Eureka服务端源码-初始化

Eureka服务端初始化

1. 项目依赖中会依赖spring-cloud-netflix-eureka-server 找到spring.factories文件

   org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
     org.springframework.cloud.netflix.eureka.server.EurekaServerAutoConfiguration
   

2. 以下是EurekaServerAutoConfiguration自动配置类

   @Configuration(proxyBeanMethods = false)
   //EurekaServer初始化配置
   @Import(EurekaServerInitializerConfiguration.class)
   //对于EurekaServerMarkerConfiguration 这个就是一个标识  在@EurekaServer注册里面也进行了import
   //在启动的时候EurekaServerMarkerConfiguration.Marker就会存在
   @ConditionalOnBean(EurekaServerMarkerConfiguration.Marker.class)
   @EnableConfigurationProperties({ EurekaDashboardProperties.class,
   		InstanceRegistryProperties.class })
   @PropertySource("classpath:/eureka/server.properties")
   public class EurekaServerAutoConfiguration implements WebMvcConfigurer {
   	@Bean
   	public PeerAwareInstanceRegistry peerAwareInstanceRegistry(
   			ServerCodecs serverCodecs) {
   		this.eurekaClient.getApplications(); // force initialization
   		return new InstanceRegistry(this.eurekaServerConfig, this.eurekaClientConfig,
   				serverCodecs, this.eurekaClient,
   				this.instanceRegistryProperties.getExpectedNumberOfClientsSendingRenews(),
   				this.instanceRegistryProperties.getDefaultOpenForTrafficCount());
   	}
   
     //EurekaServer对应的节点信息
   	@Bean
   	@ConditionalOnMissingBean
   	public PeerEurekaNodes peerEurekaNodes(PeerAwareInstanceRegistry registry,
   			ServerCodecs serverCodecs,
   			ReplicationClientAdditionalFilters replicationClientAdditionalFilters) {
   		return new RefreshablePeerEurekaNodes(registry, this.eurekaServerConfig,
   				this.eurekaClientConfig, serverCodecs, this.applicationInfoManager,
   				replicationClientAdditionalFilters);
   	}
     
   	@Bean
   	public EurekaServerBootstrap eurekaServerBootstrap(PeerAwareInstanceRegistry registry,
   			EurekaServerContext serverContext) {
   		return new EurekaServerBootstrap(this.applicationInfoManager,
   				this.eurekaClientConfig, this.eurekaServerConfig, registry,
   				serverContext);
   	}
   

   @Configuration(proxyBeanMethods = false)
   public class EurekaServerInitializerConfiguration
   		implements ServletContextAware, SmartLifecycle, Ordered {
   	@Override
   	public void start() {
   		new Thread(() -> {
   			try {
           // eurekaServerBootstrap在EurekaServerAutoConfiguration已经进行了初始化
   				eurekaServerBootstrap.contextInitialized(
   						EurekaServerInitializerConfiguration.this.servletContext);
   				log.info("Started Eureka Server");
   			}
   			catch (Exception ex) {
   			}
   		}).start();
   	}
   }
   

   EventServerBootStrap类中的contextInitialized方法

   public void contextInitialized(ServletContext context) {
     try {
       //设置一些eureka的配置信息
       initEurekaEnvironment();
       //初始化Eureka Server context，也会从临近的eureka server 节点copy对应的注册信息
   		// int registryCount = this.registry.syncUp();
       initEurekaServerContext();
     }
   }
   

   对于EurekaServerContext的初始化如下

   @Bean
   @ConditionalOnMissingBean
   public EurekaServerContext eurekaServerContext(ServerCodecs serverCodecs,
   			PeerAwareInstanceRegistry registry, PeerEurekaNodes peerEurekaNodes) {
   		return new DefaultEurekaServerContext(this.eurekaServerConfig, serverCodecs,
   				registry, peerEurekaNodes, this.applicationInfoManager);
   }
   

   DefaultEurekaServerContext中核心代码如下：

   /**
    * 表示本地server 上下文，并提供组件的get方法
    */
   @Singleton
   public class DefaultEurekaServerContext implements EurekaServerContext {
       //省去了构造器和一些getter等方法
       @PostConstruct
       @Override
       public void initialize() {
           //eureka server节点启动
           peerEurekaNodes.start();
           try {
               //registry初始化，具体执行的试PeerAwareInstanceRegistryImpl#init方法
               registry.init(peerEurekaNodes);
           }
       }
   }
   

   PeerEurekaNodes#start详解

   默认情况下 每10分钟定时更新PeerEurekaNode

   public void start() {
     //任务执行器
     taskExecutor = Executors.newSingleThreadScheduledExecutor(
       new ThreadFactory() {
         @Override
         public Thread newThread(Runnable r) {
           Thread thread = new Thread(r, "Eureka-PeerNodesUpdater");
           thread.setDaemon(true);
           return thread;
         }
       }
     );
     try {
       //更新节点信息
       updatePeerEurekaNodes(resolvePeerUrls());
       Runnable peersUpdateTask = new Runnable() {
         @Override
         public void run() {
           try {
             updatePeerEurekaNodes(resolvePeerUrls());
           } catch (Throwable e) {
             logger.error("Cannot update the replica Nodes", e);
           }
         }
       };
       //定时更新节点信息
       taskExecutor.scheduleWithFixedDelay(
         peersUpdateTask,
         //Eureka节点之间更新信息 默认试10分钟
         serverConfig.getPeerEurekaNodesUpdateIntervalMs(),
         serverConfig.getPeerEurekaNodesUpdateIntervalMs(),
         TimeUnit.MILLISECONDS
       );
     }
   }
   

   PeerAwareInstanceRegistryImpl#init方法详解

   @Override
   public void init(PeerEurekaNodes peerEurekaNodes) throws Exception {
     this.numberOfReplicationsLastMin.start();
     this.peerEurekaNodes = peerEurekaNodes;
     initializedResponseCache();
     //定时更新租约阀值
     scheduleRenewalThresholdUpdateTask();
     //如果配置了远程region，则把远程region的中设置到regionNameVSRemoteRegistry
     initRemoteRegionRegistry();
   }
   

3. 总结

   • EurekaServer端加入了@EnableEurekaServer ，则会创建bean EurekaServerMarkerConfiguration.Marker
   • 有了Markerbean了，也就是激活了EurekaServerAutoConfiguration，在该类中创建EurekaServerBootstrap、PeerAwareInstanceRegistry、PeerEurekaNodes、EurekaServerContext等核心类
   • EurekaServerBootstrap会做一些初始化动作 eurekaServer上下文初始化设置等
   • EurekaServerContext进行创建初始化的时候：启动peerEurekaNodes、初始化PeerAwareInstanceRegistry