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地址 : https://mp.weixin.qq.com/s/FfJrAGQuHyVrsedtbr0Ihw
上一篇文章《Eureka 源码分析之 Eureka Client》 通过源码知道 ，eureka Client 是通过 http rest来 与 eureka server 交互，实现 注册服务，续约服务，服务下线 等。本篇探究下eureka server。
源码分析从 @EnableEurekaServer 注解为入口分析，通过源码可以看出他是一个标记注解：
/** * Annotation to activate Eureka Server related configuration {@link */ @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Import(EurekaServerMarkerConfiguration.class) public @interface EnableEurekaServer { }从注释可以知道，用来激活 eureka server 的 配置类 EurekaServerAutoConfiguration 中相关配置，EurekaServerAutoConfiguration 的关键代码如下：
@Configuration @Import(EurekaServerInitializerConfiguration.class) @ConditionalOnBean(EurekaServerMarkerConfiguration.Marker.class) @EnableConfigurationProperties({ EurekaDashboardProperties.class, InstanceRegistryProperties.class }) @PropertySource("classpath:/eureka/server.properties") public class EurekaServerAutoConfiguration extends WebMvcConfigurerAdapter { /** * List of packages containing Jersey resources required by the Eureka server */ private static final String[] EUREKA_PACKAGES = new String[] { "com.netflix.discovery", "com.netflix.eureka" }; @Autowired private ApplicationInfoManager applicationInfoManager; @Autowired private EurekaServerConfig eurekaServerConfig; @Autowired private EurekaClientConfig eurekaClientConfig; @Autowired private EurekaClient eurekaClient; @Autowired private InstanceRegistryProperties instanceRegistryProperties; public static final CloudJacksonJson JACKSON_JSON = new CloudJacksonJson(); @Bean public HasFeatures eurekaServerFeature() { return HasFeatures.namedFeature("Eureka Server", EurekaServerAutoConfiguration.class); } @Configuration protected static class EurekaServerConfigBeanConfiguration { // 创建并加载EurekaServerConfig的实现类，主要是Eureka-server的配置信息 @Bean @ConditionalOnMissingBean public EurekaServerConfig eurekaServerConfig(EurekaClientConfig clientConfig) { EurekaServerConfigBean server = new EurekaServerConfigBean(); if (clientConfig.shouldRegisterWithEureka()) { // Set a sensible default if we are supposed to replicate server.setRegistrySyncRetries(5); } return server; } } //加载EurekaController，SpringCloud 提供了一些额外的接口，用来获取eurekaServer的信息 @Bean @ConditionalOnProperty(prefix = "eureka.dashboard", name = "enabled", matchIfMissing = true) public EurekaController eurekaController() { return new EurekaController(this.applicationInfoManager); } //省略 ... // 接收客户端的注册等请求就是通过InstanceRegistry来处理的，是真正处理业务的类，接下来会详细分析 @Bean public PeerAwareInstanceRegistry peerAwareInstanceRegistry( ServerCodecs serverCodecs) { this.eurekaClient.getApplications(); // force initialization return new InstanceRegistry(this.eurekaServerConfig, this.eurekaClientConfig, serverCodecs, this.eurekaClient, this.instanceRegistryProperties.getExpectedNumberOfRenewsPerMin(), this.instanceRegistryProperties.getDefaultOpenForTrafficCount()); } //配置服务节点信息，这里的作用主要是为了配置Eureka的peer节点，也就是说当有收到有节点注册上来的时候，需要通知给哪些节点 @Bean @ConditionalOnMissingBean public PeerEurekaNodes peerEurekaNodes(PeerAwareInstanceRegistry registry, ServerCodecs serverCodecs) { return new RefreshablePeerEurekaNodes(registry, this.eurekaServerConfig, this.eurekaClientConfig, serverCodecs, this.applicationInfoManager); } //省略 ... //EurekaServer的上下文 @Bean public EurekaServerContext eurekaServerContext(ServerCodecs serverCodecs, PeerAwareInstanceRegistry registry, PeerEurekaNodes peerEurekaNodes) { return new DefaultEurekaServerContext(this.eurekaServerConfig, serverCodecs, registry, peerEurekaNodes, this.applicationInfoManager); } // 初始化Eureka-server，会同步其他注册中心的数据到当前注册中心 @Bean public EurekaServerBootstrap eurekaServerBootstrap(PeerAwareInstanceRegistry registry, EurekaServerContext serverContext) { return new EurekaServerBootstrap(this.applicationInfoManager, this.eurekaClientConfig, this.eurekaServerConfig, registry, serverContext); } // 配置拦截器，ServletContainer里面实现了jersey框架，通过他来实现eurekaServer对外的restFull接口 @Bean public FilterRegistrationBean jerseyFilterRegistration( javax.ws.rs.core.Application eurekaJerseyApp) { FilterRegistrationBean bean = new FilterRegistrationBean(); bean.setFilter(new ServletContainer(eurekaJerseyApp)); bean.setOrder(Ordered.LOWEST_PRECEDENCE); bean.setUrlPatterns( Collections.singletonList(EurekaConstants.DEFAULT_PREFIX + "/*")); return bean; } //省略 ... }从EurekaServerAutoConfiguration 类上的注解@Import(EurekaServerInitializerConfiguration.class) 可以到，实例化类EurekaServerAutoConfiguration之前，已经实例化了EurekaServerInitializerConfiguration类，代码如下：
@Configuration @CommonsLog public class EurekaServerInitializerConfiguration implements ServletContextAware, SmartLifecycle, Ordered { // 此处省略部分代码 @Override public void start() { // 启动一个线程 new Thread(new Runnable() { @Override public void run() { try { //初始化EurekaServer，同时启动Eureka Server ，后面着重讲这里 eurekaServerBootstrap.contextInitialized(EurekaServerInitializerConfiguration.this.servletContext); log.info("Started Eureka Server"); // 发布EurekaServer的注册事件 publish(new EurekaRegistryAvailableEvent(getEurekaServerConfig())); // 设置启动的状态为true EurekaServerInitializerConfiguration.this.running = true; // 发送Eureka Start 事件 ， 其他还有各种事件，我们可以监听这种时间，然后做一些特定的业务需求，后面会讲到。 publish(new EurekaServerStartedEvent(getEurekaServerConfig())); } catch (Exception ex) { // Help! log.error("Could not initialize Eureka servlet context", ex); } } }).start(); } // 此处省略部分代码 }