Spring Cloud Alibaba Nacos 客户端服务注册心跳和健康监测

1、注册HealthIndicator

@Configuration(proxyBeanMethods = false)
@ConditionalOnClass(Endpoint.class)
@ConditionalOnNacosDiscoveryEnabled
public class NacosDiscoveryEndpointAutoConfiguration {
   
   

	@Bean
	@ConditionalOnMissingBean
	@ConditionalOnAvailableEndpoint
	public NacosDiscoveryEndpoint nacosDiscoveryEndpoint(
			NacosServiceManager nacosServiceManager,
			NacosDiscoveryProperties nacosDiscoveryProperties) {
   
   
		return new NacosDiscoveryEndpoint(nacosServiceManager, nacosDiscoveryProperties);
	}

	@Bean
	@ConditionalOnEnabledHealthIndicator("nacos-discovery")
	public HealthIndicator nacosDiscoveryHealthIndicator(
			NacosServiceManager nacosServiceManager,
			NacosDiscoveryProperties nacosDiscoveryProperties) {
   
   
		Properties nacosProperties = nacosDiscoveryProperties.getNacosProperties();
		return new NacosDiscoveryHealthIndicator(
				nacosServiceManager.getNamingService(nacosProperties));
	}

}

nacosServiceManager在NacosServiceAutoConfiguration中生成。

@Configuration(proxyBeanMethods = false)
@ConditionalOnDiscoveryEnabled
@ConditionalOnNacosDiscoveryEnabled
public class NacosServiceAutoConfiguration {
   
   

   @Bean
   public NacosServiceManager nacosServiceManager() {
   
   
      return new NacosServiceManager();
   }

}

可以看到，注册HealthIndicator 时，获取了NamingService，并构造了NacosDiscoveryHealthIndicator。

public NacosDiscoveryHealthIndicator(NamingService namingService) {
   
   
   this.namingService = namingService;
}

NacosDiscoveryHealthIndicator中只有一个方法，检查健康状态。

protected void doHealthCheck(Health.Builder builder) throws Exception {
   
   
   // Just return "UP" or "DOWN"
   String status = namingService.getServerStatus();
   // Set the status to Builder
   builder.status(status);
   switch (status) {
   
   
   case STATUS_UP:
      builder.up();
      break;
   case STATUS_DOWN:
      builder.down();
      break;
   default:
      builder.unknown();
      break;
   }
}

2、获取NamingService

//com.alibaba.cloud.nacos.NacosServiceManager#getNamingService
public NamingService getNamingService(Properties properties) {
   
   
    if (Objects.isNull(this.namingService)) {
   
   
        buildNamingService(properties);
    }
    return namingService;
}

创建NamingService

//com.alibaba.cloud.nacos.NacosServiceManager#buildNamingService
private NamingService buildNamingService(Properties properties) {
   
   
   if (Objects.isNull(namingService)) {
   
   
      synchronized (NacosServiceManager.class) {
   
   
         if (Objects.isNull(namingService)) {
   
   
            namingService = createNewNamingService(properties);
         }
      }
   }
   return namingService;
}

//com.alibaba.cloud.nacos.NacosServiceManager#createNewNamingService
private NamingService createNewNamingService(Properties properties) {
   
   
   try {
   
   
      return createNamingService(properties);
   }
   catch (NacosException e) {
   
   
      throw new RuntimeException(e);
   }
}

//NamingFactory#createNamingService(java.util.Properties)
public static NamingService createNamingService(Properties properties) throws NacosException {
   
   
    return NamingFactory.createNamingService(properties);
}

public static NamingService createNamingService(Properties properties) throws NacosException {
   
   
    try {
   
   
        Class<?> driverImplClass = Class.forName("com.alibaba.nacos.client.naming.NacosNamingService");
        Constructor constructor = driverImplClass.getConstructor(Properties.class);
        return (NamingService) constructor.newInstance(properties);
    } catch (Throwable e) {
   
   
        throw new NacosException(NacosException.CLIENT_INVALID_PARAM, e);
    }
}

//com.alibaba.nacos.client.naming.NacosNamingService#NacosNamingService
public NacosNamingService(Properties properties) throws NacosException {
   
   
    init(properties);
}

3、初始化NamingService

private void init(Properties properties) throws NacosException {
   
   
    ValidatorUtils.checkInitParam(properties);
    this.namespace = InitUtils.initNamespaceForNaming(properties);
    InitUtils.initSerialization();
    InitUtils.initWebRootContext(properties);
    initLogName(properties);
    
    this.changeNotifier = new InstancesChangeNotifier();
    NotifyCenter.registerToPublisher(InstancesChangeEvent.class, 16384);
    NotifyCenter.registerSubscriber(changeNotifier);
    //构建ServiceInfoHolder，里面有个定时任务刷新磁盘
    this.serviceInfoHolder = new ServiceInfoHolder(namespace, properties);
    //生成NamingClientProxyDelegate
    this.clientProxy = new NamingClientProxyDelegate(this.namespace, serviceInfoHolder, properties, changeNotifier);
}

3.1、ServiceInfoHolder

ServiceInfoHolder构建时会初始化磁盘目录并且生成任务操作磁盘缓存

public ServiceInfoHolder(String namespace, Properties properties) {
   
   
    //初始化磁盘缓存目录
    initCacheDir(namespace, properties);
    //判断是否启动时加载缓存	namingLoadCacheAtStart 配置
    if (isLoadCacheAtStart(properties)) {
   
   
        this.serviceInfoMap = new ConcurrentHashMap<String, ServiceInfo>(DiskCache.read(this.cacheDir));
    } else {
   
   
        this.serviceInfoMap = new ConcurrentHashMap<String, ServiceInfo>(16);
    }
    //故障切换任务
    this.failoverReactor = new FailoverReactor(this, cacheDir);
    //加载 namingPushEmptyProtection 配置的值
    this.pushEmptyProtection = isPushEmptyProtect(properties);
}

public FailoverReactor(ServiceInfoHolder serviceInfoHolder, String cacheDir) {
   
   
    this.serviceInfoHolder = serviceInfoHolder;
    this.failoverDir = cacheDir + FAILOVER_DIR;
    // init executorService
    this.executorService = new ScheduledThreadPoolExecutor(1, new ThreadFactory() {
   
   
        @Override
        public Thread newThread(Runnable r) {
   
   
            Thread thread = new Thread(r);
            thread.setDaemon(true);
            thread.setName("com.alibaba.nacos.naming.failover");
            return thread;
        }
    });
    this.init();
}

public void init() {
   
   
    //故障切换 每5秒一次
    executorService.scheduleWithFixedDelay(new SwitchRefresher(), 0L, 5000L, TimeUnit.MILLISECONDS);
    //写磁盘   30分钟后开始，每天一次
    executorService.scheduleWithFixedDelay(new DiskFileWriter(), 30, DAY_PERIOD_MINUTES, TimeUnit.MINUTES);
    //备份	每10秒一次
    // backup file on startup if failover directory is empty.
    executorService.schedule(new Runnable() {
   
   
        @Override
        public void run() {
   
   
            try {
   
   
                File cacheDir = new File(failoverDir);
                
                if