Nacos 服务注册注销源码浅析

墨蓝 2023-09-27 09:20 83阅读 0赞

从引入的 Nacos Discovery 的 starter 中找 `spring.factories` 文件，咱们能看到下图，既然是了解服务注册的，按照 Spring Boot 的习俗，咱们应该重点关注红框中的内容 `NacosServiceRegistryAutoConfiguration`。  
![在这里插入图片描述][6e6dd7c8325543818ee8490ee31e99ce.png]

## 入口 ##

从上面咱们知道了入口是 `NacosServiceRegistryAutoConfiguration`，点进去看下：

@Configuration(proxyBeanMethods = false)
    @EnableConfigurationProperties
    @ConditionalOnNacosDiscoveryEnabled
    @ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled",
    		matchIfMissing = true)
    @AutoConfigureAfter({
         AutoServiceRegistrationConfiguration.class,
    		AutoServiceRegistrationAutoConfiguration.class,
    		NacosDiscoveryAutoConfiguration.class })
    public class NacosServiceRegistryAutoConfiguration {
        
    
    	@Bean
    	public NacosServiceRegistry nacosServiceRegistry(
    			NacosServiceManager nacosServiceManager,
    			NacosDiscoveryProperties nacosDiscoveryProperties) {
        
    		return new NacosServiceRegistry(nacosServiceManager, nacosDiscoveryProperties);
    	}
    
    	@Bean
    	@ConditionalOnBean(AutoServiceRegistrationProperties.class)
    	public NacosRegistration nacosRegistration(
    			ObjectProvider<List<NacosRegistrationCustomizer>> registrationCustomizers,
    			NacosDiscoveryProperties nacosDiscoveryProperties,
    			ApplicationContext context) {
        
    		return new NacosRegistration(registrationCustomizers.getIfAvailable(),
    				nacosDiscoveryProperties, context);
    	}
    
    	@Bean
    	@ConditionalOnBean(AutoServiceRegistrationProperties.class)
    	public NacosAutoServiceRegistration nacosAutoServiceRegistration(
    			NacosServiceRegistry registry,
    			AutoServiceRegistrationProperties autoServiceRegistrationProperties,
    			NacosRegistration registration) {
        
    		return new NacosAutoServiceRegistration(registry,
    				autoServiceRegistrationProperties, registration);
    	}
    
    }

`@ConditionalOnXxxYyy` 注解是一些条件注解，这里不再赘述，`@AutoConfigureAfter` 代表加载了制定的类之后再加载当前类。

## NacosAutoServiceRegistration ##

public class NacosAutoServiceRegistration
    		extends AbstractAutoServiceRegistration<Registration> {
        
    
    	private static final Logger log = LoggerFactory
    			.getLogger(NacosAutoServiceRegistration.class);
    
    	private NacosRegistration registration;
    
    	public NacosAutoServiceRegistration(ServiceRegistry<Registration> serviceRegistry,
    			AutoServiceRegistrationProperties autoServiceRegistrationProperties,
    			NacosRegistration registration) {
        
    		super(serviceRegistry, autoServiceRegistrationProperties);
    		this.registration = registration;
    	}
    	// 省略部分代码
    
    }

先看下类图，我们会发现通过继承实现了 `ApplicationListener` 接口的抽象类 `AbstractAutoServiceRegistration` 获得了以下能力：

public void onApplicationEvent(WebServerInitializedEvent event) {
        
    		bind(event);
    	}

![在这里插入图片描述][e761fe5a621c4ae9922bcd0f5701c24b.png]

## AbstractAutoServiceRegistration ##

### 注册 ###

#### AbstractAutoServiceRegistration\#bind(WebServerInitializedEvent event) ####

@Deprecated
    	public void bind(WebServerInitializedEvent event) {
        
    		ApplicationContext context = event.getApplicationContext();
    		if (context instanceof ConfigurableWebServerApplicationContext) {
        
    			if ("management".equals(((ConfigurableWebServerApplicationContext) context)
    					.getServerNamespace())) {
        
    				return;
    			}
    		}
    		this.port.compareAndSet(0, event.getWebServer().getPort());]
    		// 直接看 start() 方法
    		this.start();
    	}

#### AbstractAutoServiceRegistration\#start() ####

public void start() {
        
    		if (!isEnabled()) {
        
    			if (logger.isDebugEnabled()) {
        
    				logger.debug("Discovery Lifecycle disabled. Not starting");
    			}
    			return;
    		}
    
    		// only initialize if nonSecurePort is greater than 0 and it isn't already running
    		// because of containerPortInitializer below
    		if (!this.running.get()) {
        
    			// 发布预注册事件
    			this.context.publishEvent(
    					new InstancePreRegisteredEvent(this, getRegistration()));
    			register();
    			if (shouldRegisterManagement()) {
        
    				registerManagement();
    			}
    			// 发布注册事件
    			this.context.publishEvent(
    					new InstanceRegisteredEvent<>(this, getConfiguration()));
    			this.running.compareAndSet(false, true);
    		}
    
    	}

其中 `register()` 和 `registerManagement()` 都会调用到 `ServiceRegistry#register(R registration)`

#### NacosServiceRegistry ####

> NacosServiceRegistry 是 ServiceRegistry 的一个实现。

@Override
    	public void register(Registration registration) {
        
    
    		if (StringUtils.isEmpty(registration.getServiceId())) {
        
    			log.warn("No service to register for nacos client...");
    			return;
    		}
    
    		NamingService namingService = namingService();
    		String serviceId = registration.getServiceId();
    		String group = nacosDiscoveryProperties.getGroup();
    		// 获取实例
    		Instance instance = getNacosInstanceFromRegistration(registration);
    
    		try {
        
    			// 注册实例
    			namingService.registerInstance(serviceId, group, instance);
    			log.info("nacos registry, {} {} {}:{} register finished", group, serviceId,
    					instance.getIp(), instance.getPort());
    		}
    		catch (Exception e) {
        
    			if (nacosDiscoveryProperties.isFailFast()) {
        
    				log.error("nacos registry, {} register failed...{},", serviceId,
    						registration.toString(), e);
    				rethrowRuntimeException(e);
    			}
    			else {
        
    				log.warn("Failfast is false. {} register failed...{},", serviceId,
    						registration.toString(), e);
    			}
    		}
    	}

#### NacosNamingService ####

public class NacosNamingService implements NamingService {
        
    
    	// 省略代码
    	
        private NamingClientProxy clientProxy;
        
        @Override
        public void registerInstance(String serviceName, String groupName, Instance instance) throws NacosException {
        
            NamingUtils.checkInstanceIsLegal(instance);
            clientProxy.registerService(serviceName, groupName, instance);
        }

看到最终是通过 `clientProxy.registerService(serviceName, groupName, instance);` 完成了实例的注册。

### 注销 ###

回到 `AbstractAutoServiceRegistration` 类中，我们看到了被 `@PreDestroy` 标注的方法，含义是在应用程序关闭时执行被 `@PreDestroy` 标注的方法：

@PreDestroy
    	public void destroy() {
        
    		stop();
    	}

#### AbstractAutoServiceRegistration\#stop() ####

public void stop() {
        
    		if (this.getRunning().compareAndSet(true, false) && isEnabled()) {
        
    			deregister();
    			if (shouldRegisterManagement()) {
        
    				deregisterManagement();
    			}
    			this.serviceRegistry.close();
    		}
    	}

其中 `deregister()` 以及 `deregisterManagement()` 都会执行 `serviceRegistry.deregister(registration)`，进行服务的注销。

#### NacosServiceRegistry\#deregister(Registration registration) ####

上文说到的 serviceRegistry 在 Nacos 中的实现是 NacosServiceRegistry，看下具体的方法：

@Override
    	public void deregister(Registration registration) {
        
    
    		log.info("De-registering from Nacos Server now...");
    
    		if (StringUtils.isEmpty(registration.getServiceId())) {
        
    			log.warn("No dom to de-register for nacos client...");
    			return;
    		}
    
    		NamingService namingService = namingService();
    		String serviceId = registration.getServiceId();
    		String group = nacosDiscoveryProperties.getGroup();
    
    		try {
        
    			namingService.deregisterInstance(serviceId, group, registration.getHost(),
    					registration.getPort(), nacosDiscoveryProperties.getClusterName());
    		}
    		catch (Exception e) {
        
    			log.error("ERR_NACOS_DEREGISTER, de-register failed...{},",
    					registration.toString(), e);
    		}
    
    		log.info("De-registration finished.");
    	}

`namingService.deregisterInstance(serviceId, group, registration.getHost(), registration.getPort(), nacosDiscoveryProperties.getClusterName());` 交由 `NacosNamingService` 完成

#### NacosNamingService\#deregisterInstance(String serviceName, String groupName, String ip, int port, String clusterName) ####

@Override
        public void deregisterInstance(String serviceName, String groupName, String ip, int port, String clusterName)
                throws NacosException {
        
            Instance instance = new Instance();
            instance.setIp(ip);
            instance.setPort(port);
            instance.setClusterName(clusterName);
           	// 注销实例
            deregisterInstance(serviceName, groupName, instance);
        }

#### NacosNamingService\#deregisterInstance(String serviceName, String groupName, Instance instance) ####

@Override
        public void deregisterInstance(String serviceName, String groupName, Instance instance) throws NacosException {
        
            clientProxy.deregisterService(serviceName, groupName, instance);
        }

其实在上面能看到最终是通过 `clientProxy.deregisterService(serviceName, groupName, instance);` 完成了服务的注销。

## 总结 ##

Nacos 通过监听事件完成服务的注册，通过 `@PreDestroy` 标注的方法完成服务的注销。

> 剧透下：
> 
> 1.  NamingClientProxy 有两种，分别是 NamingHttpClientProxy 以及 NamingGrpcClientProxy，选择哪个进行注册通过 NamingClientProxyDelegate 做了委托（下图的一个判断）。临时实例走 grpc，持久化实例走 httpclient。  
>     ![在这里插入图片描述][9551e1f268204c1f911caca8092a2a36.png]
> 2.  NamingHttpClientProxy 会执行向 Nacos Server 端发送 HTTP 请求的方式注册和注销。

[6e6dd7c8325543818ee8490ee31e99ce.png]: https://img-blog.csdnimg.cn/6e6dd7c8325543818ee8490ee31e99ce.png
[e761fe5a621c4ae9922bcd0f5701c24b.png]: https://img-blog.csdnimg.cn/e761fe5a621c4ae9922bcd0f5701c24b.png
[9551e1f268204c1f911caca8092a2a36.png]: https://img-blog.csdnimg.cn/9551e1f268204c1f911caca8092a2a36.png