Spring Cloud Eureka Client

使用Eureka Client

在pom中包含jar

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<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

注册

指定注册中心的位置

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eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

注册认证

HTTP Basic认证已经自动添加到eureka客户端中, 更复杂的需求，参考文档实现

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http://user:password@localhost:8761/eureka

源码分析

在阅读源码的时候，我们根据它本身提供的功能去关注它实现的过程，以及代码是怎么被触发的

1. 入口

   通过观察spring-cloud-netflix-eureka-client包中的META-INF/spring.factories可以看到里面配置了一组EnableAutoConfiguration, 我们重点关注EurekaClientAutoConfiguration

2. EurekaClientAutoConfiguration

   在这个对象中，主要是根据条件创建了一组spring bean, 包括

   • EurekaClientConfigBean
   • ManagementMetadataProvider
   • EurekaInstanceConfigBean
   • DiscoveryClient
   • EurekaServiceRegistry
   • EurekaClient

3. EurekaClient

   继续跟踪代码，观察EurekaClient的初始化过程

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   public class CloudEurekaClient extends DiscoveryClient { ... public CloudEurekaClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs<?> args, ApplicationEventPublisher publisher) { super(applicationInfoManager, config, args); this.applicationInfoManager = applicationInfoManager; this.publisher = publisher; this.eurekaTransportField = ReflectionUtils.findField(DiscoveryClient.class, "eurekaTransport"); ReflectionUtils.makeAccessible(this.eurekaTransportField); } ... }

   这里会调用父级的构造方法去执行注册、心跳、缓存刷新等任务

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   DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args, Provider<BackupRegistry> backupRegistryProvider) { ... // default size of 2 - 1 each for heartbeat and cacheRefresh scheduler = Executors.newScheduledThreadPool(2, new ThreadFactoryBuilder() .setNameFormat("DiscoveryClient-%d") .setDaemon(true) .build()); heartbeatExecutor = new ThreadPoolExecutor( 1, clientConfig.getHeartbeatExecutorThreadPoolSize(), 0, TimeUnit.SECONDS, new SynchronousQueue<Runnable>(), new ThreadFactoryBuilder() .setNameFormat("DiscoveryClient-HeartbeatExecutor-%d") .setDaemon(true) .build() ); // use direct handoff cacheRefreshExecutor = new ThreadPoolExecutor( 1, clientConfig.getCacheRefreshExecutorThreadPoolSize(), 0, TimeUnit.SECONDS, new SynchronousQueue<Runnable>(), new ThreadFactoryBuilder() .setNameFormat("DiscoveryClient-CacheRefreshExecutor-%d") .setDaemon(true) .build() ); // use direct handoff ... }

   到这里我们可以发现，spring cloud eureka client将这些任务都委托给了Netflix的Eureka组建去执行