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.
+Version: Brixton.SR7
+Features
+Spring Cloud focuses on providing good out of box experience for typical use cases +and extensibility mechanism to cover others.
+-
+
-
+
Distributed/versioned configuration
+
+ -
+
Service registration and discovery
+
+ -
+
Routing
+
+ -
+
Service-to-service calls
+
+ -
+
Load balancing
+
+ -
+
Circuit Breakers
+
+ -
+
Global locks
+
+ -
+
Leadership election and cluster state
+
+ -
+
Distributed messaging
+
+
Cloud Native Applications
+Cloud Native 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 12-factor Apps 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.
+Many of those features are covered by Spring Boot, 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 ApplicationContext 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).
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:
+-
+
- + + +
- + + +
- + + +
Extract files into JDK/jre/lib/security folder (whichever version of JRE/JDK x64/x86 you are using).
+|
+ Note
+ |
++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 github. + | +
Spring Cloud Context: Application Context Services
+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.
+The Bootstrap Application Context
+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 Environment
+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, by default.
The bootstrap context uses a different convention for locating
+external configuration than the main application context, so instead
+of application.yml (or .properties) you use bootstrap.yml,
+keeping the external configuration for bootstrap and main context
+nicely separate. Example:
spring:
+ application:
+ name: foo
+ cloud:
+ config:
+ uri: ${SPRING_CONFIG_URI:http://localhost:8888}
+It is a good idea to set the spring.application.name (in
+bootstrap.yml or application.yml) if your application needs any
+application-specific configuration from the server.
You can disable the bootstrap process completely by setting
+spring.cloud.bootstrap.enabled=false (e.g. in System properties).
Application Context Hierarchies
+If you build an application context from SpringApplication or
+SpringApplicationBuilder, 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:
-
+
-
+
"bootstrap": an optional
+CompositePropertySourceappears with high +priority if anyPropertySourceLocatorsare found in the Bootstrap +context, and they have non-empty properties. An example would be +properties from the Spring Cloud Config Server. See +below for instructions +on how to customize the contents of this property source.
+ -
+
"applicationConfig: [classpath:bootstrap.yml]" (and friends if +Spring profiles are active). If you have a
+bootstrap.yml(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 theapplication.yml(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 below for +instructions on how to customize the contents of these property +sources.
+
Because of the ordering rules of property sources the "bootstrap"
+entries take precedence, but note that these do not contain any data
+from bootstrap.yml, which has very low precedence, but can be used
+to set defaults.
You can extend the context hierarchy by simply setting the parent
+context of any ApplicationContext you create, e.g. using its own
+interface, or with the SpringApplicationBuilder convenience methods
+(parent(), child() and sibling()). 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 spring.application.name 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).
Note that the SpringApplicationBuilder allows you to share an
+Environment 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.
Changing the Location of Bootstrap Properties
+The bootstrap.yml (or .properties) location can be specified using
+spring.cloud.bootstrap.name (default "bootstrap") or
+spring.cloud.bootstrap.location (default empty), e.g. in System
+properties. Those properties behave like the spring.config.*
+variants with the same name, in fact they are used to set up the
+bootstrap ApplicationContext by setting those properties in its
+Environment. If there is an active profile (from
+spring.profiles.active or through the Environment 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
+bootstrap-development.properties for a "development" profile.
Overriding the Values of Remote Properties
+The property sources that are added to you application by the
+bootstrap context are often "remote" (e.g. from a Config Server), and
+by default they cannot be overridden locally, except on the command
+line. If you want to allow your applications to override the remote
+properties with their own System properties or config files, the
+remote property source has to grant it permission by setting
+spring.cloud.config.allowOverride=true (it doesn’t work to set this
+locally). Once that flag is set there are some finer grained settings
+to control the location of the remote properties in relation to System
+properties and the application’s local configuration:
+spring.cloud.config.overrideNone=true to override with any local
+property source, and
+spring.cloud.config.overrideSystemProperties=false if only System
+properties and env vars should override the remote settings, but not
+the local config files.
Customizing the Bootstrap Configuration
+The bootstrap context can be trained to do anything you like by adding
+entries to /META-INF/spring.factories under the key
+org.springframework.cloud.bootstrap.BootstrapConfiguration. This is
+a comma-separated list of Spring @Configuration 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 @Beans of type
+ApplicationContextInitializer. Classes can be marked with an @Order
+if you want to control the startup sequence (the default order is
+"last").
|
+ Warning
+ |
+
+Be careful when adding custom BootstrapConfiguration that the
+classes you add are not @ComponentScanned 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 @ComponentScan or @SpringBootApplication
+annotated configuration classes.
+ |
+
The bootstrap process ends by injecting initializers into the main
+SpringApplication 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 spring.factories and then all @Beans of type
+ApplicationContextInitializer are added to the main
+SpringApplication before it is started.
Customizing the Bootstrap Property Sources
+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 PropertySourceLocator to the
+bootstrap context (via spring.factories). You could use this to
+insert additional properties from a different server, or from a
+database, for instance.
As an example, consider the following trivial custom locator:
+@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"));
+ }
+
+}The Environment that is passed in is the one for the
+ApplicationContext 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 Environment (e.g. by
+keying it on the spring.application.name, as is done in the default
+Config Server property source locator).
If you create a jar with this class in it and then add a
+META-INF/spring.factories containing:
org.springframework.cloud.bootstrap.BootstrapConfiguration=sample.custom.CustomPropertySourceLocator+
then the "customProperty" PropertySource will show up in any
+application that includes that jar on its classpath.
Environment Changes
+The application will listen for an EnvironmentChangedEvent and react
+to the change in a couple of standard ways (additional
+ApplicationListeners can be added as @Beans by the user in the
+normal way). When an EnvironmentChangedEvent is observed it will
+have a list of key values that have changed, and the application will
+use those to:
-
+
-
+
Re-bind any
+@ConfigurationPropertiesbeans in the context
+ -
+
Set the logger levels for any properties in
+logging.level.*
+
Note that the Config Client does not by default poll for changes in
+the Environment, and generally we would not recommend that approach
+for detecting changes (although you could set it up with a
+@Scheduled annotation). If you have a scaled-out client application
+then it is better to broadcast the EnvironmentChangedEvent to all
+the instances instead of having them polling for changes (e.g. using
+the Spring Cloud
+Bus).
The EnvironmentChangedEvent covers a large class of refresh use
+cases, as long as you can actually make a change to the Environment
+and publish the event (those APIs are public and part of core
+Spring). You can verify the changes are bound to
+@ConfigurationProperties beans by visiting the /configprops
+endpoint (normal Spring Boot Actuator feature). For instance a
+DataSource can have its maxPoolSize changed at runtime (the
+default DataSource created by Spring Boot is an
+@ConfigurationProperties bean) and grow capacity
+dynamically. Re-binding @ConfigurationProperties 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
+ApplicationContext. To address those concerns we have
+@RefreshScope.
Refresh Scope
+A Spring @Bean that is marked as @RefreshScope 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 DataSource has open
+connections when the database URL is changed via the Environment, 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.
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.
+The RefreshScope is a bean in the context and it has a public method
+refreshAll() to refresh all beans in the scope by clearing the
+target cache. There is also a refresh(String) method to refresh an
+individual bean by name. This functionality is exposed in the
+/refresh endpoint (over HTTP or JMX).
|
+ Note
+ |
+
+@RefreshScope works (technically) on an @Configuration
+class, but it might lead to surprising behaviour: e.g. it does not
+mean that all the @Beans defined in that class are themselves
+@RefreshScope. Specifically, anything that depends on those beans
+cannot rely on them being updated when a refresh is initiated, unless
+it is itself in @RefreshScope (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 @Configuration).
+ |
+
Encryption and Decryption
+Spring Cloud has an Environment pre-processor for decrypting
+property values locally. It follows the same rules as the Config
+Server, and has the same external configuration via encrypt.*. Thus
+you can use encrypted values in the form {cipher}* and as long as
+there is a valid key then they will be decrypted before the main
+application context gets the Environment. To use the encryption
+features in an application 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.
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:
+-
+
- + + +
- + + +
- + + +
Extract files into JDK/jre/lib/security folder (whichever version of JRE/JDK x64/x86 you are using).
+Endpoints
+For a Spring Boot Actuator application there are some additional management endpoints:
+-
+
-
+
POST to
+/envto update theEnvironmentand rebind@ConfigurationPropertiesand log levels
+ -
+
+/refreshfor re-loading the boot strap context and refreshing the@RefreshScopebeans
+ -
+
+/restartfor closing theApplicationContextand restarting it (disabled by default)
+ -
+
+/pauseand/resumefor calling theLifecyclemethods (stop()andstart()on theApplicationContext)
+
Spring Cloud Commons: Common Abstractions
+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).
+Spring RestTemplate as a Load Balancer Client
+RestTemplate can be automatically configured to use ribbon. To create a load balanced RestTemplate create a RestTemplate @Bean and use the @LoadBalanced qualifier.
|
+ Warning
+ |
+
+A RestTemplate bean is no longer created via auto configuration. It must be created by individual applications.
+ |
+
@Configuration
+public class MyConfiguration {
+
+ @LoadBalanced
+ @Bean
+ RestTemplate restTemplate() {
+ return new RestTemplate();
+ }
+}
+
+public class MyClass {
+ @Autowired
+ private RestTemplate restTemplate;
+
+ public String doOtherStuff() {
+ String results = restTemplate.getForObject("http://stores/stores", String.class);
+ return results;
+ }
+}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
+RibbonAutoConfiguration
+for details of how the RestTemplate is set up.
Multiple RestTemplate objects
+If you want a RestTemplate that is not load balanced, create a RestTemplate
+bean and inject it as normal. To access the load balanced RestTemplate use
+the `@LoadBalanced qualifier when you create your @Bean.
|
+ Important
+ |
+
+Notice the @Primary annotation on the plain RestTemplate declaration in the example below, to disambiguate the unqualified @Autowired injection.
+ |
+
@Configuration
+public class MyConfiguration {
+
+ @LoadBalanced
+ @Bean
+ RestTemplate loadBalanced() {
+ return new RestTemplate();
+ }
+
+ @Primary
+ @Bean
+ RestTemplate restTemplate() {
+ return new RestTemplate();
+ }
+}
+
+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);
+ }
+}|
+ Tip
+ |
+
+If you see errors like java.lang.IllegalArgumentException: Can not set org.springframework.web.client.RestTemplate field com.my.app.Foo.restTemplate to com.sun.proxy.$Proxy89 try injecting RestOperations instead or setting spring.aop.proxyTargetClass=true.
+ |
+
Ignore Network Interfaces
+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".
+spring: + cloud: + inetutils: + ignoredInterfaces: + - docker0 + - veth.*+
You can also force to use only specified network addresses using list of regular expressions:
+spring: + cloud: + inetutils: + preferredNetworks: + - 192.168 + - 10.0+
You can also force to use only site local addresses. See Inet4Address.html.isSiteLocalAddress() for more details what is site local address.
+spring: + cloud: + inetutils: + useOnlySiteLocalInterfaces: true+
Spring Cloud Config
+Environment and PropertySource 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.
+Quick Start
+Start the server:
+$ cd spring-cloud-config-server +$ ../mvnw spring-boot:run+
The server is a Spring Boot application so you can run it from your
+IDE instead if you prefer (the main class is
+ConfigServerApplication). Then try out a client:
$ 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"}}
+]}
+The default strategy for locating property sources is to clone a git
+repository (at spring.cloud.config.server.git.uri) and use it to
+initialize a mini SpringApplication. The mini-application’s
+Environment is used to enumerate property sources and publish them
+via a JSON endpoint.
The HTTP service has resources in the form:
+/{application}/{profile}[/{label}]
+/{application}-{profile}.yml
+/{label}/{application}-{profile}.yml
+/{application}-{profile}.properties
+/{label}/{application}-{profile}.properties
+where the "application" is injected as the spring.config.name in the
+SpringApplication (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".)
Spring Cloud Config Server pulls configuration for remote clients +from a git repository (which must be provided):
+spring:
+ cloud:
+ config:
+ server:
+ git:
+ uri: https://github.com/spring-cloud-samples/config-repoClient Side Usage
+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
+org.springframework.cloud:spring-cloud-starter-config. There is also a
+parent pom and BOM (spring-cloud-starter-parent) for Maven users and a
+Spring IO version management properties file for Gradle and Spring CLI
+users. Example Maven configuration:
<parent>
+ <groupId>org.springframework.boot</groupId>
+ <artifactId>spring-boot-starter-parent</artifactId>
+ <version>1.3.5.RELEASE</version>
+ <relativePath /> <!-- lookup parent from repository -->
+ </parent>
+
+<dependencyManagement>
+ <dependencies>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-dependencies</artifactId>
+ <version>Brixton.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 -->Then you can create a standard Spring Boot application, like this simple HTTP server:
+@SpringBootApplication
+@RestController
+public class Application {
+
+ @RequestMapping("/")
+ public String home() {
+ return "Hello World!";
+ }
+
+ public static void main(String[] args) {
+ SpringApplication.run(Application.class, args);
+ }
+
+}
+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 bootstrap.properties (like application.properties but for
+the bootstrap phase of an application context), e.g.
spring.cloud.config.uri: http://myconfigserver.com+
The bootstrap properties will show up in the /env endpoint as a
+high-priority property source, e.g.
$ curl localhost:8080/env
+{
+ "profiles":[],
+ "configService:https://github.com/spring-cloud-samples/config-repo/bar.properties":{"foo":"bar"},
+ "servletContextInitParams":{},
+ "systemProperties":{...},
+ ...
+}
+(a property source called "configService:<URL of remote +repository>/<file name>" contains the property "foo" with value +"bar" and is highest priority).
+|
+ Note
+ |
++the URL in the property source name is the git repository not +the config server URL. + | +
Spring Cloud Config Server
+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
+@EnableConfigServer annotation. So this app is a config server:
@SpringBootApplication
+@EnableConfigServer
+public class ConfigServer {
+ public static void main(String[] args) {
+ SpringApplication.run(ConfigServer.class, args);
+ }
+}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 spring.config.name=configserver (there
+is a configserver.yml in the Config Server jar). Another is
+to use your own application.properties, e.g.
server.port: 8888
+spring.cloud.config.server.git.uri: file://${user.home}/config-repowhere ${user.home}/config-repo is a git repository containing
+YAML and properties files.
|
+ Note
+ |
+
+in Windows you need an extra "/" in the file URL if it is
+absolute with a drive prefix, e.g. file:///${user.home}/config-repo.
+ |
+
|
+ Tip
+ |
+
+
+
+Here’s a recipe for creating the git repository in the example +above: +
+
+
+
+$ 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"+ |
+
|
+ Warning
+ |
++using the local filesystem for your git repository is +intended for testing only. Use a server to host your +configuration repositories in production. + | +
|
+ Warning
+ |
++the initial clone of your configuration repository will +be quick and efficient if you only keep text files in it. If you start +to store binary files, especially large ones, you may experience +delays on the first request for configuration and/or out of memory +errors in the server. + | +
Environment Repository
+Where do you want to store the configuration data for the Config
+Server? The strategy that governs this behaviour is the
+EnvironmentRepository, serving Environment objects. This
+Environment is a shallow copy of the domain from the Spring
+Environment (including propertySources as the main feature). The
+Environment resources are parametrized by three variables:
-
+
-
+
+{application}maps to "spring.application.name" on the client side;
+ -
+
+{profile}maps to "spring.profiles.active" on the client (comma separated list); and
+ -
+
+{label}which is a server side feature labelling a "versioned" set of config files.
+
Repository implementations generally behave just like a Spring Boot
+application loading configuration files from a "spring.config.name"
+equal to the {application} parameter, and "spring.profiles.active"
+equal to the {profiles} 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 Map).
Example: a client application has this bootstrap configuration:
+spring:
+ application:
+ name: foo
+ profiles:
+ active: dev,mysql(as usual with a Spring Boot application, these properties could also +be set as environment variables or command line arguments).
+If the repository is file-based, the server will create an
+Environment from application.yml (shared between all clients), and
+foo.yml (with foo.yml taking precedence). If the YAML files have
+documents inside them that point to Spring profiles, those are applied
+with higher precedence (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 precedence
+translates to a PropertySource listed earlier in the
+Environment. (These are the same rules as apply in a standalone
+Spring Boot application.)
Git Backend
+The default implementation of EnvironmentRepository 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
+application.yml). If you set it with a file: 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 ssh: protocol for a shared
+filesystem repository, so that the server can clone it and use a local
+working copy as a cache.
This repository implementation maps the {label} 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 '').
Placeholders in Git URI
+Spring Cloud Config Server supports a git repository URL with
+placeholders for the {application} and {profile} (and {label} 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):
spring:
+ cloud:
+ config:
+ server:
+ git:
+ uri: https://github.com/myorg/{application}or a "one repo per profile" policy using a similar pattern but with
+{profile}.
Pattern Matching and Multiple Repositories
+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 {application}/{profile} names with wildcards
+(where a pattern beginning with a wildcard may need to be
+quoted). Example:
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-repoIf {application}/{profile} 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 simple/* (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 /* suffix is added automatically to any pattern that
+doesn’t have a profile matcher).
|
+ Note
+ |
++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. + | +
The pattern property in the repo is actually an array, so you can
+use a YAML array (or [0], [1], 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:
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|
+ Note
+ |
+
+Spring Cloud will guess that a pattern containing a profile that
+doesn’t end in * implies that you actually want to match a list of
+profiles starting with this pattern (so */staging is a shortcut for
+["*/staging", "*/staging,*"]). This is common where you need to run
+apps in the "development" profile locally but also the "cloud" profile
+remotely, for instance.
+ |
+
Every repository can also optionally store config files in
+sub-directories, and patterns to search for those directories can be
+specified as searchPaths. For example at the top level:
spring:
+ cloud:
+ config:
+ server:
+ git:
+ uri: https://github.com/spring-cloud-samples/config-repo
+ searchPaths: foo,bar*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".
+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:
+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.gitIn 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.
+To use HTTP basic authentication on the remote repository add the +"username" and "password" properties separately (not in the URL), +e.g.
+spring:
+ cloud:
+ config:
+ server:
+ git:
+ uri: https://github.com/spring-cloud-samples/config-repo
+ username: trolley
+ password: strongpasswordIf you don’t use HTTPS and user credentials, SSH should also work out
+of the box when you store keys in the default directories (~/.ssh)
+and the uri points to an SSH location,
+e.g. "git@github.com: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
+~/.git/config or in the same way as for any other JVM process via
+system properties (-Dhttps.proxyHost and -Dhttps.proxyPort).
|
+ Tip
+ |
+
+If you don’t know where your ~/.git directory is us git config
+--global to manipulate the settings (e.g. git config --global
+http.sslVerify false).
+ |
+
Placeholders in Git Search Paths
+Spring Cloud Config Server also supports a search path with
+placeholders for the {application} and {profile} (and {label} if
+you need it). Example:
spring:
+ cloud:
+ config:
+ server:
+ git:
+ uri: https://github.com/spring-cloud-samples/config-repo
+ searchPaths: '{application}'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).
+Version Control Backend Filesystem Use
+|
+ Warning
+ |
+
+With VCS based backends (git, svn) files are checked out or cloned to the local filesystem. By default they are put in the system temporary directory with a prefix of config-repo-. On linux, for example it could be /tmp/config-repo-<randomid>. Some operating systems routinely clean out temporary directories. This can lead to unexpected behaviour such as missing properties. To avoid this problem, change the directory Config Server uses, by setting spring.cloud.config.server.git.basedir or spring.cloud.config.server.svn.basedir to a directory that does not reside in the system temp structure.
+ |
+
File System Backend
+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".
+|
+ Note
+ |
+
+Remember to use the file: prefix for file resources (the
+default without a prefix is usually the classpath). Just as with any
+Spring Boot configuration you can embed ${}-style environment
+placeholders, but remember that absolute paths in Windows require an
+extra "/", e.g. file:///${user.home}/config-repo
+ |
+
|
+ Warning
+ |
+
+The default value of the searchLocations is identical to a
+local Spring Boot application (so [classpath:/, classpath:/config,
+file:./, file:./config]). This does not expose the
+application.properties from the server to all clients because any
+property sources present in the server are removed before being sent
+to the client.
+ |
+
|
+ Tip
+ |
++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. + | +
The search locations can contain placeholders for {application},
+{profile} and {label}. 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).
If you don’t use placeholders in the search locations, this repository
+also appends the {label} parameter of the HTTP resource to a suffix
+on the search path, so properties files are loaded from each search
+location and 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 /{label}/. For example `file:/tmp/config
+is the same as file:/tmp/config,file:/tmp/config/{label}
Sharing Configuration With All Applications
+With file-based (i.e. git, svn and native) repositories, resources
+with file names in application* are shared between all client
+applications (so application.properties, application.yml,
+application-*.properties etc.). You can use resources with these
+file names to configure global defaults and have them overridden by
+application-specific files as necessary.
The #_property_overrides[property overrides] feature can also be used +for setting global defaults, and with placeholders applications are +allowed to override them locally.
+|
+ Tip
+ |
+
+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 application*
+resources in the default search locations are removed because they are
+part of the server.
+ |
+
Property Overrides
+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
+spring.cloud.config.server.overrides. For example
spring:
+ cloud:
+ config:
+ server:
+ overrides:
+ foo: barwill cause all applications that are config clients to read foo=bar
+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.)
|
+ Tip
+ |
+
+Normal, Spring environment placeholders with "${}" can be escaped
+(and resolved on the client) by using backslash ("\") to escape the
+"$" or the "{", e.g. \${app.foo:bar} 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.
+ |
+
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
+spring.cloud.config.overrideNone=true (default is false) in the
+remote repository.
Health Indicator
+Config Server comes with a Health Indicator that checks if the configured
+EnvironmentRepository is working. By default it asks the EnvironmentRepository
+for an application named app, the default profile and the default
+label provided by the EnvironmentRepository implementation.
You can configure the Health Indicator to check more applications +along with custom profiles and custom labels, e.g.
+spring:
+ cloud:
+ config:
+ server:
+ health:
+ repositories:
+ myservice:
+ label: mylabel
+ myservice-dev:
+ name: myservice
+ profiles: developmentYou can disable the Health Indicator by setting spring.cloud.config.server.health.enabled=false.
Security
+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.
+To use the default Spring Boot configured HTTP Basic security, just
+include Spring Security on the classpath (e.g. through
+spring-boot-starter-security). 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
+security.user.password) and encrypt it (see below for instructions
+on how to do that).
Encryption and Decryption
+|
+ Important
+ |
++Prerequisites: 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). + | +
If the remote property sources contain encrypted content (values
+starting with {cipher}) 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.
If you are setting up a remote config repository for config client
+applications it might contain an application.yml like this, for
+instance:
spring:
+ datasource:
+ username: dbuser
+ password: '{cipher}FKSAJDFGYOS8F7GLHAKERGFHLSAJ'Encrypted values in a .properties file must not be wrapped in quotes, otherwise the value will not be decrypted:
+spring.datasource.username: dbuser
+spring.datasource.password: {cipher}FKSAJDFGYOS8F7GLHAKERGFHLSAJ
+You can safely push this plain text to a shared git repository and the +secret password is protected.
+The server also exposes /encrypt and /decrypt 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 /encrypt endpoint, e.g.
$ curl localhost:8888/encrypt -d mysecret +682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda+
The inverse operation is also available via /decrypt (provided the server is
+configured with a symmetric key or a full key pair):
$ curl localhost:8888/decrypt -d 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda +mysecret+
|
+ Tip
+ |
+
+If you are testing like this with curl, then use
+--data-urlencode (instead of -d) or set an explicit Content-Type:
+text/plain to make sure curl encodes the data correctly when there
+are special characters ('+' is particularly tricky).
+ |
+
Take the encrypted value and add the {cipher} prefix before you put
+it in the YAML or properties file, and before you commit and push it
+to a remote, potentially insecure store.
The /encrypt and /decrypt endpoints also both accept paths of the
+form /*/{name}/{profiles} which can be used to control cryptography
+per application (name) and profile when clients call into the main
+Environment resource.
|
+ Note
+ |
+
+to control the cryptography in this granular way you must also
+provide a @Bean of type TextEncryptorLocator 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).
+ |
+
The spring command line client (with Spring Cloud CLI extensions
+installed) can also be used to encrypt and decrypt, e.g.
$ spring encrypt mysecret --key foo +682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda +$ spring decrypt --key foo 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda +mysecret+
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.
+$ spring encrypt mysecret --key @${HOME}/.ssh/id_rsa.pub
+AQAjPgt3eFZQXwt8tsHAVv/QHiY5sI2dRcR+...
+The key argument is mandatory (despite having a -- prefix).
Key Management
+The Config Server can use a symmetric (shared) key or an asymmetric +one (RSA key pair). The asymmetric choice is superior in terms of +security, but it is often more convenient to use a symmetric key since +it is just a single property value to configure.
+To configure a symmetric key you just need to set encrypt.key to a
+secret String (or use an enviroment variable ENCRYPT_KEY to keep it
+out of plain text configuration files).
To configure an asymmetric key you can either set the key as a
+PEM-encoded text value (in encrypt.key), or via a keystore (e.g. as
+created by the keytool utility that comes with the JDK). The
+keystore properties are encrypt.keyStore.* with * equal to
-
+
-
+
+location(aResourcelocation),
+ -
+
+password(to unlock the keystore) and
+ -
+
+alias(to identify which key in the store is to be +used).
+
The encryption is done with the public key, and a private key is +needed for decryption. Thus in principle you can configure only the +public key in the server if you only want to do encryption (and are +prepared to decrypt the values yourself locally with the private +key). In practice you might not want to do that because it spreads the +key management process around all the clients, instead of +concentrating it in the server. On the other hand it’s a useful option +if your config server really is relatively insecure and only a +handful of clients need the encrypted properties.
+Creating a Key Store for Testing
+To create a keystore for testing you can do something like this:
+$ 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+
Put the server.jks file in the classpath (for instance) and then in
+your application.yml for the Config Server:
encrypt:
+ keyStore:
+ location: classpath:/server.jks
+ password: letmein
+ alias: mytestkey
+ secret: changemeUsing Multiple Keys and Key Rotation
+In addition to the {cipher} prefix in encrypted property values, the
+Config Server looks for {name:value} prefixes (zero or many) before
+the start of the (Base64 encoded) cipher text. The keys are passed to
+a TextEncryptorLocator which can do whatever logic it needs to
+locate a TextEncryptor for the cipher. If you have configured a
+keystore (encrypt.keystore.location) 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:
foo:
+ bar: `{cipher}{key:testkey}...`the locator will look for a key named "testkey". A secret can also be
+supplied via a {secret:…} 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 do
+supply a secret it is recommended that you also encrypt the secrets
+using a custom SecretLocator.
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 {key:…} prefix in all the
+ciphers, checking beforehand of course that the key alias is available
+in the Config Server keystore.
|
+ Tip
+ |
+
+the {name:value} prefixes can also be added to plaintext posted
+to the /encrypt endpoint, if you want to let the Config Server
+handle all encryption as well as decryption.
+ |
+
Serving Encrypted Properties
+Sometimes you want the clients to decrypt the configuration locally,
+instead of doing it in the server. In that case you can still have
+/encrypt and /decrypt endpoints (if you provide the encrypt.*
+configuration to locate a key), but you need to explicitly switch off
+the decryption of outgoing properties using
+spring.cloud.config.server.encrypt.enabled=false. If you don’t care
+about the endpoints, then it should work if you configure neither the
+key nor the enabled flag.
Serving Alternative Formats
+The default JSON format from the environment endpoints is perfect for
+consumption by Spring applications because it maps directly onto the
+Environment abstraction. If you prefer you can consume the same data
+as YAML or Java properties by adding a suffix to the resource path
+(".yml", ".yaml" or ".properties"). This can be useful for consumption
+by applications that do not care about the structure of the JSON
+endpoints, or the extra metadata they provide, for example an
+application that is not using Spring might benefit from the simplicity
+of this approach.
The YAML and properties representations have an additional flag
+(provided as a boolean query parameter resolvePlaceholders) to
+signal that placeholders in the source documents, in the standard
+Spring ${…} form, should be resolved in the output where possible
+before rendering. This is a useful feature for consumers that don’t
+know about the Spring placeholder conventions.
|
+ Note
+ |
++there are limitations in using the YAML or properties formats, +mainly in relation to the loss of metadata. The JSON is structured as +an ordered list of property sources, for example, with names that +correlate with the source. The YAML and properties forms are coalesced +into a single map, even if the origin of the values has multiple +sources, and the names of the original source files are lost. The YAML +representation is not necessarily a faithful representation of the +YAML source in a backing repository either: it is constructed from a +list of flat property sources, and assumptions have to be made about +the form of the keys. + | +
Serving Plain Text
+Instead of using the Environment abstraction (or one of the
+alternative representations of it in YAML or properties format) your
+applications might need generic plain text configuration files,
+tailored to their environment. The Config Server provides these
+through an additional endpoint at /{name}/{profile}/{label}/{path}
+where "name", "profile" and "label" have the same meaning as the
+regular environment endpoint, but "path" is a file name
+(e.g. log.xml). The source files for this endpoint are located in
+the same way as for the environment endpoints: the same search path is
+used as for properties or YAML files, but instead of aggregating all
+matching resources, only the first one to match is returned.
After a resource is located, placeholders in the normal format
+(${…}) are resolved using the effective Environment 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:
application.yml +nginx.conf+
where nginx.conf looks like this:
server {
+ listen 80;
+ server_name ${nginx.server.name};
+}
+and application.yml like this:
nginx:
+ server:
+ name: example.com
+---
+spring:
+ profiles: development
+nginx:
+ server:
+ name: develop.comthen the /foo/default/master/nginx.conf resource looks like this:
server {
+ listen 80;
+ server_name example.com;
+}
+and /foo/development/master/nginx.conf like this:
server {
+ listen 80;
+ server_name develop.com;
+}
+|
+ Note
+ |
+
+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 /*/development/*/logback.xml will be
+resolved by a file called logback-development.xml (in preference
+to logback.xml).
+ |
+
Embedding the Config Server
+The Config Server runs best as a standalone application, but if you
+need to you can embed it in another application. Just use the
+@EnableConfigServer annotation. An optional property that can be
+useful in this case is spring.cloud.config.server.bootstrap 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.
|
+ Note
+ |
+
+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 bootstrap.yml.
+ |
+
To change the location of the server endpoints you can (optionally)
+set spring.cloud.config.server.prefix, e.g. "/config", to serve the
+resources under a prefix. The prefix should start but not end with a
+"/". It is applied to the @RequestMappings in the Config Server
+(i.e. underneath the Spring Boot prefixes server.servletPath and
+server.contextPath).
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 @EnableConfigServer
+annotation (just set spring.cloud.config.server.bootstrap=true).
Push Notifications and Spring Cloud Bus
+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
+Github
+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 spring-cloud-config-monitor library and activate
+the Spring Cloud Bus in your Config Server, then a "/monitor" endpoint
+is enabled.
When the webhook is activated the Config Server will send a
+RefreshRemoteApplicationEvent 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 PropertyPathNotificationExtractor
+which accepts the request headers and body as parameters and returns a list
+of file paths that changed.
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 path={name}. This will
+broadcast to applications matching the "{name}" pattern (can contain
+wildcards).
|
+ Note
+ |
+
+the RefreshRemoteApplicationEvent will only be transmitted if
+the spring-cloud-bus is activated in the Config Server and in the
+client application.
+ |
+
|
+ Note
+ |
++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). + | +
Spring Cloud Config Client
+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 Environment change events.
Config First Bootstrap
+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 spring.cloud.config.uri) and initializes Spring
+Environment with remote property sources.
The net result of this is that all client apps that want to consume
+the Config Server need a bootstrap.yml (or an environment variable)
+with the server address in spring.cloud.config.uri (defaults to
+"http://localhost:8888").
Discovery First Bootstrap
+If you are using a `DiscoveryClient implementation, such as Spring Cloud Netflix +and Eureka Service Discovery or Spring Cloud Consul (Spring Cloud Zookeeper does +not support this yet), then you can have the Config Server register with the +Discovery Service if you want to, but in the default "Config First" mode, +clients won’t be able to take advantage of the registration.
+If you prefer to use DiscoveryClient to locate the Config Server, you can do
+that by setting spring.cloud.config.discovery.enabled=true (default
+"false"). The net result of that is that client apps all need a
+bootstrap.yml (or an environment variable) with the appropriate discovery
+configuration. For example, with Spring Cloud Netflix, you need to define the
+Eureka server address, e.g. in eureka.client.serviceUrl.defaultZone. 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 the Discovery Service is a fixed point. The
+default service id is "configserver" but you can change that on the
+client with spring.cloud.config.discovery.serviceId (and on the server
+in the usual way for a service, e.g. by setting spring.application.name).
The discovery client implementations all support some kind of metadata
+map (e.g. for Eureka we have eureka.instance.metadataMap). 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:
eureka:
+ instance:
+ ...
+ metadataMap:
+ user: osufhalskjrtl
+ password: lviuhlszvaorhvlo5847
+ configPath: /configConfig Client Fail Fast
+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
+spring.cloud.config.failFast=true and the client will halt with
+an Exception.
Config Client Retry
+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 spring.cloud.config.failFast=true, and then you need to add
+spring-retry and spring-boot-starter-aop 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 spring.cloud.config.retry.* configuration properties.
|
+ Tip
+ |
+
+To take full control of the retry add a @Bean of type
+RetryOperationsInterceptor with id "configServerRetryInterceptor". Spring
+Retry has a RetryInterceptorBuilder that makes it easy to create one.
+ |
+
Locating Remote Configuration Resources
+The Config Service serves property sources from /{name}/{profile}/{label}, where the default bindings in the client app are
-
+
-
+
"name" =
+${spring.application.name}
+ -
+
"profile" =
+${spring.profiles.active}(actuallyEnvironment.getActiveProfiles())
+ -
+
"label" = "master"
+
+
All of them can be overridden by setting spring.cloud.config.*
+(where * 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. spring.cloud.config.label=myfeature,develop).
Security
+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.
+spring:
+ cloud:
+ config:
+ uri: https://user:secret@myconfig.mycompany.comor
+spring:
+ cloud:
+ config:
+ uri: https://myconfig.mycompany.com
+ username: user
+ password: secretThe spring.cloud.config.password and spring.cloud.config.username
+values override anything that is provided in the URI.
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":
+spring:
+ cloud:
+ config:
+ uri: ${vcap.services.configserver.credentials.uri:http://user:password@localhost:8888}If you use another form of security you might need to provide a
+RestTemplate to the ConfigServicePropertySourceLocator (e.g. by
+grabbing it in the bootstrap context and injecting one).
Spring Cloud Netflix
+Service Discovery: Eureka Clients
+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.
+Registering with Eureka
+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.
+Example eureka client:
+@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);
+ }
+
+}(i.e. utterly normal Spring Boot app). In this example we use
+@EnableEurekaClient explicitly, but with only Eureka available you
+could also use @EnableDiscoveryClient. Configuration is required to
+locate the Eureka server. Example:
eureka: + client: + serviceUrl: + defaultZone: http://localhost:8761/eureka/+
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).
+The default application name (service ID), virtual host and non-secure
+port, taken from the Environment, are ${spring.application.name},
+${spring.application.name} and ${server.port} respectively.
@EnableEurekaClient 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 eureka.instance.* configuration keys, but the defaults will be
+fine if you ensure that your application has a
+spring.application.name (this is the default for the Eureka service
+ID, or VIP).
See EurekaInstanceConfigBean and EurekaClientConfigBean for more details of the configurable options.
+Authenticating with the Eureka Server
+HTTP basic authentication will be automatically added to your eureka
+client if one of the eureka.client.serviceUrl.defaultZone URLs has
+credentials embedded in it (curl style, like
+http://user:password@localhost:8761/eureka). For more complex needs
+you can create a @Bean of type DiscoveryClientOptionalArgs and
+inject ClientFilter instances into it, all of which will be applied
+to the calls from the client to the server.
|
+ Note
+ |
++Because of a limitation in Eureka it isn’t possible to support +per-server basic auth credentials, so only the first set that are +found will be used. + | +
Status Page and Health Indicator
+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. server.servletPath=/foo) or management endpoint path
+(e.g. management.contextPath=/admin). Example:
eureka:
+ instance:
+ statusPageUrlPath: ${management.context-path}/info
+ healthCheckUrlPath: ${management.context-path}/health
+These links show up in the metadata that is consumed by clients, and +used in some scenarios to decide whether to send requests to your +application, so it’s helpful if they are accurate.
+Registering a Secure Application
+If your app wants to be contacted over HTTPS you can set two flags in
+the EurekaInstanceConfig, viz
+eureka.instance.[nonSecurePortEnabled,securePortEnabled]=[false,true]
+respectively. This will make Eureka publish instance information
+showing an explicit preference for secure communication. The Spring
+Cloud DiscoveryClient will always return an https://…; URI for a
+service configured this way, and the Eureka (native) instance
+information will have a secure health check URL.
Because of the way +Eureka works internally, it will still publish a non-secure URL for +status and home page unless you also override those explicitly. +You can use placeholders to configure the eureka instance urls, +e.g.
+eureka:
+ instance:
+ statusPageUrl: https://${eureka.hostname}/info
+ healthCheckUrl: https://${eureka.hostname}/health
+ homePageUrl: https://${eureka.hostname}/
+(Note that ${eureka.hostname} 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 ${eureka.instance.hostName}.)
|
+ Note
+ |
++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). + | +
Eureka’s Health Checks
+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'.
+eureka: + client: + healthcheck: + enabled: true+
If you require more control over the health checks, you may consider
+implementing your own com.netflix.appinfo.HealthCheckHandler.
Eureka Metadata for Instances and Clients
+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 eureka.instance.metadataMap, 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.
Using Eureka on Cloudfoundry
+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 eureka.instance.instanceId is vcap.application.instance_id. For example:
eureka:
+ instance:
+ hostname: ${vcap.application.uris[0]}
+ nonSecurePort: 80
+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 (PWS).
+Using Eureka on AWS
+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 EurekaInstanceConfigBean the following way:
+@Bean
+@Profile("!default")
+public EurekaInstanceConfigBean eurekaInstanceConfig() {
+ EurekaInstanceConfigBean b = new EurekaInstanceConfigBean();
+ AmazonInfo info = AmazonInfo.Builder.newBuilder().autoBuild("eureka");
+ b.setDataCenterInfo(info);
+ return b;
+}Changing the Eureka Instance ID
+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: ${spring.cloud.client.hostname}:${spring.application.name}:${spring.application.instance_id:${server.port}}}. For example myhost:myappname:8080.
Using Spring Cloud you can override this by providing a unique identifier in eureka.instance.instanceId. For example:
eureka:
+ instance:
+ instanceId: ${spring.application.name}:${spring.application.instance_id:${random.value}}
+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 spring.application.instance_id will be
+populated automatically in a Spring Boot Actuator application, so the
+random value will not be needed.
Using the EurekaClient
+Once you have an app that is @EnableDiscoveryClient (or @EnableEurekaClient) you can use it to
+discover service instances from the Eureka Server. One way to do that is to use the native
+com.netflix.discovery.EurekaClient (as opposed to the Spring
+Cloud DiscoveryClient), e.g.
@Autowired
+private EurekaClient discoveryClient;
+
+public String serviceUrl() {
+ InstanceInfo instance = discoveryClient.getNextServerFromEureka("STORES", false);
+ return instance.getHomePageUrl();
+}
+|
+ Tip
+ |
+
+
+
+Don’t use the |
+
Alternatives to the native Netflix EurekaClient
+You don’t have to use the raw Netflix EurekaClient and usually it
+is more convenient to use it behind a wrapper of some sort. Spring
+Cloud has support for Feign (a REST client
+builder) and also Spring RestTemplate 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 <client>.ribbon.listOfServers to a comma-separated
+list of physical addresses (or hostnames), where <client> is the ID
+of the client.
You can also use the org.springframework.cloud.client.discovery.DiscoveryClient
+which provides a simple API for discovery clients that is not specific
+to Netflix, e.g.
@Autowired
+private DiscoveryClient discoveryClient;
+
+public String serviceUrl() {
+ List<ServiceInstance> list = discoveryClient.getInstances("STORES");
+ if (list != null && list.size() > 0 ) {
+ return list.get(0).getUri();
+ }
+ return null;
+}
+Why is it so Slow to Register a Service?
+Being an instance also involves a periodic heartbeat to the registry
+(via the client’s serviceUrl) 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 heartbeats). You can change the period using
+eureka.instance.leaseRenewalIntervalInSeconds 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.
Service Discovery: Eureka Server
+Example eureka server (e.g. using spring-cloud-starter-eureka-server to set up the classpath):
+@SpringBootApplication
+@EnableEurekaServer
+public class Application {
+
+ public static void main(String[] args) {
+ new SpringApplicationBuilder(Application.class).web(true).run(args);
+ }
+
+}The server has a home page with a UI, and HTTP API endpoints per the
+normal Eureka functionality under /eureka/*.
Eureka background reading: see flux capacitor and google group discussion.
+|
+ Tip
+ |
+
+
+
+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 Boot Gradle plugin must be added and the Spring cloud starter parent bom must be imported like so: +
+
+build.gradle
+
+
+ |
+
High Availability, Zones and Regions
+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).
+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.
+See also below for details of Ribbon +support on the client side for Zones and Regions.
+Standalone Mode
+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:
+server:
+ port: 8761
+
+eureka:
+ instance:
+ hostname: localhost
+ client:
+ registerWithEureka: false
+ fetchRegistry: false
+ serviceUrl:
+ defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
+Notice that the serviceUrl is pointing to the same host as the local
+instance.
Peer Awareness
+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 serviceUrl to a peer, e.g.
--- +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/+
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 /etc/hosts to resolve the host names. In
+fact, the eureka.instance.hostname is not needed if you are running
+on a machine that knows its own hostname (it is looked up using
+java.net.InetAddress by default).
You can add multiple peers to a system, and as long as they are all +directly connected to each other, they will synchronize +the registrations amongst themselves.
+eureka: + client: + serviceUrl: + defaultZone: http://peer1/eureka/,http://peer2/eureka/,http://peer3/eureka/ + +--- +spring: + profiles: peer1 +eureka: + instance: + hostname: peer1 + +--- +spring: + profiles: peer2 +eureka: + instance: + hostname: peer2 + +--- +spring: + profiles: peer3 +eureka: + instance: + hostname: peer3+
Prefer IP Address
+In some cases, it is preferable for Eureka to advertise the IP Adresses
+of services rather than the hostname. Set eureka.instance.preferIpAddress
+to true and when the application registers with eureka, it will use its
+IP Address rather than its hostname.
Circuit Breaker: Hystrix Clients
+Netflix has created a library called Hystrix that implements the circuit breaker pattern. In a microservice architecture it is common to have multiple layers of service calls.
+
+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.
+
+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.
+Example boot app:
+@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 */;
+ }
+}
+The @HystrixCommand is provided by a Netflix contrib library called
+"javanica".
+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.
To configure the @HystrixCommand you can use the commandProperties
+attribute with a list of @HystrixProperty annotations. See
+here
+for more details. See the Hystrix wiki
+for details on the properties available.
Propagating the Security Context or using Spring Scopes
+If you want some thread local context to propagate into a @HystrixCommand 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:
@HystrixCommand(fallbackMethod = "stubMyService",
+ commandProperties = {
+ @HystrixProperty(name="execution.isolation.strategy", value="SEMAPHORE")
+ }
+)
+...The same thing applies if you are using @SessionScope or @RequestScope. You will know when you need to do this because of a runtime exception that says it can’t find the scoped context.
Health Indicator
+The state of the connected circuit breakers are also exposed in the
+/health endpoint of the calling application.
{
+ "hystrix": {
+ "openCircuitBreakers": [
+ "StoreIntegration::getStoresByLocationLink"
+ ],
+ "status": "CIRCUIT_OPEN"
+ },
+ "status": "UP"
+}Hystrix Metrics Stream
+To enable the Hystrix metrics stream include a dependency on spring-boot-starter-actuator. This will expose the /hystrix.stream as a management endpoint.
<dependency>
+ <groupId>org.springframework.boot</groupId>
+ <artifactId>spring-boot-starter-actuator</artifactId>
+ </dependency>Circuit Breaker: Hystrix Dashboard
+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.
+
+To run the Hystrix Dashboard annotate your Spring Boot main class with @EnableHystrixDashboard. You then visit /hystrix and point the dashboard to an individual instances /hystrix.stream endpoint in a Hystrix client application.
Turbine
+Looking at an individual instances Hystrix data is not very useful in terms of the overall health of the system. Turbine is an application that aggregates all of the relevant /hystrix.stream endpoints into a combined /turbine.stream for use in the Hystrix Dashboard. Individual instances are located via Eureka. Running Turbine is as simple as annotating your main class with the @EnableTurbine annotation (e.g. using spring-cloud-starter-turbine to set up the classpath). All of the documented configuration properties from the Turbine 1 wiki apply. The only difference is that the turbine.instanceUrlSuffix does not need the port prepended as this is handled automatically unless turbine.instanceInsertPort=false.
The configuration key turbine.appConfig 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: http://my.turbine.sever:8080/turbine.stream?cluster=<CLUSTERNAME>; (the cluster parameter can be omitted if the name is "default"). The cluster parameter must match an entry in turbine.aggregator.clusterConfig. Values returned from eureka are uppercase, thus we expect this example to work if there is an app registered with Eureka called "customers":
turbine: + aggregator: + clusterConfig: CUSTOMERS + appConfig: customers+
The clusterName can be customized by a SPEL expression in turbine.clusterNameExpression with root an instance of InstanceInfo. The default value is appName, which means that the Eureka serviceId ends up as the cluster key (i.e. the InstanceInfo for customers has an appName of "CUSTOMERS"). A different example would be turbine.clusterNameExpression=aSGName, which would get the cluster name from the AWS ASG name. Another example:
turbine: + aggregator: + clusterConfig: SYSTEM,USER + appConfig: customers,stores,ui,admin + clusterNameExpression: metadata['cluster']+
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".
+To use the "default" cluster for all apps you need a string literal expression (with single quotes, and escaped with double quotes if it is in YAML as well):
+turbine: + appConfig: customers,stores + clusterNameExpression: "'default'"+
Spring Cloud provides a spring-cloud-starter-turbine that has all the dependencies you need to get a Turbine server running. Just create a Spring Boot application and annotate it with @EnableTurbine.
|
+ Note
+ |
+
+by default the native Netflix behaviour built into Turbine does not allow multiple processes per host, per cluster (the key to the instance id is the hostname). Spring Cloud generalizes this a bit, allowing the host and port to be used as the key, but only if you set the property turbine.combineHostPort=true
+ |
+
Turbine Stream
+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 messaging. All you need to do on the client is add a dependency to spring-cloud-netflix-hystrix-stream and the spring-cloud-starter-stream-* of your choice (see Spring Cloud Stream documentation for details on the brokers, and how to configure the client credentials, but it should work out of the box for a local broker).
On the server side Just create a Spring Boot application and annotate it with @EnableTurbineStream 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 server.port or turbine.stream.port. If you have spring-boot-starter-web and spring-boot-starter-actuator on the classpath as well, then you can open up the Actuator endpoints on a separate port (with Tomcat by default) by providing a management.port which is different.
You can then point the Hystrix Dashboard to the Turbine Stream Server instead of individual Hystrix streams. If Turbine Stream is running on port 8989 on myhost, then put http://myhost:8989 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.
Spring Cloud provides a spring-cloud-starter-turbine-stream that has all the dependencies you need to get a Turbine Stream server running - just add the Stream binder of your choice, e.g. spring-cloud-starter-stream-rabbit. You need Java 8 to run the app because it is Netty-based.
Client Side Load Balancer: Ribbon
+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 @FeignClient then this section also applies.
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 @FeignClient
+annotation). Spring Cloud creates a new ensemble as an
+ApplicationContext on demand for each named client using
+RibbonClientConfiguration. This contains (amongst other things) an
+ILoadBalancer, a RestClient, and a ServerListFilter.
Customizing the Ribbon Client
+You can configure some bits of a Ribbon client using external
+properties in <client>.ribbon.*, 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 CommonClientConfigKey (part of
+ribbon-core).
Spring Cloud also lets you take full control of the client by
+declaring additional configuration (on top of the
+RibbonClientConfiguration) using @RibbonClient. Example:
@Configuration
+@RibbonClient(name = "foo", configuration = FooConfiguration.class)
+public class TestConfiguration {
+}In this case the client is composed from the components already in
+RibbonClientConfiguration together with any in FooConfiguration
+(where the latter generally will override the former).
|
+ Warning
+ |
+
+The FooConfiguration has to be @Configuration but take
+care that it is not in a @ComponentScan for the main application
+context, otherwise it will be shared by all the @RibbonClients. If
+you use @ComponentScan (or @SpringBootApplication) 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 @ComponentScan).
+ |
+
Spring Cloud Netflix provides the following beans by default for ribbon
+(BeanType beanName: ClassName):
-
+
-
+
+IClientConfigribbonClientConfig:DefaultClientConfigImpl
+ -
+
+IRuleribbonRule:ZoneAvoidanceRule
+ -
+
+IPingribbonPing:NoOpPing
+ -
+
+ServerList<Server>ribbonServerList:ConfigurationBasedServerList
+ -
+
+ServerListFilter<Server>ribbonServerListFilter:ZonePreferenceServerListFilter
+ -
+
+ILoadBalancerribbonLoadBalancer:ZoneAwareLoadBalancer
+
Creating a bean of one of those type and placing it in a @RibbonClient
+configuration (such as FooConfiguration above) allows you to override each
+one of the beans described. Example:
@Configuration
+public class FooConfiguration {
+ @Bean
+ public IPing ribbonPing(IClientConfig config) {
+ return new PingUrl();
+ }
+}This replaces the NoOpPing with PingUrl.
Using Ribbon with Eureka
+When Eureka is used in conjunction with Ribbon the ribbonServerList
+is overridden with an extension of DiscoveryEnabledNIWSServerList
+which populates the list of servers from Eureka. It also replaces the
+IPing interface with NIWSDiscoveryPing which delegates to Eureka
+to determine if a server is up. The ServerList that is installed by
+default is a DomainExtractingServerList 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 remote clients set
+eureka.instance.metadataMap.zone), and if that is missing it can use
+the domain name from the server hostname as a proxy for zone (if the
+flag approximateZoneFromHostname is set). Once the zone information
+is available it can be used in a ServerListFilter. By default it
+will be used to locate a server in the same zone as the client because
+the default is a ZonePreferenceServerListFilter. The zone of the
+client is determined the same way as the remote instances by default,
+i.e. via eureka.instance.metadataMap.zone.
|
+ Note
+ |
++The orthodox "archaius" way to set the client zone is via a +configuration property called "@zone", and Spring Cloud will use that +in preference to all other settings if it is available (note that the +key will have to be quoted in YAML configuration). + | +
|
+ Note
+ |
+
+If there is no other source of zone data then a guess is made
+based on the client configuration (as opposed to the instance
+configuration). We take eureka.client.availabilityZones, which is a
+map from region name to a list of zones, and pull out the first zone
+for the instance’s own region (i.e. the eureka.client.region, which
+defaults to "us-east-1" for comatibility with native Netflix).
+ |
+
Example: How to Use Ribbon Without Eureka
+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 @RibbonClient 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
stores: + ribbon: + listOfServers: example.com,google.com+
Example: Disable Eureka use in Ribbon
+Setting the property ribbon.eureka.enabled = false will explicitly
+disable the use of Eureka in Ribbon.
ribbon: + eureka: + enabled: false+
Using the Ribbon API Directly
+You can also use the LoadBalancerClient directly. Example:
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
+ }
+}Declarative REST Client: Feign
+Feign 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 HttpMessageConverters used by default in Spring Web. Spring Cloud integrates Ribbon and Eureka to provide a load balanced http client when using Feign.
Example spring boot app
+@Configuration
+@ComponentScan
+@EnableAutoConfiguration
+@EnableEurekaClient
+@EnableFeignClients
+public class Application {
+
+ public static void main(String[] args) {
+ SpringApplication.run(Application.class, args);
+ }
+
+}@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);
+}In the @FeignClient annotation the String value ("stores" above) is
+an arbitrary client name, which is used to create a Ribbon load
+balancer (see below for details of Ribbon
+support). You can also specify a URL using the url attribute
+(absolute value or just a hostname). The name of the bean in the application context is the fully qualified name of the interface. An alias is also created which is the 'name' attribute plus 'FeignClient'. For the example above, @Qualifier("storesFeignClient") could be used to reference the bean.
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 +above for example).
+Overriding Feign Defaults
+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 @FeignClient annotation. Spring Cloud creates a new ensemble as an
+ApplicationContext on demand for each named client using FeignClientsConfiguration. This contains (amongst other things) an feign.Decoder, a feign.Encoder, and a feign.Contract.
Spring Cloud lets you take full control of the feign client by declaring additional configuration (on top of the FeignClientsConfiguration) using @FeignClient. Example:
@FeignClient(name = "stores", configuration = FooConfiguration.class)
+public interface StoreClient {
+ //..
+}In this case the client is composed from the components already in FeignClientsConfiguration together with any in FooConfiguration (where the latter will override the former).
|
+ Warning
+ |
+
+The FooConfiguration has to be @Configuration but take care that it is not in a @ComponentScan for the main application context, otherwise it will be used for every @FeignClient. If you use @ComponentScan (or @SpringBootApplication) 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 @ComponentScan).
+ |
+
|
+ Note
+ |
+
+The serviceId attribute is now deprecated in favor of the name attribute.
+ |
+
|
+ Warning
+ |
+
+Previously, using the url attribute, did not require the name attribute. Using name is now required.
+ |
+
Placeholders are supported in the name and url attributes.
@FeignClient(name = "${feign.name}", url = "${feign.url}")
+public interface StoreClient {
+ //..
+}Spring Cloud Netflix provides the following beans by default for feign (BeanType beanName: ClassName):
-
+
-
+
+DecoderfeignDecoder:ResponseEntityDecoder(which wraps aSpringDecoder)
+ -
+
+EncoderfeignEncoder:SpringEncoder
+ -
+
+LoggerfeignLogger:Slf4jLogger
+ -
+
+ContractfeignContract:SpringMvcContract
+ -
+
+Feign.BuilderfeignBuilder:HystrixFeign.Builder
+
Spring Cloud Netflix does not 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:
+-
+
-
+
+Logger.Level
+ -
+
+Retryer
+ -
+
+ErrorDecoder
+ -
+
+Request.Options
+ -
+
+Collection<RequestInterceptor>
+
Creating a bean of one of those type and placing it in a @FeignClient configuration (such as FooConfiguration above) allows you to override each one of the beans described. Example:
@Configuration
+public class FooConfiguration {
+ @Bean
+ public Contract feignContract() {
+ return new feign.Contract.Default();
+ }
+
+ @Bean
+ public BasicAuthRequestInterceptor basicAuthRequestInterceptor() {
+ return new BasicAuthRequestInterceptor("user", "password");
+ }
+}This replaces the SpringMvcContract with feign.Contract.Default and adds a RequestInterceptor to the collection of RequestInterceptor.
Default configurations can be specified in the @EnableFeignClients attribute defaultConfiguration in a similar manner as described above. The difference is that this configuration will apply to all feign clients.
Feign Hystrix Support
+If Hystrix is on the classpath, by default Feign will wrap all methods with a circuit breaker. Returning a com.netflix.hystrix.HystrixCommand is also available. This lets you use reactive patterns (with a call to .toObservable() or .observe() or asynchronous use (with a call to .queue()).
To disable Hystrix support for Feign, set feign.hystrix.enabled=false.
To disable Hystrix support on a per-client basis create a vanilla Feign.Builder with the "prototype" scope, e.g.:
@Configuration
+public class FooConfiguration {
+ @Bean
+ @Scope("prototype")
+ public Feign.Builder feignBuilder() {
+ return Feign.builder();
+ }
+}Feign Hystrix Fallbacks
+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 @FeignClient set the fallback attribute to the class name that implements the fallback.
@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");
+ }
+}|
+ Warning
+ |
+
+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 com.netflix.hystrix.HystrixCommand and rx.Observable.
+ |
+
Feign Inheritance Support
+Feign supports boilerplate apis via single-inheritance interfaces. +This allows grouping common operations into convenient base interfaces.
+public interface UserService {
+
+ @RequestMapping(method = RequestMethod.GET, value ="/users/{id}")
+ User getUser(@PathVariable("id") long id);
+}@RestController
+public class UserResource implements UserService {
+
+}package project.user;
+
+@FeignClient("users")
+public interface UserClient extends UserService {
+
+}|
+ Note
+ |
++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). + | +
Feign request/response compression
+You may consider enabling the request or response GZIP compression for your +Feign requests. You can do this by enabling one of the properties:
+feign.compression.request.enabled=true
+feign.compression.response.enabled=trueFeign request compression gives you settings similar to what you may set for your web server:
+feign.compression.request.enabled=true
+feign.compression.request.mime-types=text/xml,application/xml,application/json
+feign.compression.request.min-request-size=2048These properties allow you to be selective about the compressed media types and minimum request threshold length.
+Feign logging
+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 DEBUG level.
logging.level.project.user.UserClient: DEBUGThe Logger.Level object that you may configure per client, tells Feign how much to log. Choices are:
-
+
-
+
+NONE, No logging (DEFAULT).
+ -
+
+BASIC, Log only the request method and URL and the response status code and execution time.
+ -
+
+HEADERS, Log the basic information along with request and response headers.
+ -
+
+FULL, Log the headers, body, and metadata for both requests and responses.
+
For example, the following would set the Logger.Level to FULL:
@Configuration
+public class FooConfiguration {
+ @Bean
+ Logger.Level feignLoggerLevel() {
+ return Logger.Level.FULL;
+ }
+}External Configuration: Archaius
+Archaius 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 Apache Commons Configuration 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.
+class ArchaiusTest {
+ DynamicStringProperty myprop = DynamicPropertyFactory
+ .getInstance()
+ .getStringProperty("my.prop");
+
+ void doSomething() {
+ OtherClass.someMethod(myprop.get());
+ }
+}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.
+Router and Filter: Zuul
+Routing in an integral part of a microservice architecture. For example, / may be mapped to your web application, /api/users is mapped to the user service and /api/shop is mapped to the shop service. Zuul is a JVM based router and server side load balancer by Netflix.
Netflix uses Zuul for the following:
+-
+
-
+
Authentication
+
+ -
+
Insights
+
+ -
+
Stress Testing
+
+ -
+
Canary Testing
+
+ -
+
Dynamic Routing
+
+ -
+
Service Migration
+
+ -
+
Load Shedding
+
+ -
+
Security
+
+ -
+
Static Response handling
+
+ -
+
Active/Active traffic management
+
+
Zuul’s rule engine allows rules and filters to be written in essentially any JVM language, with built in support for Java and Groovy.
+|
+ Note
+ |
+
+The configuration property zuul.max.host.connections has been replaced by two new properties, zuul.host.maxTotalConnections and zuul.host.maxPerRouteConnections which default to 200 and 20 respectively.
+ |
+
Embedded Zuul Reverse Proxy
+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.
+To enable it, annotate a Spring Boot main class with
+@EnableZuulProxy, and this forwards local calls to the appropriate
+service. By convention, a service with the ID "users", will
+receive requests from the proxy located at /users (with the prefix
+stripped). The proxy uses Ribbon to locate an instance to forward to
+via discovery, 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.
|
+ Note
+ |
++the Zuul starter does not include a discovery client, so for +routes based on service IDs you need to provide one of those +on the classpath as well (e.g. Eureka is one choice). + | +
To skip having a service automatically added, set
+zuul.ignored-services 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:
zuul:
+ ignoredServices: '*'
+ routes:
+ users: /myusers/**In this example, all services are ignored except "users".
+To augment or change +the proxy routes, you can add external configuration like the +following:
+ zuul:
+ routes:
+ users: /myusers/**This means that http calls to "/myusers" get forwarded to the "users" +service (for example "/myusers/101" is forwarded to "/101").
+To get more fine-grained control over a route you can specify the path +and the serviceId independently:
+ zuul:
+ routes:
+ users:
+ path: /myusers/**
+ serviceId: users_serviceThis 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/**" matches hierarchically.
+The location of the backend can be specified as either a "serviceId" +(for a service from discovery) or a "url" (for a physical location), e.g.
+ zuul:
+ routes:
+ users:
+ path: /myusers/**
+ url: http://example.com/users_serviceThese simple url-routes don’t get executed as a HystrixCommand nor can you loadbalance multiple URLs 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 above for more information), e.g.
zuul:
+ routes:
+ users:
+ path: /myusers/**
+ serviceId: users
+
+ribbon:
+ eureka:
+ enabled: false
+
+users:
+ ribbon:
+ listOfServers: example.com,google.comYou can provide convention between serviceId and routes using +regexmapper. It uses regular expression named groups to extract +variables from serviceId and inject them into a route pattern.
+@Bean
+public PatternServiceRouteMapper serviceRouteMapper() {
+ return new PatternServiceRouteMapper(
+ "(?<name>^.+)-(?<version>v.+$)",
+ "${version}/${name}");
+}This means that a serviceId "myusers-v1" will be mapped to route +"/v1/myusers/**". Any regular expression is accepted but all named +groups must be present in both servicePattern and routePattern. If +servicePattern does not match a serviceId, the default behavior is +used. In the example above, a serviceId "myusers" will be mapped to route +"/myusers/**" (no version detected) This feature is disable by +default and only applies to discovered services.
+To add a prefix to all mappings, set zuul.prefix to a value, such as
+/api. The proxy prefix is stripped from the request before the
+request is forwarded by default (switch this behaviour off with
+zuul.stripPrefix=false). You can also switch off the stripping of
+the service-specific prefix from individual routes, e.g.
zuul:
+ routes:
+ users:
+ path: /myusers/**
+ stripPrefix: falseIn this example, requests to "/myusers/101" will be forwarded to "/myusers/101" on the "users" service.
+The zuul.routes entries actually bind to an object of type ZuulProperties. 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).
The X-Forwarded-Host header is added to the forwarded requests by
+default. To turn it off set zuul.addProxyHeaders = false. 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).
An application with @EnableZuulProxy could act as a standalone
+server if you set a default route ("/"), for example zuul.route.home:
+/ would route all traffic (i.e. "/**") to the "home" service.
If more fine-grained ignoring is needed, you can specify specific patterns to ignore. +These patterns are 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.
+ zuul:
+ ignoredPatterns: /**/admin/**
+ routes:
+ users: /myusers/**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.
+Cookies and Sensitive Headers
+It’s OK to share headers between services in the same system, but you +probably don’t want sensitive headers leaking downstream into external +servers. You can specify a list of ignored headers as part of the +route configuration. Cookies play a special role because they have +well-defined semantics in browsers, and they are always to be treated +as sensitive. If the consumer of your proxy is a browser, then cookies +for downstream services also cause problems for the user because they +all get jumbled up (all downstream services look like they come from +the same place).
+If you are careful with the design of your services, for example if +only one of the downstream services sets cookies, then you might be +able to let them flow from the backend all the way up to the +caller. Also, if your proxy sets cookies and all your back end +services are part of the same system, it can be natural to simply +share them (and for instance use Spring Session to link them up to some +shared state). Other than that, any cookies that get set by downstream +services are likely to be not very useful to the caller, so it is +recommended that you make (at least) "Set-Cookie" and "Cookie" into +sensitive headers for routes that are not part of your domain. Even +for routes that are part of your domain, try to think carefully +about what it means before allowing cookies to flow between them and +the proxy.
+The sensitive headers can be configured as a comma-separated list per +route, e.g.
+ zuul:
+ routes:
+ users:
+ path: /myusers/**
+ sensitiveHeaders: Cookie,Set-Cookie,Authorization
+ url: https://downstreamSensitive headers can also be set globally by setting zuul.sensitiveHeaders. If sensitiveHeaders is set on a route, this will override the global sensitiveHeaders setting.
|
+ Note
+ |
+
+this is the default value for sensitiveHeaders, so you don’t
+need to set it unless you want it to be different. N.B. this is new in
+Spring Cloud Netflix 1.1 (in 1.0 the user had no control over headers
+and all cookies flow in both directions).
+ |
+
In addition to the per-route sensitive headers, you can set a global
+value for zuul.ignoredHeaders for values that should be discarded
+(both request and response) during interactions with downstream
+services. By default these are empty, if Spring Security is not on the
+classpath, and otherwise they are initialized to a set of well-known
+"security" headers (e.g. involving caching) as specified by Spring
+Security. The assumption in this case is that the downstream services
+might add these headers too, and we want the values from the proxy.
The Routes Endpoint
+If you are using @EnableZuulProxy with tha Spring Boot Actuator you
+will enable (by default) an additional endpoint, available via HTTP as
+/routes. A GET to this endpoint will return a list of the mapped
+routes. A POST will force a refresh of the existing routes (e.g. in
+case there have been changes in the service catalog).
|
+ Note
+ |
++the routes should respond automatically to changes in the +service catalog, but the POST to /routes is a way to force the change +to happen immediately. + | +
Strangulation Patterns and Local Forwards
+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.
+Example configuration:
+ 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.comIn 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
+/first/** have been extracted into a new service with an external
+URL. And paths in /second/** are forwared so they can be handled
+locally, e.g. with a normal Spring @RequestMapping. Paths in
+/third/** are also forwarded, but with a different prefix
+(i.e. /third/foo is forwarded to /3rd/foo).
|
+ Note
+ |
++The ignored patterns aren’t completely ignored, they just +aren’t handled by the proxy (so they are also effectively forwarded +locally). + | +
Uploading Files through Zuul
+If you @EnableZuulProxy 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 DispatcherServlet (to
+avoid multipart processing) in "/zuul/*". I.e. if
+zuul.routes.customers=/customers/** then you can
+POST large files to "/zuul/customers/*". The servlet
+path is externalized via zuul.servletPath. Extremely
+large files will also require elevated timeout settings
+if the proxy route takes you through a Ribbon load
+balancer, e.g.
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds: 60000
+ribbon:
+ ConnectTimeout: 3000
+ ReadTimeout: 60000Note 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:
+$ curl -v -H "Transfer-Encoding: chunked" \ + -F "file=@mylarge.iso" localhost:9999/zuul/simple/file+
Plain Embedded Zuul
+You can also run a Zuul server without the proxying, or switch on parts of the proxying platform selectively, if you
+use @EnableZuulServer (instead of @EnableZuulProxy). Any beans that you add to the application of type ZuulFilter
+will be installed automatically, as they are with @EnableZuulProxy, but without any of the proxy filters being added
+automatically.
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:
+ zuul:
+ routes:
+ api: /api/**maps all paths in "/api/**" to the Zuul filter chain.
+Disable Zuul Filters
+Zuul for Spring Cloud comes with a number of ZuulFilter beans enabled by default
+in both proxy and server mode. See the zuul filters package for the
+possible filters that are enabled. If you want to disable one, simply set
+zuul.<SimpleClassName>.<filterType>.disable=true. By convention, the package after
+filters is the Zuul filter type. For example to disable
+org.springframework.cloud.netflix.zuul.filters.post.SendResponseFilter set
+zuul.SendResponseFilter.post.disable=true.
Polyglot support with Sidecar
+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 +Netflix Prana. 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.
+To enable the Sidecar, create a Spring Boot application with @EnableSidecar.
+This annotation includes @EnableCircuitBreaker, @EnableDiscoveryClient,
+and @EnableZuulProxy. Run the resulting application on the same host as the
+non-jvm application.
To configure the side car add sidecar.port and sidecar.health-uri to application.yml.
+The sidecar.port property is the port the non-jvm app is listening on. This
+is so the Sidecar can properly register the app with Eureka. The sidecar.health-uri
+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:
{
+ "status":"UP"
+}Here is an example application.yml for a Sidecar application:
+server:
+ port: 5678
+spring:
+ application:
+ name: sidecar
+
+sidecar:
+ port: 8000
+ health-uri: http://localhost:8000/health.jsonThe api for the DiscoveryClient.getInstances() method is /hosts/{serviceId}.
+Here is an example response for /hosts/customers that returns two instances on
+different hosts. This api is accessible to the non-jvm app (if the sidecar is
+on port 5678) at http://localhost:5678/hosts/{serviceId}.
[
+ {
+ "host": "myhost",
+ "port": 9000,
+ "uri": "http://myhost:9000",
+ "serviceId": "CUSTOMERS",
+ "secure": false
+ },
+ {
+ "host": "myhost2",
+ "port": 9000,
+ "uri": "http://myhost2:9000",
+ "serviceId": "CUSTOMERS",
+ "secure": false
+ }
+]The Zuul proxy automatically adds routes for each service known in eureka to
+/<serviceId>, so the customers service is available at /customers. The
+Non-jvm app can access the customer service via http://localhost:5678/customers
+(assuming the sidecar is listening on port 5678).
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 configserver
+and the Sidecar is on port 5678, then it can be accessed at
+http://localhost:5678/configserver
Non-jvm app can take advantage of the Config Server’s ability to return YAML +documents. For example, a call to http://sidecar.local.spring.io:5678/configserver/default-master.yml +might result in a YAML document like the following
+eureka:
+ client:
+ serviceUrl:
+ defaultZone: http://localhost:8761/eureka/
+ password: password
+info:
+ description: Spring Cloud Samples
+ url: https://github.com/spring-cloud-samplesRxJava with Spring MVC
+Spring Cloud Netflix includes the RxJava.
+++++RxJava is a Java VM implementation of Reactive Extensions: a library for composing asynchronous and event-based programs by using observable sequences.
+
Spring Cloud Netflix provides support for returning rx.Single objects from Spring MVC Controllers. It also supports using rx.Observable objects for Server-sent events (SSE). This can be very convenient if your internal APIs are already built using RxJava (see Feign Hystrix Support for examples).
Here are some examples of using rx.Single:
@RequestMapping(method = RequestMethod.GET, value = "/single")
+ public Single<String> single() {
+ return Single.just("single value");
+ }
+
+@RequestMapping(method = RequestMethod.GET, value = "/singleWithResponse")
+public ResponseEntity<Single<String>> singleWithResponse() {
+ return new ResponseEntity<>(Single.just("single value"),
+ HttpStatus.NOT_FOUND);
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/singleCreatedWithResponse")
+public Single<ResponseEntity<String>> singleOuterWithResponse() {
+ return Single.just(new ResponseEntity<>("single value", HttpStatus.CREATED));
+}
+
+ @RequestMapping(method = RequestMethod.GET, value = "/throw")
+ public Single<Object> error() {
+ return Single.error(new RuntimeException("Unexpected"));
+ }If you have an Observable, rather than a single, you can use .toSingle() or .toList().toSingle(). Here are some examples:
@RequestMapping(method = RequestMethod.GET, value = "/single")
+public Single<String> single() {
+ return Observable.just("single value").toSingle();
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/multiple")
+public Single<List<String>> multiple() {
+ return Observable.just("multiple", "values").toList().toSingle();
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/responseWithObservable")
+public ResponseEntity<Single<String>> responseWithObservable() {
+
+ Observable<String> observable = Observable.just("single value");
+ HttpHeaders headers = new HttpHeaders();
+ headers.setContentType(APPLICATION_JSON_UTF8);
+ return new ResponseEntity<>(observable.toSingle(), headers, HttpStatus.CREATED);
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/timeout")
+public Observable<String> timeout() {
+ return Observable.timer(1, TimeUnit.MINUTES).map(new Func1<Long, String>() {
+ @Override
+ public String call(Long aLong) {
+ return "single value";
+ }
+ });
+}If you have a streaming endpoint and client, SSE could be an option. To convert rx.Observable to a Spring SseEmitter use RxResponse.sse(). Here are some examples:
@RequestMapping(method = RequestMethod.GET, value = "/sse")
+public SseEmitter single() {
+ return RxResponse.sse(Observable.just("single value"));
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/messages")
+public SseEmitter messages() {
+ return RxResponse.sse(Observable.just("message 1", "message 2", "message 3"));
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/events")
+public SseEmitter event() {
+ return RxResponse.sse(APPLICATION_JSON_UTF8, Observable.just(
+ new EventDto("Spring io", getDate(2016, 5, 19)),
+ new EventDto("SpringOnePlatform", getDate(2016, 8, 1))
+ ));
+}Metrics: Spectator, Servo, and Atlas
+When used together, Spectator/Servo and Atlas provide a near real-time operational insight platform.
+Spectator and Servo are Netflix’s metrics collection libraries. Atlas is a Netflix metrics backend to manage dimensional time series data.
+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.
+Dimensional vs. Hierarchical Metrics
+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:
+{
+ "counter.status.200.root": 20,
+ "counter.status.400.root": 3,
+ "counter.status.200.star-star": 5,
+}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 counter.status.200. that would read all 20 metrics and aggregate the results. Alternatively, you could provide a HandlerInterceptorAdapter that intercepts and records a metric like counter.status.200.all 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 counter.status.2.*.
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 counter.status.200.root becomes counter.status.200.method.get.root, etc. Our counter.status.200.* 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.
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.
+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:
+{
+ "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,
+}Default Metrics Collection
+Without any additional dependencies or configuration, a Spring Cloud based service will autoconfigure a Servo MonitorRegistry and begin collecting metrics on every Spring MVC request. By default, a Servo timer with the name rest will be recorded for each MVC request which is tagged with:
-
+
-
+
HTTP method
+
+ -
+
HTTP status (e.g. 200, 400, 500)
+
+ -
+
URI (or "root" if the URI is empty), sanitized for Atlas
+
+ -
+
The exception class name, if the request handler threw an exception
+
+ -
+
The caller, if a request header with a key matching
+netflix.metrics.rest.callerHeaderis set on the request. There is no default key fornetflix.metrics.rest.callerHeader. You must add it to your application properties if you wish to collect caller information.
+
Set the netflix.metrics.rest.metricName property to change the name of the metric from rest to a name you provide.
If Spring AOP is enabled and org.aspectj:aspectjweaver is present on your runtime classpath, Spring Cloud will also collect metrics on every client call made with RestTemplate. A Servo timer with the name of restclient will be recorded for each MVC request which is tagged with:
-
+
-
+
HTTP method
+
+ -
+
HTTP status (e.g. 200, 400, 500), "CLIENT_ERROR" if the response returned null, or "IO_ERROR" if an
+IOExceptionoccurred during the execution of theRestTemplatemethod
+ -
+
URI, sanitized for Atlas
+
+ -
+
Client name
+
+
Metrics Collection: Spectator
+To enable Spectator metrics, include a dependency on spring-boot-starter-spectator:
<dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-starter-spectator</artifactId>
+ </dependency>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.
+Spring Cloud Spectator integration configures an injectable com.netflix.spectator.api.Registry instance for you. Specifically, it configures a ServoRegistry 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 MetricReader instances and both will be shipped to the Atlas backend.
Spectator Counter
+A counter is used to measure the rate at which some event is occurring.
+// 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 amountThe counter records a single time-normalized statistic.
+Spectator Timer
+A timer is used to measure how long some event is taking. Spring Cloud automatically records timers for Spring MVC requests and conditionally RestTemplate requests, which can later be used to create dashboards for request related metrics like latency:
image::RequestLatency.png []
+// 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);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 increment() 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.
For long running operations, Spectator provides a special LongTaskTimer.
Spectator Gauge
+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.
+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 the note in Spectator’s documentation about potential memory leaks if this API is misused.
+// 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);Spectator Distribution Summaries
+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.
+// the registry will automatically sample this gauge periodically
+DistributionSummary ds = registry.distributionSummary("dsName", "tagKey1", "tagValue1", ...);
+ds.record(request.sizeInBytes());Metrics Collection: Servo
+|
+ Warning
+ |
++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. + | +
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 MonitorRegistry. In spite of the above warning, Servo does have a wider array of monitor options than Spectator has meters.
Spring Cloud integration configures an injectable com.netflix.servo.MonitorRegistry instance for you. Once you have created the appropriate Monitor type in Servo, the process of recording data is wholly similar to Spectator.
Creating Servo Monitors
+If you are using the Servo MonitorRegistry instance provided by Spring Cloud (specifically, an instance of DefaultMonitorRegistry), Servo provides convenience classes for retrieving counters and timers. These convenience classes ensure that only one Monitor is registered for each unique combination of name and tags.
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 MonitorConfig instance:
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);Metrics Backend: Atlas
+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.
+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.
+Spring Cloud provides a spring-cloud-starter-atlas that has all the dependencies you need. Then just annotate your Spring Boot application with @EnableAtlas and provide a location for your running Atlas server with the netflix.atlas.uri property.
Global tags
+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.
+Each bean implementing AtlasTagProvider will contribute to the global tag list:
@Bean
+AtlasTagProvider atlasCommonTags(
+ @Value("${spring.application.name}") String appName) {
+ return () -> Collections.singletonMap("app", appName);
+}Using Atlas
+To bootstrap a in-memory standalone Atlas instance:
+$ 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|
+ Tip
+ |
++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. + | +
Once running and you have collected a handful of metrics, verify that your setup is correct by listing tags on the Atlas server:
+$ curl http://ATLAS/api/v1/tags|
+ Tip
+ |
+
+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: http://ATLAS/api/v1/graph?q=name,rest,:eq,:avg
+ |
+
The Atlas wiki contains a compilation of sample queries for various scenarios.
+Make sure to check out the alerting philosophy and docs on using double exponential smoothing to generate dynamic alert thresholds.
+Spring Cloud Stream
+ +Spring Cloud Stream Reference Guide
+Reference Guide
+This section goes into more detail about how you can work with Spring Cloud Stream. +It covers topics such as creating and running stream applications.
+Introducing Spring Cloud Stream
+Spring Cloud Stream is a framework for building message-driven microservice applications. +Spring Cloud Stream builds upon Spring Boot to create standalone, production-grade Spring applications, and uses Spring Integration to provide connectivity to message brokers. +It provides opinionated configuration of middleware from several vendors, introducing the concepts of persistent publish-subscribe semantics, consumer groups, and partitions.
+You can add the @EnableBinding annotation to your application to get immediate connectivity to a message broker, and you can add @StreamListener to a method to cause it to receive events for stream processing.
+The following is a simple sink application which receives external messages.
@SpringBootApplication
+public class StreamApplication {
+
+ public static void main(String[] args) {
+ SpringApplication.run(StreamApplication.class, args);
+ }
+}
+
+@EnableBinding(Sink.class)
+public class TimerSource {
+
+ ...
+
+ @StreamListener(Sink.INPUT)
+ public void processVote(Vote vote) {
+ votingService.recordVote(vote);
+ }
+}The @EnableBinding annotation takes one or more interfaces as parameters (in this case, the parameter is a single Sink interface).
+An interface declares input and/or output channels.
+Spring Cloud Stream provides the interfaces Source, Sink, and Processor; you can also define your own interfaces.
The following is the definition of the Source interface:
public interface Sink {
+ String INPUT = "input";
+
+ @Input(Sink.INPUT)
+ SubscribableChannel input();
+}The @Input annotation identifies an input channel, through which received messages enter the application; the @Output annotation identifies an output channel, through which published messages leave the application.
+The @Input and @Output annotations can take a channel name as a parameter; if a name is not provided, the name of the annotated method will be used.
Spring Cloud Stream will create an implementation of the interface for you. +You can use this in the application by autowiring it, as in the following example of a test case.
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = StreamApplication.class)
+@WebAppConfiguration
+@DirtiesContext
+public class StreamApplicationTests {
+
+ @Autowired
+ private Sink sink;
+
+ @Test
+ public void contextLoads() {
+ assertNotNull(this.sink.input());
+ }
+}Main Concepts
+Spring Cloud Stream provides a number of abstractions and primitives that simplify the writing of message-driven microservice applications. +This section gives an overview of the following:
+-
+
-
+
Spring Cloud Stream’s application model
+
+ -
+
The Binder abstraction
+
+ -
+
Persistent publish-subscribe support
+
+ -
+
Consumer group support
+
+ -
+
Partitioning support
+
+ -
+
A pluggable Binder API
+
+
Application Model
+A Spring Cloud Stream application consists of a middleware-neutral core. +The application communicates with the outside world through input and output channels injected into it by Spring Cloud Stream. +Channels are connected to external brokers through middleware-specific Binder implementations.
+
+Fat JAR
+Spring Cloud Stream applications can be run in standalone mode from your IDE for testing. +To run a Spring Cloud Stream application in production, you can create an executable (or "fat") JAR by using the standard Spring Boot tooling provided for Maven or Gradle.
+The Binder Abstraction
+Spring Cloud Stream provides Binder implementations for Kafka, Rabbit MQ, Redis, and Gemfire. +Spring Cloud Stream also includes a TestSupportBinder, which leaves a channel unmodified so that tests can interact with channels directly and reliably assert on what is received. +You can use the extensible API to write your own Binder.
+Spring Cloud Stream uses Spring Boot for configuration, and the Binder abstraction makes it possible for a Spring Cloud Stream application to be flexible in how it connects to middleware.
+For example, deployers can dynamically choose, at runtime, the destinations (e.g., the Kafka topics or RabbitMQ exchanges) to which channels connect.
+Such configuration can be provided through external configuration properties and in any form supported by Spring Boot (including application arguments, environment variables, and application.yml or application.properties files).
+In the sink example from the Introducing Spring Cloud Stream section, setting the application property spring.cloud.stream.bindings.input.destination to raw-sensor-data will cause it to read from the raw-sensor-data Kafka topic, or from a queue bound to the raw-sensor-data RabbitMQ exchange.
Spring Cloud Stream automatically detects and uses a binder found on the classpath. +You can easily use different types of middleware with the same code: just include a different binder at build time. +For more complex use cases, you can also package multiple binders with your application and have it choose the binder, and even whether to use different binders for different channels, at runtime.
+Persistent Publish-Subscribe Support
+Communication between applications follows a publish-subscribe model, where data is broadcast through shared topics. +This can be seen in the following figure, which shows a typical deployment for a set of interacting Spring Cloud Stream applications.
+
+Data reported by sensors to an HTTP endpoint is sent to a common destination named raw-sensor-data.
+From the destination, it is independently processed by a microservice application that computes time-windowed averages and by another microservice application that ingests the raw data into HDFS.
+In order to process the data, both applications declare the topic as their input at runtime.
The publish-subscribe communication model reduces the complexity of both the producer and the consumer, and allows new applications to be added to the topology without disruption of the existing flow. +For example, downstream from the average-calculating application, you can add an application that calculates the highest temperature values for display and monitoring. +You can then add another application that interprets the same flow of averages for fault detection. +Doing all communication through shared topics rather than point-to-point queues reduces coupling between microservices.
+While the concept of publish-subscribe messaging is not new, Spring Cloud Stream takes the extra step of making it an opinionated choice for its application model. +By using native middleware support, Spring Cloud Stream also simplifies use of the publish-subscribe model across different platforms.
+Consumer Groups
+While the publish-subscribe model makes it easy to connect applications through shared topics, the ability to scale up by creating multiple instances of a given application is equally important. +When doing this, different instances of an application are placed in a competing consumer relationship, where only one of the instances is expected to handle a given message.
+Spring Cloud Stream models this behavior through the concept of a consumer group.
+(Spring Cloud Stream consumer groups are similar to and inspired by Kafka consumer groups.)
+Each consumer binding can use the spring.cloud.stream.bindings.input.group property to specify a group name.
+For the consumers shown in the following figure, this property would be set as spring.cloud.stream.bindings.input.group=hdfsWrite or spring.cloud.stream.bindings.input.group=average.
+All groups which subscribe to a given destination receive a copy of published data, but only one member of each group receives a given message from that destination. +By default, when a group is not specified, Spring Cloud Stream assigns the application to an anonymous and independent single-member consumer group that is in a publish-subscribe relationship with all other consumer groups.
+Durability
+Consistent with the opinionated application model of Spring Cloud Stream, consumer group subscriptions are durable. +That is, a binder implementation ensures that group subscriptions are persistent, and once at least one subscription for a group has been created, the group will receive messages, even if they are sent while all applications in the group are stopped.
+|
+ Note
+ |
+
+
+
+Anonymous subscriptions are non-durable by nature. +For some binder implementations (e.g., RabbitMQ), it is possible to have non-durable group subscriptions. + |
+
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, you must specify a consumer group for each of its input bindings. +This prevents the application’s instances from receiving duplicate messages (unless that behavior is desired, which is unusual).
+Partitioning Support
+Spring Cloud Stream provides support for partitioning data between multiple instances of a given application. +In a partitioned scenario, the physical communication medium (e.g., the broker topic) is viewed as being structured into multiple partitions. +One or more producer application instances send data to multiple consumer application instances and ensure that data identified by common characteristics are processed by the same consumer instance.
+Spring Cloud Stream provides a common abstraction for implementing partitioned processing use cases in a uniform fashion. +Partitioning can thus be used whether the broker itself is naturally partitioned (e.g., Kafka) or not (e.g., RabbitMQ).
+
+Partitioning is a critical concept in stateful processing, where it is critiical, for either performance or consistency reasons, to ensure that all related data is processed together. +For example, in the time-windowed average calculation example, it is important that all measurements from any given sensor are processed by the same application instance.
+|
+ Note
+ |
+
+
+
+To set up a partitioned processing scenario, you must configure both the data-producing and the data-consuming ends. + |
+
Programming Model
+This section describes Spring Cloud Stream’s programming model. +Spring Cloud Stream provides a number of predefined annotations for declaring bound input and output channels as well as how to listen to channels.
+Declaring and Binding Channels
+Triggering Binding Via @EnableBinding
+You can turn a Spring application into a Spring Cloud Stream application by applying the @EnableBinding annotation to one of the application’s configuration classes.
+The @EnableBinding annotation itself is meta-annotated with @Configuration and triggers the configuration of Spring Cloud Stream infrastructure:
...
+@Import(...)
+@Configuration
+@EnableIntegration
+public @interface EnableBinding {
+ ...
+ Class<?>[] value() default {};
+}The @EnableBinding annotation can take as parameters one or more interface classes that contain methods which represent bindable components (typically message channels).
|
+ Note
+ |
+
+
+
+In Spring Cloud Stream 1.0, the only supported bindable components are the Spring Messaging |
+
@Input and @Output
+A Spring Cloud Stream application can have an arbitrary number of input and output channels defined in an interface as @Input and @Output methods:
public interface Barista {
+
+ @Input
+ SubscribableChannel orders();
+
+ @Output
+ MessageChannel hotDrinks();
+
+ @Output
+ MessageChannel coldDrinks();
+}Using this interface as a parameter to @EnableBinding will trigger the creation of three bound channels named orders, hotDrinks, and coldDrinks, respectively.
@EnableBinding(Barista.class)
+public class CafeConfiguration {
+
+ ...
+}Customizing Channel Names
+Using the @Input and @Output annotations, you can specify a customized channel name for the channel, as shown in the following example:
public interface Barista {
+ ...
+ @Input("inboundOrders")
+ SubscribableChannel orders();
+}In this example, the created bound channel will be named inboundOrders.
Source, Sink, and Processor
+For easy addressing of the most common use cases, which involve either an input channel, an output channel, or both, Spring Cloud Stream provides three predefined interfaces out of the box.
+Source can be used for an application which has a single outbound channel.
public interface Source {
+
+ String OUTPUT = "output";
+
+ @Output(Source.OUTPUT)
+ MessageChannel output();
+
+}Sink can be used for an application which has a single inbound channel.
public interface Sink {
+
+ String INPUT = "input";
+
+ @Input(Sink.INPUT)
+ SubscribableChannel input();
+
+}Processor can be used for an application which has both an inbound channel and an outbound channel.
public interface Processor extends Source, Sink {
+}Spring Cloud Stream provides no special handling for any of these interfaces; they are only provided out of the box.
+Accessing Bound Channels
+Injecting the Bound Interfaces
+For each bound interface, Spring Cloud Stream will generate a bean that implements the interface.
+Invoking a @Input-annotated or @Output-annotated method of one of these beans will return the relevant bound channel.
The bean in the following example sends a message on the output channel when its hello method is invoked.
+It invokes output() on the injected Source bean to retrieve the target channel.
@Component
+public class SendingBean {
+
+ private Source source;
+
+ @Autowired
+ public SendingBean(Source source) {
+ this.source = source;
+ }
+
+ public void sayHello(String name) {
+ source.output().send(MessageBuilder.withPayload(body).build());
+ }
+}Injecting Channels Directly
+Bound channels can be also injected directly:
+@Component
+public class SendingBean {
+
+ private MessageChannel output;
+
+ @Autowired
+ public SendingBean(MessageChannel output) {
+ this.output = output;
+ }
+
+ public void sayHello(String name) {
+ output.send(MessageBuilder.withPayload(body).build());
+ }
+}If the name of the channel is customized on the declaring annotation, that name should be used instead of the method name. +Given the following declaration:
+public interface CustomSource {
+ ...
+ @Output("customOutput")
+ MessageChannel output();
+}The channel will be injected as shown in the following example:
+@Component
+public class SendingBean {
+
+ @Autowired
+ private MessageChannel output;
+
+ @Autowired @Qualifier("customOutput")
+ public SendingBean(MessageChannel output) {
+ this.output = output;
+ }
+
+ public void sayHello(String name) {
+ customOutput.send(MessageBuilder.withPayload(body).build());
+ }
+}Producing and Consuming Messages
+You can write a Spring Cloud Stream application using either Spring Integration annotations or Spring Cloud Stream’s @StreamListener annotation.
+The @StreamListener annotation is modeled after other Spring Messaging annotations (such as @MessageMapping, @JmsListener, @RabbitListener, etc.) but adds content type management and type coercion features.
Native Spring Integration Support
+Because Spring Cloud Stream is based on Spring Integration, Stream completely inherits Integration’s foundation and infrastructure as well as the component itself.
+For example, you can attach the output channel of a Source to a MessageSource:
@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()));
+ }
+}Or you can use a processor’s channels in a transformer:
+@EnableBinding(Processor.class)
+public class TransformProcessor {
+ @Transformer(inputChannel = Processor.INPUT, outputChannel = Processor.OUTPUT)
+ public Object transform(String message) {
+ return message.toUpper();
+ }
+}Using @StreamListener for Automatic Content Type Handling
+Complementary to its Spring Integration support, Spring Cloud Stream provides its own @StreamListener annotation, modeled after other Spring Messaging annotations (e.g. @MessageMapping, @JmsListener, @RabbitListener, etc.).
+The @StreamListener annotation provides a simpler model for handling inbound messages, especially when dealing with use cases that involve content type management and type coercion.
Spring Cloud Stream provides an extensible MessageConverter mechanism for handling data conversion by bound channels and for, in this case, dispatching to methods annotated with @StreamListener.
+The following is an example of an application which processes external Vote events:
@EnableBinding(Sink.class)
+public class VoteHandler {
+
+ @Autowired
+ VotingService votingService;
+
+ @StreamListener(Sink.INPUT)
+ public void handle(Vote vote) {
+ votingService.record(vote);
+ }
+}The distinction between @StreamListener and a Spring Integration @ServiceActivator is seen when considering an inbound Message that has a String payload and a contentType header of application/json.
+In the case of @StreamListener, the MessageConverter mechanism will use the contentType header to parse the String payload into a Vote object.
As with other Spring Messaging methods, method arguments can be annotated with @Payload, @Headers and @Header.
|
+ Note
+ |
+
+
+
+For methods which return data, you must use the
+
+
+
+ |
+
|
+ Note
+ |
+
+
+
+In the case of RabbitMQ, content type headers can be set by external applications. +Spring Cloud Stream supports them as part of an extended internal protocol used for any type of transport (including transports, such as Kafka, that do not normally support headers). + |
+
Aggregation
+Spring Cloud Stream provides support for aggregating multiple applications together, connecting their input and output channels directly and avoiding the additional cost of exchanging messages via a broker. +As of version 1.0 of Spring Cloud Stream, aggregation is supported only for the following types of applications:
+-
+
-
+
sources - applications with a single output channel named
+output, typically having a single binding of the typeorg.springframework.cloud.stream.messaging.Source
+ -
+
sinks - applications with a single input channel named
+input, typically having a single binding of the typeorg.springframework.cloud.stream.messaging.Sink
+ -
+
processors - applications with a single input channel named
+inputand a single output channel namedoutput, typically having a single binding of the typeorg.springframework.cloud.stream.messaging.Processor.
+
They can be aggregated together by creating a sequence of interconnected applications, in which the output channel of an element in the sequence is connected to the input channel of the next element, if it exists. +A sequence can start with either a source or a processor, it can contain an arbitrary number of processors and must end with either a processor or a sink.
+Depending on the nature of the starting and ending element, the sequence may have one or more bindable channels, as follows:
+-
+
-
+
if the sequence starts with a source and ends with a sink, all communication between the applications is direct and no channels will be bound
+
+ -
+
if the sequence starts with a processor, then its input channel will become the
+inputchannel of the aggregate and will be bound accordingly
+ -
+
if the sequence ends with a processor, then its output channel will become the
+outputchannel of the aggregate and will be bound accordingly
+
Aggregation is performed using the AggregateApplicationBuilder utility class, as in the following example.
+Let’s consider a project in which we have source, processor and a sink, which may be defined in the project, or may be contained in one of the project’s dependencies.
@SpringBootApplication
+@EnableBinding(Sink.class)
+public class SinkApplication {
+
+ private static Logger logger = LoggerFactory.getLogger(SinkModuleDefinition.class);
+
+ @ServiceActivator(inputChannel=Sink.INPUT)
+ public void loggerSink(Object payload) {
+ logger.info("Received: " + payload);
+ }
+}@SpringBootApplication
+@EnableBinding(Processor.class)
+public class ProcessorApplication {
+
+ @Transformer
+ public String loggerSink(String payload) {
+ return payload.toUpperCase();
+ }
+}@SpringBootApplication
+@EnableBinding(Source.class)
+public class SourceApplication {
+
+ @Bean
+ @InboundChannelAdapter(value = Source.OUTPUT)
+ public String timerMessageSource() {
+ return new SimpleDateFormat().format(new Date());
+ }
+}Each configuration can be used for running a separate component, but in this case they can be aggregated together as follows:
+@SpringBootApplication
+public class SampleAggregateApplication {
+
+ public static void main(String[] args) {
+ new AggregateApplicationBuilder()
+ .from(SourceApplication.class).args("--fixedDelay=5000")
+ .via(ProcessorApplication.class)
+ .to(SinkApplication.class).args("--debug=true").run(args);
+ }
+}The starting component of the sequence is provided as argument to the from() method.
+The ending component of the sequence is provided as argument to the to() method.
+Intermediate processors are provided as argument to the via() method.
+Multiple processors of the same type can be chained together (e.g. for pipelining transformations with different configurations).
+For each component, the builder can provide runtime arguments for Spring Boot configuration.
RxJava support
+Spring Cloud Stream provides support for RxJava-based processors through the RxJavaProcessor available in spring-cloud-stream-rxjava.
public interface RxJavaProcessor<I, O> {
+ Observable<O> process(Observable<I> input);
+}An implementation of RxJavaProcessor will receive Observable as an input that represents the flow of inbound message payloads.
+The process method is invoked once at startup for setting up the data flow.
You can enable the use of RxJava-based processors and use them in your processor application by using the @EnableRxJavaProcessor annotation.
+@EnableRxJavaProcessor is meta-annotated with @EnableBinding(Processor.class) and will create the Processor binding.
+Here is an example of an RxJava-based processor:
@EnableRxJavaProcessor
+public class RxJavaTransformer {
+
+ private static Logger logger = LoggerFactory.getLogger(RxJavaTransformer.class);
+
+ @Bean
+ public RxJavaProcessor<String,String> processor() {
+ return inputStream -> inputStream.map(data -> {
+ logger.info("Got data = " + data);
+ return data;
+ })
+ .buffer(5)
+ .map(data -> String.valueOf(avg(data)));
+ }
+
+ private static Double avg(List<String> data) {
+ double sum = 0;
+ double count = 0;
+ for(String d : data) {
+ count++;
+ sum += Double.valueOf(d);
+ }
+ return sum/count;
+ }
+}|
+ Note
+ |
+
+
+
+When implementing an RxJava processor, it is important to handle exceptions as part of your processing flow.
+Uncaught exceptions will be treated as errors by RxJava and will cause the |
+
Binders
+Spring Cloud Stream provides a Binder abstraction for use in connecting to physical destinations at the external middleware. +This section provides information about the main concepts behind the Binder SPI, its main components, and implementation-specific details.
+Producers and Consumers
+
+A producer is any component that sends messages to a channel.
+The channel can be bound to an external message broker via a Binder implementation for that broker.
+When invoking the bindProducer() method, the first parameter is the name of the destination within the broker, the second parameter is the local channel instance to which the producer will send messages, and the third parameter contains properties (such as a partition key expression) to be used within the adapter that is created for that channel.
A consumer is any component that receives messages from a channel.
+As with a producer, the consumer’s channel can be bound to an external message broker.
+When invoking the bindConsumer() method, the first parameter is the destination name, and a second parameter provides the name of a logical group of consumers.
+Each group that is represented by consumer bindings for a given destination receives a copy of each message that a producer sends to that destination (i.e., publish-subscribe 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 is consumed by only a single consumer instance within each group (i.e., queueing semantics).
Binder SPI
+The Binder SPI consists of a number of interfaces, out-of-the box utility classes and discovery strategies that provide a pluggable mechanism for connecting to external middleware.
+The key point of the SPI is the Binder interface which is a strategy for connecting inputs and outputs to external middleware.
public interface Binder<T, C extends ConsumerProperties, P extends ProducerProperties> {
+ Binding<T> bindConsumer(String name, String group, T inboundBindTarget, C consumerProperties);
+
+ Binding<T> bindProducer(String name, T outboundBindTarget, P producerProperties);
+}The interface is parameterized, offering a number of extension points:
+-
+
-
+
input and output bind targets - as of version 1.0, only
+MessageChannelis supported, but this is intended to be used as an extension point in the future;
+ -
+
extended consumer and producer properties - allowing specific Binder implementations to add supplemental properties which can be supported in a type-safe manner.
+
+
A typical binder implementation consists of the following
+-
+
-
+
a class that implements the
+Binderinterface;
+ -
+
a Spring
+@Configurationclass that creates a bean of the type above along with the middleware connection infrastructure;
+ -
+
a
+META-INF/spring.bindersfile found on the classpath containing one or more binder definitions, e.g.
+
kafka:\
+org.springframework.cloud.stream.binder.kafka.config.KafkaBinderConfigurationBinder Detection
+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. +Out of the box, Spring Cloud Stream provides binders for Kafka, RabbitMQ, and Redis.
+Classpath Detection
+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. +For example, a Spring Cloud Stream project that aims to bind only to RabbitMQ can simply add the following dependency:
+<dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-stream-binder-rabbit</artifactId>
+</dependency>Multiple Binders on the Classpath
+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 META-INF/spring.binders, which is a simple properties file:
rabbit:\
+org.springframework.cloud.stream.binder.rabbit.config.RabbitServiceAutoConfigurationSimilar files exist for the other provided binder implementations (e.g., Kafka), and custom binder implementations are expected to provide them, as well.
+The key represents an identifying name for the binder implementation, whereas the value is a comma-separated list of configuration classes that each contain one and only one bean definition of type org.springframework.cloud.stream.binder.Binder.
Binder selection can either be performed globally, using the spring.cloud.stream.defaultBinder property (e.g., spring.cloud.stream.defaultBinder=rabbit) or individually, by configuring the binder on each channel binding.
+For instance, a processor application which reads from Kafka and writes to RabbitMQ can specify the following configuration:
spring.cloud.stream.bindings.input.binder=kafka +spring.cloud.stream.bindings.output.binder=rabbit+
Connecting to Multiple Systems
+By default, binders share the application’s Spring Boot auto-configuration, so that one instance of each binder found on the classpath will be created. +If your application should connect to more than one broker of the same type, you can specify multiple binder configurations, each with different environment settings.
+|
+ Note
+ |
+
+
+
+Turning on explicit binder configuration will disable the default binder configuration process altogether.
+If you do this, all binders in use must be included in the configuration.
+Frameworks that intend to use Spring Cloud Stream transparently may create binder configurations that can be referenced by name, but will not affect the default binder configuration.
+In order to do so, a binder configuration may have its |
+
For example, this is the typical configuration for a processor application which connects to two RabbitMQ broker instances:
+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>Binder configuration properties
+The following properties are available when creating custom binder configurations.
+They must be prefixed with spring.cloud.stream.binders.<configurationName>.
-
+
- type +
-
+
The binder type. +It typically references one of the binders found on the classpath, in particular a key in a
+META-INF/spring.bindersfile.++By default, it has the same value as the configuration name.
+
+ - inheritEnvironment +
-
+
Whether the configuration will inherit the environment of the application itself.
+++Default
+true.
+ - environment +
-
+
Root for a set of properties that can be used to customize the environment of the binder. +When this is configured, the context in which the binder is being created is not a child of the application context. +This allows for complete separation between the binder components and the application components.
+++Default
+empty.
+ - defaultCandidate +
-
+
Whether the binder configuration is a candidate for being considered a default binder, or can be used only when explicitly referenced. +This allows adding binder configurations without interfering with the default processing.
+++Default
+true.
+
Implementation strategies
+This section details the binder implementation strategies for Kafka and Rabbit MQ, in what concerns mapping the Spring Cloud Stream concepts onto the middleware concepts.
+Kafka Binder
+
+The Kafka Binder implementation maps the destination to a Kafka topic. +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.
+RabbitMQ Binder
+
+The RabbitMQ Binder implementation maps the destination to a TopicExchange.
+For each consumer group, a Queue will be bound to that TopicExchange.
+Each consumer instance that binds will trigger creation of a corresponding RabbitMQ Consumer instance for its group’s Queue.
Configuration Options
+Spring Cloud Stream supports general configuration options as well as configuration for bindings and binders. +Some binders allow additional binding properties to support middleware-specific features.
+Configuration options can be provided to Spring Cloud Stream applications via any mechanism supported by Spring Boot. +This includes application arguments, environment variables, and YAML or .properties files.
+Spring Cloud Stream Properties
+-
+
- spring.cloud.stream.instanceCount +
-
+
The number of deployed instances of an application. +Must be set for partitioning and if using Kafka.
+++Default:
+1.
+ - spring.cloud.stream.instanceIndex +
-
+
The instance index of the application: a number from
+0toinstanceCount-1. +Used for partitioning and with Kafka. +Automatically set in Cloud Foundry to match the application’s instance index.
+ - spring.cloud.stream.dynamicDestinations +
-
+
A list of destinations that can be bound dynamically (for example, in a dynamic routing scenario). +If set, only listed destinations can be bound.
+++Default: empty (allowing any destination to be bound).
+
+ - spring.cloud.stream.defaultBinder +
-
+
The default binder to use, if multiple binders are configured. +See Multiple Binders on the Classpath.
+++Default: empty.
+
+ - spring.cloud.stream.overrideCloudConnectors +
-
+
This property is only applicable when the
+cloudprofile is active and Spring Cloud Connectors are provided with the application. +If the property is false (the default), the binder will detect a suitable bound service (e.g. a RabbitMQ service bound in Cloud Foundry for the RabbitMQ binder) and will use it for creating connections (usually via Spring Cloud Connectors). +When set to true, this property instructs binders to completely ignore the bound services and rely on Spring Boot properties (e.g. relying on thespring.rabbitmq.*properties provided in the environment for the RabbitMQ binder). +The typical usage of this property is to be nested in a customized environment when connecting to multiple systems.++Default: false.
+
+
Binding Properties
+Binding properties are supplied using the format spring.cloud.stream.bindings.<channelName>.<property>=<value>.
+The <channelName> represents the name of the channel being configured (e.g., output for a Source).
In what follows, we indicate where we have omitted the spring.cloud.stream.bindings.<channelName>. prefix and focus just on the property name, with the understanding that the prefix will be included at runtime.
Properties for Use of Spring Cloud Stream
+The following binding properties are available for both input and output bindings and
+must be prefixed with spring.cloud.stream.bindings.<channelName>..
-
+
- destination +
-
+
The target destination of a channel on the bound middleware (e.g., the RabbitMQ exchange or Kafka topic). +If the channel is bound as a consumer, it could be bound to multiple destinations and the destination names can be specified as comma separated String values. +If not set, the channel name is used instead.
+
+ - group +
-
+
The consumer group of the channel. +Applies only to inbound bindings. +See Consumer Groups.
+++Default: null (indicating an anonymous consumer).
+
+ - contentType +
-
+
The content type of the channel.
+++Default: null (so that no type coercion is performed).
+
+ - binder +
-
+
The binder used by this binding. +See Multiple Binders on the Classpath for details.
+++Default: null (the default binder will be used, if one exists).
+
+
Consumer properties
+The following binding properties are available for input bindings only and must be prefixed with spring.cloud.stream.bindings.<channelName>.consumer..
-
+
- concurrency +
-
+
The concurrency of the inbound consumer.
+++Default:
+1.
+ - partitioned +
-
+
Whether the consumer receives data from a partitioned producer.
+++Default:
+false.
+ - headerMode +
-
+
When set to
+raw, disables header parsing on input. +Effective only for messaging middleware that does not support message headers natively and requires header embedding. +Useful when inbound data is coming from outside Spring Cloud Stream applications.++Default:
+embeddedHeaders.
+ - maxAttempts +
-
+
The number of attempts of re-processing an inbound message.
+++Default:
+3.
+ - backOffInitialInterval +
-
+
The backoff initial interval on retry.
+++Default:
+1000.
+ - backOffMaxInterval +
-
+
The maximum backoff interval.
+++Default:
+10000.
+ - backOffMultiplier +
-
+
The backoff multiplier.
+++Default:
+2.0.
+
Producer Properties
+The following binding properties are available for output bindings only and must be prefixed with spring.cloud.stream.bindings.<channelName>.producer..
-
+
- partitionKeyExpression +
-
+
A SpEL expression that determines how to partition outbound data. +If set, or if
+partitionKeyExtractorClassis set, outbound data on this channel will be partitioned, andpartitionCountmust be set to a value greater than 1 to be effective. +The two options are mutually exclusive. +See Partitioning Support.++Default: null.
+
+ - partitionKeyExtractorClass +
-
+
A
+PartitionKeyExtractorStrategyimplementation. +If set, or ifpartitionKeyExpressionis set, outbound data on this channel will be partitioned, andpartitionCountmust be set to a value greater than 1 to be effective. +The two options are mutually exclusive. +See Partitioning Support.++Default: null.
+
+ - partitionSelectorClass +
-
+
A
+PartitionSelectorStrategyimplementation. +Mutually exclusive withpartitionSelectorExpression. +If neither is set, the partition will be selected as thehashCode(key) % partitionCount, wherekeyis computed via eitherpartitionKeyExpressionorpartitionKeyExtractorClass.++Default: null.
+
+ - partitionSelectorExpression +
-
+
A SpEL expression for customizing partition selection. +Mutually exclusive with
+partitionSelectorClass. +If neither is set, the partition will be selected as thehashCode(key) % partitionCount, wherekeyis computed via eitherpartitionKeyExpressionorpartitionKeyExtractorClass.++Default: null.
+
+ - partitionCount +
-
+
The number of target partitions for the data, if partitioning is enabled. +Must be + set to a value greater than 1 if the producer is partitioned. +On Kafka, interpreted as a + hint; the larger of this and the partition count of the target topic is used instead.
+++Default:
+1.
+ - requiredGroups +
-
+
A comma-separated list of groups to which the producer must ensure message delivery even if they start after it has been created (e.g., by pre-creating durable queues in RabbitMQ).
+
+ - headerMode +
-
+
When set to
+raw, disables header embedding on output. +Effective only for messaging middleware that does not support message headers natively and requires header embedding. +Useful when producing data for non-Spring Cloud Stream applications.++Default:
+embeddedHeaders.
+
Binder-Specific Configuration
+The following binder, consumer, and producer properties are specific to binder implementations.
+Rabbit-Specific Settings
+RabbitMQ Binder Properties
+By default, the RabbitMQ binder uses Spring Boot’s ConnectionFactory, and it therefore supports all Spring Boot configuration options for RabbitMQ.
+(For reference, consult the Spring Boot documentation.) RabbitMQ configuration options use the spring.rabbitmq prefix.
In addition to the Spring Boot options, the RabbitMQ binder supports the following properties:
+-
+
- spring.cloud.stream.rabbit.binder.adminAddresses +
-
+
A comma-separated list of RabbitMQ management plugin URLs. +Only used when
+nodescontains more than one entry. +Each entry in this list must have a corresponding entry inspring.rabbitmq.addresses.++Default: empty.
+
+ - spring.cloud.stream.rabbit.binder.nodes +
-
+
A comma-separated list of RabbitMQ node names. +When more than one entry, used to locate the server address where a queue is located. +Each entry in this list must have a corresponding entry in
+spring.rabbitmq.addresses.++Default: empty.
+
+ - spring.cloud.stream.rabbit.binder.compressionLevel +
-
+
Compression level for compressed bindings. +See
+java.util.zip.Deflater.++Default:
+1(BEST_LEVEL).
+
RabbitMQ Consumer Properties
+The following properties are available for Rabbit consumers only and
+must be prefixed with spring.cloud.stream.rabbit.bindings.<channelName>.consumer..
-
+
- acknowledgeMode +
-
+
The acknowledge mode.
+++Default:
+AUTO.
+ - autoBindDlq +
-
+
Whether to automatically declare the DLQ and bind it to the binder DLX.
+++Default:
+false.
+ - durableSubscription +
-
+
Whether subscription should be durable. +Only effective if
+groupis also set.++Default:
+true.
+ - maxConcurrency +
-
+
Default:
+1.
+ - prefetch +
-
+
Prefetch count.
+++Default:
+1.
+ - prefix +
-
+
A prefix to be added to the name of the
+destinationand queues.++Default: "".
+
+ - recoveryInterval +
-
+
The interval between connection recovery attempts, in milliseconds.
+++Default:
+5000.
+ - requeueRejected +
-
+
Whether delivery failures should be requeued.
+++Default:
+true.
+ - requestHeaderPatterns +
-
+
The request headers to be transported.
+++Default:
+[STANDARD_REQUEST_HEADERS,'*'].
+ - replyHeaderPatterns +
-
+
The reply headers to be transported.
+++Default:
+[STANDARD_REQUEST_HEADERS,'*'].
+ - republishToDlq +
-
+
By default, messages which fail after retries are exhausted are rejected. +If a dead-letter queue (DLQ) is configured, RabbitMQ will route the failed message (unchanged) to the DLQ. +If set to
+true, the bus will republish failed messages to the DLQ with additional headers, including the exception message and stack trace from the cause of the final failure.
+ - transacted +
-
+
Whether to use transacted channels.
+++Default:
+false.
+ - txSize +
-
+
The number of deliveries between acks.
+++Default:
+1.
+
Rabbit Producer Properties
+The following properties are available for Rabbit producers only and
+must be prefixed with spring.cloud.stream.rabbit.bindings.<channelName>.producer..
-
+
- autoBindDlq +
-
+
Whether to automatically declare the DLQ and bind it to the binder DLX.
+++Default:
+false.
+ - batchingEnabled +
-
+
Whether to enable message batching by producers.
+++Default:
+false.
+ - batchSize +
-
+
The number of messages to buffer when batching is enabled.
+++Default:
+100.
+ - batchBufferLimit +
-
+
Default:
+10000.
+ - batchTimeout +
-
+
Default:
+5000.
+ - compress +
-
+
Whether data should be compressed when sent.
+++Default:
+false.
+ - deliveryMode +
-
+
Delivery mode.
+++Default:
+PERSISTENT.
+ - prefix +
-
+
A prefix to be added to the name of the
+destinationexchange.++Default: "".
+
+ - requestHeaderPatterns +
-
+
The request headers to be transported.
+++Default:
+[STANDARD_REQUEST_HEADERS,'*'].
+ - replyHeaderPatterns +
-
+
The reply headers to be transported.
+++Default:
+[STANDARD_REQUEST_HEADERS,'*'].
+
Kafka-Specific Settings
+Kafka Binder Properties
+-
+
- spring.cloud.stream.kafka.binder.brokers +
-
+
A list of brokers to which the Kafka binder will connect.
+++Default:
+localhost.
+ - spring.cloud.stream.kafka.binder.defaultBrokerPort +
-
+
+brokersallows hosts specified with or without port information (e.g.,host1,host2:port2). +This sets the default port when no port is configured in the broker list.++Default:
+9092.
+ - spring.cloud.stream.kafka.binder.zkNodes +
-
+
A list of ZooKeeper nodes to which the Kafka binder can connect.
+++Default:
+localhost.
+ - spring.cloud.stream.kafka.binder.defaultZkPort +
-
+
+zkNodesallows hosts specified with or without port information (e.g.,host1,host2:port2). +This sets the default port when no port is configured in the node list.++Default:
+2181.
+ - spring.cloud.stream.kafka.binder.headers +
-
+
The list of custom headers that will be transported by the binder.
+++Default: empty.
+
+ - spring.cloud.stream.kafka.binder.offsetUpdateTimeWindow +
-
+
The frequency, in milliseconds, with which offsets are saved. +Ignored if
+0.++Default:
+10000.
+ - spring.cloud.stream.kafka.binder.offsetUpdateCount +
-
+
The frequency, in number of updates, which which consumed offsets are persisted. +Ignored if
+0. +Mutually exclusive withoffsetUpdateTimeWindow.++Default:
+0.
+ - spring.cloud.stream.kafka.binder.requiredAcks +
-
+
The number of required acks on the broker.
+++Default:
+1.
+ - spring.cloud.stream.kafka.binder.minPartitionCount +
-
+
Effective only if
+autoCreateTopicsorautoAddPartitionsis set. +The global minimum number of partitions that the binder will configure on topics on which it produces/consumes data. +It can be superseded by thepartitionCountsetting of the producer or by the value ofinstanceCount*concurrencysettings of the producer (if either is larger).++Default:
+1.
+ - spring.cloud.stream.kafka.binder.replicationFactor +
-
+
The replication factor of auto-created topics if
+autoCreateTopicsis active.++Default:
+1.
+ - spring.cloud.stream.kafka.binder.autoCreateTopics +
-
+
If set to
+true, the binder will create new topics automatically. +If set tofalse, the binder will rely on the topics being already configured. +In the latter case, if the topics do not exist, the binder will fail to start. +Of note, this setting is independent of theauto.topic.create.enablesetting of the broker and it does not influence it: if the server is set to auto-create topics, they may be created as part of the metadata retrieval request, with default broker settings.++Default:
+true.
+ - spring.cloud.stream.kafka.binder.autoAddPartitions +
-
+
If set to
+true, the binder will create add new partitions if required. +If set tofalse, the binder will rely on the partition size of the topic being already configured. +If the partition count of the target topic is smaller than the expected value, the binder will fail to start.++Default:
+false.
+ - spring.cloud.stream.kafka.binder.socketBufferSize +
-
+
Size (in bytes) of the socket buffer to be used by the Kafka consumers.
+++Default:
+2097152.
+
Kafka Consumer Properties
+The following properties are available for Kafka consumers only and
+must be prefixed with spring.cloud.stream.kafka.bindings.<channelName>.consumer..
-
+
- autoCommitOffset +
-
+
Whether to autocommit offsets when a message has been processed. +If set to
+false, anAcknowledgmentheader will be available in the message headers for late acknowledgment.++Default:
+true.
+ - autoCommitOnError +
-
+
Effective only if
+autoCommitOffsetis set totrue. +If set tofalseit suppresses auto-commits for messages that result in errors, and will commit only for successful messages, allows a stream to automatically replay from the last successfully processed message, in case of persistent failures. +If set totrue, it will always auto-commit (if auto-commit is enabled). +If not set (default), it effectively has the same value asenableDlq, auto-committing erroneous messages if they are sent to a DLQ, and not committing them otherwise.++Default: not set.
+
+ - recoveryInterval +
-
+
The interval between connection recovery attempts, in milliseconds.
+++Default:
+5000.
+ - resetOffsets +
-
+
Whether to reset offsets on the consumer to the value provided by
+startOffset.++Default:
+false.
+ - startOffset +
-
+
The starting offset for new groups, or when
+resetOffsetsistrue. +Allowed values:earliest,latest.++Default: null (equivalent to
+earliest).
+ - enableDlq +
-
+
When set to true, it will send enable DLQ behavior for the consumer. +Messages that result in errors will be forwarded to a topic named
+error.<destination>.<group>. +This provides an alternative option to the more common Kafka replay scenario for the case when the number of errors is relatively small and replaying the entire original topic may be too cumbersome.++Default:
+false.
+
Kafka Producer Properties
+The following properties are available for Kafka producers only and
+must be prefixed with spring.cloud.stream.kafka.bindings.<channelName>.producer..
-
+
- bufferSize +
-
+
Upper limit, in bytes, of how much data the Kafka producer will attempt to batch before sending.
+++Default:
+16384.
+ - sync +
-
+
Whether the producer is synchronous.
+++Default:
+false.
+ - batchTimeout +
-
+
How long the producer will wait before sending in order to allow more messages to accumulate in the same batch. +(Normally the producer does not wait at all, and simply sends all the messages that accumulated while the previous send was in progress.) A non-zero value may increase throughput at the expense of latency.
+++Default:
+0.
+
Content Type and Transformation
+To allow you to propagate information about the content type of produced messages, Spring Cloud Stream attaches, by default, a contentType header to outbound messages.
+For middleware that does not directly support headers, Spring Cloud Stream provides its own mechanism of automatically wrapping outbound messages in an envelope of its own.
+For middleware that does support headers, Spring Cloud Stream applications may receive messages with a given content type from non-Spring Cloud Stream applications.
Spring Cloud Stream can handle messages based on this information in two ways:
+-
+
-
+
Through its
+contentTypesettings on inbound and outbound channels
+ -
+
Through its argument mapping performed for methods annotated with
+@StreamListener
+
Spring Cloud Stream allows you to declaratively configure type conversion for inputs and outputs using the content-type property of a binding.
+Note that general type conversion may also be accomplished easily by using a transformer inside your application.
+Currently, Spring Cloud Stream natively supports the following type conversions commonly used in streams:
-
+
-
+
JSON to/from POJO
+
+ -
+
JSON to/from org.springframework.tuple.Tuple
+
+ -
+
Object to/from byte[] : Either the raw bytes serialized for remote transport, bytes emitted by an application, or converted to bytes using Java serialization(requires the object to be Serializable)
+
+ -
+
String to/from byte[]
+
+ -
+
Object to plain text (invokes the object’s toString() method)
+
+
Where JSON represents either a byte array or String payload containing JSON. +Currently, Objects may be converted from a JSON byte array or String. +Converting to JSON always produces a String.
+MIME types
+content-type values are parsed as media types, e.g., application/json or text/plain;charset=UTF-8.
+MIME types are especially useful for indicating how to convert to String or byte[] content.
+Spring Cloud Stream also uses MIME type format to represent Java types, using the general type application/x-java-object with a type parameter.
+For example, application/x-java-object;type=java.util.Map or application/x-java-object;type=com.bar.Foo can be set as the content-type property of an input binding.
+In addition, Spring Cloud Stream provides custom MIME types, notably, application/x-spring-tuple to specify a Tuple.
MIME types and Java types
+The type conversions Spring Cloud Stream provides out of the box are summarized in the following table:
+| Source Payload | +Target Payload | +content-type header | +content-type | +Comments | +
|---|---|---|---|---|
POJO |
+JSON String |
+ignored |
+application/json |
++ |
Tuple |
+JSON String |
+ignored |
+application/json |
+JSON is tailored for Tuple |
+
POJO |
+String (toString()) |
+ignored |
+text/plain, java.lang.String |
++ |
POJO |
+byte[] (java.io serialized) |
+ignored |
+application/x-java-serialized-object |
++ |
JSON byte[] or String |
+POJO |
+application/json (or none) |
+application/x-java-object |
++ |
byte[] or String |
+Serializable |
+application/x-java-serialized-object |
+application/x-java-object |
++ |
JSON byte[] or String |
+Tuple |
+application/json (or none) |
+application/x-spring-tuple |
++ |
byte[] |
+String |
+any |
+text/plain, java.lang.String |
+will apply any Charset specified in the content-type header |
+
String |
+byte[] |
+any |
+application/octet-stream |
+will apply any Charset specified in the content-type header |
+
Conversion applies to payloads that require type conversion. +For example, if a module produces an XML string with outputType=application/json, the payload will not be converted from XML to JSON. +This is because the payload at the module’s output channel is already a String so no conversion will be applied at runtime.
+While conversion is supported for both input and output channels, it is especially recommended to be used for the conversion of outbound messages.
+For the conversion of inbound messages, especially when the target is a POJO, the @StreamListener support will perform the conversion automatically.
`@StreamListener and Message Conversion
+The @StreamListener annotation provides a convenient way for converting incoming messages without the need to specify the content type of an input channel.
+During the dispatching process to methods annotated with @StreamListener, a conversion will be applied automatically if the argument requires it.
For example, let’s consider a message with the String content {"greeting":"Hello, world"} and a content-type header of application/json is received on the input channel.
+Let us consider the following application that receives it:
public class GreetingMessage {
+
+ String greeting;
+
+ public String getGreeting() {
+ return greeting;
+ }
+
+ public void setGreeting(String greeting) {
+ this.greeting = greeting;
+ }
+}
+
+@EnableBinding(Sink.class)
+@EnableAutoConfiguration
+public static class GreetingSink {
+
+ @StreamListener(Sink.INPUT)
+ public void receive(Greeting greeting) {
+ // handle Greeting
+ }
+ }The argument of the method will be populated automatically with the POJO containing the unmarshalled form of the JSON String.
+Inter-Application Communication
+Connecting Multiple Application Instances
+While Spring Cloud Stream makes it easy for individual Spring Boot applications to connect to messaging systems, the typical scenario for Spring Cloud Stream is the creation of multi-application pipelines, where microservice applications send data to each other. +You can achieve this scenario by correlating the input and output destinations of adjacent applications.
+Supposing that a design calls for the Time Source application to send data to the Log Sink application, you can use a common destination named ticktock for bindings within both applications.
Time Source will set the following property:
+spring.cloud.stream.bindings.output.destination=ticktock+
Log Sink will set the following property:
+spring.cloud.stream.bindings.input.destination=ticktock+
Instance Index and Instance Count
+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.
+Spring Cloud Stream does this through the spring.cloud.stream.instanceCount and spring.cloud.stream.instanceIndex properties.
+For example, if there are three instances of a HDFS sink application, all three instances will have spring.cloud.stream.instanceCount set to 3, and the individual applications will have spring.cloud.stream.instanceIndex set to 0, 1, and 2, respectively.
When Spring Cloud Stream applications are deployed via Spring Cloud Data Flow, these properties are configured automatically; when Spring Cloud Stream applications are launched independently, these properties must be set correctly.
+By default, spring.cloud.stream.instanceCount is 1, and spring.cloud.stream.instanceIndex is 0.
In a scaled-up scenario, correct configuration of these two properties is important for addressing partitioning behavior (see below) in general, and the two properties are always required by certain binders (e.g., the Kafka binder) in order to ensure that data are split correctly across multiple consumer instances.
+Partitioning
+Configuring Output Bindings for Partitioning
+An output binding is configured to send partitioned data by setting one and only one of its partitionKeyExpression or partitionKeyExtractorClass properties, as well as its partitionCount property.
+For example, the following is a valid and typical configuration:
spring.cloud.stream.bindings.output.producer.partitionKeyExpression=payload.id +spring.cloud.stream.bindings.output.producer.partitionCount=5+
Based on the above example configuration, 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 partitionKeyExpression.
+The partitionKeyExpression is a SpEL expression which is evaluated against the outbound message for extracting the partitioning key.
|
+ Tip
+ |
+
+
+
+If a SpEL expression is not sufficient for your needs, you can instead calculate the partition key value by setting the property |
+
Once the message key is calculated, the partition selection process will determine the target partition as a value between 0 and partitionCount - 1.
+The default calculation, applicable in most scenarios, is based on the formula key.hashCode() % partitionCount.
+This can be customized on the binding, either by setting a SpEL expression to be evaluated against the key (via the partitionSelectorExpression property) or by setting a org.springframework.cloud.stream.binder.PartitionSelectorStrategy implementation (via the partitionSelectorClass property).
Additional properties can be configured for more advanced scenarios, as described in the following section.
+|
+ Note
+ |
+
+
+
+The Kafka binder will use the |
+
Configuring Input Bindings for Partitioning
+An input binding is configured to receive partitioned data by setting its partitioned property, as well as the instanceIndex and instanceCount properties on the application itself, as in the following example:
spring.cloud.stream.bindings.input.consumer.partitioned=true +spring.cloud.stream.instanceIndex=3 +spring.cloud.stream.instanceCount=5+
The instanceCount value represents the total number of application instances between which the data need to be partitioned, and the instanceIndex must be a unique value across the multiple instances, between 0 and instanceCount - 1.
+The instance index helps each application instance to identify the unique partition (or, in the case of Kafka, the partition set) from which it receives data.
+It is important to set both values correctly in order to ensure that all of the data is consumed and that the application instances receive mutually exclusive datasets.
While a scenario which using multiple instances for partitioned data processing may be complex to set up in a standalone case, Spring Cloud Dataflow 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.
+Testing
+Spring Cloud Stream provides support for testing your microservice applications without connecting to a messaging system.
+You can do that by using the TestSupportBinder.
+This is useful especially for unit testing your microservices.
The TestSupportBinder allows users to interact with the bound channels and inspect what messages are sent and received by the application
For outbound message channels, the TestSupportBinder registers a single subscriber and retains the messages emitted by the application in a MessageCollector.
+They can be retrieved during tests and have assertions made against them.
The user can also send messages to inbound message channels, so that the consumer application can consume the messages. +The following example shows how to test both input and output channels on a processor.
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = ExampleTest.MyProcessor.class)
+@IntegrationTest({"server.port=-1"})
+@DirtiesContext
+public class ExampleTest {
+
+ @Autowired
+ private Processor processor;
+
+ @Autowired
+ private BinderFactory<MessageChannel> binderFactory;
+
+ @Autowired
+ private MessageCollector messageCollector;
+
+ @Test
+ @SuppressWarnings("unchecked")
+ public void testWiring() {
+ Message<String> message = new GenericMessage<>("hello");
+ processor.input().send(message);
+ Message<String> received = (Message<String>) messageCollector.forChannel(processor.output()).poll();
+ assertThat(received.getPayload(), equalTo("hello world"));
+ }
+
+
+ @SpringBootApplication
+ @EnableBinding(Processor.class)
+ public static class MyProcessor {
+
+ @Autowired
+ private Processor channels;
+
+ @Transformer(inputChannel = Processor.INPUT, outputChannel = Processor.OUTPUT)
+ public String transform(String in) {
+ return in + " world";
+ }
+ }
+}In the example above, we are creating an application that has an input and an output channel, bound through the Processor interface.
+The bound interface is injected into the test so we can have access to both channels.
+We are sending a message on the input channel and we are using the MessageCollector provided by Spring Cloud Stream’s test support to capture the message has been sent to the output channel as a result.
+Once we have received the message, we can validate that the component functions correctly.
Health Indicator
+Spring Cloud Stream provides a health indicator for binders.
+It is registered under the name of binders and can be enabled or disabled by setting the management.health.binders.enabled property.
Samples
+For Spring Cloud Stream samples, please refer to the spring-cloud-stream-samples repository on GitHub.
+Getting Started
+To get started with creating Spring Cloud Stream applications, visit the Spring Initializr and create a new Maven project named "GreetingSource". +Select Spring Boot version 1.3.4 SNAPSHOT and search or tick the checkbox for Stream Kafka (we will be using Kafka for messaging).
+Next, create a new class, GreetingSource, in the same package as the GreetingSourceApplication class.
+Give it the following code:
import org.springframework.cloud.stream.annotation.EnableBinding;
+import org.springframework.cloud.stream.messaging.Source;
+import org.springframework.integration.annotation.InboundChannelAdapter;
+
+@EnableBinding(Source.class)
+public class GreetingSource {
+
+ @InboundChannelAdapter(Source.OUTPUT)
+ public String greet() {
+ return "hello world " + System.currentTimeMillis();
+ }
+}The @EnableBinding annotation is what triggers the creation of Spring Integration infrastructure components.
+Specifically, it will create a Kafka connection factory, a Kafka outbound channel adapter, and the message channel defined inside the Source interface:
public interface Source {
+
+ String OUTPUT = "output";
+
+ @Output(Source.OUTPUT)
+ MessageChannel output();
+
+}The auto-configuration also creates a default poller, so that the greet() method will be invoked once per second.
+The standard Spring Integration @InboundChannelAdapter annotation sends a message to the source’s output channel, using the return value as the payload of the message.
To test-drive this setup, run a Kafka message broker. +An easy way to do this is to use a Docker image:
+# On OS X
+$ docker run -p 2181:2181 -p 9092:9092 --env ADVERTISED_HOST=`docker-machine ip \`docker-machine active\`` --env ADVERTISED_PORT=9092 spotify/kafka
+
+# On Linux
+$ docker run -p 2181:2181 -p 9092:9092 --env ADVERTISED_HOST=localhost --env ADVERTISED_PORT=9092 spotify/kafkaBuild the application:
+./mvnw clean package+
The consumer application is coded in a similar manner.
+Go back to Initializr and create another project, named LoggingSink.
+Then create a new class, LoggingSink, in the same package as the class LoggingSinkApplication and with the following code:
import org.springframework.cloud.stream.annotation.EnableBinding;
+import org.springframework.cloud.stream.annotation.StreamListener;
+import org.springframework.cloud.stream.messaging.Sink;
+
+@EnableBinding(Sink.class)
+public class LoggingSink {
+
+ @StreamListener(Sink.INPUT)
+ public void log(String message) {
+ System.out.println(message);
+ }
+}Build the application:
+./mvnw clean package+
To connect the GreetingSource application to the LoggingSink application, each application must share the same destination name. +Starting up both applications as shown below, you will see the consumer application printing "hello world" and a timestamp to the console:
+cd GreetingSource
+java -jar target/GreetingSource-0.0.1-SNAPSHOT.jar --spring.cloud.stream.bindings.output.destination=mydest
+
+cd LoggingSink
+java -jar target/LoggingSink-0.0.1-SNAPSHOT.jar --server.port=8090 --spring.cloud.stream.bindings.input.destination=mydest(The different server port prevents collisions of the HTTP port used to service the Spring Boot Actuator endpoints in the two applications.)
+The output of the LoggingSink application will look something like the following:
+[ main] s.b.c.e.t.TomcatEmbeddedServletContainer : Tomcat started on port(s): 8090 (http)
+[ main] com.example.LoggingSinkApplication : Started LoggingSinkApplication in 6.828 seconds (JVM running for 7.371)
+hello world 1458595076731
+hello world 1458595077732
+hello world 1458595078733
+hello world 1458595079734
+hello world 1458595080735Appendices
+Appendix A: Building
+Basic Compile and Test
+To build the source you will need to install JDK 1.7.
+The build uses the Maven wrapper so you don’t have to install a specific +version of Maven. To enable the tests for Redis, Rabbit, and Kafka bindings you +should have those servers running before building. See below for more +information on running the servers.
+The main build command is
+$ ./mvnw clean install+
You can also add '-DskipTests' if you like, to avoid running the tests.
+|
+ Note
+ |
+
+You can also install Maven (>=3.3.3) yourself and run the mvn command
+in place of ./mvnw in the examples below. If you do that you also
+might need to add -P spring if your local Maven settings do not
+contain repository declarations for spring pre-release artifacts.
+ |
+
|
+ Note
+ |
+
+Be aware that you might need to increase the amount of memory
+available to Maven by setting a MAVEN_OPTS environment variable with
+a value like -Xmx512m -XX:MaxPermSize=128m. We try to cover this in
+the .mvn configuration, so if you find you have to do it to make a
+build succeed, please raise a ticket to get the settings added to
+source control.
+ |
+
The projects that require middleware generally include a
+docker-compose.yml, so consider using
+Docker Compose to run the middeware servers
+in Docker containers. See the README in the
+scripts demo
+repository for specific instructions about the common cases of mongo,
+rabbit and redis.
Documentation
+There is a "full" profile that will generate documentation.
+Working with the code
+If you don’t have an IDE preference we would recommend that you use +Spring Tools Suite or +Eclipse when working with the code. We use the +m2eclipe eclipse plugin for maven support. Other IDEs and tools +should also work without issue.
+Importing into eclipse with m2eclipse
+We recommend the m2eclipe eclipse plugin when working with +eclipse. If you don’t already have m2eclipse installed it is available from the "eclipse +marketplace".
+Unfortunately m2e does not yet support Maven 3.3, so once the projects
+are imported into Eclipse you will also need to tell m2eclipse to use
+the .settings.xml file for the projects. If you do not do this you
+may see many different errors related to the POMs in the
+projects. Open your Eclipse preferences, expand the Maven
+preferences, and select User Settings. In the User Settings field
+click Browse and navigate to the Spring Cloud project you imported
+selecting the .settings.xml file in that project. Click Apply and
+then OK to save the preference changes.
|
+ Note
+ |
+
+Alternatively you can copy the repository settings from .settings.xml into your own ~/.m2/settings.xml.
+ |
+
Importing into eclipse without m2eclipse
+If you prefer not to use m2eclipse you can generate eclipse project metadata using the +following command:
+$ ./mvnw eclipse:eclipse+
The generated eclipse projects can be imported by selecting import existing projects
+from the file menu.
+[[contributing]
+== Contributing
Spring Cloud is released under the non-restrictive Apache 2.0 license, +and follows a very standard Github development process, using Github +tracker for issues and merging pull requests into master. If you want +to contribute even something trivial please do not hesitate, but +follow the guidelines below.
+Sign the Contributor License Agreement
+Before we accept a non-trivial patch or pull request we will need you to sign the +contributor’s agreement. +Signing the contributor’s agreement does not grant anyone commit rights to the main +repository, but it does mean that we can accept your contributions, and you will get an +author credit if we do. Active contributors might be asked to join the core team, and +given the ability to merge pull requests.
+Code Conventions and Housekeeping
+None of these is essential for a pull request, but they will all help. They can also be +added after the original pull request but before a merge.
+-
+
-
+
Use the Spring Framework code format conventions. If you use Eclipse +you can import formatter settings using the +
+eclipse-code-formatter.xmlfile from the +Spring +Cloud Build project. If using IntelliJ, you can use the +Eclipse Code Formatter +Plugin to import the same file.
+ -
+
Make sure all new
+.javafiles to have a simple Javadoc class comment with at least an +@authortag identifying you, and preferably at least a paragraph on what the class is +for.
+ -
+
Add the ASF license header comment to all new
+.javafiles (copy from existing files +in the project)
+ -
+
Add yourself as an
+@authorto the .java files that you modify substantially (more +than cosmetic changes).
+ -
+
Add some Javadocs and, if you change the namespace, some XSD doc elements.
+
+ -
+
A few unit tests would help a lot as well — someone has to do it.
+
+ -
+
If no-one else is using your branch, please rebase it against the current master (or +other target branch in the main project).
+
+ -
+
When writing a commit message please follow these conventions, +if you are fixing an existing issue please add
+Fixes gh-XXXXat the end of the commit +message (where XXXX is the issue number).
+
Spring Cloud Bus
+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.
+|
+ Note
+ |
++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 github. + | +
Quick Start
+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 spring-cloud-starter-bus-amqp or spring-cloud-starter-bus-kafka to your dependency management and Spring Cloud takes care of the rest. Make sure the broker (RabbitMQ or Kafka) is available and configured: 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. for Rabbit
spring: + rabbitmq: + host: mybroker.com + port: 5672 + username: user + password: secret+
The bus currently supports sending messages to all nodes listening or all nodes for a particular service (as defined by Eureka). More selector criteria may be added in the future (ie. only service X nodes in data center Y, etc…). There are also some http endpoints under the /bus/* actuator namespace. There are currently two implemented. The first, /bus/env, sends key/value pairs to update each node’s Spring Environment. The second, /bus/refresh, will reload each application’s configuration, just as if they had all been pinged on their /refresh endpoint.
|
+ Note
+ |
+
+The Bus starters cover Rabbit and Kafka, because those are the two most common implementations, but Spring Cloud Stream is quite flexible and binder will work combined with spring-cloud-bus.
+ |
+
Addressing an Instance
+The HTTP endpoints accept a "destination" parameter, e.g. "/bus/refresh?destination=customers:9000", where the destination is an ApplicationContext 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 ContextIdApplicationContextInitializer to a combination of the spring.application.name, active profiles and server.port by default.
Addressing all instances of a service
+The "destination" parameter is used in a Spring PathMatcher (with the path separator as a colon :) 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 ApplicationContext ID.
Application Context ID must be unique
+The bus tries to eliminate processing an event twice, once from the original ApplicationEvent 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 spring.application.index to something unique for each instance of a service. For example, in lattice, set spring.application.index=${INSTANCE_INDEX} in application.properties (or bootstrap.properties if using configserver).
Customizing the Message Broker
+Spring Cloud Bus uses
+Spring Cloud Stream 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 (RabbitMQ) and Kafka
+(spring-cloud-starter-bus-[amqp,kafka]). 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 spring.rabbitmq.*
+configuration properties. Spring Cloud Bus has a handful of native
+configuration properties in spring.cloud.bus.*
+(e.g. spring.cloud.bus.destination is the name of the topic to use
+the the externall middleware). Normally the defaults will suffice.
To lean more about how to customize the message broker settings +consult the Spring Cloud Stream documentation.
+Tracing Bus Events
+Bus events (subclasses of RemoteApplicationEvent) can be traced by
+setting spring.cloud.bus.trace.enabled=true. If you do this then the
+Spring Boot TraceRepository (if it is present) will show each event
+sent and all the acks from each service instance. Example (from the
+/trace endpoint):
{
+ "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": "*:**"
+ }
+}This trace shows that a RefreshRemoteApplicationEvent was sent from
+customers:9000, broadcast to all services, and it was received
+(acked) by customers:9000 and stores:8081.
To handle the ack signals yourself you could add an @EventListener
+for the AckRemoteApplicationEvent and SentApplicationEvent types
+to your app (and enable tracing). Or you could tap into the
+TraceRepository and mine the data from there.
|
+ Note
+ |
++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. + | +
Broadcasting Your Own Events
+The Bus can carry any event of type RemoteApplicationEvent, but the
+default transport is JSON and the deserializer needs to know which
+types are going to be used ahead of time. To register a new type it
+needs to be in a subpackage of org.springframework.cloud.bus.event.
+You can use @JsonTypeName on your custom class or rely on the
+default strategy which is to use the simple name of the class. Note
+that both the producer and the consumer will need access to the class
+definition.
Spring Cloud Sleuth
+Adrian Cole, Spencer Gibb, Marcin Grzejszczak, Dave Syer
+Brixton.SR7
+Spring Cloud Sleuth implements a distributed tracing solution for Spring Cloud.
+Terminology
+Spring Cloud Sleuth borrows Dapper’s terminology.
+Span: 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).
+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.
+|
+ Tip
+ |
+
+The initial span that starts a trace is called a root span. The value of span id
+of that span is equal to trace id.
+ |
+
Trace: 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.
+Annotation: is used to record existence of an event in time. Some of the core annotations used to define +the start and stop of a request are:
+-
+
-
+
cs - Client Sent - The client has made a request. This annotation depicts the start of the span.
+
+ -
+
sr - Server Received - The server side got the request and will start processing it. +If one subtracts the cs timestamp from this timestamp one will receive the network latency.
+
+ -
+
ss - Server Sent - Annotated upon completion of request processing (when the response +got sent back to the client). If one subtracts the sr timestamp from this timestamp one +will receive the time needed by the server side to process the request.
+
+ -
+
cr - Client Received - Signifies the end of the span. The client has successfully received the +response from the server side. If one subtracts the cs timestamp from this timestamp one +will receive the whole time needed by the client to receive the response from the server.
+
+
Visualization of what Span and Trace will look in a system together with the Zipkin annotations:
+
+Each color of a note signifies a span (7 spans - from A to G). If you have such information in the note:
+Trace Id = X
+Span Id = D
+Client SentThat means that the current span has Trace-Id set to X, Span-Id set to D. It also has emitted + Client Sent event.
+This is how the visualization of the parent / child relationship of spans would look like:
+
+Purpose
+In the following sections the example from the image above will be taken into consideration.
+Distributed tracing with Zipkin
+Altogether there are 10 spans . If you go to traces in Zipkin you will see this number:
+
+However if you pick a particular trace then you will see 7 spans:
+
+|
+ Note
+ |
++When picking a particular trace you will see merged spans. That means that if there were 2 spans sent to +Zipkin with Server Received and Server Sent / Client Received and Client Sent +annotations then they will presented as a single span. + | +
In the image depicting the visualization of what Span and Trace is you can see 20 +colorful labels. How does it happen that in Zipkin 10 spans are received?
+-
+
-
+
2 span A labels signify span started and closed. Upon closing a single span is sent to Zipkin.
+
+ -
+
4 span B labels are in fact are single span with 4 annotations. However this span is composed of +two separate instances. One sent from service 1 and one from service 2. So in fact two span instances will be sent +to Zipkin and merged there.
+
+ -
+
2 span C labels signify span started and closed. Upon closing a single span is sent to Zipkin.
+
+ -
+
4 span B labels are in fact are single span with 4 annotations. However this span is composed of +two separate instances. One sent from service 2 and one from service 3. So in fact two span instances will be sent +to Zipkin and merged there.
+
+ -
+
2 span E labels signify span started and closed. Upon closing a single span is sent to Zipkin.
+
+ -
+
4 span B labels are in fact are single span with 4 annotations. However this span is composed of +two separate instances. One sent from service 2 and one from service 4. So in fact two span instances will be sent +to Zipkin and merged there.
+
+ -
+
2 span G labels signify span started and closed. Upon closing a single span is sent to Zipkin.
+
+
So 1 span from A, 2 spans from B, 1 span from C, 2 spans from D, 1 span from E, 2 spans from F and 1 from G. +Altogether 10 spans.
+
+The dependency graph in Zipkin would look like this:
+
+
+Log correlation
+When grepping the logs of those four applications by trace id equal to e.g. 2485ec27856c56f4 one would get the following:
service1.log:2016-02-26 11:15:47.561 INFO [service1,2485ec27856c56f4,2485ec27856c56f4,true] 68058 --- [nio-8081-exec-1] i.s.c.sleuth.docs.service1.Application : Hello from service1. Calling service2
+service2.log:2016-02-26 11:15:47.710 INFO [service2,2485ec27856c56f4,9aa10ee6fbde75fa,true] 68059 --- [nio-8082-exec-1] i.s.c.sleuth.docs.service2.Application : Hello from service2. Calling service3 and then service4
+service3.log:2016-02-26 11:15:47.895 INFO [service3,2485ec27856c56f4,1210be13194bfe5,true] 68060 --- [nio-8083-exec-1] i.s.c.sleuth.docs.service3.Application : Hello from service3
+service2.log:2016-02-26 11:15:47.924 INFO [service2,2485ec27856c56f4,9aa10ee6fbde75fa,true] 68059 --- [nio-8082-exec-1] i.s.c.sleuth.docs.service2.Application : Got response from service3 [Hello from service3]
+service4.log:2016-02-26 11:15:48.134 INFO [service4,2485ec27856c56f4,1b1845262ffba49d,true] 68061 --- [nio-8084-exec-1] i.s.c.sleuth.docs.service4.Application : Hello from service4
+service2.log:2016-02-26 11:15:48.156 INFO [service2,2485ec27856c56f4,9aa10ee6fbde75fa,true] 68059 --- [nio-8082-exec-1] i.s.c.sleuth.docs.service2.Application : Got response from service4 [Hello from service4]
+service1.log:2016-02-26 11:15:48.182 INFO [service1,2485ec27856c56f4,2485ec27856c56f4,true] 68058 --- [nio-8081-exec-1] i.s.c.sleuth.docs.service1.Application : Got response from service2 [Hello from service2, response from service3 [Hello from service3] and from service4 [Hello from service4]]If you’re using a log aggregating tool like Kibana, +Splunk etc. you can order the events that took place. An example of +Kibana would look like this:
+
+If you want to use Logstash here is the Grok pattern for Logstash:
+filter {
+ # pattern matching logback pattern
+ grok {
+ match => { "message" => "%{TIMESTAMP_ISO8601:timestamp}\s+%{LOGLEVEL:severity}\s+\[%{DATA:service},%{DATA:trace},%{DATA:span},%{DATA:exportable}\]\s+%{DATA:pid}---\s+\[%{DATA:thread}\]\s+%{DATA:class}\s+:\s+%{GREEDYDATA:rest}" }
+ }
+}|
+ Note
+ |
++If you want to use Grok together with the logs from Cloud Foundry you have to use this pattern: + | +
filter {
+ # pattern matching logback pattern
+ grok {
+ match => { "message" => "(?m)OUT\s+%{TIMESTAMP_ISO8601:timestamp}\s+%{LOGLEVEL:severity}\s+\[%{DATA:service},%{DATA:trace},%{DATA:span},%{DATA:exportable}\]\s+%{DATA:pid}---\s+\[%{DATA:thread}\]\s+%{DATA:class}\s+:\s+%{GREEDYDATA:rest}" }
+ }
+}JSON Logback with Logstash
+Often you do not want to store your logs in a text file but in a JSON file that Logstash can immediately pick. To do that you have to do the following (for readability
+we’re passing the dependencies in the groupId:artifactId:version notation.
Dependencies setup
+-
+
-
+
Ensure that Logback is on the classpath (
+ch.qos.logback:logback-core)
+ -
+
Add Logstash Logback encode - example for version
+4.6:net.logstash.logback:logstash-logback-encoder:4.6
+
Logback setup
+Below you can find an example of a Logback configuration (file named logback-spring.xml) that:
-
+
-
+
logs information from the application in a JSON format to a
+build/${spring.application.name}.jsonfile
+ -
+
has commented out two additional appenders - console and standard log file
+
+ -
+
has the same logging pattern as the one presented in the previous section
+
+
<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+ <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
+ ​
+ <springProperty scope="context" name="springAppName" source="spring.application.name"/>
+ <!-- Example for logging into the build folder of your project -->
+ <property name="LOG_FILE" value="${BUILD_FOLDER:-build}/${springAppName}"/>​
+
+ <property name="CONSOLE_LOG_PATTERN"
+ value="%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %clr(${LOG_LEVEL_PATTERN:-%5p}) %clr([${springAppName:-},%X{X-B3-TraceId:-},%X{X-B3-SpanId:-},%X{X-Span-Export:-}]){yellow} %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}"/>
+
+ <!-- Appender to log to console -->
+ <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
+ <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
+ <!-- Minimum logging level to be presented in the console logs-->
+ <level>INFO</level>
+ </filter>
+ <encoder>
+ <pattern>${CONSOLE_LOG_PATTERN}</pattern>
+ <charset>utf8</charset>
+ </encoder>
+ </appender>
+
+ <!-- Appender to log to file -->​
+ <appender name="flatfile" class="ch.qos.logback.core.rolling.RollingFileAppender">
+ <file>${LOG_FILE}</file>
+ <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
+ <fileNamePattern>${LOG_FILE}.%d{yyyy-MM-dd}.gz</fileNamePattern>
+ <maxHistory>7</maxHistory>
+ </rollingPolicy>
+ <encoder>
+ <pattern>${CONSOLE_LOG_PATTERN}</pattern>
+ <charset>utf8</charset>
+ </encoder>
+ </appender>
+ ​
+ <!-- Appender to log to file in a JSON format -->
+ <appender name="logstash" class="ch.qos.logback.core.rolling.RollingFileAppender">
+ <file>${LOG_FILE}.json</file>
+ <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
+ <fileNamePattern>${LOG_FILE}.json.%d{yyyy-MM-dd}.gz</fileNamePattern>
+ <maxHistory>7</maxHistory>
+ </rollingPolicy>
+ <encoder class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder">
+ <providers>
+ <timestamp>
+ <timeZone>UTC</timeZone>
+ </timestamp>
+ <pattern>
+ <pattern>
+ {
+ "severity": "%level",
+ "service": "${springAppName:-}",
+ "trace": "%X{X-B3-TraceId:-}",
+ "span": "%X{X-B3-SpanId:-}",
+ "exportable": "%X{X-Span-Export:-}",
+ "pid": "${PID:-}",
+ "thread": "%thread",
+ "class": "%logger{40}",
+ "rest": "%message"
+ }
+ </pattern>
+ </pattern>
+ </providers>
+ </encoder>
+ </appender>
+ ​
+ <root level="INFO">
+ <!--<appender-ref ref="console"/>-->
+ <appender-ref ref="logstash"/>
+ <!--<appender-ref ref="flatfile"/>-->
+ </root>
+</configuration>|
+ Note
+ |
+
+If you’re using a custom logback-spring.xml then you have to pass the spring.application.name in
+bootstrap instead of application property file. Otherwise your custom logback file won’t read the property properly.
+ |
+
Adding to the project
+Only Sleuth (log correlation)
+If you want to profit only from Spring Cloud Sleuth without the Zipkin integration just add
+the spring-cloud-starter-sleuth module to your project.
<dependencyManagement> (1)
+ <dependencies>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-dependencies</artifactId>
+ <version>Brixton.RELEASE</version>
+ <type>pom</type>
+ <scope>import</scope>
+ </dependency>
+ </dependencies>
+ </dependencyManagement>
+
+ <dependency> (2)
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-starter-sleuth</artifactId>
+ </dependency>-
+
-
+
In order not to pick versions by yourself it’s much better if you add the dependency management via +the Spring BOM
+
+ -
+
Add the dependency to
+spring-cloud-starter-sleuth
+
dependencyManagement { (1)
+ imports {
+ mavenBom "org.springframework.cloud:spring-cloud-dependencies:Brixton.RELEASE"
+ }
+}
+
+dependencies { (2)
+ compile "org.springframework.cloud:spring-cloud-starter-sleuth"
+}-
+
-
+
In order not to pick versions by yourself it’s much better if you add the dependency management via +the Spring BOM
+
+ -
+
Add the dependency to
+spring-cloud-starter-sleuth
+
Sleuth with Zipkin via HTTP
+If you want both Sleuth and Zipkin just add the spring-cloud-starter-zipkin dependency.
<dependencyManagement> (1)
+ <dependencies>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-dependencies</artifactId>
+ <version>Brixton.RELEASE</version>
+ <type>pom</type>
+ <scope>import</scope>
+ </dependency>
+ </dependencies>
+ </dependencyManagement>
+
+ <dependency> (2)
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-starter-zipkin</artifactId>
+ </dependency>-
+
-
+
In order not to pick versions by yourself it’s much better if you add the dependency management via +the Spring BOM
+
+ -
+
Add the dependency to
+spring-cloud-starter-zipkin
+
dependencyManagement { (1)
+ imports {
+ mavenBom "org.springframework.cloud:spring-cloud-dependencies:Brixton.RELEASE"
+ }
+}
+
+dependencies { (2)
+ compile "org.springframework.cloud:spring-cloud-starter-zipkin"
+}-
+
-
+
In order not to pick versions by yourself it’s much better if you add the dependency management via +the Spring BOM
+
+ -
+
Add the dependency to
+spring-cloud-starter-zipkin
+
Sleuth with Zipkin via Spring Cloud Stream
+If you want both Sleuth and Zipkin just add the spring-cloud-sleuth-stream dependency.
<dependencyManagement> (1)
+ <dependencies>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-dependencies</artifactId>
+ <version>Brixton.RELEASE</version>
+ <type>pom</type>
+ <scope>import</scope>
+ </dependency>
+ </dependencies>
+ </dependencyManagement>
+
+ <dependency> (2)
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-sleuth-stream</artifactId>
+ </dependency>
+ <dependency> (3)
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-starter-sleuth</artifactId>
+ </dependency>
+ <!-- EXAMPLE FOR RABBIT BINDING -->
+ <dependency> (4)
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-stream-binder-rabbit</artifactId>
+ </dependency>-
+
-
+
In order not to pick versions by yourself it’s much better if you add the dependency management via +the Spring BOM
+
+ -
+
Add the dependency to
+spring-cloud-sleuth-stream
+ -
+
Add the dependency to
+spring-cloud-starter-sleuth- that way all dependant dependencies will be downloaded
+ -
+
Add a binder (e.g. Rabbit binder) to tell Spring Cloud Stream what it should bind to
+
+
dependencyManagement { (1)
+ imports {
+ mavenBom "org.springframework.cloud:spring-cloud-dependencies:Brixton.RELEASE"
+ }
+}
+
+dependencies {
+ compile "org.springframework.cloud:spring-cloud-sleuth-stream" (2)
+ compile "org.springframework.cloud:spring-cloud-starter-sleuth" (3)
+ // Example for Rabbit binding
+ compile "org.springframework.cloud:spring-cloud-stream-binder-rabbit" (4)
+}-
+
-
+
In order not to pick versions by yourself it’s much better if you add the dependency management via +the Spring BOM
+
+ -
+
Add the dependency to
+spring-cloud-sleuth-stream
+ -
+
Add the dependency to
+spring-cloud-starter-sleuth- that way all dependant dependencies will be downloaded
+ -
+
Add a binder (e.g. Rabbit binder) to tell Spring Cloud Stream what it should bind to
+
+
Spring Cloud Sleuth Stream Zipkin Collector
+If you want to start a Spring Cloud Sleuth Stream Zipkin collector just add the spring-cloud-sleuth-zipkin-stream
+dependency
<dependencyManagement> (1)
+ <dependencies>
+ <dependency>
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-dependencies</artifactId>
+ <version>Brixton.RELEASE</version>
+ <type>pom</type>
+ <scope>import</scope>
+ </dependency>
+ </dependencies>
+ </dependencyManagement>
+
+ <dependency> (2)
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-sleuth-zipkin-stream</artifactId>
+ </dependency>
+ <dependency> (3)
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-starter-sleuth</artifactId>
+ </dependency>
+ <!-- EXAMPLE FOR RABBIT BINDING -->
+ <dependency> (4)
+ <groupId>org.springframework.cloud</groupId>
+ <artifactId>spring-cloud-stream-binder-rabbit</artifactId>
+ </dependency>-
+
-
+
In order not to pick versions by yourself it’s much better if you add the dependency management via +the Spring BOM
+
+ -
+
Add the dependency to
+spring-cloud-sleuth-zipkin-stream
+ -
+
Add the dependency to
+spring-cloud-starter-sleuth- that way all dependant dependencies will be downloaded
+ -
+
Add a binder (e.g. Rabbit binder) to tell Spring Cloud Stream what it should bind to
+
+
dependencyManagement { (1)
+ imports {
+ mavenBom "org.springframework.cloud:spring-cloud-dependencies:Brixton.RELEASE"
+ }
+}
+
+dependencies {
+ compile "org.springframework.cloud:spring-cloud-sleuth-zipkin-stream" (2)
+ compile "org.springframework.cloud:spring-cloud-starter-sleuth" (3)
+ // Example for Rabbit binding
+ compile "org.springframework.cloud:spring-cloud-stream-binder-rabbit" (4)
+}-
+
-
+
In order not to pick versions by yourself it’s much better if you add the dependency management via +the Spring BOM
+
+ -
+
Add the dependency to
+spring-cloud-sleuth-zipkin-stream
+ -
+
Add the dependency to
+spring-cloud-starter-sleuth- that way all dependant dependencies will be downloaded
+ -
+
Add a binder (e.g. Rabbit binder) to tell Spring Cloud Stream what it should bind to
+
+
and then just annotate your main class with @EnableZipkinStreamServer annotation:
package example;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.cloud.sleuth.zipkin.stream.EnableZipkinStreamServer;
+
+@SpringBootApplication
+@EnableZipkinStreamServer
+public class ZipkinStreamServerApplication {
+
+ public static void main(String[] args) throws Exception {
+ SpringApplication.run(ZipkinStreamServerApplication.class, args);
+ }
+
+}Features
+-
+
-
+
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:
+++++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] ...
+++notice the
+[appname,traceId,spanId,exportable]entries from the MDC:++-
+
-
+
spanId - the id of a specific operation that took place
+
+ -
+
appname - the name of the application that logged the span
+
+ -
+
traceId - the id of the latency graph that contains the span
+
+ -
+
exportable - whether the log should be exported to Zipkin or not. When would you like the span not to be +exportable? In the case in which you want to wrap some operation in a Span and have it written to the logs +only.
+
+
+ -
+
-
+
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.
+
+ -
+
Sleuth records timing information to aid in latency analysis. Using sleuth, you can pinpoint causes of +latency in your applications. Sleuth is written to not log too much, and to not cause your production application to crash.
+++-
+
-
+
propagates structural data about your call-graph in-band, and the rest out-of-band.
+
+ -
+
includes opinionated instrumentation of layers such as HTTP
+
+ -
+
includes sampling policy to manage volume
+
+ -
+
can report to a Zipkin system for query and visualization
+
+
+ -
+
-
+
Instruments common ingress and egress points from Spring applications (servlet filter, async endpoints, +rest template, scheduled actions, message channels, zuul filters, feign client).
+
+ -
+
Sleuth includes default logic to join a trace across http or messaging boundaries. For example, http propagation +works via Zipkin-compatible request headers. This propagation logic is defined and customized via +
+SpanInjectorandSpanExtractorimplementations.
+ -
+
Provides simple metrics of accepted / dropped spans.
+
+ -
+
If
+spring-cloud-sleuth-zipkinthen the app will generate and collect Zipkin-compatible traces. +By default it sends them via HTTP to a Zipkin server on localhost (port 9411). +Configure the location of the service usingspring.zipkin.baseUrl.
+ -
+
If
+spring-cloud-sleuth-streamthen 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).
+
|
+ Important
+ |
+
+If using Zipkin or Stream, configure the percentage of spans exported using spring.sleuth.sampler.percentage
+(default 0.1, i.e. 10%). Otherwise you might think that Sleuth is not working cause it’s omitting some spans.
+ |
+
|
+ Note
+ |
+
+the SLF4J MDC is always set and logback users will immediately see the trace and span ids in logs per the example
+ above. Other logging systems have to configure their own formatter to get the same result. The default is
+ logging.pattern.level set to %clr(%5p) %clr([${spring.application.name:},%X{X-B3-TraceId:-},%X{X-B3-SpanId:-},%X{X-Span-Export:-}]){yellow}
+ (this is a Spring Boot feature for logback users).
+ This means that if you’re not using SLF4J this pattern WILL NOT be automatically applied.
+ |
+
Sampling
+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
+Sampler 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 AlwaysSampler
+that exports everything and a PercentageBasedSampler that samples a
+fixed fraction of spans.
|
+ Note
+ |
+
+the PercentageBasedSampler is the default if you are using
+spring-cloud-sleuth-zipkin or spring-cloud-sleuth-stream. You can
+configure the exports using spring.sleuth.sampler.percentage. The passed
+value needs to be a double from 0.0 to 1.0 so it’s not a percentage.
+For backwards compatibility reasons we’re not changing the property name.
+ |
+
A sampler can be installed just by creating a bean definition, e.g:
+@Bean
+public Sampler defaultSampler() {
+ return new AlwaysSampler();
+}Instrumentation
+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 Filter, and for Spring Integration we use
+ChannelInterceptors.
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 spring.sleuth.keys.http.headers (a
+list of header names).
|
+ Note
+ |
+
+Remember that tags are only collected and exported if there is a
+Sampler that allows it (by default there is not, so there is no
+danger of accidentally collecting too much data without configuring
+something).
+ |
+
|
+ Note
+ |
++Currently the instrumentation in Spring Cloud Sleuth is eager - it means that +we’re actively trying to pass the tracing context between threads. Also timing events +are captured even when sleuth isn’t exporting data to a tracing system. +This approach may change in the future towards being lazy on this matter. + | +
Span lifecycle
+You can do the following operations on the Span by means of org.springframework.cloud.sleuth.Tracer interface:
+-
+
-
+
start - when you start a span its name is assigned and start timestamp is recorded.
+
+ -
+
close - the span gets finished (the end time of the span is recorded) and if +the span is exportable then it will be eligible for collection to Zipkin. +The span is also removed from the current thread.
+
+ -
+
continue - a new instance of span will be created whereas it will be a copy of the +one that it continues.
+
+ -
+
detach - the span doesn’t get stopped or closed. It only gets removed from the current thread.
+
+ -
+
create with explicit parent - you can create a new span and set an explicit parent to it
+
+
|
+ Tip
+ |
+
+Spring creates the instance of Tracer for you. In order to use it all you need is to just autowire it.
+ |
+
Creating and closing spans
+You can manually create spans by using the Tracer interface.
+// Start a span. If there was a span present in this thread it will become
+// the `newSpan`'s parent.
+Span newSpan = this.tracer.createSpan("calculateTax");
+try {
+ // ...
+ // You can tag a span
+ this.tracer.addTag("taxValue", taxValue);
+ // ...
+ // You can log an event on a span
+ newSpan.logEvent("taxCalculated");
+} finally {
+ // Once done remember to close the span. This will allow collecting
+ // the span to send it to Zipkin
+ this.tracer.close(newSpan);
+}In this example we could see how to create a new instance of span. Assuming that there already +was a span present in this thread then it would become the parent of that span.
+|
+ Important
+ |
++Always clean after you create a span! Don’t forget to close a span if you want to send it to Zipkin. + | +
Continuing spans
+Sometimes you don’t want to create a new span but you want to continue one. Example of such a +situation might be (of course it all depends on the use-case):
+-
+
-
+
AOP - If there was already a span created before an aspect was reached then you might not want to create a new span.
+
+ -
+
Hystrix - executing a Hystrix command is most likely a logical part of the current processing. It’s in fact +only a technical implementation detail that you wouldn’t necessarily want to reflect in tracing as a separate being.
+
+
The continued instance of span is equal to the one that it continues:
+Span continuedSpan = this.tracer.continueSpan(spanToContinue);
+assertThat(continuedSpan).isEqualTo(spanToContinue);To continue a span you can use the Tracer interface.
+// let's assume that we're in a thread Y and we've received
+// the `initialSpan` from thread X
+Span continuedSpan = this.tracer.continueSpan(initialSpan);
+try {
+ // ...
+ // You can tag a span
+ this.tracer.addTag("taxValue", taxValue);
+ // ...
+ // You can log an event on a span
+ continuedSpan.logEvent("taxCalculated");
+} finally {
+ // Once done remember to detach the span. That way you'll
+ // safely remove it from the current thread without closing it
+ this.tracer.detach(continuedSpan);
+}|
+ Important
+ |
++Always clean after you create a span! Don’t forget to detach a span if some work was done started in one + thread (e.g. thread X) and it’s waiting for other threads (e.g. Y, Z) to finish. + Then the spans in the threads Y, Z should be detached at the end of their work. When the results are collected + the span in thread X should be closed. + | +
Creating spans with an explicit parent
+There is a possibility that you want to start a new span and provide an explicit parent of that span.
+Let’s assume that the parent of a span is in one thread and you want to start a new span in another thread. The
+startSpan method of the Tracer interface is the method you are looking for.
// let's assume that we're in a thread Y and we've received
+// the `initialSpan` from thread X. `initialSpan` will be the parent
+// of the `newSpan`
+Span newSpan = this.tracer.createSpan("calculateCommission", initialSpan);
+try {
+ // ...
+ // You can tag a span
+ this.tracer.addTag("commissionValue", commissionValue);
+ // ...
+ // You can log an event on a span
+ newSpan.logEvent("commissionCalculated");
+} finally {
+ // Once done remember to close the span. This will allow collecting
+ // the span to send it to Zipkin. The tags and events set on the
+ // newSpan will not be present on the parent
+ this.tracer.close(newSpan);
+}|
+ Important
+ |
++After having created such a span remember to close it. Otherwise you will see a lot of warnings in your logs + related to the fact that you have a span present in the current thread other than the one you’re trying to close. + What’s worse your spans won’t get closed properly thus will not get collected to Zipkin. + | +
Naming spans
+Picking a span name is not a trivial task. Span name should depict an operation name. The name should +be low cardinality (e.g. not include identifiers).
+Since there is a lot of instrumentation going on some of the span names will be +artificial like:
+-
+
-
+
+controller-method-namewhen received by a Controller with a method nameconrollerMethodName
+ -
+
+asyncfor asynchronous operations done via wrappedCallableandRunnable.
+ -
+
+@Scheduledannotated methods will return the simple name of the class.
+
Fortunately, for the asynchronous processing you can provide explicit naming.
+@SpanName annotation
+You can do name the span explicitly via the @SpanName annotation.
@SpanName("calculateTax")
+class TaxCountingRunnable implements Runnable {
+
+ @Override public void run() {
+ // perform logic
+ }
+}In this case, when processed in the following manner:
+Runnable runnable = new TraceRunnable(tracer, spanNamer, new TaxCountingRunnable());
+Future<?> future = executorService.submit(runnable);
+// ... some additional logic ...
+future.get();The span will be named calculateTax.
toString() method
+It’s pretty rare to create separate classes for Runnable or Callable. Typically one creates an anonymous
+instance of those classes. You can’t annotate such classes thus to override that, if there is no @SpanName annotation present,
+we’re checking if the class has a custom implementation of the toString() method.
So executing such code:
+Runnable runnable = new TraceRunnable(tracer, spanNamer, new Runnable() {
+ @Override public void run() {
+ // perform logic
+ }
+
+ @Override public String toString() {
+ return "calculateTax";
+ }
+});
+Future<?> future = executorService.submit(runnable);
+// ... some additional logic ...
+future.get();will lead in creating a span named calculateTax.
Customizations
+Thanks to the SpanInjector and SpanExtractor you can customize the way spans
+are created and propagated.
There are currently two built-in ways to pass tracing information between processes:
+-
+
-
+
via Spring Integration
+
+ -
+
via HTTP
+
+
Span ids are extracted from Zipkin-compatible (B3) headers (either Message
+or HTTP headers), to start or join an existing trace. Trace information is
+injected into any outbound requests so the next hop can extract them.
Spring Integration
+For Spring Integration these are the beans responsible for creation of a Span from a Message
+ and filling in the MessageBuilder with tracing information.
@Bean
+public SpanExtractor<Message> messagingSpanExtractor() {
+ ...
+}
+
+@Bean
+public SpanInjector<MessageBuilder> messagingSpanInjector() {
+ ...
+}You can override them by providing your own implementation and by adding a @Primary annotation
+to your bean definition.
HTTP
+For HTTP these are the beans responsible for creation of a Span from a HttpServletRequest.
@Bean
+public SpanExtractor<HttpServletRequest> httpServletRequestSpanExtractor() {
+ ...
+}You can override them by providing your own implementation and by adding a @Primary annotation
+to your bean definition.
Example
+Let’s assume that instead of the standard Zipkin compatible tracing HTTP header names +you have
+-
+
-
+
for trace id -
+correlationId
+ -
+
for span id -
+mySpanId
+
This is a an example of a SpanExtractor
static class CustomHttpServletRequestSpanExtractor
+ implements SpanExtractor<HttpServletRequest> {
+
+ @Override
+ public Span joinTrace(HttpServletRequest carrier) {
+ long traceId = Span.hexToId(carrier.getHeader("correlationId"));
+ long spanId = Span.hexToId(carrier.getHeader("mySpanId"));
+ // extract all necessary headers
+ Span.SpanBuilder builder = Span.builder().traceId(traceId).spanId(spanId);
+ // build rest of the Span
+ return builder.build();
+ }
+}And you could register it like this:
+@Bean
+@Primary
+SpanExtractor<HttpServletRequest> customHttpServletRequestSpanExtractor() {
+ return new CustomHttpServletRequestSpanExtractor();
+}Spring Cloud Sleuth does not add trace/span related headers to the Http Response for security reasons. If you need the headers then a custom SpanInjector
+that injects the headers into the Http Response and a Servlet filter which makes use of this can be added the following way:
static class CustomHttpServletResponseSpanInjector
+ implements SpanInjector<HttpServletResponse> {
+
+ @Override
+ public void inject(Span span, HttpServletResponse carrier) {
+ carrier.addHeader(Span.TRACE_ID_NAME, span.traceIdString());
+ carrier.addHeader(Span.SPAN_ID_NAME, Span.idToHex(span.getSpanId()));
+ }
+}
+
+static class HttpResponseInjectingTraceFilter extends GenericFilterBean {
+
+ private final Tracer tracer;
+ private final SpanInjector<HttpServletResponse> spanInjector;
+
+ public HttpResponseInjectingTraceFilter(Tracer tracer, SpanInjector<HttpServletResponse> spanInjector) {
+ this.tracer = tracer;
+ this.spanInjector = spanInjector;
+ }
+
+ @Override
+ public void doFilter(ServletRequest request, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
+ HttpServletResponse response = (HttpServletResponse) servletResponse;
+ Span currentSpan = this.tracer.getCurrentSpan();
+ this.spanInjector.inject(currentSpan, response);
+ filterChain.doFilter(request, response);
+ }
+}And you could register them like this:
+@Bean
+SpanInjector<HttpServletResponse> customHttpServletResponseSpanInjector() {
+ return new CustomHttpServletResponseSpanInjector();
+}
+
+@Bean
+HttpResponseInjectingTraceFilter responseInjectingTraceFilter(Tracer tracer) {
+ return new HttpResponseInjectingTraceFilter(tracer, customHttpServletResponseSpanInjector());
+}Custom SA tag in Zipkin
+Sometimes you want to create a manual Span that will wrap a call to an external service which is not instrumented.
+What you can do is to create a span with the peer.service tag that will contain a value of the service that you want to call.
+Below you can see an example of a call to Redis that is wrapped in such a span.
org.springframework.cloud.sleuth.Span newSpan = tracer.createSpan("redis");
+try {
+ newSpan.tag("redis.op", "get");
+ newSpan.tag("lc", "redis");
+ newSpan.logEvent(org.springframework.cloud.sleuth.Span.CLIENT_SEND);
+ // call redis service e.g
+ // return (SomeObj) redisTemplate.opsForHash().get("MYHASH", someObjKey);
+} finally {
+ newSpan.tag("peer.service", "redisService");
+ newSpan.tag("peer.ipv4", "1.2.3.4");
+ newSpan.tag("peer.port", "1234");
+ newSpan.logEvent(org.springframework.cloud.sleuth.Span.CLIENT_RECV);
+ tracer.close(newSpan);
+}|
+ Important
+ |
+
+Remember not to add both peer.service tag and the SA tag! You have to add only peer.service.
+ |
+
Span Data as Messages
+You can accumulate and send span data over
+Spring Cloud Stream by
+including the spring-cloud-sleuth-stream jar as a dependency, and
+adding a Channel Binder implementation
+(e.g. spring-cloud-starter-stream-rabbit for RabbitMQ or
+spring-cloud-starter-stream-kafka for Kafka). This will
+automatically turn your app into a producer of messages with payload
+type Spans.
Zipkin Consumer
+There is a special convenience annotation for setting up a message consumer
+for the Span data and pushing it into a Zipkin SpanStore. This application
@SpringBootApplication
+@EnableZipkinStreamServer
+public class Consumer {
+ public static void main(String[] args) {
+ SpringApplication.run(Consumer.class, args);
+ }
+}will listen for the Span data on whatever transport you provide via a
+Spring Cloud Stream Binder (e.g. include
+spring-cloud-starter-stream-rabbit for RabbitMQ, and similar
+starters exist for Redis and Kafka). If you add the following UI dependency
<groupId>io.zipkin.java</groupId>
+<artifactId>zipkin-autoconfigure-ui</artifactId>Then you’ll have your app a +Zipkin server, which hosts +the UI and api on port 9411.
+The default SpanStore is in-memory (good for demos and getting
+started quickly). For a more robust solution you can add MySQL and
+spring-boot-starter-jdbc to your classpath and enable the JDBC
+SpanStore via configuration, e.g.:
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:
+ storage:
+ type: mysql|
+ Note
+ |
+
+The @EnableZipkinStreamServer is also annotated with
+@EnableZipkinServer so the process will also expose the standard
+Zipkin server endpoints for collecting spans over HTTP, and for
+querying in the Zipkin Web UI.
+ |
+
Custom Consumer
+A custom consumer can also easily be implemented using
+spring-cloud-sleuth-stream and binding to the SleuthSink. Example:
@EnableBinding(SleuthSink.class)
+@SpringBootApplication(exclude = SleuthStreamAutoConfiguration.class)
+@MessageEndpoint
+public class Consumer {
+
+ @ServiceActivator(inputChannel = SleuthSink.INPUT)
+ public void sink(Spans input) throws Exception {
+ // ... process spans
+ }
+}|
+ Note
+ |
+
+the sample consumer application above explicitly excludes
+SleuthStreamAutoConfiguration so it doesn’t send messages to itself,
+but this is optional (you might actually want to trace requests into
+the consumer app).
+ |
+
Metrics
+Currently Spring Cloud Sleuth registers very simple metrics related to spans. +It’s using the Spring Boot’s metrics support +to calculate the number of accepted and dropped spans. Each time a span gets +sent to Zipkin the number of accepted spans will increase. If there’s an error then +the number of dropped spans will get increased.
+Integrations
+Runnable and Callable
+If you’re wrapping your logic in Runnable or Callable it’s enough to wrap those classes in their Sleuth representative.
Example for Runnable:
Runnable runnable = new Runnable() {
+ @Override
+ public void run() {
+ // do some work
+ }
+
+ @Override
+ public String toString() {
+ return "spanNameFromToStringMethod";
+ }
+};
+// Manual `TraceRunnable` creation with explicit "calculateTax" Span name
+Runnable traceRunnable = new TraceRunnable(tracer, spanNamer, runnable, "calculateTax");
+// Wrapping `Runnable` with `Tracer`. The Span name will be taken either from the
+// `@SpanName` annotation or from `toString` method
+Runnable traceRunnableFromTracer = tracer.wrap(runnable);Example for Callable:
Callable<String> callable = new Callable<String>() {
+ @Override
+ public String call() throws Exception {
+ return someLogic();
+ }
+
+ @Override
+ public String toString() {
+ return "spanNameFromToStringMethod";
+ }
+};
+// Manual `TraceCallable` creation with explicit "calculateTax" Span name
+Callable<String> traceCallable = new TraceCallable<>(tracer, spanNamer, callable, "calculateTax");
+// Wrapping `Callable` with `Tracer`. The Span name will be taken either from the
+// `@SpanName` annotation or from `toString` method
+Callable<String> traceCallableFromTracer = tracer.wrap(callable);That way you will ensure that a new Span is created and closed for each execution.
+Hystrix
+Custom Concurrency Strategy
+We’re registering a custom HystrixConcurrencyStrategy
+that wraps all Callable instances into their Sleuth representative -
+the TraceCallable. The strategy either starts or continues a span depending on the fact whether tracing was already going
+on before the Hystrix command was called. To disable the custom Hystrix Concurrency Strategy set the spring.sleuth.hystrix.strategy.enabled to false.
Manual Command setting
+Assuming that you have the following HystrixCommand:
HystrixCommand<String> hystrixCommand = new HystrixCommand<String>(setter) {
+ @Override
+ protected String run() throws Exception {
+ return someLogic();
+ }
+};In order to pass the tracing information you have to wrap the same logic in the Sleuth version of the HystrixCommand which is the
+TraceCommand:
TraceCommand<String> traceCommand = new TraceCommand<String>(tracer, traceKeys, setter) {
+ @Override
+ public String doRun() throws Exception {
+ return someLogic();
+ }
+};RxJava
+We’re registering a custom RxJavaSchedulersHook
+that wraps all Action0 instances into their Sleuth representative -
+the TraceAction. The hook either starts or continues a span depending on the fact whether tracing was already going
+on before the Action was scheduled. To disable the custom RxJavaSchedulersHook set the spring.sleuth.rxjava.schedulers.hook.enabled to false.
You can define a list of regular expressions for thread names, for which you don’t want a Span to be created. Just provide a comma separated list
+of regular expressions in the spring.sleuth.rxjava.schedulers.ignoredthreads property.
HTTP integration
+Features from this section can be disabled by providing the spring.sleuth.web.enabled property with value equal to false.
HTTP Filter
+Via the TraceFilter all sampled incoming requests result in creation of a Span. That Span’s name is http: + the path to which
+ the request was sent. E.g. if the request was sent to /foo/bar then the name will be http:/foo/bar. You can configure which URIs you would
+ like to skip via the spring.sleuth.web.skipPattern property. If you have ManagementServerProperties on classpath then
+ its value of contextPath gets appended to the provided skip pattern.
HandlerInterceptor
+Since we want the span names to be precise we’re using a TraceHandlerInterceptor that either wraps an
+ existing HandlerInterceptor or is added directly to the list of existing HandlerInterceptors. The
+ TraceHandlerInterceptor adds a special request attribute to the given HttpServletRequest. If the
+ the TraceFilter doesn’t see this attribute set it will create a "fallback" span which is an additional
+ span created on the server side so that the trace is presented properly in the UI. Seeing that most likely
+ signifies that there is a missing instrumentation. In that case please file an issue in Spring Cloud Sleuth.
Async Servlet support
+If your controller returns a Callable or a WebAsyncTask Spring Cloud Sleuth will continue the existing span instead of creating a new one.
HTTP client integration
+Synchronous Rest Template
+We’re injecting a RestTemplate interceptor that ensures that all the tracing information is passed to the requests. Each time a
+call is made a new Span is created. It gets closed upon receiving the response. In order to block the synchronous RestTemplate features
+just set spring.sleuth.web.client.enabled to false.
|
+ Important
+ |
+
+You have to register RestTemplate as a bean so that the interceptors will get injected.
+If you create a RestTemplate instance with a new keyword then the instrumentation WILL NOT work.
+ |
+
Asynchronous Rest Template
+Custom instrumentation is set to create and close Spans upon sending and receiving requests. You can customize the ClientHttpRequestFactory
+and the AsyncClientHttpRequestFactory by registering your beans. Remember to use tracing compatible implementations (e.g. don’t forget to
+wrap ThreadPoolTaskScheduler in a TraceAsyncListenableTaskExecutor). Example of custom request factories:
@EnableAutoConfiguration
+@Configuration
+public static class TestConfiguration {
+
+ @Bean
+ ClientHttpRequestFactory mySyncClientFactory() {
+ return new MySyncClientHttpRequestFactory();
+ }
+
+ @Bean
+ AsyncClientHttpRequestFactory myAsyncClientFactory() {
+ return new MyAsyncClientHttpRequestFactory();
+ }
+}To block the AsyncRestTemplate features set spring.sleuth.web.async.client.enabled to false.
+To disable creation of the default TraceAsyncClientHttpRequestFactoryWrapper set spring.sleuth.web.async.client.factory.enabled
+to false. If you don’t want to create AsyncRestClient at all set spring.sleuth.web.async.client.template.enabled to false.
Feign
+By default Spring Cloud Sleuth provides integration with feign via the TraceFeignClientAutoConfiguration. You can disable it entirely
+by setting spring.sleuth.feign.enabled to false. If you do so then no Feign related instrumentation will take place.
Part of Feign instrumentation is done via a FeignBeanPostProcessor. You can disable it by providing the spring.sleuth.feign.processor.enabled equal to false.
+If you set it like this then Spring Cloud Sleuth will not instrument any of your custom Feign components. All the default instrumentation
+however will be still there.
Asynchronous communication
+@Async annotated methods
+In Spring Cloud Sleuth we’re instrumenting async related components so that the tracing information is passed between threads.
+You can disable this behaviour by setting the value of spring.sleuth.async.enabled to false.
If you annotate your method with @Async then we’ll automatically create a new Span with the following characteristics:
-
+
-
+
the Span name will be the annotated method name
+
+ -
+
the Span will be tagged with that method’s class name and the method name too
+
+
@Scheduled annotated methods
+In Spring Cloud Sleuth we’re instrumenting scheduled method execution so that the tracing information is passed between threads. You can disable this behaviour
+by setting the value of spring.sleuth.scheduled.enabled to false.
If you annotate your method with @Scheduled then we’ll automatically create a new Span with the following characteristics:
-
+
-
+
the Span name will be the annotated method name
+
+ -
+
the Span will be tagged with that method’s class name and the method name too
+
+
If you want to skip Span creation for some @Scheduled annotated classes you can set the
+spring.sleuth.scheduled.skipPattern with a regular expression that will match the fully qualified name of the
+@Scheduled annotated class.
Executor, ExecutorService and ScheduledExecutorService
+We’re providing LazyTraceExecutor, TraceableExecutorService and TraceableScheduledExecutorService. Those implementations
+are creating Spans each time a new task is submitted, invoked or scheduled.
Here you can see an example of how to pass tracing information with TraceableExecutorService when working with CompletableFuture:
CompletableFuture<Long> completableFuture = CompletableFuture.supplyAsync(() -> {
+ // perform some logic
+ return 1_000_000L;
+}, new TraceableExecutorService(executorService,
+ // 'calculateTax' explicitly names the span - this param is optional
+ tracer, traceKeys, spanNamer, "calculateTax"));Messaging
+Spring Cloud Sleuth integrates with Spring Integration. It creates spans for publish and
+subscribe events. To disable Spring Integration instrumentation, set spring.sleuth.integration.enabled to false.
Spring Cloud Sleuth up till version 1.0.4 is sending invalid tracing headers when using messaging. Those headers are actually
+the same as the ones sent in HTTP (they contain a -) in its name. For the sake of
+backwards compatibility in 1.0.4 we’ve started sending both valid and invalid headers. Please upgrade to 1.0.4 because
+in Spring Cloud Sleuth 1.1 we will remove the support for the deprecated headers.
Since 1.0.4 you can provide the spring.sleuth.integration.patterns pattern to explicitly
+provide the names of channels that you want to include for tracing. By default all channels
+are included.
Zuul
+We’re registering Zuul filters to propagate the tracing information (the request header is enriched with tracing data).
+To disable Zuul support set the spring.sleuth.zuul.enabled property to false.
Running examples
+You can find the running examples deployed in the Pivotal Web Services. Check them out in the following links:
+Spring Cloud Consul
+Install Consul
+Please see the installation documentation for instructions on how to install Consul.
+Consul Agent
+A Consul Agent client must be available to all Spring Cloud Consul applications. By default, the Agent client is expected to be at localhost:8500. See the Agent documentation 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:
./src/main/bash/local_run_consul.sh+
This will start an agent in server mode on port 8500, with the ui available at http://localhost:8500
+Service Discovery with Consul
+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 HTTP API and DNS. 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 cluster that communicates via a gossip protocol and uses the Raft consensus protocol.
+Registering with Consul
+When a client registers with Consul, it provides meta-data about itself such as host and port, id, name and tags. An HTTP Check is created by default that Consul hits the /health endpoint every 10 seconds. If the health check fails, the service instance is marked as critical.
Example Consul client:
+@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);
+ }
+
+}(i.e. utterly normal Spring Boot app). If the Consul client is located somewhere other than localhost:8500, the configuration is required to locate the client. Example:
spring: + cloud: + consul: + host: localhost + port: 8500+
|
+ Caution
+ |
+
+If you use Spring Cloud Consul Config, the above values will need to be placed in bootstrap.yml instead of application.yml.
+ |
+
The default service name, instance id and port, taken from the Environment, are ${spring.application.name}, the Spring Context ID and ${server.port} respectively.
@EnableDiscoveryClient 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).
HTTP Health Check
+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. server.servletPath=/foo) or management endpoint path (e.g. management.contextPath=/admin). 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:
spring:
+ cloud:
+ consul:
+ discovery:
+ healthCheckPath: ${management.contextPath}/health
+ healthCheckInterval: 15s
+Metadata and Consul tags
+Consul does not yet support metadata on services. Spring Cloud’s ServiceInstance has a Map<String, String> metadata field. Spring Cloud Consul uses Consul tags to approximate metadata until Consul officially supports metadata. Tags with the form key=value will be split and used as a Map key and value respectively. Tags without the equal = sign, will be used as both the key and value.
spring: + cloud: + consul: + discovery: + tags: foo=bar, baz+
The above configuration will result in a map with foo→bar and baz→baz.
Making the Consul Instance ID Unique
+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 ${spring.application.name}:comma,separated,profiles:${server.port}. 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 spring.cloud.consul.discovery.instanceId. For example:
spring:
+ cloud:
+ consul:
+ discovery:
+ instanceId: ${spring.application.name}:${spring.application.instance_id:${random.value}}
+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 spring.application.instance_id will be populated automatically in a Spring Boot Actuator application, so the random value will not be needed.
Using the DiscoveryClient
+Spring Cloud has support for Feign (a REST client builder) and also Spring RestTemplate using the logical service names instead of physical URLs.
You can also use the org.springframework.cloud.client.discovery.DiscoveryClient which provides a simple API for discovery clients that is not specific to Netflix, e.g.
@Autowired
+private DiscoveryClient discoveryClient;
+
+public String serviceUrl() {
+ List<ServiceInstance> list = discoveryClient.getInstances("STORES");
+ if (list != null && list.size() > 0 ) {
+ return list.get(0).getUri();
+ }
+ return null;
+}
+Distributed Configuration with Consul
+Consul provides a Key/Value Store for storing configuration and other metadata. Spring Cloud Consul Config is an alternative to the Config Server and Client. Configuration is loaded into the Spring Environment during the special "bootstrap" phase. Configuration is stored in the /config folder by default. Multiple PropertySource 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:
config/testApp,dev/ +config/testApp/ +config/application,dev/ +config/application/+
The most specific property source is at the top, with the least specific at the bottom. Properties is the config/application folder are applicable to all applications using consul for configuration. Properties in the config/testApp folder are only available to the instances of the service named "testApp".
Configuration is currently read on startup of the application. Sending a HTTP POST to /refresh 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.
How to activate
+Including a dependency on org.springframework.cloud:spring-cloud-consul-config will enable auto-configuration that will setup Spring Cloud Consul Config.
Customizing
+Consul Config may be customized using the following properties:
+spring: + cloud: + consul: + config: + enabled: true + prefix: configuration + defaultContext: apps + profileSeparator: '::'+
-
+
-
+
+enabledsetting this value to "false" disables Consul Config
+ -
+
+prefixsets the base folder for configuration values
+ -
+
+defaultContextsets the folder name used by all applications
+ -
+
+profileSeparatorsets the value of the separator used to separate the profile name in property sources with profiles
+
YAML or Properties with Config
+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 spring.cloud.consul.config.format property to YAML or PROPERTIES. For example to use YAML:
spring: + cloud: + consul: + config: + format: YAML+
YAML must be set in the appropriate data key in consul. Using the defaults above the keys would look like:
config/testApp,dev/data +config/testApp/data +config/application,dev/data +config/application/data+
You could store a YAML document in any of the keys listed above.
+You can change the data key using spring.cloud.consul.config.data-key.
git2consul with Config
+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 .yml and .properties respectively. Set the spring.cloud.consul.config.format property to FILES. For example:
spring: + cloud: + consul: + config: + format: FILES+
Given the following keys in /config, the development profile and an application name of foo:
.gitignore +application.yml +bar.properties +foo-development.properties +foo-production.yml +foo.properties +master.ref+
the following property sources would be created:
+config/foo-development.properties +config/foo.properties +config/application.yml+
The value of each key needs to be a properly formatted YAML or Properties file.
+Fail Fast
+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 spring.cloud.consul.config.failFast=false in bootstrap.yml will cause the configuration module to log a warning rather than throw an exception. This will allow the application to continue startup normally.
Consul Retry
+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
+spring-retry and spring-boot-starter-aop 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 spring.cloud.consul.retry.* configuration properties.
+This works with both Spring Cloud Consul Config and Discovery registration.
|
+ Tip
+ |
+
+To take full control of the retry add a @Bean of type
+RetryOperationsInterceptor with id "consulRetryInterceptor". Spring
+Retry has a RetryInterceptorBuilder that makes it easy to create one.
+ |
+
Spring Cloud Bus with Consul
+Coming in a later release.
+Circuit Breaker with Hystrix
+Applications can use the Hystrix Circuit Breaker provided by the Spring Cloud Netflix project by including this starter in the projects pom.xml: spring-cloud-starter-hystrix. Hystrix doesn’t depend on the Netflix Discovery Client. The @EnableHystrix annotation should be placed on a configuration class (usually the main class). Then methods can be annotated with @HystrixCommand to be protected by a circuit breaker. See the documentation for more details.
Hystrix metrics aggregation with Turbine and Consul
+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 DiscoveryClient interface to lookup relevant instances. To use Turbine with Spring Cloud Consul, configure the Turbine application in a manner similar to the following examples:
<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>+
Notice that the Turbine dependency is not a starter. The turbine starter includes support for Netflix Eureka.
+spring.application.name: turbine
+applications: consulhystrixclient
+turbine:
+ aggregator:
+ clusterConfig: ${applications}
+ appConfig: ${applications}
+The clusterConfig and appConfig sections must match, so it’s useful to put the comma-separated list of service ID’s into a separate configuration property.
@EnableTurbine
+@EnableDiscoveryClient
+@SpringBootApplication
+public class Turbine {
+ public static void main(String[] args) {
+ SpringApplication.run(DemoturbinecommonsApplication.class, args);
+ }
+}
+Spring Cloud Zookeeper
+Install Zookeeper
+Please see the installation documentation for instructions on how to install Zookeeper.
+Service Discovery with Zookeeper
+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. Curator(A java library for Zookeeper) provides Service Discovery services via Service Discovery Extension. Spring Cloud Zookeeper leverages this extension for service registration and discovery.
+How to activate
+Including a dependency on org.springframework.cloud:spring-cloud-starter-zookeeper-discovery will enable auto-configuration that will setup Spring Cloud Zookeeper Discovery.
Registering with Zookeeper
+When a client registers with Zookeeper, it provides meta-data about itself such as host and port, id and name.
+Example Zookeeper client:
+@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);
+ }
+
+}(i.e. utterly normal Spring Boot app). If Zookeeper is located somewhere other than localhost:2181, the configuration is required to locate the server. Example:
spring: + cloud: + zookeeper: + connect-string: localhost:2181+
|
+ Caution
+ |
+
+If you use Spring Cloud Zookeeper Config, the above values will need to be placed in bootstrap.yml instead of application.yml.
+ |
+
The default service name, instance id and port, taken from the Environment, are ${spring.application.name}, the Spring Context ID and ${server.port} respectively.
@EnableDiscoveryClient 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).
Using the DiscoveryClient
+Spring Cloud has support for Feign (a REST client builder) and also Spring RestTemplate using the logical service names instead of physical URLs.
You can also use the org.springframework.cloud.client.discovery.DiscoveryClient which provides a simple API for discovery clients that is not specific to Netflix, e.g.
@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;
+}
+Zookeeper Dependencies
+Using the Zookeeper Dependencies
+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 Feign (a REST client builder)
+and also Spring RestTemplate.
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.
+How to activate Zookeeper Dependencies
+-
+
-
+
Including a dependency on
+org.springframework.cloud:spring-cloud-starter-zookeeper-discoverywill enable auto-configuration that will setup Spring Cloud Zookeeper Dependencies.
+ -
+
If you have to have the
+spring.cloud.zookeeper.dependenciessection properly set up - check the subsequent section for more details then the feature is active
+ -
+
You can have the dependencies turned off even if you’ve provided the dependencies in your properties. Just set the property
+spring.cloud.zookeeper.dependency.enabledto false (defaults totrue).
+
Setting up Zookeeper Dependencies
+Let’s take a closer look at an example of dependencies representation:
+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+
Let’s now go through each part of the dependency one by one. The root property name is spring.cloud.zookeeper.dependencies.
Aliases
+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 DiscoveryClient, Feign or RestTemplate.
In the aforementioned examples the aliases are newsletter and mailing. Example of Feign usage with newsletter would be:
@FeignClient("newsletter")
+public interface NewsletterService {
+ @RequestMapping(method = RequestMethod.GET, value = "/newsletter")
+ String getNewsletters();
+}
+Path
+Represented by path yaml property.
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.
+Load balancer type
+Represented by loadBalancerType yaml property.
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
+-
+
-
+
STICKY - once chosen the instance will always be called
+
+ -
+
RANDOM - picks an instance randomly
+
+ -
+
ROUND_ROBIN - iterates over instances over and over again
+
+
Content-Type template and version
+Represented by contentTypeTemplate and version yaml property.
If you version your api via the Content-Type 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 contentTypeTemplate with a special $version placeholder. That placeholder will be filled by the value of the
+version yaml property. Let’s take a look at an example.
Having the following contentTypeTemplate:
application/vnd.newsletter.$version+json+
and the following version:
v1+
Will result in setting up of a Content-Type header for each request:
application/vnd.newsletter.v1+json+
Default headers
+Represented by headers map in yaml
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 headers section:
headers: + Accept: + - text/html + - application/xhtml+xml + Cache-Control: + - no-cache+
Results in adding the Accept and Cache-Control headers with appropriate list of values in your HTTP request.
Obligatory dependencies
+Represented by required property in yaml
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 required: true property in the yaml file.
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.
+You can read more about Spring Cloud Zookeeper Presence Checker in the following sections.
+Stubs
+You can provide a colon separated path to the JAR containing stubs of the dependency. Example
+stubs: org.springframework:foo:stubsmeans that for a particular dependencies can be found under:
+-
+
-
+
groupId:
+org.springframework
+ -
+
artifactId:
+foo
+ -
+
classifier:
+stubs- this is the default value
+
This is actually equal to
+stubs: org.springframework:foosince stubs is the default classifier.
Configuring Spring Cloud Zookeeper Dependencies
+There is a bunch of properties that you can set to enable / disable parts of Zookeeper Dependencies functionalities.
+-
+
-
+
+spring.cloud.zookeeper.dependencies- if you don’t set this property you won’t benefit from Zookeeper Dependencies
+ -
+
+spring.cloud.zookeeper.dependency.ribbon.enabled(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 theloadBalancerTypesection of the Zookeeper Dependencies. The configuration that needs this property +has an implementation ofLoadBalancerClientthat delegates to theILoadBalancerpresented in the next bullet
+ -
+
+spring.cloud.zookeeper.dependency.ribbon.loadbalancer(enabled by default) - thanks to this property the customILoadBalancerknows 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.
+ -
+
+spring.cloud.zookeeper.dependency.headers.enabled(enabled by default) - this property registers such aRibbonClientthat 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.
+ -
+
+spring.cloud.zookeeper.dependency.resttemplate.enabled(enabled by default) - when enabled will modify the request headers of@LoadBalancedannotatedRestTemplateso that it passes +headers and content type with version set in Dependency configuration. Wihtout this setting of those two parameters will not be operational.
+
Spring Cloud Zookeeper Dependency Watcher
+The Dependency Watcher mechanism allows you to register listeners to your dependencies. The functionality is in fact an implementation of the Observator pattern. When a dependency changes
+its state (UP or DOWN) then some custom logic can be applied.
How to activate
+Spring Cloud Zookeeper Dependencies functionality needs to be enabled to profit from Dependency Watcher mechanism.
+Registering a listener
+In order to register a listener you have to implement an interface org.springframework.cloud.zookeeper.discovery.watcher.DependencyWatcherListener and register it as a bean.
+The interface gives you one method:
void stateChanged(String dependencyName, DependencyState newState);+
If you want to register a listener for a particular dependency then the dependencyName would be the discriminator for your concrete implementation. newState will provide you with information
+ whether your dependency has changed to CONNECTED or DISCONNECTED.
Presence Checker
+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.
+The default implementation of the abstract org.springframework.cloud.zookeeper.discovery.watcher.presence.DependencyPresenceOnStartupVerifier class is the
+org.springframework.cloud.zookeeper.discovery.watcher.presence.DefaultDependencyPresenceOnStartupVerifier which works in the following way.
-
+
-
+
If the dependency is marked us
+requiredand it’s not in Zookeeper then upon booting your application will throw an exception and shutdown
+ -
+
If dependency is not
+requiredtheorg.springframework.cloud.zookeeper.discovery.watcher.presence.LogMissingDependencyCheckerwill log that application is missing atWARNlevel
+
The functionality can be overriden since the DefaultDependencyPresenceOnStartupVerifier is registered only when there is no bean of DependencyPresenceOnStartupVerifier.
Distributed Configuration with Zookeeper
+Zookeeper provides a hierarchical namespace that allows clients to store arbitrary data, such as configuration data. Spring Cloud Zookeeper Config is an alternative to the Config Server and Client. Configuration is loaded into the Spring Environment during the special "bootstrap" phase. Configuration is stored in the /config namespace by default. Multiple PropertySource 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:
config/testApp,dev +config/testApp +config/application,dev +config/application+
The most specific property source is at the top, with the least specific at the bottom. Properties is the config/application namespace are applicable to all applications using zookeeper for configuration. Properties in the config/testApp namespace are only available to the instances of the service named "testApp".
Configuration is currently read on startup of the application. Sending a HTTP POST to /refresh 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.
How to activate
+Including a dependency on org.springframework.cloud:spring-cloud-starter-zookeeper-config will enable auto-configuration that will setup Spring Cloud Zookeeper Config.
Customizing
+Zookeeper Config may be customized using the following properties:
+spring: + cloud: + zookeeper: + config: + enabled: true + root: configuration + defaultContext: apps + profileSeparator: '::'+
-
+
-
+
+enabledsetting this value to "false" disables Zookeeper Config
+ -
+
+rootsets the base namespace for configuration values
+ -
+
+defaultContextsets the name used by all applications
+ -
+
+profileSeparatorsets the value of the separator used to separate the profile name in property sources with profiles
+
Spring Boot Cloud CLI
+Spring Boot CLI provides Spring
+Boot command line features for Spring
+Cloud. You can write Groovy scripts to run Spring Cloud component
+applications (e.g. @EnableEurekaServer). You can also easily do
+things like encryption and decryption to support Spring Cloud Config
+clients with secret configuration values. With the Launcher CLI you
+can launch services like Eureka, Zipkin, Config Server
+conveniently all at once from the command line (very useful at
+development time).
|
+ Note
+ |
++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 github. + | +
Installation
+To install, make +sure you have +Spring Boot CLI +(1.3.5 or better):
+$ spring version +Spring CLI v1.3.5.RELEASE+
E.g. for SDKMan users
+$ sdk install springboot 1.3.5.RELEASE
+$ sdk use springboot 1.3.5.RELEASEand install the Spring Cloud plugins (they are independent, so you can install one or the other or both):
+$ mvn install
+$ spring install org.springframework.cloud:spring-cloud-cli:1.2.0.BUILD-SNAPSHOT
+$ spring install org.springframework.cloud.launcher:spring-cloud-launcher-cli:1.2.0.BUILD-SNAPSHOT|
+ Important
+ |
++Prerequisites: 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). + | +
Running Spring Cloud Services in Development
+The Launcher CLI can be used to run common services like Eureka,
+Config Server etc. from the command line. To list the available
+services you can do spring cloud --list, and to launch a default set
+of services just spring cloud. To choose the services to deploy,
+just list them on the command line, e.g.
$ spring cloud eureka configserver h2 kafka zipkin+
Summary of supported deployables:
+| Service | +Name | +Address | +Description | +
|---|---|---|---|
eureka |
+Eureka Server |
++ | Eureka server for service registration and discovery. All the other services show up in its catalog by default. |
+
configserver |
+Config Server |
++ | Spring Cloud Config Server running in the "native" profile and serving configuration from the local directory ./launcher |
+
h2 |
+H2 Database |
+http://localhost:9095 (console), jdbc:h2:tcp://localhost:9096/{data} |
+Relation database service. Use a file path for |
+
kafka |
+Kafka Broker |
+http://localhost:9091 (actuator endpoints), localhost:9092 |
++ |
hystrixdashboard |
+Hystrix Dashboard |
++ | Any Spring Cloud app that declares Hystrix circuit breakers publishes metrics on |
+
dataflow |
+Dataflow Server |
++ | Spring Cloud Dataflow server with UI at /admin-ui. Connect the Dataflow shell to target at root path. |
+
zipkin |
+Zipkin Server |
++ | Zipkin Server with UI for visualizing traces. Stores span data in memory and accepts them via HTTP POST of JSON data. |
+
Each of these apps can be configured using a local YAML file with the same name (in the current
+working directory or a subdirectory called "config"). E.g. in configserver.yml you might want to
+do something like this to locate a local git repository for the backend:
spring:
+ profiles:
+ active: git
+ cloud:
+ config:
+ server:
+ git:
+ uri: file://${user.home}/dev/demo/config-repoWriting Groovy Scripts and Running Applications
+Spring Cloud CLI has support for most of the Spring Cloud declarative
+features, such as the @Enable* class of annotations. For example,
+here is a fully functional Eureka server
@EnableEurekaServer
+class Eureka {}which you can run from the command line like this
+$ spring run app.groovy+
To include additional dependencies, often it suffices just to add the
+appropriate feature-enabling annotation, e.g. @EnableConfigServer,
+@EnableOAuth2Sso or @EnableEurekaClient. To manually include a
+dependency you can use a @Grab 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:
@Grab('spring-cloud-starter-bus-amqp')
+@RestController
+class Service {
+ @RequestMapping('/')
+ def home() { [message: 'Hello'] }
+}Encryption and Decryption
+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.
+$ spring encrypt mysecret --key foo +682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda +$ spring decrypt --key foo 682bc583f4641835fa2db009355293665d2647dade3375c0ee201de2a49f7bda +mysecret+
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.
+$ spring encrypt mysecret --key @${HOME}/.ssh/id_rsa.pub
+AQAjPgt3eFZQXwt8tsHAVv/QHiY5sI2dRcR+...
+Spring Cloud Security
+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.
+|
+ Note
+ |
++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 github. + | +
Quickstart
+OAuth2 Single Sign On
+Here’s a Spring Cloud "Hello World" app with HTTP Basic +authentication and a single user account:
+@Grab('spring-boot-starter-security')
+@Controller
+class Application {
+
+ @RequestMapping('/')
+ String home() {
+ 'Hello World'
+ }
+
+}You can run it with spring run app.groovy and watch the logs for the password (username is "user"). So far this is just the default for a Spring Boot app.
Here’s a Spring Cloud app with OAuth2 SSO:
+@Controller
+@EnableOAuth2Sso
+class Application {
+
+ @RequestMapping('/')
+ String home() {
+ 'Hello World'
+ }
+
+}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.
+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:
+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: falserun 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.
+To limit the scope that the client asks for when it obtains an access token
+you can set spring.oauth2.client.scope (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.
|
+ Note
+ |
++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 +sample here). + | +
OAuth2 Protected Resource
+You want to protect an API resource with an OAuth2 token? Here’s a +simple example (paired with the client above):
+@Grab('spring-cloud-starter-security')
+@RestController
+@EnableResourceServer
+class Application {
+
+ @RequestMapping('/')
+ def home() {
+ [message: 'Hello World']
+ }
+
+}and
+spring:
+ oauth2:
+ resource:
+ userInfoUri: https://api.github.com/user
+ preferTokenInfo: falseMore Detail
+Single Sign On
+|
+ Note
+ |
++All of the OAuth2 SSO and resource server features moved to Spring Boot +in version 1.3. You can find documentation in the +Spring Boot user guide. + | +
Token Relay
+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.
+Client Token Relay
+If your app is a user facing OAuth2 client (i.e. has declared
+@EnableOAuth2Sso or @EnableOAuth2Client) then it has an
+OAuth2ClientContext in request scope from Spring Boot. You can
+create your own OAuth2RestTemplate from this context and an
+autowired OAuth2ProtectedResourceDetails, and then the context will
+always forward the access token downstream, also refreshing the access
+token automatically if it expires. (These are features of Spring
+Security and Spring Boot.)
Client Token Relay in Zuul Proxy
+If your app also has a
+Spring
+Cloud Zuul embedded reverse proxy (using @EnableZuulProxy) 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:
@Controller
+@EnableOAuth2Sso
+@EnableZuulProxy
+class Application {
+
+}and it will (in addition to logging the user in and grabbing a token)
+pass the authentication token downstream to the /proxy/*
+services. If those services are implemented with
+@EnableOAuth2Resource then they will get a valid token in the
+correct header.
How does it work? The @EnableOAuth2Sso annotation pulls in
+spring-cloud-starter-security (which you could do manually in a
+traditional app), and that in turn triggers some autoconfiguration for
+a ZuulFilter, which itself is activated because Zuul is on the
+classpath (via @EnableZuulProxy). The
+filter
+just extracts an access token from the currently authenticated user,
+and puts it in a request header for the downstream requests.
Resource Server Token Relay
+If your app has @EnableOAuth2Resource you might want to relay the
+incoming token downstream to other services. If you use a
+RestTemplate to contact the downstream services then this is just a
+matter of how to create the template with the right context.
If your service uses UserInfoTokenServices to authenticate incoming
+tokens (i.e. it is using the security.oauth2.user-info-uri
+configuration), then you can simply create an OAuth2RestTemplate
+using an autowired OAuth2ClientContext (it will be populated by the
+authentication process before it hits the backend code). Equivalently
+(with Spring Boot 1.4), you could inject a
+UserInfoRestTemplateFactory and grab its OAuth2RestTemplate in
+your configuration. For example:
@Bean
+public OAuth2RestTemplate restTemplate(UserInfoRestTemplateFactory factory) {
+ return factory.getUserInfoRestTemplate();
+}This rest template will then have the same OAuth2ClientContext
+(request-scoped) that is used by the authentication filter, so you can
+use it to send requests with the same access token.
If your app is not using UserInfoTokenServices but is still a client
+(i.e. it declares @EnableOAuth2Client or @EnableOAuth2Sso), then
+with Spring Security Cloud any OAuth2RestOperations that the user
+creates from an @Autowired @OAuth2Context will also forward
+tokens. This feature is implemented by default as an MVC handler
+interceptor, so it only works in Spring MVC. If you are not using MVC
+you could use a custom filter or AOP interceptor wrapping an
+AccessTokenContextRelay to provide the same feature.
Here’s a basic +example showing the use of an autowired rest template created +elsewhere ("foo.com" is a Resource Server accepting the same tokens as +the surrounding app):
+@Autowired
+private OAuth2RestOperations restTemplate;
+
+@RequestMapping("/relay")
+public String relay() {
+ ResponseEntity<String> response =
+ restTemplate.getForEntity("https://foo.com/bar", String.class);
+ return "Success! (" + response.getBody() + ")";
+}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
+OAuth2Context instead of autowiring the default one.
Feign clients will also pick up an interceptor that uses the
+OAuth2ClientContext if it is available, so they should also do a
+token relay anywhere where a RestTemplate would.
Configuring Authentication Downstream of a Zuul Proxy
+You can control the authorization behaviour downstream of an
+@EnableZuulProxy through the proxy.auth.* settings. Example:
proxy:
+ auth:
+ routes:
+ customers: oauth2
+ stores: passthru
+ recommendations: noneIn 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.
+See + +ProxyAuthenticationProperties for full details.
+Spring Cloud for Cloud Foundry
+Spring Cloud for Cloudfoundry makes it easy to run +Spring Cloud apps in +Cloud Foundry (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).
+The spring-cloud-cloudfoundry-web 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.
The spring-cloud-cloudfoundry-discovery project provides an
+implementation of Spring Cloud Commons DiscoveryClient so you can
+@EnableDiscoveryClient and provide your credentials as
+spring.cloud.cloudfoundry.discovery.[email,password] and then you
+can use the DiscoveryClient directly or via a LoadBalancerClient
+(also *.url if you are not connecting to
+Pivotal Web Services).
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.
+Discovery
+Here’s a Spring Cloud app with Cloud Foundry discovery:
+@Grab('org.springframework.cloud:spring-cloud-cloudfoundry')
+@RestController
+@EnableDiscoveryClient
+class Application {
+
+ @Autowired
+ DiscoveryClient client
+
+ @RequestMapping('/')
+ String home() {
+ 'Hello from ' + client.getLocalServiceInstance()
+ }
+
+}If you run it without any service bindings:
+$ spring jar app.jar app.groovy +$ cf push -p app.jar+
It will show its app name in the home page.
+The DiscoveryClient can lists all the apps in a space, according to
+the credentials it is authenticated with, where the space defaults to
+the one the client is running in (if any). If neither org nor space
+are configured, they default per the user’s profile in Cloud Foundry.
Single Sign On
+|
+ Note
+ |
++All of the OAuth2 SSO and resource server features moved to Spring Boot +in version 1.3. You can find documentation in the +Spring Boot user guide. + | +
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
+@EnableOAuth2Sso (from Spring Boot). The name of the service can be
+parameterized using spring.oauth2.sso.serviceId.
Spring Cloud Cluster
+Leader Election
+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 zookeeper, hazelcast and etcd.
From user perspective election is working via interfaces
+org.springframework.cloud.cluster.leader.Candidate and
+org.springframework.cloud.cluster.leader.Context. Candidate
+contains access to leadership’s role and id and also have methods
+onGranted and onRevoked. These callback methods are useful if
+default Candidate implementation is changed.
Leader election is auto-configured if spring-cloud-cluster-autoconfigure
+and either spring-cloud-cluster-hazelcast, spring-cloud-cluster-zookeeper
+or spring-cloud-cluster-etcd jars are found from a classpath. In
+case where both jars are found leader election is created using both
+systems. See sections Zookeeper,
+Hazelcast and
+Etcd for more
+information about a created beans.
Default Candidate created from auto-configuration is
+org.springframework.cloud.cluster.leader.DefaultCandidate which
+currently only logs granted and revoked events.
If there’s a need for disable all leader related auto-configuration,
+a spring.cloud.cluster.leader.enabled can be set to false which
+then allows to do manual configuration even if the jars an on a
+classpath. Properties spring.cloud.cluster.leader.id and
+spring.cloud.cluster.leader.role can be used to set default
+identifier and role.
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 OnGrantedEvent and OnRevokedEvent are
+sent as spring event objects.
Simply create your own event listener class:
+class MyEventListener implements ApplicationListener<AbstractLeaderEvent> {
+
+ @Override
+ public void onApplicationEvent(AbstractLeaderEvent event) {
+ // do something with OnGrantedEvent or OnRevokedEvent
+ }
+}and then create it as a bean.
+@Configuration
+static class Config {
+ @Bean
+ public MyEventListener myEventListener() {
+ return new MyEventListener();
+ }
+}For simply log events you can also use a utility class
+LoggingListener which allows easy configuration.
import org.springframework.cloud.cluster.leader.event.LoggingListener;
+
+@Configuration
+static class Config {
+ @Bean
+ public LoggingListener loggingListener() {
+ return new LoggingListener("info");
+ }
+}Zookeeper
+Candidate implementation for zookeeper is created with a bean name
+zookeeperLeaderCandidate which can be used to override the one
+created during auto-configuration.
Zookeeper based election can be explicitly disabled using property
+spring.cloud.cluster.zookeeper.leader.enabled.
Other properties spring.cloud.cluster.zookeeper.namespace and
+spring.cloud.cluster.zookeeper.connect can be used to set the
+zookeeper base namespace path and connect string.
Hazelcast
+Candidate implementation for hazelcast is created with a bean name
+hazelcastLeaderCandidate which can be used to override the one
+created during auto-configuration.
Hazelcast based election can be explicitly disabled using property
+spring.cloud.cluster.hazelcast.leader.enabled. If you want to provide xml
+based configuration for Hazelcast instance use property
+spring.cloud.cluster.hazelcast.config-location to tell location of a
+Hazelcast xml configuration file. config-location is a normal spring
+Resource.
Etcd
+Candidate implementation for etcd is created with a bean name
+etcdLeaderCandidate which can be used to override the one
+created during auto-configuration.
Etcd based election can be explicitly disabled using property
+spring.cloud.cluster.etcd.leader.enabled.
Multiple etcd cluster uris can be specified using property
+spring.cloud.cluster.etcd.connect
Unresolved directive in spring-cloud.adoc - include::/Users/ryanjbaxter/git-repos/spring-cloud/scripts/docs/../contract/docs/src/main/asciidoc/spring-cloud-contract.adoc[]
+Appendix: Compendium of Configuration Properties
+| Name | +Default | +Description | +
|---|---|---|
encrypt.fail-on-error |
+true |
+Flag to say that a process should fail if there is an encryption or decryption + error. |
+
encrypt.key |
++ | A symmetric key. As a stronger alternative consider using a keystore. |
+
encrypt.key-store.alias |
++ | Alias for a key in the store. |
+
encrypt.key-store.location |
++ | Location of the key store file, e.g. classpath:/keystore.jks. |
+
encrypt.key-store.password |
++ | Password that locks the keystore. |
+
encrypt.key-store.secret |
++ | Secret protecting the key (defaults to the same as the password). |
+
encrypt.rsa.algorithm |
++ | The RSA algorithm to use (DEFAULT or OEAP). Once it is set do not change it (or + existing ciphers will not a decryptable). |
+
encrypt.rsa.salt |
+deadbeef |
+Salt for the random secret used to encrypt cipher text. Once it is set do not + change it (or existing ciphers will not a decryptable). |
+
encrypt.rsa.strong |
+false |
+Flag to indicate that "strong" AES encryption should be used internally. If + true then the GCM algorithm is applied to the AES encrypted bytes. Default is + false (in which case "standard" CBC is used instead). Once it is set do not + change it (or existing ciphers will not a decryptable). |
+
endpoints.bus.enabled |
++ | + |
endpoints.bus.id |
++ | + |
endpoints.bus.sensitive |
++ | + |
endpoints.consul.enabled |
++ | + |
endpoints.consul.id |
++ | + |
endpoints.consul.sensitive |
++ | + |
endpoints.env.post.enabled |
+true |
+Enable changing the Environment through a POST to /env. |
+
endpoints.features.enabled |
++ | + |
endpoints.features.id |
++ | + |
endpoints.features.sensitive |
++ | + |
endpoints.pause.enabled |
+true |
+Enable the /pause endpoint (to send Lifecycle.stop()). |
+
endpoints.pause.id |
++ | + |
endpoints.pause.sensitive |
++ | + |
endpoints.refresh.enabled |
+true |
+Enable the /refresh endpoint to refresh configuration and re-initialize refresh scoped beans. |
+
endpoints.refresh.id |
++ | + |
endpoints.refresh.sensitive |
++ | + |
endpoints.restart.enabled |
+true |
+Enable the /restart endpoint to restart the application context. |
+
endpoints.restart.id |
++ | + |
endpoints.restart.pause-endpoint.enabled |
++ | + |
endpoints.restart.pause-endpoint.id |
++ | + |
endpoints.restart.pause-endpoint.sensitive |
++ | + |
endpoints.restart.resume-endpoint.enabled |
++ | + |
endpoints.restart.resume-endpoint.id |
++ | + |
endpoints.restart.resume-endpoint.sensitive |
++ | + |
endpoints.restart.sensitive |
++ | + |
endpoints.restart.timeout |
+0 |
++ |
endpoints.resume.enabled |
+true |
+Enable the /resume endpoint (to send Lifecycle.start()). |
+
endpoints.resume.id |
++ | + |
endpoints.resume.sensitive |
++ | + |
endpoints.zookeeper.enabled |
+true |
+Enable the /zookeeper endpoint to inspect the state of zookeeper. |
+
eureka.client.allow-redirects |
+false |
+Indicates whether server can redirect a client request to a backup server/cluster. + If set to false, the server will handle the request directly, If set to true, it + may send HTTP redirect to the client, with a new server location. |
+
eureka.client.availability-zones |
++ | Gets the list of availability zones (used in AWS data centers) for the region in + which this instance resides. + The changes are effective at runtime at the next registry fetch cycle as specified + by registryFetchIntervalSeconds. |
+
eureka.client.backup-registry-impl |
++ | Gets the name of the implementation which implements BackupRegistry to fetch the + registry information as a fall back option for only the first time when the eureka + client starts. + This may be needed for applications which needs additional resiliency for registry + information without which it cannot operate. |
+
eureka.client.cache-refresh-executor-exponential-back-off-bound |
+10 |
+Cache refresh executor exponential back off related property. It is a maximum + multiplier value for retry delay, in case where a sequence of timeouts occurred. |
+
eureka.client.cache-refresh-executor-thread-pool-size |
+2 |
+The thread pool size for the cacheRefreshExecutor to initialise with |
+
eureka.client.client-data-accept |
++ | EurekaAccept name for client data accept |
+
eureka.client.decoder-name |
++ | This is a transient config and once the latest codecs are stable, can be removed + (as there will only be one) |
+
eureka.client.disable-delta |
+false |
+Indicates whether the eureka client should disable fetching of delta and should + rather resort to getting the full registry information. + Note that the delta fetches can reduce the traffic tremendously, because the rate + of change with the eureka server is normally much lower than the rate of fetches. + The changes are effective at runtime at the next registry fetch cycle as specified + by registryFetchIntervalSeconds |
+
eureka.client.dollar-replacement |
+_- |
+Get a replacement string for Dollar sign <code>$</code> during + serializing/deserializing information in eureka server. |
+
eureka.client.enabled |
+true |
+Flag to indicate that the Eureka client is enabled. |
+
eureka.client.encoder-name |
++ | This is a transient config and once the latest codecs are stable, can be removed + (as there will only be one) |
+
eureka.client.escape-char-replacement |
+__ |
+Get a replacement string for underscore sign <code>_</code> during + serializing/deserializing information in eureka server. |
+
eureka.client.eureka-connection-idle-timeout-seconds |
+30 |
+Indicates how much time (in seconds) that the HTTP connections to eureka server can + stay idle before it can be closed. + In the AWS environment, it is recommended that the values is 30 seconds or less, + since the firewall cleans up the connection information after a few mins leaving + the connection hanging in limbo |
+
eureka.client.eureka-server-connect-timeout-seconds |
+5 |
+Indicates how long to wait (in seconds) before a connection to eureka server needs + to timeout. Note that the connections in the client are pooled by + org.apache.http.client.HttpClient and this setting affects the actual connection + creation and also the wait time to get the connection from the pool. |
+
eureka.client.eureka-server-d-n-s-name |
++ | Gets the DNS name to be queried to get the list of eureka servers.This information + is not required if the contract returns the service urls by implementing + serviceUrls. + The DNS mechanism is used when useDnsForFetchingServiceUrls is set to true and the + eureka client expects the DNS to configured a certain way so that it can fetch + changing eureka servers dynamically. + The changes are effective at runtime. |
+
eureka.client.eureka-server-port |
++ | Gets the port to be used to construct the service url to contact eureka server when + the list of eureka servers come from the DNS.This information is not required if + the contract returns the service urls eurekaServerServiceUrls(String). + The DNS mechanism is used when useDnsForFetchingServiceUrls is set to true and the + eureka client expects the DNS to configured a certain way so that it can fetch + changing eureka servers dynamically. + The changes are effective at runtime. |
+
eureka.client.eureka-server-read-timeout-seconds |
+8 |
+Indicates how long to wait (in seconds) before a read from eureka server needs to + timeout. |
+
eureka.client.eureka-server-total-connections |
+200 |
+Gets the total number of connections that is allowed from eureka client to all + eureka servers. |
+
eureka.client.eureka-server-total-connections-per-host |
+50 |
+Gets the total number of connections that is allowed from eureka client to a eureka + server host. |
+
eureka.client.eureka-server-u-r-l-context |
++ | Gets the URL context to be used to construct the service url to contact eureka + server when the list of eureka servers come from the DNS. This information is not + required if the contract returns the service urls from eurekaServerServiceUrls. + The DNS mechanism is used when useDnsForFetchingServiceUrls is set to true and the + eureka client expects the DNS to configured a certain way so that it can fetch + changing eureka servers dynamically. The changes are effective at runtime. |
+
eureka.client.eureka-service-url-poll-interval-seconds |
+0 |
+Indicates how often(in seconds) to poll for changes to eureka server information. + Eureka servers could be added or removed and this setting controls how soon the + eureka clients should know about it. |
+
eureka.client.fetch-registry |
+true |
+Indicates whether this client should fetch eureka registry information from eureka + server. |
+
eureka.client.fetch-remote-regions-registry |
++ | Comma separated list of regions for which the eureka registry information will be + fetched. It is mandatory to define the availability zones for each of these regions + as returned by availabilityZones. Failing to do so, will result in failure of + discovery client startup. |
+
eureka.client.filter-only-up-instances |
+true |
+Indicates whether to get the applications after filtering the applications for + instances with only InstanceStatus UP states. |
+
eureka.client.g-zip-content |
+true |
+Indicates whether the content fetched from eureka server has to be compressed + whenever it is supported by the server. The registry information from the eureka + server is compressed for optimum network traffic. |
+
eureka.client.heartbeat-executor-exponential-back-off-bound |
+10 |
+Heartbeat executor exponential back off related property. It is a maximum + multiplier value for retry delay, in case where a sequence of timeouts occurred. |
+
eureka.client.heartbeat-executor-thread-pool-size |
+2 |
+The thread pool size for the heartbeatExecutor to initialise with |
+
eureka.client.initial-instance-info-replication-interval-seconds |
+40 |
+Indicates how long initially (in seconds) to replicate instance info to the eureka + server |
+
eureka.client.instance-info-replication-interval-seconds |
+30 |
+Indicates how often(in seconds) to replicate instance changes to be replicated to + the eureka server. |
+
eureka.client.log-delta-diff |
+false |
+Indicates whether to log differences between the eureka server and the eureka + client in terms of registry information. + Eureka client tries to retrieve only delta changes from eureka server to minimize + network traffic. After receiving the deltas, eureka client reconciles the + information from the server to verify it has not missed out some information. + Reconciliation failures could happen when the client has had network issues + communicating to server.If the reconciliation fails, eureka client gets the full + registry information. + While getting the full registry information, the eureka client can log the + differences between the client and the server and this setting controls that. + The changes are effective at runtime at the next registry fetch cycle as specified + by registryFetchIntervalSecondsr |
+
eureka.client.on-demand-update-status-change |
+true |
+If set to true, local status updates via ApplicationInfoManager will trigger + on-demand (but rate limited) register/updates to remote eureka servers |
+
eureka.client.prefer-same-zone-eureka |
+true |
+Indicates whether or not this instance should try to use the eureka server in the + same zone for latency and/or other reason. + Ideally eureka clients are configured to talk to servers in the same zone + The changes are effective at runtime at the next registry fetch cycle as specified + by registryFetchIntervalSeconds |
+
eureka.client.property-resolver |
++ | + |
eureka.client.proxy-host |
++ | Gets the proxy host to eureka server if any. |
+
eureka.client.proxy-password |
++ | Gets the proxy password if any. |
+
eureka.client.proxy-port |
++ | Gets the proxy port to eureka server if any. |
+
eureka.client.proxy-user-name |
++ | Gets the proxy user name if any. |
+
eureka.client.region |
+us-east-1 |
+Gets the region (used in AWS datacenters) where this instance resides. |
+
eureka.client.register-with-eureka |
+true |
+Indicates whether or not this instance should register its information with eureka + server for discovery by others. + In some cases, you do not want your instances to be discovered whereas you just + want do discover other instances. |
+
eureka.client.registry-fetch-interval-seconds |
+30 |
+Indicates how often(in seconds) to fetch the registry information from the eureka + server. |
+
eureka.client.registry-refresh-single-vip-address |
++ | Indicates whether the client is only interested in the registry information for a + single VIP. |
+
eureka.client.service-url |
++ | Map of availability zone to list of fully qualified URLs to communicate with eureka + server. Each value can be a single URL or a comma separated list of alternative + locations. + Typically the eureka server URLs carry protocol,host,port,context and version + information if any. Example: + http://ec2-256-156-243-129.compute-1.amazonaws.com:7001/eureka/ + The changes are effective at runtime at the next service url refresh cycle as + specified by eurekaServiceUrlPollIntervalSeconds. |
+
eureka.client.transport |
++ | + |
eureka.client.use-dns-for-fetching-service-urls |
+false |
+Indicates whether the eureka client should use the DNS mechanism to fetch a list of + eureka servers to talk to. When the DNS name is updated to have additional servers, + that information is used immediately after the eureka client polls for that + information as specified in eurekaServiceUrlPollIntervalSeconds. + Alternatively, the service urls can be returned serviceUrls, but the users should + implement their own mechanism to return the updated list in case of changes. + The changes are effective at runtime. |
+
eureka.dashboard.enabled |
+true |
+Flag to enable the Eureka dashboard. Default true. |
+
eureka.dashboard.path |
+/ |
+The path to the Eureka dashboard (relative to the servlet path). Defaults to "/". |
+
eureka.instance.a-s-g-name |
++ | Gets the AWS autoscaling group name associated with this instance. This information + is specifically used in an AWS environment to automatically put an instance out of + service after the instance is launched and it has been disabled for traffic.. |
+
eureka.instance.app-group-name |
++ | Get the name of the application group to be registered with eureka. |
+
eureka.instance.appname |
+unknown |
+Get the name of the application to be registered with eureka. |
+
eureka.instance.data-center-info |
++ | Returns the data center this instance is deployed. This information is used to get + some AWS specific instance information if the instance is deployed in AWS. |
+
eureka.instance.default-address-resolution-order |
+[] |
++ |
eureka.instance.health-check-url |
++ | Gets the absolute health check page URL for this instance. The users can provide + the healthCheckUrlPath if the health check page resides in the same instance + talking to eureka, else in the cases where the instance is a proxy for some other + server, users can provide the full URL. If the full URL is provided it takes + precedence. + <p> + It is normally used for making educated decisions based on the health of the + instance - for example, it can be used to determine whether to proceed deployments + to an entire farm or stop the deployments without causing further damage. The full + URL should follow the format http://${eureka.hostname}:7001/ where the value + ${eureka.hostname} is replaced at runtime. |
+
eureka.instance.health-check-url-path |
+/health |
+Gets the relative health check URL path for this instance. The health check page + URL is then constructed out of the hostname and the type of communication - secure + or unsecure as specified in securePort and nonSecurePort. + It is normally used for making educated decisions based on the health of the + instance - for example, it can be used to determine whether to proceed deployments + to an entire farm or stop the deployments without causing further damage. |
+
eureka.instance.home-page-url |
++ | Gets the absolute home page URL for this instance. The users can provide the + homePageUrlPath if the home page resides in the same instance talking to eureka, + else in the cases where the instance is a proxy for some other server, users can + provide the full URL. If the full URL is provided it takes precedence. + It is normally used for informational purposes for other services to use it as a + landing page. The full URL should follow the format http://${eureka.hostname}:7001/ + where the value ${eureka.hostname} is replaced at runtime. |
+
eureka.instance.home-page-url-path |
+/ |
+Gets the relative home page URL Path for this instance. The home page URL is then + constructed out of the hostName and the type of communication - secure or unsecure. + It is normally used for informational purposes for other services to use it as a + landing page. |
+
eureka.instance.host-info |
++ | + |
eureka.instance.hostname |
++ | The hostname if it can be determined at configuration time (otherwise it will be + guessed from OS primitives). |
+
eureka.instance.inet-utils |
++ | + |
eureka.instance.initial-status |
++ | Initial status to register with rmeote Eureka server. |
+
eureka.instance.instance-enabled-onit |
+false |
+Indicates whether the instance should be enabled for taking traffic as soon as it + is registered with eureka. Sometimes the application might need to do some + pre-processing before it is ready to take traffic. |
+
eureka.instance.instance-id |
++ | Get the unique Id (within the scope of the appName) of this instance to be + registered with eureka. |
+
eureka.instance.ip-address |
++ | Get the IPAdress of the instance. This information is for academic purposes only as + the communication from other instances primarily happen using the information + supplied in {@link #getHostName(boolean)}. |
+
eureka.instance.lease-expiration-duration-in-seconds |
+90 |
+Indicates the time in seconds that the eureka server waits since it received the + last heartbeat before it can remove this instance from its view and there by + disallowing traffic to this instance. + Setting this value too long could mean that the traffic could be routed to the + instance even though the instance is not alive. Setting this value too small could + mean, the instance may be taken out of traffic because of temporary network + glitches.This value to be set to atleast higher than the value specified in + leaseRenewalIntervalInSeconds. |
+
eureka.instance.lease-renewal-interval-in-seconds |
+30 |
+Indicates how often (in seconds) the eureka client needs to send heartbeats to + eureka server to indicate that it is still alive. If the heartbeats are not + received for the period specified in leaseExpirationDurationInSeconds, eureka + server will remove the instance from its view, there by disallowing traffic to this + instance. + Note that the instance could still not take traffic if it implements + HealthCheckCallback and then decides to make itself unavailable. |
+
eureka.instance.metadata-map |
++ | Gets the metadata name/value pairs associated with this instance. This information + is sent to eureka server and can be used by other instances. |
+
eureka.instance.namespace |
+eureka |
+Get the namespace used to find properties. Ignored in Spring Cloud. |
+
eureka.instance.non-secure-port |
+80 |
+Get the non-secure port on which the instance should receive traffic. |
+
eureka.instance.non-secure-port-enabled |
+true |
+Indicates whether the non-secure port should be enabled for traffic or not. |
+
eureka.instance.prefer-ip-address |
+false |
+Flag to say that, when guessing a hostname, the IP address of the server should be + used in prference to the hostname reported by the OS. |
+
eureka.instance.secure-health-check-url |
++ | Gets the absolute secure health check page URL for this instance. The users can + provide the secureHealthCheckUrl if the health check page resides in the same + instance talking to eureka, else in the cases where the instance is a proxy for + some other server, users can provide the full URL. If the full URL is provided it + takes precedence. + <p> + It is normally used for making educated decisions based on the health of the + instance - for example, it can be used to determine whether to proceed deployments + to an entire farm or stop the deployments without causing further damage. The full + URL should follow the format http://${eureka.hostname}:7001/ where the value + ${eureka.hostname} is replaced at runtime. |
+
eureka.instance.secure-port |
+443 |
+Get the Secure port on which the instance should receive traffic. |
+
eureka.instance.secure-port-enabled |
+false |
+Indicates whether the secure port should be enabled for traffic or not. |
+
eureka.instance.secure-virtual-host-name |
++ | Gets the secure virtual host name defined for this instance. + This is typically the way other instance would find this instance by using the + secure virtual host name.Think of this as similar to the fully qualified domain + name, that the users of your services will need to find this instance. |
+
eureka.instance.status-page-url |
++ | Gets the absolute status page URL path for this instance. The users can provide the + statusPageUrlPath if the status page resides in the same instance talking to + eureka, else in the cases where the instance is a proxy for some other server, + users can provide the full URL. If the full URL is provided it takes precedence. + It is normally used for informational purposes for other services to find about the + status of this instance. Users can provide a simple HTML indicating what is the + current status of the instance. |
+
eureka.instance.status-page-url-path |
+/info |
+Gets the relative status page URL path for this instance. The status page URL is + then constructed out of the hostName and the type of communication - secure or + unsecure as specified in securePort and nonSecurePort. + It is normally used for informational purposes for other services to find about the + status of this instance. Users can provide a simple HTML indicating what is the + current status of the instance. |
+
eureka.instance.virtual-host-name |
++ | Gets the virtual host name defined for this instance. + This is typically the way other instance would find this instance by using the + virtual host name.Think of this as similar to the fully qualified domain name, that + the users of your services will need to find this instance. |
+
eureka.server.a-s-g-cache-expiry-timeout-ms |
+0 |
++ |
eureka.server.a-s-g-query-timeout-ms |
+300 |
++ |
eureka.server.a-s-g-update-interval-ms |
+0 |
++ |
eureka.server.a-w-s-access-id |
++ | + |
eureka.server.a-w-s-secret-key |
++ | + |
eureka.server.batch-replication |
+false |
++ |
eureka.server.binding-strategy |
++ | + |
eureka.server.delta-retention-timer-interval-in-ms |
+0 |
++ |
eureka.server.disable-delta |
+false |
++ |
eureka.server.disable-delta-for-remote-regions |
+false |
++ |
eureka.server.disable-transparent-fallback-to-other-region |
+false |
++ |
eureka.server.e-i-p-bind-rebind-retries |
+3 |
++ |
eureka.server.e-i-p-binding-retry-interval-ms |
+0 |
++ |
eureka.server.e-i-p-binding-retry-interval-ms-when-unbound |
+0 |
++ |
eureka.server.enable-replicated-request-compression |
+false |
++ |
eureka.server.enable-self-preservation |
+true |
++ |
eureka.server.eviction-interval-timer-in-ms |
+0 |
++ |
eureka.server.g-zip-content-from-remote-region |
+true |
++ |
eureka.server.json-codec-name |
++ | + |
eureka.server.list-auto-scaling-groups-role-name |
+ListAutoScalingGroups |
++ |
eureka.server.log-identity-headers |
+true |
++ |
eureka.server.max-elements-in-peer-replication-pool |
+10000 |
++ |
eureka.server.max-elements-in-status-replication-pool |
+10000 |
++ |
eureka.server.max-idle-thread-age-in-minutes-for-peer-replication |
+15 |
++ |
eureka.server.max-idle-thread-in-minutes-age-for-status-replication |
+10 |
++ |
eureka.server.max-threads-for-peer-replication |
+20 |
++ |
eureka.server.max-threads-for-status-replication |
+1 |
++ |
eureka.server.max-time-for-replication |
+30000 |
++ |
eureka.server.min-threads-for-peer-replication |
+5 |
++ |
eureka.server.min-threads-for-status-replication |
+1 |
++ |
eureka.server.number-of-replication-retries |
+5 |
++ |
eureka.server.peer-eureka-nodes-update-interval-ms |
+0 |
++ |
eureka.server.peer-eureka-status-refresh-time-interval-ms |
+0 |
++ |
eureka.server.peer-node-connect-timeout-ms |
+200 |
++ |
eureka.server.peer-node-connection-idle-timeout-seconds |
+30 |
++ |
eureka.server.peer-node-read-timeout-ms |
+200 |
++ |
eureka.server.peer-node-total-connections |
+1000 |
++ |
eureka.server.peer-node-total-connections-per-host |
+500 |
++ |
eureka.server.prime-aws-replica-connections |
+true |
++ |
eureka.server.property-resolver |
++ | + |
eureka.server.rate-limiter-burst-size |
+10 |
++ |
eureka.server.rate-limiter-enabled |
+false |
++ |
eureka.server.rate-limiter-full-fetch-average-rate |
+100 |
++ |
eureka.server.rate-limiter-privileged-clients |
++ | + |
eureka.server.rate-limiter-registry-fetch-average-rate |
+500 |
++ |
eureka.server.rate-limiter-throttle-standard-clients |
+false |
++ |
eureka.server.registry-sync-retries |
+0 |
++ |
eureka.server.registry-sync-retry-wait-ms |
+0 |
++ |
eureka.server.remote-region-app-whitelist |
++ | + |
eureka.server.remote-region-connect-timeout-ms |
+1000 |
++ |
eureka.server.remote-region-connection-idle-timeout-seconds |
+30 |
++ |
eureka.server.remote-region-fetch-thread-pool-size |
+20 |
++ |
eureka.server.remote-region-read-timeout-ms |
+1000 |
++ |
eureka.server.remote-region-registry-fetch-interval |
+30 |
++ |
eureka.server.remote-region-total-connections |
+1000 |
++ |
eureka.server.remote-region-total-connections-per-host |
+500 |
++ |
eureka.server.remote-region-trust-store |
++ | + |
eureka.server.remote-region-trust-store-password |
+changeit |
++ |
eureka.server.remote-region-urls |
++ | + |
eureka.server.remote-region-urls-with-name |
++ | + |
eureka.server.renewal-percent-threshold |
+0.85 |
++ |
eureka.server.renewal-threshold-update-interval-ms |
+0 |
++ |
eureka.server.response-cache-auto-expiration-in-seconds |
+180 |
++ |
eureka.server.response-cache-update-interval-ms |
+0 |
++ |
eureka.server.retention-time-in-m-s-in-delta-queue |
+0 |
++ |
eureka.server.route53-bind-rebind-retries |
+3 |
++ |
eureka.server.route53-binding-retry-interval-ms |
+0 |
++ |
eureka.server.route53-domain-t-t-l |
+30 |
++ |
eureka.server.sync-when-timestamp-differs |
+true |
++ |
eureka.server.use-read-only-response-cache |
+true |
++ |
eureka.server.wait-time-in-ms-when-sync-empty |
+0 |
++ |
eureka.server.xml-codec-name |
++ | + |
feign.compression.request.mime-types |
+[text/xml, application/xml, application/json] |
+The list of supported mime types. |
+
feign.compression.request.min-request-size |
+2048 |
+The minimum threshold content size. |
+
health.config.enabled |
+false |
+Flag to indicate that the config server health indicator should be installed. |
+
hystrix.metrics.enabled |
+true |
+Enable Hystrix metrics polling. Defaults to true. |
+
hystrix.metrics.polling-interval-ms |
+2000 |
+Interval between subsequent polling of metrics. Defaults to 2000 ms. |
+
management.health.refresh.enabled |
+true |
+Enable the health endpoint for the refresh scope. |
+
management.health.zookeeper.enabled |
+true |
+Enable the health endpoint for zookeeper. |
+
netflix.atlas.batch-size |
+10000 |
++ |
netflix.atlas.enabled |
+true |
++ |
netflix.atlas.uri |
++ | + |
netflix.metrics.servo.cache-warning-threshold |
+1000 |
+When the |
+
netflix.metrics.servo.registry-class |
+com.netflix.servo.BasicMonitorRegistry |
+Fully qualified class name for monitor registry used by Servo. |
+
spring.cloud.bus.ack.destination-service |
++ | Service that wants to listen to acks. By default null (meaning all services). |
+
spring.cloud.bus.ack.enabled |
+true |
+Flag to switch off acks (default on). |
+
spring.cloud.bus.destination |
+springCloudBus |
+Name of Spring Cloud Stream destination for messages. |
+
spring.cloud.bus.enabled |
+true |
+Flag to indicate that the bus is enabled. |
+
spring.cloud.bus.env.enabled |
+true |
+Flag to switch off environment change events (default on). |
+
spring.cloud.bus.refresh.enabled |
+true |
+Flag to switch off refresh events (default on). |
+
spring.cloud.bus.trace.enabled |
+false |
+Flag to switch on tracing of acks (default off). |
+
spring.cloud.cloudfoundry.discovery.enabled |
+true |
+Flag to indicate that discovery is enabled. |
+
spring.cloud.cloudfoundry.discovery.heartbeat-frequency |
+5000 |
+Frequency in milliseconds of poll for heart beat. The client will poll on this + frequency and broadcast a list of service ids. |
+
spring.cloud.cloudfoundry.discovery.org |
++ | Organization name to authenticate with (default to user’s default). |
+
spring.cloud.cloudfoundry.discovery.password |
++ | Password for user to authenticate and obtain token. |
+
spring.cloud.cloudfoundry.discovery.space |
++ | Space name to authenticate with (default to user’s default). |
+
spring.cloud.cloudfoundry.discovery.url |
++ | URL of Cloud Foundry API (Cloud Controller). |
+
spring.cloud.cloudfoundry.discovery.username |
++ | Username to authenticate (usually an email address). |
+
spring.cloud.config.allow-override |
+true |
+Flag to indicate that {@link #isSystemPropertiesOverride() + systemPropertiesOverride} can be used. Set to false to prevent users from changing + the default accidentally. Default true. |
+
spring.cloud.config.authorization |
++ | Authorization token used by the client to connect to the server. |
+
spring.cloud.config.discovery.enabled |
+false |
+Flag to indicate that config server discovery is enabled (config server URL will be + looked up via discovery). |
+
spring.cloud.config.discovery.service-id |
+configserver |
+Service id to locate config server. |
+
spring.cloud.config.enabled |
+true |
+Flag to say that remote configuration is enabled. Default true; |
+
spring.cloud.config.fail-fast |
+false |
+Flag to indicate that failure to connect to the server is fatal (default false). |
+
spring.cloud.config.label |
++ | The label name to use to pull remote configuration properties. The default is set + on the server (generally "master" for a git based server). |
+
spring.cloud.config.name |
++ | Name of application used to fetch remote properties. |
+
spring.cloud.config.override-none |
+false |
+Flag to indicate that when {@link #setAllowOverride(boolean) allowOverride} is + true, external properties should take lowest priority, and not override any + existing property sources (including local config files). Default false. |
+
spring.cloud.config.override-system-properties |
+true |
+Flag to indicate that the external properties should override system properties. + Default true. |
+
spring.cloud.config.password |
++ | The password to use (HTTP Basic) when contacting the remote server. |
+
spring.cloud.config.profile |
+default |
+The default profile to use when fetching remote configuration (comma-separated). + Default is "default". |
+
spring.cloud.config.retry.initial-interval |
+1000 |
+Initial retry interval in milliseconds. |
+
spring.cloud.config.retry.max-attempts |
+6 |
+Maximum number of attempts. |
+
spring.cloud.config.retry.max-interval |
+2000 |
+Maximum interval for backoff. |
+
spring.cloud.config.retry.multiplier |
+1.1 |
+Multiplier for next interval. |
+
spring.cloud.config.token |
++ | Security Token passed thru to underlying environment repository. |
+
spring.cloud.config.uri |
++ | The URI of the remote server (default http://localhost:8888). |
+
spring.cloud.config.username |
++ | The username to use (HTTP Basic) when contacting the remote server. |
+
spring.cloud.consul.config.acl-token |
++ | + |
spring.cloud.consul.config.data-key |
+data |
+If format is Format.PROPERTIES or Format.YAML + then the following field is used as key to look up consul for configuration. |
+
spring.cloud.consul.config.default-context |
+application |
++ |
spring.cloud.consul.config.enabled |
+true |
++ |
spring.cloud.consul.config.fail-fast |
+true |
+Throw exceptions during config lookup if true, otherwise, log warnings. |
+
spring.cloud.consul.config.format |
++ | + |
spring.cloud.consul.config.prefix |
+config |
++ |
spring.cloud.consul.config.profile-separator |
+, |
++ |
spring.cloud.consul.config.watch.delay |
+1000 |
+The value of the fixed delay for the watch in millis. Defaults to 1000. |
+
spring.cloud.consul.config.watch.enabled |
+true |
+If the watch is enabled. Defaults to true. |
+
spring.cloud.consul.config.watch.wait-time |
+60 |
+The number of seconds to wait (or block) for watch query. Defaults to 60. |
+
spring.cloud.consul.discovery.acl-token |
++ | + |
spring.cloud.consul.discovery.catalog-services-watch-delay |
+10 |
++ |
spring.cloud.consul.discovery.catalog-services-watch-timeout |
+2 |
++ |
spring.cloud.consul.discovery.default-query-tag |
++ | Tag to query for in service list if one is not listed in serverListQueryTags. |
+
spring.cloud.consul.discovery.enabled |
+true |
+Is service discovery enabled? |
+
spring.cloud.consul.discovery.health-check-interval |
+10s |
+How often to perform the health check (e.g. 10s) |
+
spring.cloud.consul.discovery.health-check-path |
+/health |
+Alternate server path to invoke for health checking |
+
spring.cloud.consul.discovery.health-check-timeout |
++ | Timeout for health check (e.g. 10s) |
+
spring.cloud.consul.discovery.health-check-url |
++ | Custom health check url to override default |
+
spring.cloud.consul.discovery.heartbeat.enabled |
+false |
++ |
spring.cloud.consul.discovery.heartbeat.heartbeat-interval |
++ | + |
spring.cloud.consul.discovery.heartbeat.interval-ratio |
++ | + |
spring.cloud.consul.discovery.heartbeat.ttl-unit |
+s |
++ |
spring.cloud.consul.discovery.heartbeat.ttl-value |
+30 |
++ |
spring.cloud.consul.discovery.host-info |
++ | + |
spring.cloud.consul.discovery.hostname |
++ | Hostname to use when accessing server |
+
spring.cloud.consul.discovery.instance-id |
++ | Unique service instance id |
+
spring.cloud.consul.discovery.ip-address |
++ | IP address to use when accessing service (must also set preferIpAddress + to use) |
+
spring.cloud.consul.discovery.lifecycle.enabled |
+true |
++ |
spring.cloud.consul.discovery.management-port |
++ | Port to register the management service under (defaults to management port) |
+
spring.cloud.consul.discovery.management-suffix |
+management |
+Suffix to use when registering management service |
+
spring.cloud.consul.discovery.management-tags |
++ | Tags to use when registering management service |
+
spring.cloud.consul.discovery.port |
++ | Port to register the service under (defaults to listening port) |
+
spring.cloud.consul.discovery.prefer-agent-address |
+false |
+Source of how we will determine the address to use |
+
spring.cloud.consul.discovery.prefer-ip-address |
+false |
+Use ip address rather than hostname during registration |
+
spring.cloud.consul.discovery.query-passing |
+false |
+Add the 'passing` parameter to /v1/health/service/serviceName. + This pushes health check passing to the server. |
+
spring.cloud.consul.discovery.register |
+true |
+Register as a service in consul. |
+
spring.cloud.consul.discovery.register-health-check |
+true |
+Register health check in consul. Useful during development of a service. |
+
spring.cloud.consul.discovery.scheme |
+http |
+Whether to register an http or https service |
+
spring.cloud.consul.discovery.server-list-query-tags |
++ | Map of serviceId’s → tag to query for in server list. + This allows filtering services by a single tag. |
+
spring.cloud.consul.discovery.service-name |
++ | Service name |
+
spring.cloud.consul.discovery.tags |
++ | Tags to use when registering service |
+
spring.cloud.consul.enabled |
+true |
+Is spring cloud consul enabled |
+
spring.cloud.consul.host |
+localhost |
+Consul agent hostname. Defaults to 'localhost'. |
+
spring.cloud.consul.port |
+8500 |
+Consul agent port. Defaults to '8500'. |
+
spring.cloud.consul.retry.initial-interval |
+1000 |
+Initial retry interval in milliseconds. |
+
spring.cloud.consul.retry.max-attempts |
+6 |
+Maximum number of attempts. |
+
spring.cloud.consul.retry.max-interval |
+2000 |
+Maximum interval for backoff. |
+
spring.cloud.consul.retry.multiplier |
+1.1 |
+Multiplier for next interval. |
+
spring.cloud.hypermedia.refresh.fixed-delay |
+5000 |
++ |
spring.cloud.hypermedia.refresh.initial-delay |
+10000 |
++ |
spring.cloud.inetutils.default-hostname |
+localhost |
+The default hostname. Used in case of errors. |
+
spring.cloud.inetutils.default-ip-address |
+127.0.0.1 |
+The default ipaddress. Used in case of errors. |
+
spring.cloud.inetutils.ignored-interfaces |
++ | List of Java regex expressions for network interfaces that will be ignored. |
+
spring.cloud.inetutils.timeout-seconds |
+1 |
+Timeout in seconds for calculating hostname. |
+
spring.cloud.stream.binders |
++ | + |
spring.cloud.stream.bindings |
++ | + |
spring.cloud.stream.consul.binder.event-timeout |
+5 |
++ |
spring.cloud.stream.consumer-defaults |
++ | + |
spring.cloud.stream.default-binder |
++ | + |
spring.cloud.stream.dynamic-destinations |
+[] |
++ |
spring.cloud.stream.ignore-unknown-properties |
+true |
++ |
spring.cloud.stream.instance-count |
+1 |
++ |
spring.cloud.stream.instance-index |
+0 |
++ |
spring.cloud.stream.producer-defaults |
++ | + |
spring.cloud.stream.rabbit.binder.admin-adresses |
+[] |
++ |
spring.cloud.stream.rabbit.binder.compression-level |
+0 |
++ |
spring.cloud.stream.rabbit.binder.nodes |
+[] |
++ |
spring.cloud.stream.rabbit.bindings |
++ | + |
spring.cloud.zookeeper.base-sleep-time-ms |
+50 |
+Initial amount of time to wait between retries |
+
spring.cloud.zookeeper.block-until-connected-unit |
++ | The unit of time related to blocking on connection to Zookeeper |
+
spring.cloud.zookeeper.block-until-connected-wait |
+10 |
+Wait time to block on connection to Zookeeper |
+
spring.cloud.zookeeper.connect-string |
+localhost:2181 |
+Connection string to the Zookeeper cluster |
+
spring.cloud.zookeeper.default-health-endpoint |
++ | Default health endpoint that will be checked to verify that a dependency is alive |
+
spring.cloud.zookeeper.dependencies |
++ | Mapping of alias to ZookeeperDependency. From Ribbon perspective the alias + is actually serviceID since Ribbon can’t accept nested structures in serviceID |
+
spring.cloud.zookeeper.dependency-configurations |
++ | + |
spring.cloud.zookeeper.dependency-names |
++ | + |
spring.cloud.zookeeper.discovery.enabled |
+true |
++ |
spring.cloud.zookeeper.discovery.instance-host |
++ | Predefined host with which a service can register itself in Zookeeper. Corresponds + to the {code address} from the URI spec. |
+
spring.cloud.zookeeper.discovery.instance-port |
++ | Port to register the service under (defaults to listening port) |
+
spring.cloud.zookeeper.discovery.metadata |
++ | Gets the metadata name/value pairs associated with this instance. This information + is sent to zookeeper and can be used by other instances. |
+
spring.cloud.zookeeper.discovery.register |
+true |
+Register as a service in zookeeper. |
+
spring.cloud.zookeeper.discovery.root |
+/services |
+Root Zookeeper folder in which all instances are registered |
+
spring.cloud.zookeeper.discovery.uri-spec |
+{scheme}://{address}:{port} |
+The URI specification to resolve during service registration in Zookeeper |
+
spring.cloud.zookeeper.enabled |
+true |
+Is Zookeeper enabled |
+
spring.cloud.zookeeper.max-retries |
+10 |
+Max number of times to retry |
+
spring.cloud.zookeeper.max-sleep-ms |
+500 |
+Max time in ms to sleep on each retry |
+
spring.cloud.zookeeper.prefix |
++ | Common prefix that will be applied to all Zookeeper dependencies' paths |
+
spring.integration.poller.fixed-delay |
+1000 |
+Fixed delay for default poller. |
+
spring.integration.poller.max-messages-per-poll |
+1 |
+Maximum messages per poll for the default poller. |
+
spring.sleuth.integration.enabled |
+true |
+Enable Spring Integration sleuth instrumentation. |
+
spring.sleuth.integration.patterns |
+* |
+An array of simple patterns against which channel names will be matched. Default is * (all channels). See org.springframework.util.PatternMatchUtils.simpleMatch(String, String). |
+
spring.sleuth.keys.async.class-name-key |
+class |
+Simple name of the class with a method annotated with {@code @Async} + from which the asynchronous process started + @see org.springframework.scheduling.annotation.Async |
+
spring.sleuth.keys.async.method-name-key |
+method |
+Name of the method annotated with {@code @Async} + @see org.springframework.scheduling.annotation.Async |
+
spring.sleuth.keys.async.prefix |
++ | Prefix for header names if they are added as tags. |
+
spring.sleuth.keys.async.thread-name-key |
+thread |
+Name of the thread that executed the async method + @see org.springframework.scheduling.annotation.Async |
+
spring.sleuth.keys.http.headers |
++ | Additional headers that should be added as tags if they exist. If the header + value is multi-valued, the tag value will be a comma-separated, single-quoted + list. |
+
spring.sleuth.keys.http.host |
+http.host |
+The domain portion of the URL or host header. Example: + "mybucket.s3.amazonaws.com". Used to filter by host as opposed to ip address. |
+
spring.sleuth.keys.http.method |
+http.method |
+The HTTP method, or verb, such as "GET" or "POST". Used to filter against an + http route. |
+
spring.sleuth.keys.http.path |
+http.path |
+The absolute http path, without any query parameters. Example: + "/objects/abcd-ff". Used to filter against an http route, portably with zipkin + v1. In zipkin v1, only equals filters are supported. Dropping query parameters + makes the number of distinct URIs less. For example, one can query for the same + resource, regardless of signing parameters encoded in the query line. This does + not reduce cardinality to a HTTP single route. For example, it is common to + express a route as an http URI template like "/resource/{resource_id}". In + systems where only equals queries are available, searching for + {@code http.uri=/resource} won’t match if the actual request was + "/resource/abcd-ff". Historical note: This was commonly expressed as "http.uri" + in zipkin, eventhough it was most often just a path. |
+
spring.sleuth.keys.http.prefix |
+http. |
+Prefix for header names if they are added as tags. |
+
spring.sleuth.keys.http.request-size |
+http.request.size |
+The size of the non-empty HTTP request body, in bytes. Ex. "16384" + <p>Large uploads can exceed limits or contribute directly to latency. |
+
spring.sleuth.keys.http.response-size |
+http.response.size |
+The size of the non-empty HTTP response body, in bytes. Ex. "16384" + <p>Large downloads can exceed limits or contribute directly to latency. |
+
spring.sleuth.keys.http.status-code |
+http.status_code |
+The HTTP response code, when not in 2xx range. Ex. "503" Used to filter for + error status. 2xx range are not logged as success codes are less interesting + for latency troubleshooting. Omitting saves at least 20 bytes per span. |
+
spring.sleuth.keys.http.url |
+http.url |
+The entire URL, including the scheme, host and query parameters if available. + Ex. + "https://mybucket.s3.amazonaws.com/objects/abcd-ff?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Algorithm=AWS4-HMAC-SHA256…" + Combined with {@link #method}, you can understand the fully-qualified + request line. This is optional as it may include private data or be of + considerable length. |
+
spring.sleuth.keys.hystrix.command-group |
+commandGroup |
+Name of the command group. Hystrix uses the command group key to group + together commands such as for reporting, alerting, dashboards, + or team/library ownership. + @see com.netflix.hystrix.HystrixCommandGroupKey |
+
spring.sleuth.keys.hystrix.command-key |
+commandKey |
+Name of the command key. Describes the name for the given command. + A key to represent a {@link com.netflix.hystrix.HystrixCommand} for + monitoring, circuit-breakers, metrics publishing, caching and other such uses. + @see com.netflix.hystrix.HystrixCommandKey |
+
spring.sleuth.keys.hystrix.prefix |
++ | Prefix for header names if they are added as tags. |
+
spring.sleuth.keys.hystrix.thread-pool-key |
+threadPoolKey |
+Name of the thread pool key. The thread-pool key represents a {@link com.netflix.hystrix.HystrixThreadPool} + for monitoring, metrics publishing, caching, and other such uses. A {@link com.netflix.hystrix.HystrixCommand} + is associated with a single {@link com.netflix.hystrix.HystrixThreadPool} as + retrieved by the {@link com.netflix.hystrix.HystrixThreadPoolKey} injected into it, + or it defaults to one created using the {@link com.netflix.hystrix.HystrixCommandGroupKey} + it is created with. + @see com.netflix.hystrix.HystrixThreadPoolKey |
+
spring.sleuth.keys.message.headers |
++ | Additional headers that should be added as tags if they exist. If the header + value is not a String it will be converted to a String using its toString() + method. |
+
spring.sleuth.keys.message.payload.size |
+message/payload-size |
+An estimate of the size of the payload if available. |
+
spring.sleuth.keys.message.payload.type |
+message/payload-type |
+The type of the payload. |
+
spring.sleuth.keys.message.prefix |
+message/ |
+Prefix for header names if they are added as tags. |
+
spring.sleuth.keys.mvc.controller-class |
+mvc.controller.class |
+The lower case, hyphen delimited name of the class that processes the request. + Ex. class named "BookController" will result in "book-controller" tag value. |
+
spring.sleuth.keys.mvc.controller-method |
+mvc.controller.method |
+The lower case, hyphen delimited name of the class that processes the request. + Ex. method named "listOfBooks" will result in "list-of-books" tag value. |
+
spring.sleuth.metric.span.accepted-name |
+counter.span.accepted |
++ |
spring.sleuth.metric.span.dropped-name |
+counter.span.dropped |
++ |
spring.sleuth.sampler.percentage |
+0.1 |
+Percentage of requests that should be sampled. E.g. 1.0 - 100% requests should be + sampled. The precision is whole-numbers only (i.e. there’s no support for 0.1% of + the traces). |
+
zuul.add-host-header |
+false |
+Flag to determine whether the proxy forwards the Host header. |
+
zuul.add-proxy-headers |
+true |
+Flag to determine whether the proxy adds X-Forwarded-* headers. |
+
zuul.host.max-per-route-connections |
+20 |
+The maximum number of connections that can be used by a single route. |
+
zuul.host.max-total-connections |
+200 |
+The maximum number of total connections the proxy can hold open to backends. |
+
zuul.ignore-local-service |
+true |
++ |
zuul.ignored-headers |
++ | Names of HTTP headers to ignore completely (i.e. leave them out of downstream + requests and drop them from downstream responses). |
+
zuul.ignored-patterns |
++ | + |
zuul.ignored-services |
++ | Set of service names not to consider for proxying automatically. By default all + services in the discovery client will be proxied. |
+
zuul.prefix |
++ | A common prefix for all routes. |
+
zuul.remove-semicolon-content |
+true |
+Flag to say that path elements past the first semicolon can be dropped. |
+
zuul.retryable |
++ | Flag for whether retry is supported by default (assuming the routes themselves + support it). |
+
zuul.ribbon-isolation-strategy |
++ | + |
zuul.routes |
++ | Map of route names to properties. |
+
zuul.security_headers |
++ | Headers that are generally expected to be added by Spring Security, and hence often + duplicated if the proxy and the backend are secured with Spring. By default they + are added to the ignored headers if Spring Security is present. |
+
zuul.semaphore.max-semaphores |
+100 |
+The maximum number of total semaphores for Hystrix. |
+
zuul.sensitive-headers |
++ | List of sensitive headers that are not passed to downstream requests. Defaults to a + "safe" set of headers that commonly contain user credentials. It’s OK to remove + those from the list if the downstream service is part of the same system as the + proxy, so they are sharing authentication data. If using a physical URL outside + your own domain, then generally it would be a bad idea to leak user credentials. |
+
zuul.servlet-path |
+/zuul |
+Path to install Zuul as a servlet (not part of Spring MVC). The servlet is more + memory efficient for requests with large bodies, e.g. file uploads. |
+
zuul.ssl-hostname-validation-enabled |
+true |
+Flag to say whether the hostname for ssl connections should be verified or not. Default is true. + This should only be used in test setups! |
+
zuul.strip-prefix |
+true |
+Flag saying whether to strip the prefix from the path before forwarding. |
+
zuul.trace-request-body |
+true |
+Flag to say that request bodies can be traced. |
+