190 lines
6.5 KiB
HTML
190 lines
6.5 KiB
HTML
<!DOCTYPE html>
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<html lang="en">
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<title>DiscoveryClient for Kubernetes</title>
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<body class="book toc2 toc-left">
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<div id="toc" class="toc2">
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<div id="toctitle">Table of Contents</div>
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<ul class="sectlevel1">
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<li><a href="#_discoveryclient_for_kubernetes">DiscoveryClient for Kubernetes</a></li>
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</ul>
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</div>
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</div>
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<div id="content">
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<div class="sect1">
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<h2 id="_discoveryclient_for_kubernetes"><a class="link" href="#_discoveryclient_for_kubernetes">DiscoveryClient for Kubernetes</a></h2>
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<div class="sectionbody">
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<div class="paragraph">
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<p>This project provides an implementation of <a href="https://github.com/spring-cloud/spring-cloud-commons/blob/master/spring-cloud-commons/src/main/java/org/springframework/cloud/client/discovery/DiscoveryClient.java">Discovery Client</a>
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for <a href="https://kubernetes.io">Kubernetes</a>.
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This client lets you query Kubernetes endpoints (see <a href="https://kubernetes.io/docs/user-guide/services/">services</a>) by name.
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A service is typically exposed by the Kubernetes API server as a collection of endpoints that represent <code>http</code> and <code>https</code> addresses and that a client can
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access from a Spring Boot application running as a pod. This discovery feature is also used by the Spring Cloud Kubernetes Ribbon project
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to fetch the list of the endpoints defined for an application to be load balanced.</p>
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</div>
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<div class="paragraph">
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<p>This is something that you get for free by adding the following dependency inside your project:</p>
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</div>
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<div class="exampleblock">
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<div class="content">
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<div class="listingblock">
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<div class="content">
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<pre class="highlightjs highlight"><code class="language-xml hljs" data-lang="xml"><dependency>
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<groupId>org.springframework.cloud</groupId>
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<artifactId>spring-cloud-starter-kubernetes</artifactId>
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</dependency></code></pre>
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</div>
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</div>
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</div>
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</div>
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<div class="paragraph">
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<p>To enable loading of the <code>DiscoveryClient</code>, add <code>@EnableDiscoveryClient</code> to the according configuration or application class, as the following example shows:</p>
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</div>
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<div class="exampleblock">
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<div class="content">
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<div class="listingblock">
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<div class="content">
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<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@SpringBootApplication
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@EnableDiscoveryClient
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public class Application {
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public static void main(String[] args) {
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SpringApplication.run(Application.class, args);
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}
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}</code></pre>
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</div>
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</div>
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</div>
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</div>
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<div class="paragraph">
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<p>Then you can inject the client in your code simply by autowiring it, as the following example shows:</p>
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</div>
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<div class="exampleblock">
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<div class="content">
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<div class="listingblock">
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<div class="content">
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<pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">@Autowired
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private DiscoveryClient discoveryClient;</code></pre>
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</div>
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</div>
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</div>
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</div>
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<div class="paragraph">
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<p>If, for any reason, you need to disable the <code>DiscoveryClient</code>, you can set the following property in <code>application.properties</code>:</p>
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</div>
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<div class="exampleblock">
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<div class="content">
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<div class="listingblock">
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<div class="content">
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<pre class="highlightjs highlight"><code>spring.cloud.kubernetes.discovery.enabled=false</code></pre>
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</div>
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</div>
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</div>
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</div>
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<div class="paragraph">
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<p>Some Spring Cloud components use the <code>DiscoveryClient</code> in order to obtain information about the local service instance. For
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this to work, you need to align the Kubernetes service name with the <code>spring.application.name</code> property.</p>
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</div>
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<div class="paragraph">
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<p>Spring Cloud Kubernetes can also watch the Kubernetes service catalog for changes and update the
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<code>DiscoveryClient</code> implementation accordingly. In order to enable this functionality you need to add
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<code>@EnableScheduling</code> on a configuration class in your application.</p>
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</div>
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</div>
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</div>
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