springcloud heartbeat executor 是每个微服务向注册中心定时发送自己的一些信息

最新推荐文章于 2024-07-10 17:50:18 发布

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本文详细解析了Springcloud微服务架构下，Eureka注册中心的心跳机制实现原理。介绍了如何通过DiscoveryClient组件在微服务启动时初始化心跳线程池，设定心跳间隔，并定时向Eureka服务器发送心跳，保持服务实例的有效状态。

Springcloud微服务的启动日志中会出现
2020-03-04 10:19:24.215 INFO 15128 — [ main] com.netflix.discovery.DiscoveryClient : Starting heartbeat executor: renew interval is: 30

heartbeat executor 是每个微服务向注册中心定时发送自己的一些信息

启动过程

启动类上面加注解@DiscoveryClient
启动的时候会执行DiscoveryClient类中，下面的构造方法

@Inject
DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args, Provider<BackupRegistry> backupRegistryProvider, EndpointRandomizer endpointRandomizer) {.......................}

在这个构造方法中会创建一个发送心跳的线程池，就是以下代码

this.heartbeatExecutor = new ThreadPoolExecutor(1, this.clientConfig.getHeartbeatExecutorThreadPoolSize(), 0L, TimeUnit.SECONDS, new SynchronousQueue(), (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-HeartbeatExecutor-%d").setDaemon(true).build());

this.clientConfig.getHeartbeatExecutorThreadPoolSize() 这个值默认是2，可以通过EurekaClientConfigBean 这个类查看默认值

同样是这个方法里面有一段代码，初始化调度任务
this.initScheduledTasks();

private void initScheduledTasks() {
    int renewalIntervalInSecs;
    int expBackOffBound;
    if (this.clientConfig.shouldFetchRegistry()) {
	//默认30s，可以从LeaseInfo类中查看默认值
        renewalIntervalInSecs = this.clientConfig.getRegistryFetchIntervalSeconds();         expBackOffBound = this.clientConfig.getCacheRefreshExecutorExponentialBackOffBound();
        this.scheduler.schedule(new TimedSupervisorTask("cacheRefresh", this.scheduler, this.cacheRefreshExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.CacheRefreshThread()), (long)renewalIntervalInSecs, TimeUnit.SECONDS);
    }

    if (this.clientConfig.shouldRegisterWithEureka()) {
        renewalIntervalInSecs = this.instanceInfo.getLeaseInfo().getRenewalIntervalInSecs();
        expBackOffBound = this.clientConfig.getHeartbeatExecutorExponentialBackOffBound();
//输出日志        
logger.info("Starting heartbeat executor: renew interval is: {}", renewalIntervalInSecs);
//启动定时任务
        this.scheduler.schedule(new TimedSupervisorTask("heartbeat", this.scheduler, this.heartbeatExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.HeartbeatThread()), (long)renewalIntervalInSecs, TimeUnit.SECONDS);
        this.instanceInfoReplicator = new InstanceInfoReplicator(this, this.instanceInfo, this.clientConfig.getInstanceInfoReplicationIntervalSeconds(), 2);
        this.statusChangeListener = new StatusChangeListener() {
            public String getId() {
                return "statusChangeListener";
            }

            public void notify(StatusChangeEvent statusChangeEvent) {
                if (InstanceStatus.DOWN != statusChangeEvent.getStatus() && InstanceStatus.DOWN != statusChangeEvent.getPreviousStatus()) {
                    DiscoveryClient.logger.info("Saw local status change event {}", statusChangeEvent);
                } else {
                    DiscoveryClient.logger.warn("Saw local status change event {}", statusChangeEvent);
                }

                DiscoveryClient.this.instanceInfoReplicator.onDemandUpdate();
            }
        };
        if (this.clientConfig.shouldOnDemandUpdateStatusChange()) {
            this.applicationInfoManager.registerStatusChangeListener(this.statusChangeListener);
        }

        this.instanceInfoReplicator.start(this.clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());
    } else {
        logger.info("Not registering with Eureka server per configuration");
    }

}

定时通过DiscoveryClient类中的下面 renew()发送信息

boolean renew() {
    try {
        EurekaHttpResponse<InstanceInfo> httpResponse = this.eurekaTransport.registrationClient.sendHeartBeat(this.instanceInfo.getAppName(), this.instanceInfo.getId(), this.instanceInfo, (InstanceStatus)null);
        logger.debug("DiscoveryClient_{} - Heartbeat status: {}", this.appPathIdentifier, httpResponse.getStatusCode());
        if (httpResponse.getStatusCode() == Status.NOT_FOUND.getStatusCode()) {
            this.REREGISTER_COUNTER.increment();
            logger.info("DiscoveryClient_{} - Re-registering apps/{}", this.appPathIdentifier, this.instanceInfo.getAppName());
            long timestamp = this.instanceInfo.setIsDirtyWithTime();
            boolean success = this.register();
            if (success) {
                this.instanceInfo.unsetIsDirty(timestamp);
            }

            return success;
        } else {
            return httpResponse.getStatusCode() == Status.OK.getStatusCode();
        }
    } catch (Throwable var5) {
        logger.error("DiscoveryClient_{} - was unable to send heartbeat!", this.appPathIdentifier, var5);
        return false;
    }
}