六.SpringCloud源码剖析-Eureka Client取消注册

- 日理万妓 2022-12-02 13:51 114阅读 0赞

### 系列文章目录 ###

[一.SpringCloud源码剖析-Eureka核心API][.SpringCloud_-Eureka_API]

[二.SpringCloud源码剖析-Eureka Client 初始化过程][.SpringCloud_-Eureka Client]

[三.SpringCloud源码剖析-Eureka服务注册][.SpringCloud_-Eureka]

[四.SpringCloud源码剖析-Eureka服务发现][.SpringCloud_-Eureka 1]

[五.SpringCloud源码剖析-Eureka Client服务续约][.SpringCloud_-Eureka Client 1]

[六.SpringCloud源码剖析-Eureka Client取消注册][.SpringCloud_-Eureka Client 2]

[七.SpringCloud源码剖析-Eureka Server的自动配置][.SpringCloud_-Eureka Server]

[八.SpringCloud源码剖析-Eureka Server初始化流程][.SpringCloud_-Eureka Server 1]

[九.SpringCloud源码剖析-Eureka Server服务注册流程][.SpringCloud_-Eureka Server 2]

[十.SpringCloud源码剖析-Eureka Server服务续约][.SpringCloud_-Eureka Server 3]

[十一.SpringCloud源码剖析-Eureka Server服务注册表拉取][.SpringCloud_-Eureka Server 4]

[十二.SpringCloud源码剖析-Eureka Server服务剔除][.SpringCloud_-Eureka Server 5]

[十三.SpringCloud源码剖析-Eureka Server服务下线][.SpringCloud_-Eureka Server 6]

### 取消注册 ###

取消注册(服务下线)指的是EureakClient正常关闭之前，微服务会主动向EurekaServer发送下线请求，EureakServer接收到请求从注册表中剔除下线的服务

### DiscoveryClient.shutdown 方法 ###

DiscoveryClient是服务发现最核心的实现，DiscoveryClient通过shutdown 方法取消服务注册，方法上通过@PreDestroy标记该方法是实例的销毁方法，当应用关闭，容器正常关闭，Bean的销毁方法执行，源码如下：

@Singleton
    public class DiscoveryClient implements EurekaClient { 
    ....省略部分代码...
     /** //关闭Eureak Client，从Eureak Server中取消服务的注册 * Shuts down Eureka Client. Also sends a deregistration request to the * eureka server. */
        @PreDestroy
        @Override
        public synchronized void shutdown() { 
            if (isShutdown.compareAndSet(false, true)) { 
                logger.info("Shutting down DiscoveryClient ...");
    			//1.移除掉服务状态监听器
                if (statusChangeListener != null && applicationInfoManager != null) { 
                    applicationInfoManager.unregisterStatusChangeListener(statusChangeListener.getId());
                }
    			//2.注销定时任务
                cancelScheduledTasks();
    
                // If APPINFO was registered
                //如果开启了shouldUnregisterOnShutdown 取消注册(默认true)，
                if (applicationInfoManager != null
                        && clientConfig.shouldRegisterWithEureka()
                        && clientConfig.shouldUnregisterOnShutdown()) { 
                        //3.修改实例的注册状态为 DOWN
                    applicationInfoManager.setInstanceStatus(InstanceStatus.DOWN);
                    //4.取消注册
                    unregister();
                }
    
    			//5.注销eurekaTransport
                if (eurekaTransport != null) { 
                    eurekaTransport.shutdown();
                }
    			//6.注销心跳状态监视器
                heartbeatStalenessMonitor.shutdown();
                //7.注销注册表状态监视器
                registryStalenessMonitor.shutdown();
    
                logger.info("Completed shut down of DiscoveryClient");
            }
        }
    	//注销定时任务
        private void cancelScheduledTasks() { 
            if (instanceInfoReplicator != null) { 
                instanceInfoReplicator.stop();
            }
            if (heartbeatExecutor != null) { 
                heartbeatExecutor.shutdownNow();
            }
            if (cacheRefreshExecutor != null) { 
                cacheRefreshExecutor.shutdownNow();
            }
            if (scheduler != null) { 
                scheduler.shutdownNow();
            }
        }
        //注销EurekaTransport ，
    	private static final class EurekaTransport { 
            private ClosableResolver bootstrapResolver;
            private TransportClientFactory transportClientFactory;
    
            private EurekaHttpClient registrationClient;
            private EurekaHttpClientFactory registrationClientFactory;
    
            private EurekaHttpClient queryClient;
            private EurekaHttpClientFactory queryClientFactory;
    
            void shutdown() { 
                if (registrationClientFactory != null) { 
                    registrationClientFactory.shutdown();
                }
    
                if (queryClientFactory != null) { 
                    queryClientFactory.shutdown();
                }
    
                if (registrationClient != null) { 
                    registrationClient.shutdown();
                }
    
                if (queryClient != null) { 
                    queryClient.shutdown();
                }
    
                if (transportClientFactory != null) { 
                    transportClientFactory.shutdown();
                }
    
                if (bootstrapResolver != null) { 
                    bootstrapResolver.shutdown();
                }
            }
        }

总结一下，在shutdown方法中做了如下事情

*  通过 `applicationInfoManager.unregisterStatusChangeListener`移除服务实例状态监听器`StatusChangeListener`
 *  调用`DiscoveryClient.cancelScheduledTasks();`取消定时任务
 *  修改`applicationInfoManager.setInstanceStatus(InstanceStatus.DOWN);`状态为DOWN，调用`unregister`方法取消注册
 *  `eurekaTransport.shutdown();` 注销和EurekaServer交互的Http客户端
 *  注销心跳状态监视器，注册表状态监视器

我们重点跟踪一下 unregister方法源码

/** 向eureka发送取消注册请求 * unregister w/ the eureka service. */
        void unregister() { 
            // It can be null if shouldRegisterWithEureka == false
            if(eurekaTransport != null && eurekaTransport.registrationClient != null) { 
                try { 
                    logger.info("Unregistering ...");
                    //向eureka发送取消注册的http请求
                    EurekaHttpResponse<Void> httpResponse = eurekaTransport.registrationClient.cancel(instanceInfo.getAppName(), instanceInfo.getId());
                    logger.info(PREFIX + "{} - deregister status: {}", appPathIdentifier, httpResponse.getStatusCode());
                } catch (Exception e) { 
                    logger.error(PREFIX + "{} - de-registration failed{}", appPathIdentifier, e.getMessage(), e);
                }
            }
        }

这里依然通过eurekaTransport.registrationClient得到EureakHttpClient客户端发请求，最终会调用AbstractJerseyEurekaHttpClient.cancel方法发送Delete取消注册请求

@Override
        public EurekaHttpResponse<Void> cancel(String appName, String id) { 
            String urlPath = "apps/" + appName + '/' + id;
            ClientResponse response = null;
            try { 
                Builder resourceBuilder = jerseyClient.resource(serviceUrl).path(urlPath).getRequestBuilder();
                addExtraHeaders(resourceBuilder);
                //发送Delete请求
                response = resourceBuilder.delete(ClientResponse.class);
                return anEurekaHttpResponse(response.getStatus()).headers(headersOf(response)).build();
            } finally { 
                if (logger.isDebugEnabled()) { 
                    logger.debug("Jersey HTTP DELETE {}/{}; statusCode={}", serviceUrl, urlPath, response == null ? "N/A" : response.getStatus());
                }
                if (response != null) { 
                    response.close();
                }
            }
        }

### 总结 ###

1.  Eureak服务取消注册，通过 @PreDestroy标记DiscoveyClient.shutdown销毁方法，当容器正常关闭，Bean的销毁执行
2.  在shutdown方法中注销了服务注册状态监听器，注销定时任务执行器，修改服务注册状态为下线，调用unregister方法取消注册等等
3.  unregister方法中通过eurekaTransport 得到HttpClient，使用AbstractJerseyEurekaHttpClient发送delete请求到Eureak Server取消服务注册

下一章推荐《[Eureka Server 服务下线][.SpringCloud_-Eureka Server 6]》

[.SpringCloud_-Eureka_API]: https://blog.csdn.net/u014494148/article/details/107904301
[.SpringCloud_-Eureka Client]: https://blog.csdn.net/u014494148/article/details/107982920
[.SpringCloud_-Eureka]: https://blog.csdn.net/u014494148/article/details/106907911
[.SpringCloud_-Eureka 1]: https://blog.csdn.net/u014494148/article/details/108217656
[.SpringCloud_-Eureka Client 1]: https://blog.csdn.net/u014494148/article/details/108315405
[.SpringCloud_-Eureka Client 2]: https://blog.csdn.net/u014494148/article/details/108319815
[.SpringCloud_-Eureka Server]: https://blog.csdn.net/u014494148/article/details/108351827
[.SpringCloud_-Eureka Server 1]: https://blog.csdn.net/u014494148/article/details/108469231
[.SpringCloud_-Eureka Server 2]: https://blog.csdn.net/u014494148/article/details/108861409
[.SpringCloud_-Eureka Server 3]: https://blog.csdn.net/u014494148/article/details/108884210
[.SpringCloud_-Eureka Server 4]: https://blog.csdn.net/u014494148/article/details/108895557
[.SpringCloud_-Eureka Server 5]: https://blog.csdn.net/u014494148/article/details/108900884
[.SpringCloud_-Eureka Server 6]: https://blog.csdn.net/u014494148/article/details/108905727