五.SpringCloud源码剖析-Eureka Client服务续约

朱雀 2022-12-02 13:41 231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]

#### 什么是服务续约 ####

EureakClient会定时向EureakServer发送续约心跳(默认30s/次) ，来告诉EurekaServer自己的健康状况，默认情况下3次续约失败(90s)，EurekaServer考虑剔除续约失败的客户端服务

#### 初始化定时任务 ####

在EuerakClient中依然是通过scheduler定时实现，在`com.netflix.discovery.DiscoveryClient#initScheduledTasks`中进行初始化,源码如下

/** * Initializes all scheduled tasks. */
        private void initScheduledTasks() { 
        	//如果开启服务注册
     		if (clientConfig.shouldRegisterWithEureka()) { 
     			//续约心跳 30s/次
                int renewalIntervalInSecs = instanceInfo.getLeaseInfo().getRenewalIntervalInSecs();
                int expBackOffBound = clientConfig.getHeartbeatExecutorExponentialBackOffBound();
                logger.info("Starting heartbeat executor: " + "renew interval is: {}", renewalIntervalInSecs);
                // Heartbeat timer
                //心跳任务
                scheduler.schedule(
                        new TimedSupervisorTask(
                                "heartbeat",
                                scheduler,
                                heartbeatExecutor,
                                renewalIntervalInSecs,
                                TimeUnit.SECONDS,
                                expBackOffBound,
                                new HeartbeatThread()	//HeartbeatThread心跳的线程
                        ),
                        renewalIntervalInSecs, TimeUnit.SECONDS);//心跳时间30s/次
    	...省略...                    
    
    
    
    	 /** //心跳任务，本身是一个线程对象 * The heartbeat task that renews the lease in the given intervals. */
        private class HeartbeatThread implements Runnable { 
    
            public void run() { 
            	//调用renew()方法续约
                if (renew()) { 
                	//记录最后续约成功时间
                    lastSuccessfulHeartbeatTimestamp = System.currentTimeMillis();
                }
            }
        }

#### 服务续约线程HeartbeatThread ####

这里我们看到，通过scheduler定时执行`HeartbeatThread`线程，在`HeartbeatThread`中又调用了`Discovery.renew（）`方法执行服务续约，源码如下

/** 使用Rest请求像Eureak进行服务续约 * Renew with the eureka service by making the appropriate REST call */
        boolean renew() { 
        	//Http相应对象
            EurekaHttpResponse<InstanceInfo> httpResponse;
            try { 
            	//使用eurekaTransport得到http客户端，发起心跳请求
                httpResponse = eurekaTransport.registrationClient.sendHeartBeat(instanceInfo.getAppName(), instanceInfo.getId(), instanceInfo, null);
                logger.debug(PREFIX + "{} - Heartbeat status: {}", appPathIdentifier, httpResponse.getStatusCode());
                if (httpResponse.getStatusCode() == 404) { 
                    REREGISTER_COUNTER.increment();
                    logger.info(PREFIX + "{} - Re-registering apps/{}", appPathIdentifier, instanceInfo.getAppName());
                    long timestamp = instanceInfo.setIsDirtyWithTime();
                    //如果续约返回404，尝试重新发起服务注册，并设置Dirty
                    boolean success = register();
                    if (success) { 
                        instanceInfo.unsetIsDirty(timestamp);
                    }
                    return success;
                }
                return httpResponse.getStatusCode() == 200;
            } catch (Throwable e) { 
                logger.error(PREFIX + "{} - was unable to send heartbeat!", appPathIdentifier, e);
                return false;
            }
        }

这里依然使用的是eurekaTransport得到一个EurekaHttpClient实例,然后通过EurekaHttpClientDecorator装饰器执行sendHeartBeat方法，源码如下

public abstract class EurekaHttpClientDecorator implements EurekaHttpClient { 
    	...省略...
    	//发送心跳
    	@Override
        public EurekaHttpResponse<InstanceInfo> 
        						sendHeartBeat(final String appName, //服务名
                                              final String id,//服务ID
                                              final InstanceInfo info,//服务注册对象
                                              final InstanceStatus overriddenStatus) { 	//服务注册状态
            return execute(new RequestExecutor<InstanceInfo>() { 
                @Override
                public EurekaHttpResponse<InstanceInfo> execute(EurekaHttpClient delegate) { 
                	//发送心跳
                    return delegate.sendHeartBeat(appName, id, info, overriddenStatus);
                }
    
                @Override
                public RequestType getRequestType() { 
                    return RequestType.SendHeartBeat;
                }
            });
        }

通过`EurekaHttpClientDecorator` 装饰器会先后会执行`RetryableEurekaHttpClient`(失败重试),`RedirectingEurekaHttpClient`(重定向到不同的EurekaServer)`MetricsCollectingEurekaHttpClient`(统计执行情况)针对于各种情况的Http客户端，然后  
最终通过`AbstractJerseyEurekaHttpClient`(JerseyApplicationClient)，使用jerseyClient发起心跳请求

public abstract class AbstractJerseyEurekaHttpClient implements EurekaHttpClient { 
     @Override
        public EurekaHttpResponse<InstanceInfo> sendHeartBeat(String appName, String id, InstanceInfo info, InstanceStatus overriddenStatus) { 
            String urlPath = "apps/" + appName + '/' + id;
            ClientResponse response = null;
            try { 
               //webResource是对Web请求的封装
                WebResource webResource = jerseyClient.resource(serviceUrl)
                        .path(urlPath)
                        //服务状态 UP
                        .queryParam("status", info.getStatus().toString())
                        //最后刷新时间
                        .queryParam("lastDirtyTimestamp", info.getLastDirtyTimestamp().toString());
                if (overriddenStatus != null) { 
                    webResource = webResource.queryParam("overriddenstatus", overriddenStatus.name());
                }
                Builder requestBuilder = webResource.getRequestBuilder();
                addExtraHeaders(requestBuilder);
                //发送put请求
                response = requestBuilder.put(ClientResponse.class);
                EurekaHttpResponseBuilder<InstanceInfo> eurekaResponseBuilder = anEurekaHttpResponse(response.getStatus(), InstanceInfo.class).headers(headersOf(response));
                if (response.hasEntity()) { 
                    eurekaResponseBuilder.entity(response.getEntity(InstanceInfo.class));
                }
                return eurekaResponseBuilder.build();
            } finally { 
                if (logger.isDebugEnabled()) { 
                    logger.debug("Jersey HTTP PUT {}/{}; statusCode={}", serviceUrl, urlPath, response == null ? "N/A" : response.getStatus());
                }
                if (response != null) { 
                    response.close();
                }
            }
        }

这里EureakClient会向EureakServer发送自己的服务状态，以及服务最后续约时间，使用的是PUT发起Rest请求。

#### 总结 ####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0OTQxNDg_size_16_color_FFFFFF_t_70_pic_center]

1.  DiscoveryClient.initScheduledTasks初始化续约心跳定时任务,30s/次执行HeartbeatThread线程发送续约请求
2.  HeartbeatThread调用DiscoveryClient.renew()续约
3.  renew方法中使用eurekaTransport得到EureakaHttpClient实例EurekaHttpClientDecorator 装饰器执行请求
4.  EurekaHttpClientDecorator 调用JerseyApplicationClient向EureakServer发送Rest请求，把服务状态和最后的续约时间当做参数

下一章推荐《[Eureka Server服务续约][.SpringCloud_-Eureka Server 3]》

[.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
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTQ0OTQxNDg_size_16_color_FFFFFF_t_70_pic_center]: /images/20221123/b7d3b0651ac34309a62085c6e69d5f65.png