="literal">FILES</code>. For example:</p><p><b>bootstrap.yml. </b>
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</p><pre class="screen">spring:
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cloud:
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consul:
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config:
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format: FILES</pre><p>
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</p><p>Given the following keys in <code class="literal">/config</code>, the <code class="literal">development</code> profile and an application name of <code class="literal">foo</code>:</p><pre class="screen">.gitignore
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application.yml
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bar.properties
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foo-development.properties
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foo-production.yml
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foo.properties
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master.ref</pre><p>the following property sources would be created:</p><pre class="screen">config/foo-development.properties
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config/foo.properties
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config/application.yml</pre><p>The value of each key needs to be a properly formatted YAML or Properties file.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="spring-cloud-consul-failfast" href="#spring-cloud-consul-failfast"></a>4.6 Fail Fast</h2></div></div></div><p>It may be convenient in certain circumstances (like local development or certain test scenarios) to not fail if consul isn’t available for configuration. Setting <code class="literal">spring.cloud.consul.config.failFast=false</code> in <code class="literal">bootstrap.yml</code> will cause the configuration module to log a warning rather than throw an exception. This will allow the application to continue startup normally.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-retry" href="#spring-cloud-consul-retry"></a>5. Consul Retry</h1></div></div></div><p>If you expect that the consul agent may occasionally be unavailable when
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your app starts, you can ask it to keep trying after a failure. You need to add
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<code class="literal">spring-retry</code> and <code class="literal">spring-boot-starter-aop</code> to your classpath. The default
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behaviour is to retry 6 times with an initial backoff interval of 1000ms and an
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exponential multiplier of 1.1 for subsequent backoffs. You can configure these
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properties (and others) using <code class="literal">spring.cloud.consul.retry.*</code> configuration properties.
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This works with both Spring Cloud Consul Config and Discovery registration.</p><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Tip"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="images/tip.png"></td><th align="left">Tip</th></tr><tr><td align="left" valign="top"><p>To take full control of the retry add a <code class="literal">@Bean</code> of type
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<code class="literal">RetryOperationsInterceptor</code> with id "consulRetryInterceptor". Spring
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Retry has a <code class="literal">RetryInterceptorBuilder</code> that makes it easy to create one.</p></td></tr></table></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-bus" href="#spring-cloud-consul-bus"></a>6. Spring Cloud Bus with Consul</h1></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="_how_to_activate_3" href="#_how_to_activate_3"></a>6.1 How to activate</h2></div></div></div><p>To get started with the Consul Bus use the starter with group <code class="literal">org.springframework.cloud</code> and artifact id <code class="literal">spring-cloud-starter-consul-bus</code>. See the <a class="link" href="http://projects.spring.io/spring-cloud/" target="_top">Spring Cloud Project page</a> for details on setting up your build system with the current Spring Cloud Release Train.</p><p>See the <a class="link" href="https://cloud.spring.io/spring-cloud-bus/" target="_top">Spring Cloud Bus</a> documentation for the available actuator endpoints and howto send custom messages.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-hystrix" href="#spring-cloud-consul-hystrix"></a>7. Circuit Breaker with Hystrix</h1></div></div></div><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 class="literal">spring-cloud-starter-hystrix</code>. Hystrix doesn’t depend on the Netflix Discovery Client. The <code class="literal">@EnableHystrix</code> annotation should be placed on a configuration class (usually the main class). Then methods can be annotated with <code class="literal">@HystrixCommand</code> to be protected by a circuit breaker. See <a class="link" href="http://projects.spring.io/spring-cloud/spring-cloud.html#_circuit_breaker_hystrix_clients" target="_top">the documentation</a> for more details.</p></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a name="spring-cloud-consul-turbine" href="#spring-cloud-consul-turbine"></a>8. Hystrix metrics aggregation with Turbine and Consul</h1></div></div></div><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 class="literal">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><p><b>pom.xml. </b>
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</p><pre class="screen"><dependency>
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<groupId>org.springframework.cloud</groupId>
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<artifactId>spring-cloud-netflix-turbine</artifactId>
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</dependency>
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<dependency>
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<groupId>org.springframework.cloud</groupId>
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<artifactId>spring-cloud-starter-consul-discovery</artifactId>
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</dependency></pre><p>
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</p><p>Notice that the Turbine dependency is not a starter. The turbine starter includes support for Netflix Eureka.</p><p><b>application.yml. </b>
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</p><pre class="screen">spring.application.name: turbine
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applications: consulhystrixclient
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turbine:
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aggregator:
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clusterConfig: ${applications}
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appConfig: ${applications}</pre><p>
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</p><p>The <code class="literal">clusterConfig</code> and <code class="literal">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><p><b>Turbine.java. </b>
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</p><pre class="screen">@EnableTurbine
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@SpringBootApplication
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public class Turbine {
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public static void main(String[] args) {
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SpringApplication.run(DemoturbinecommonsApplication.class, args);
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}
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}</pre><p>
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</p></div></div></body></html> |