聊聊eureka client的shutdown

序

本文主要研究一下eureka client的shutdown

EurekaRegistration

spring-cloud-netflix-eureka-client-2.0.0.RC1-sources.jar!/org/springframework/cloud/netflix/eureka/EurekaClientAutoConfiguration.java

@Bean
	@ConditionalOnBean(AutoServiceRegistrationProperties.class)
	@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled", matchIfMissing = true)
	public EurekaRegistration eurekaRegistration(EurekaClient eurekaClient, CloudEurekaInstanceConfig instanceConfig, ApplicationInfoManager applicationInfoManager, ObjectProvider<HealthCheckHandler> healthCheckHandler) {
		return EurekaRegistration.builder(instanceConfig)
				.with(applicationInfoManager)
				.with(eurekaClient)
				.with(healthCheckHandler)
				.build();
	}

	@Bean
	@ConditionalOnBean(AutoServiceRegistrationProperties.class)
	@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled", matchIfMissing = true)
	public EurekaAutoServiceRegistration eurekaAutoServiceRegistration(ApplicationContext context, EurekaServiceRegistry registry, EurekaRegistration registration) {
		return new EurekaAutoServiceRegistration(context, registry, registration);
	}

	//...
	@Bean(destroyMethod = "shutdown")
	@ConditionalOnMissingBean(value = EurekaClient.class, search = SearchStrategy.CURRENT)
	public EurekaClient eurekaClient(ApplicationInfoManager manager, EurekaClientConfig config) {
		return new CloudEurekaClient(manager, config, this.optionalArgs,
					this.context);
	}

這裏自動建立EurekaRegistration，以及EurekaAutoServiceRegistration，EurekaClient

EurekaClient

eureka-client-1.8.8-sources.jar!/com/netflix/discovery/EurekaClient.java

能夠看到EurekaClient標註了@Bean(destroyMethod = "shutdown")，也就是在bean銷燬的時候，會觸發eurekaClient.shutdown方法

EurekaRegistration

spring-cloud-netflix-eureka-client-2.0.0.RC1-sources.jar!/org/springframework/cloud/netflix/eureka/serviceregistry/EurekaRegistration.java

public class EurekaRegistration implements Registration, Closeable {
	//......
	@Override
	public void close() throws IOException {
		this.eurekaClient.shutdown();
	}
}

這裏實現了Closeable接口的close方法，在spring容器關閉的時候觸發，這裏調用了eurekaClient.shutdown()

EurekaAutoServiceRegistration

spring-cloud-netflix-eureka-client-2.0.0.RC1-sources.jar!/org/springframework/cloud/netflix/eureka/serviceregistry/EurekaAutoServiceRegistration.java

@Override
	public void start() {
		// only set the port if the nonSecurePort or securePort is 0 and this.port != 0
		if (this.port.get() != 0) {
			if (this.registration.getNonSecurePort() == 0) {
				this.registration.setNonSecurePort(this.port.get());
			}

			if (this.registration.getSecurePort() == 0 && this.registration.isSecure()) {
				this.registration.setSecurePort(this.port.get());
			}
		}

		// only initialize if nonSecurePort is greater than 0 and it isn't already running
		// because of containerPortInitializer below
		if (!this.running.get() && this.registration.getNonSecurePort() > 0) {

			this.serviceRegistry.register(this.registration);

			this.context.publishEvent(
					new InstanceRegisteredEvent<>(this, this.registration.getInstanceConfig()));
			this.running.set(true);
		}
	}
	@Override
	public void stop() {
		this.serviceRegistry.deregister(this.registration);
		this.running.set(false);
	}

這裏的start，stop實現的是Lifecycle的方法，也就在spring容器關閉的時候，會觸發stop方法，而後調用的是serviceRegistry.deregister(this.registration)

RefreshScopeRefreshedEvent

spring-cloud-netflix-eureka-client-2.0.0.RC1-sources.jar!/org/springframework/cloud/netflix/eureka/EurekaDiscoveryClientConfiguration.java

@Configuration
	@ConditionalOnClass(RefreshScopeRefreshedEvent.class)
	protected static class EurekaClientConfigurationRefresher {

		@Autowired(required = false)
		private EurekaClient eurekaClient;

		@Autowired(required = false)
		private EurekaAutoServiceRegistration autoRegistration;

		@EventListener(RefreshScopeRefreshedEvent.class)
		public void onApplicationEvent(RefreshScopeRefreshedEvent event) {
			//This will force the creation of the EurkaClient bean if not already created
			//to make sure the client will be reregistered after a refresh event
			if(eurekaClient != null) {
				eurekaClient.getApplications();
			}
			if (autoRegistration != null) {
				// register in case meta data changed
				this.autoRegistration.stop();
				this.autoRegistration.start();
			}
		}
	}

接收到RefreshScopeRefreshedEvent的時候，會先stop，再start

DiscoveryClient.shutdown

eureka-client-1.8.8-sources.jar!/com/netflix/discovery/DiscoveryClient.java

public synchronized void shutdown() {
        if (isShutdown.compareAndSet(false, true)) {
            logger.info("Shutting down DiscoveryClient ...");

            if (statusChangeListener != null && applicationInfoManager != null) {
                applicationInfoManager.unregisterStatusChangeListener(statusChangeListener.getId());
            }

            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();

            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 ...");
                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);
            }
        }
    }

這裏能夠看到，先設置狀態爲DOWN，而後調用cancel方法

RestTemplateEurekaHttpClient

spring-cloud-netflix-eureka-client-2.0.0.RC1-sources.jar!/org/springframework/cloud/netflix/eureka/http/RestTemplateEurekaHttpClient.java

public EurekaHttpResponse<Void> cancel(String appName, String id) {
		String urlPath = serviceUrl + "apps/" + appName + '/' + id;

		ResponseEntity<Void> response = restTemplate.exchange(urlPath, HttpMethod.DELETE,
				null, Void.class);

		return anEurekaHttpResponse(response.getStatusCodeValue())
				.headers(headersOf(response)).build();
	}

	@Override
	public EurekaHttpResponse<Void> register(InstanceInfo info) {
		String urlPath = serviceUrl + "apps/" + info.getAppName();

		HttpHeaders headers = new HttpHeaders();
		headers.add(HttpHeaders.ACCEPT_ENCODING, "gzip");
		headers.add(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);

		ResponseEntity<Void> response = restTemplate.exchange(urlPath, HttpMethod.POST,
				new HttpEntity<>(info, headers), Void.class);

		return anEurekaHttpResponse(response.getStatusCodeValue())
				.headers(headersOf(response)).build();
	}

cancel方法就是調用REST的DELETE操做，註銷掉服務

小結

springcloud封裝的eureka自動註冊，關閉的時候主要分兩大類：

• 依賴生命週期在銷燬時調用shutdown、close

EurekaRegistration是在close的時候，會觸發eurekaClient.shutdown方法 EurekaAutoServiceRegistration則在stop的時候，標記狀態爲DOWN，發佈StatusChangeEvent事件 EurekaClient則標註了@Bean(destroyMethod = "shutdown")，也就是在bean銷燬的時候，會觸發eurekaClient.shutdown方法

• 期間狀態變動發佈StatusChangeEvent事件

com/netflix/discovery/DiscoveryClient.java有個StatusChangeListener，狀態變動在須要的時候，會觸發InstanceInfoReplicator的onDemandUpdate方法，該方法會調用discoveryClient.register()去與eureka server更新自身實例的狀態。 這裏至關於變相經過register接口更改status狀態。

這裏要區分一下cancel與StatusChangeEvent的區別，cancel是從eureka server刪掉這條instanceInfo，而StatusChangeEvent變動狀態，不會刪除這條instanceInfo，只是更新status狀態(status狀態一共有UP,DOWN,STARTING,OUT_OF_SERVICE,UNKNOWN幾類)。

doc

• ServiceRegistry Auto-Registration
• beans-factory-lifecycle