Eureka Register 服务注册

客户端注解 ：

@EnableEurekaClient

• 如果选用的注册中心是eureka，那么就推荐@EnableEurekaClient
• @EnableEurekaClient注解是基于spring-cloud-netflix依赖，只能为eureka作用；

@EnableDiscoveryClient

• 注解是基于spring-cloud-commons依赖，并且在classpath中实现；
• 如果是其他的注册中心，比如：consul, zookeeper , 那么推荐使用EnableDiscoveryClient

服务端注解

@EnableEurekaServer

• 服务端注解，表示这是个Eureka注册中心

当Eureka客户端向Eureka Server注册时，它提供自身的元数据，比如IP地址、端口，运行状况指示符URL，主页等。

# Eureka配置 发现注册中心地址
eureka:
  client:
    serviceUrl:
# 集成了Spring Security ，需访问密码
      defaultZone: http://1595****86:bruceliu@127.0.0.1:8000/eureka/

Eureka Renew 服务续约

• Eureka Client 30s 向 Eureka Server 注册中心发送一次心跳用于续约，若注册中心超过90s未收到续约，默认服务将被剔除。

Eureka Cancel 服务下线

Eureka客户端在程序关闭时向Eureka服务器发送取消请求。 发送请求后，该客户端实例信息将从服务器的实例注册表中删除。该下线请求不会自动完成，它需要调用以下内容：
DiscoveryManager.getInstance().shutdownComponent()

Eureka DiscoveryClient register 源码

    /**
     * Register with the eureka service by making the appropriate REST call.
     */
    boolean register() throws Throwable {//服务注册
        logger.info(PREFIX + appPathIdentifier + ": registering service...");
        EurekaHttpResponse<Void> httpResponse;
        try {
            httpResponse = eurekaTransport.registrationClient.register(instanceInfo);
        } catch (Exception e) {
            logger.warn("{} - registration failed {}", PREFIX + appPathIdentifier, e.getMessage(), e);
            throw e;
        }
        if (logger.isInfoEnabled()) {
            logger.info("{} - registration status: {}", PREFIX + appPathIdentifier, httpResponse.getStatusCode());
        }
        return httpResponse.getStatusCode() == 204;
    }

    /**
     * Renew with the eureka service by making the appropriate REST call
     */
    boolean renew() {//服务续约
        EurekaHttpResponse<InstanceInfo> httpResponse;
        try {
            httpResponse = eurekaTransport.registrationClient.sendHeartBeat(instanceInfo.getAppName(), instanceInfo.getId(), instanceInfo, null);
            logger.debug("{} - Heartbeat status: {}", PREFIX + appPathIdentifier, httpResponse.getStatusCode());
            if (httpResponse.getStatusCode() == 404) {
                REREGISTER_COUNTER.increment();
                logger.info("{} - Re-registering apps/{}", PREFIX + appPathIdentifier, instanceInfo.getAppName());
                return register();
            }
            return httpResponse.getStatusCode() == 200;
        } catch (Throwable e) {
            logger.error("{} - was unable to send heartbeat!", PREFIX + appPathIdentifier, e);
            return false;
        }
    }

Eureka DiscoveryManager shutdownComponent Cancel

   /**
     * Shuts down the <tt>Discovery Client</tt> which unregisters the
     * information about this instance from the <tt>Discovery Server</tt>.
     */
    public void shutdownComponent() {// 服务下线
        if (discoveryClient != null) {
            try {
                discoveryClient.shutdown();
                discoveryClient = null;
            } catch (Throwable th) {
                logger.error("Error in shutting down client", th);
            }
        }
    }