Eureka - 服务续约和注册、下线

服务续约

服务续约的线程和Eureka - 服务发现中的一样，这里不再讲解，我们直接通过HeartbeatThread的run方法看renew方法。

boolean renew() {
    EurekaHttpResponse httpResponse;
    try {
        // 调用EurekaServer地址+"apps/" + appName + '/' + id
        httpResponse = eurekaTransport.registrationClient.sendHeartBeat(instanceInfo.getAppName(), instanceInfo.getId(), instanceInfo, null);
        logger.debug(PREFIX + "{} - Heartbeat status: {}", appPathIdentifier, httpResponse.getStatusCode());
        if (httpResponse.getStatusCode() == Status.NOT_FOUND.getStatusCode()) {
            REREGISTER_COUNTER.increment();
            logger.info(PREFIX + "{} - Re-registering apps/{}", appPathIdentifier, instanceInfo.getAppName());
            long timestamp = instanceInfo.setIsDirtyWithTime();
            boolean success = register();
            if (success) {
                instanceInfo.unsetIsDirty(timestamp);
            }
            return success;
        }
        return httpResponse.getStatusCode() == Status.OK.getStatusCode();
    } catch (Throwable e) {
        logger.error(PREFIX + "{} - was unable to send heartbeat!", appPathIdentifier, e);
        return false;
    }
}

服务注册

在Eureka - Client服务启动中提到initScheduledTasks中会调用InstanceInfoReplicator#start方法。

public void start(int initialDelayMs) {
    if (started.compareAndSet(false, true)) {
        instanceInfo.setIsDirty();  // for initial register
        Future next = scheduler.schedule(this, initialDelayMs, TimeUnit.SECONDS);
        scheduledPeriodicRef.set(next);
    }
}

start方法会启动一个定时任务，就会调用InstanceInfoReplicator#run方法。refreshInstanceInfo会刷新数据中心信息和租约信息。

public void run() {
    try {
        // 刷新数据中心信息和租约信息。
        discoveryClient.refreshInstanceInfo();

        Long dirtyTimestamp = instanceInfo.isDirtyWithTime();
        // 如果信息有变化，则注册
        if (dirtyTimestamp != null) {
            // 注册,"apps/" + info.getAppName()
            discoveryClient.register();
            instanceInfo.unsetIsDirty(dirtyTimestamp);
        }
    } catch (Throwable t) {
        logger.warn("There was a problem with the instance info replicator", t);
    } finally {
        // 线程用于刷新信息以及重新注册
        Future next = scheduler.schedule(this, replicationIntervalSeconds, TimeUnit.SECONDS);
        scheduledPeriodicRef.set(next);
    }
}

服务下线

在EurekaClient加载的时候，@Bean(destroyMethod = "shutdown")bean注解的一个属性是销毁的时候调用shutdown。
这里会取消监听、各种定时任务以及向Eureka发送下线信息。

@PreDestroy
@Override
public synchronized void shutdown() {
    if (isShutdown.compareAndSet(false, true)) {
        logger.info("Shutting down DiscoveryClient ...");
        // 取消监听
        if (statusChangeListener != null && applicationInfoManager != null) {
            applicationInfoManager.unregisterStatusChangeListener(statusChangeListener.getId());
        }
        // 停止定时任务，包括续约、注册列表更新等
        cancelScheduledTasks();

        // If APPINFO was registered
        if (applicationInfoManager != null
                && clientConfig.shouldRegisterWithEureka()
                && clientConfig.shouldUnregisterOnShutdown()) {
            applicationInfoManager.setInstanceStatus(InstanceStatus.DOWN);
            unregister();
        }

        if (eurekaTransport != null) {
            eurekaTransport.shutdown();
        }
        // 
        heartbeatStalenessMonitor.shutdown();
        registryStalenessMonitor.shutdown();

        Monitors.unregisterObject(this);

        logger.info("Completed shut down of DiscoveryClient");
    }
}

/**
 * unregister w/ the eureka service.
 */
void unregister() {
    // It can be null if shouldRegisterWithEureka == false
    if(eurekaTransport != null && eurekaTransport.registrationClient != null) {
        try {
            logger.info("Unregistering ...");
            // 调用"apps/" + appName + '/' + id
            EurekaHttpResponse 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);
        }
    }
}

结束

直至，服务注册、服务发现、服务续约，client部分已经讲完了。