Nacos源码—6.Nacos升级gRPC分析一

圣罩 · 2025-6-2 23:15:01

大纲
1.Nacos 2.x版本的一些变化
2.客户端升级gRPC发起服务注册
3.服务端进行服务注册时的处理
4.客户端服务发现和服务端处理服务订阅的源码分析

1.Nacos 2.x版本的一些变化
变化一：客户端和服务端的交互方式由HTTP升级为gRPC
Nacos 1.x服务端会提供一系列的HTTP接口供客户端请求调用，Nacos 2.x服务端会定义一些列Handler处理类来处理客户端的gRPC请求。

Nacos 1.x进行服务注册时使用的是HTTP短连接，Nacos 2.x进行服务注册时使用的是RPC长连接。

变化二：注册中心的注册表由双重Map结构变为轻量的一个Map
Nacos 1.x版本中的注册中心是使用双重Map结构来存储注册表的，这样使得注册表还是比较重量级的，在并发高时也需要考虑并发冲突。

Nacos 2.x版本则把注册表轻量化了，服务端在处理服务注册时，只是简单地往一个Map记写入客户端连接的ID。

变化三：大量使用了事件驱动
Nacos 2.x版本的Nacos里，使用了非常多的事件驱动。比如服务注册、服务销毁、服务变更等都先通过通知中心来发布一个事件，然后通过处理事件来来处理后续的逻辑流程。

2.客户端升级gRPC发起服务注册
(1)客户端和服务端的版本选择
(2)Nacos客户端项目启动时自动触发服务实例注册
(3)Nacos客户端通过gRPC方式发起服务实例注册
(4)总结

(1)客户端和服务端的版本选择

<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Hoxton.SR12</spring-cloud.version>
<spring-cloud-alibaba.version>2.2.8.RELEASE</spring-cloud-alibaba.version>
</properties>

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(2)Nacos客户端项目启动时自动触发服务实例注册
spring-cloud-starter-alibaba-nacos-discovery依赖包会自动注册服务。查看这个依赖包中的spring.factories文件，会指定一些Configuration类。Spring Boot启动时会扫描spring.factories文件，然后创建里面的配置类。

在spring.pactories文件中，与注册相关的类就是：NacosServiceRegistryAutoConfiguration这个Nacos服务注册自动配置类。

Nacos服务注册自动配置类NacosServiceRegistryAutoConfiguration如下，该配置类创建了三个Bean：

第一个Bean：NacosServiceRegistry
这个Bean在创建时，会传入加载了yml配置文件内容的类NacosDiscoveryProperties。

第二个Bean：NacosRegistration
这个Bean在创建时，会传入加载了yml配置文件内容的类NacosDiscoveryProperties。

第三个Bean：NacosAutoServiceRegistration
这个Bean在创建时，会传入NacosServiceRegistry和NacosRegistration两个Bean，然后该Bean继承了AbstractAutoServiceRegistration抽象类。该抽象类实现了ApplicationListener接口，所以项目启动时便是利用了Spring的监听事件来实现自动注册服务的。因为在Spring容器启动的最后会执行finishRefresh()方法，然后会发布一个事件，该事件会触发调用onApplicationEvent()方法。

调用AbstractAutoServiceRegistration的onApplicationEvent()方法时，首先会调用AbstractAutoServiceRegistration的bind()方法，然后调用AbstractAutoServiceRegistration的start()方法，接着调用AbstractAutoServiceRegistration的register()方法发起注册，也就是调用this.serviceRegistry的register()方法完成服务注册的具体工作。

而AbstractAutoServiceRegistration的serviceRegistry属性，是在服务注册自动配置类NacosServiceRegistryAutoConfiguration，创建第三个Bean—NacosAutoServiceRegistration时，通过传入其创建的第一个Bean—NacosServiceRegistry进行赋值的。

@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);
}
}
public class NacosAutoServiceRegistration extends AbstractAutoServiceRegistration<Registration> {
...
private NacosRegistration registration;
public NacosAutoServiceRegistration(ServiceRegistry<Registration> serviceRegistry,
AutoServiceRegistrationProperties autoServiceRegistrationProperties,
NacosRegistration registration) {
super(serviceRegistry, autoServiceRegistrationProperties);
this.registration = registration;
}
...
}
public abstract class AbstractAutoServiceRegistration<R extends Registration>
implements AutoServiceRegistration, ApplicationContextAware, ApplicationListener<WebServerInitializedEvent> {
...
private final ServiceRegistry<R> serviceRegistry;
private AutoServiceRegistrationProperties properties;
protected AbstractAutoServiceRegistration(ServiceRegistry<R> serviceRegistry, AutoServiceRegistrationProperties properties) {
this.serviceRegistry = serviceRegistry;
this.properties = properties;
}
...
@Override
@SuppressWarnings("deprecation")
public void onApplicationEvent(WebServerInitializedEvent event) {
bind(event);
}
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());
this.start();
}
public void start() {
if (!isEnabled()) {
if (logger.isDebugEnabled()) {
logger.debug("Discovery Lifecycle disabled. Not starting");
}
return;
}
if (!this.running.get()) {
this.context.publishEvent(new InstancePreRegisteredEvent(this, getRegistration()));
//发起注册
register();
if (shouldRegisterManagement()) {
registerManagement();
}
this.context.publishEvent(new InstanceRegisteredEvent<>(this, getConfiguration()));
this.running.compareAndSet(false, true);
}
}
protected void register() {
//调用创建NacosAutoServiceRegistration时传入的NacosServiceRegistry实例的register()方法
this.serviceRegistry.register(getRegistration());
}
...
}
public class NacosServiceRegistry implements ServiceRegistry<Registration> {
private final NacosDiscoveryProperties nacosDiscoveryProperties;
public NacosServiceRegistry(NacosDiscoveryProperties nacosDiscoveryProperties) {
this.nacosDiscoveryProperties = nacosDiscoveryProperties;
}
@Override
public void register(Registration registration) {
if (StringUtils.isEmpty(registration.getServiceId())) {
log.warn("No service to register for nacos client...");
return;
}
NamingService namingService = namingService();
//获取服务ID、分组
String serviceId = registration.getServiceId();
String group = nacosDiscoveryProperties.getGroup();
//创建Instance对象
Instance instance = getNacosInstanceFromRegistration(registration);
try {
//发起服务实例注册
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);
}
}
}
...
}

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总结：
Nacos客户端项目启动时自动触发注册服务实例的流程：Spring监听器调用onApplicationEvent() -> bind() -> start() -> register()，最后register()方法会调用serviceRegistry属性的register()方法进行注册。

整个流程具体来说就是：首先通过spring.factories文件，找到一个注册相关的Configuration配置类，这个配置类里面定义了三个Bean对象。创建第三个Bean对象时，需要第一个、第二个Bean对象作为参数传进去。第一个Bean对象里面就有真正进行服务注册的register()方法，并且第一个Bean对象会赋值给第三个Bean对象中的serviceRegistry属性，在第三个Bean对象的父类会实现Spring的监听器方法。所以在Spring容器启动时会发布监听事件，从而触发执行Nacos注册逻辑。

(3)Nacos客户端通过gRPC方式发起服务实例注册
nacos-client会提供接口给Nacos客户端调用来进行服务实例注册。

在NacosNamingService提供的服务注册接口registerInstance()中，会调用NamingClientProxyDelegate的registerService()方法来注册服务。此时会先调用NamingClientProxyDelegate的getExecuteClientProxy()方法，来判断要注册的服务实例是否为临时实例来获取gRPC代理还是HTTP代理。如果注册的是临时实例，则使用gRPC方式注册，否则用HTTP方式注册，然后再调用NamingGrpcClientProxy的registerService()方法注册服务。

在NamingGrpcClientProxy的registerService()方法中，则会调用NamingGrpcClientProxy的doRegisterService()方法执行注册。此时先根据要注册的服务信息创建一个InstanceRequest请求参数对象，然后调用NamingGrpcClientProxy的requestToServer()方法发出请求，也就是通过调用RpcClient的request()方法向Nacos服务端发出gRPC请求。

至于RpcClient的request()方法的底层实现，则是通过一个本地存根代理类grpcFutureServiceStub调用gRPC的接口，来实现向Nacos服务端发起RPC调用的。

//Nacos Naming Service.
@SuppressWarnings("PMD.ServiceOrDaoClassShouldEndWithImplRule")
public class NacosNamingService implements NamingService {
...
private NamingClientProxy clientProxy;
private void init(Properties properties) throws NacosException {
...
//初始化clientProxy属性为NamingClientProxyDelegate对象实例
this.clientProxy = new NamingClientProxyDelegate(this.namespace, serviceInfoHolder, properties, changeNotifier);
}
//register a instance to service with specified instance properties.
@Override
public void registerInstance(String serviceName, String groupName, Instance instance) throws NacosException {
NamingUtils.checkInstanceIsLegal(instance);
//调用NamingClientProxy的注册方法registerService()，其实就是NamingClientProxyDelegate.registerService()方法
clientProxy.registerService(serviceName, groupName, instance);
}
...
}
//Delegate of naming client proxy.
public class NamingClientProxyDelegate implements NamingClientProxy {
private final NamingHttpClientProxy httpClientProxy;
private final NamingGrpcClientProxy grpcClientProxy;
public NamingClientProxyDelegate(String namespace, ServiceInfoHolder serviceInfoHolder, Properties properties, InstancesChangeNotifier changeNotifier) throws NacosException {
...
this.httpClientProxy = new NamingHttpClientProxy(namespace, securityProxy, serverListManager, properties, serviceInfoHolder);
this.grpcClientProxy = new NamingGrpcClientProxy(namespace, securityProxy, serverListManager, properties, serviceInfoHolder);
}
...
@Override
public void registerService(String serviceName, String groupName, Instance instance) throws NacosException {
getExecuteClientProxy(instance).registerService(serviceName, groupName, instance);
}
private NamingClientProxy getExecuteClientProxy(Instance instance) {
return instance.isEphemeral() ? grpcClientProxy : httpClientProxy;
}
...
}
//Naming grpc client proxy.
public class NamingGrpcClientProxy extends AbstractNamingClientProxy {
private final String namespaceId;
private final String uuid;
private final Long requestTimeout;
private final RpcClient rpcClient;
private final NamingGrpcRedoService redoService;
public NamingGrpcClientProxy(String namespaceId, SecurityProxy securityProxy, ServerListFactory serverListFactory, Properties properties, ServiceInfoHolder serviceInfoHolder) throws NacosException {
super(securityProxy);
this.namespaceId = namespaceId;
this.uuid = UUID.randomUUID().toString();
this.requestTimeout = Long.parseLong(properties.getProperty(CommonParams.NAMING_REQUEST_TIMEOUT, "-1"));
Map<String, String> labels = new HashMap<String, String>();
labels.put(RemoteConstants.LABEL_SOURCE, RemoteConstants.LABEL_SOURCE_SDK);
labels.put(RemoteConstants.LABEL_MODULE, RemoteConstants.LABEL_MODULE_NAMING);
//通过RpcClientFactory.createClient()方法创建一个GrpcSdkClient对象实例，然后赋值给rpcClient属性
this.rpcClient = RpcClientFactory.createClient(uuid, ConnectionType.GRPC, labels);
this.redoService = new NamingGrpcRedoService(this);
start(serverListFactory, serviceInfoHolder);
}
private void start(ServerListFactory serverListFactory, ServiceInfoHolder serviceInfoHolder) throws NacosException {
rpcClient.serverListFactory(serverListFactory);
rpcClient.registerConnectionListener(redoService);
rpcClient.registerServerRequestHandler(new NamingPushRequestHandler(serviceInfoHolder));
//调用RpcClient.start()方法建立与服务端的连接
rpcClient.start();
NotifyCenter.registerSubscriber(this);
}
...
//Register a instance to service with specified instance properties.
@Override
public void registerService(String serviceName, String groupName, Instance instance) throws NacosException {
NAMING_LOGGER.info("[REGISTER-SERVICE] {} registering service {} with instance {}", namespaceId, serviceName, instance);
redoService.cacheInstanceForRedo(serviceName, groupName, instance);
//执行服务实例的注册
doRegisterService(serviceName, groupName, instance);
}
//Execute register operation.
public void doRegisterService(String serviceName, String groupName, Instance instance) throws NacosException {
//创建请求参数对象InstanceRequest
InstanceRequest request = new InstanceRequest(namespaceId, serviceName, groupName, NamingRemoteConstants.REGISTER_INSTANCE, instance);
//向服务端发起请求
requestToServer(request, Response.class);
redoService.instanceRegistered(serviceName, groupName);
}
private <T extends Response> T requestToServer(AbstractNamingRequest request, Class<T> responseClass) throws NacosException {
try {
request.putAllHeader(getSecurityHeaders(request.getNamespace(), request.getGroupName(), request.getServiceName()));
//实际会调用RpcClient.request()方法发起gRPC请求
Response response = requestTimeout < 0 ? rpcClient.request(request) : rpcClient.request(request, requestTimeout);
if (ResponseCode.SUCCESS.getCode() != response.getResultCode()) {
throw new NacosException(response.getErrorCode(), response.getMessage());
}
if (responseClass.isAssignableFrom(response.getClass())) {
return (T) response;
}
NAMING_LOGGER.error("Server return unexpected response '{}', expected response should be '{}'", response.getClass().getName(), responseClass.getName());
} catch (Exception e) {
throw new NacosException(NacosException.SERVER_ERROR, "Request nacos server failed: ", e);
}
throw new NacosException(NacosException.SERVER_ERROR, "Server return invalid response");
}
...
}
//abstract remote client to connect to server.
@SuppressWarnings("PMD.AbstractClassShouldStartWithAbstractNamingRule")
public abstract class RpcClient implements Closeable {
protected volatile Connection currentConnection;
...
public final void start() throws NacosException {
...
// connect to server, try to connect to server sync RETRY_TIMES times, async starting if failed.
Connection connectToServer = null;
rpcClientStatus.set(RpcClientStatus.STARTING);
int startUpRetryTimes = RETRY_TIMES;
while (startUpRetryTimes > 0 && connectToServer == null) {
try {
startUpRetryTimes--;
ServerInfo serverInfo = nextRpcServer();
LoggerUtils.printIfInfoEnabled(LOGGER, "[{}] Try to connect to server on start up, server: {}", name, serverInfo);
//调用GrpcClient.connectToServer()方法建立和服务端的长连接
connectToServer = connectToServer(serverInfo);
} catch (Throwable e) {
LoggerUtils.printIfWarnEnabled(LOGGER, "[{}] Fail to connect to server on start up, error message = {}, start up retry times left: {}", name, e.getMessage(), startUpRetryTimes);
}
}
if (connectToServer != null) {
LoggerUtils.printIfInfoEnabled(LOGGER, "[{}] Success to connect to server [{}] on start up, connectionId = {}", name, connectToServer.serverInfo.getAddress(), connectToServer.getConnectionId());
//currentConnection其实就是一个用于客户端的GrpcConnection对象实例
this.currentConnection = connectToServer;
rpcClientStatus.set(RpcClientStatus.RUNNING);
eventLinkedBlockingQueue.offer(new ConnectionEvent(ConnectionEvent.CONNECTED));
} else {
switchServerAsync();
}
...
}
//connect to server.
public abstract Connection connectToServer(ServerInfo serverInfo) throws Exception;
...
//send request.
public Response request(Request request) throws NacosException {
return request(request, DEFAULT_TIMEOUT_MILLS);
}
//send request.
public Response request(Request request, long timeoutMills) throws NacosException {
int retryTimes = 0;
Response response;
Exception exceptionThrow = null;
long start = System.currentTimeMillis();
while (retryTimes < RETRY_TIMES && System.currentTimeMillis() < timeoutMills + start) {
boolean waitReconnect = false;
try {
if (this.currentConnection == null || !isRunning()) {
waitReconnect = true;
throw new NacosException(NacosException.CLIENT_DISCONNECT, "Client not connected, current status:" + rpcClientStatus.get());
}
//发起gRPC请求，调用GrpcConnection.request()方法
response = this.currentConnection.request(request, timeoutMills);
if (response == null) {
throw new NacosException(SERVER_ERROR, "Unknown Exception.");
}
if (response instanceof ErrorResponse) {
if (response.getErrorCode() == NacosException.UN_REGISTER) {
synchronized (this) {
waitReconnect = true;
if (rpcClientStatus.compareAndSet(RpcClientStatus.RUNNING, RpcClientStatus.UNHEALTHY)) {
LoggerUtils.printIfErrorEnabled(LOGGER, "Connection is unregistered, switch server, connectionId = {}, request = {}", currentConnection.getConnectionId(), request.getClass().getSimpleName());
switchServerAsync();
}
}
}
throw new NacosException(response.getErrorCode(), response.getMessage());
}
//return response.
lastActiveTimeStamp = System.currentTimeMillis();
return response;
} catch (Exception e) {
if (waitReconnect) {
try {
//wait client to reconnect.
Thread.sleep(Math.min(100, timeoutMills / 3));
} catch (Exception exception) {
//Do nothing.
}
}
LoggerUtils.printIfErrorEnabled(LOGGER, "Send request fail, request = {}, retryTimes = {}, errorMessage = {}", request, retryTimes, e.getMessage());
exceptionThrow = e;
}
retryTimes++;
}
if (rpcClientStatus.compareAndSet(RpcClientStatus.RUNNING, RpcClientStatus.UNHEALTHY)) {
switchServerAsyncOnRequestFail();
}
if (exceptionThrow != null) {
throw (exceptionThrow instanceof NacosException) ? (NacosException) exceptionThrow : new NacosException(SERVER_ERROR, exceptionThrow);
} else {
throw new NacosException(SERVER_ERROR, "Request fail, unknown Error");
}
}
...
}
//gRPC connection.
public class GrpcConnection extends Connection {
//stub to send request.
//grpcFutureServiceStub属性会在NamingGrpcClientProxy初始化 -> 调用RpcClient.start() -> GrpcClient.connectToServer()时，
//通过GrpcConnection.setGrpcFutureServiceStub()方法进行设置
protected RequestGrpc.RequestFutureStub grpcFutureServiceStub;
...
@Override
public Response request(Request request, long timeouts) throws NacosException {
Payload grpcRequest = GrpcUtils.convert(request);
//调用gRPC提供的接口发起请求，属于io.grpc包下的内容了
ListenableFuture<Payload> requestFuture = grpcFutureServiceStub.request(grpcRequest);
Payload grpcResponse;
try {
grpcResponse = requestFuture.get(timeouts, TimeUnit.MILLISECONDS);
} catch (Exception e) {
throw new NacosException(NacosException.SERVER_ERROR, e);
}
return (Response) GrpcUtils.parse(grpcResponse);
}
...
}

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(4)总结

3.服务端进行服务注册时的处理
(1)服务端处理客户端发起的服务注册请求
(2)服务端对客户端注册事件的处理源码
(3)总结

(1)服务端处理客户端发起的服务注册请求
客户端向服务端发起服务注册时，会先根据要注册的服务信息来创建一个InstanceRequest请求参数对象，再调用NamingGrpcClientProxy的requestToServer()方法向服务端发请求，也就是通过调用RpcClient的request()方法来向服务端发出gRPC请求。

InstanceRequestHandler的handle()方法就是用来处理服务注册请求的，该方法会继续调用InstanceRequestHandler的registerInstance()方法，根据客户端发过来的请求类型来选择是注册服务还是注销服务。

如果客户端发过来的请求类型是注册服务实例，则调用EphemeralClientOperationServiceImpl的registerInstance()方法，在该方法中：

一.首先会调用ServiceManager的getSingleton()方法
根据由请求信息创建的Service对象获取一个已注册的Service对象。

需要注意：在Nacos 1.x中，ServiceManager使用一个双层Map存放服务和命名空间。在Nacos 2.x中，ServiceManager则使用两个Map存放服务和命名空间。

在Nacos 1.x中的双层Map是：
Map<String, Map<String, Service>>；
例如Map(namespace, Map(group::serviceName, Service))；
在Nacos 2.x中的两个Map是：
ConcurrentHashMap<Service, Service>、
ConcurrentHashMap<String_namespace, Set<Service>>；

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二.然后调用ClientManagerDelegate的getClient()方法
根据请求参数中的connectionId来获取一个IpPortBasedClient对象。在执行ClientManagerDelegate的getClient()方法时，会先根据connectionId选出具体的ClientManager实现类，接着再调用比如EphemeralIpPortClientManager的getClient()方法，从EphemeralIpPortClientManager.clients属性中获取一个Client对象。clients属性是一个ConcurrentMap，key是请求参数中的connectionId，value是继承了实现Client接口的AbstractClient的IpPortBasedClient对象。

需要注意：Nacos中的gRPC底层是基于Netty实现的。当客户端和服务端建立长连接后，服务端会生成SocketChannel连接对象，这个SocketChannel连接对象就代表了客户端。Nacos会在这个SocketChannel连接对象的基础上，封装一个Client对象，并且生成一个connectionId将SocketChannel对象与Client对象关联起来。

所以当要进行服务注册的客户端和服务端建立好长连接后，服务端就会为客户端创建一个IpPortBasedClient对象，并将该对象存放在EphemeralIpPortClientManager.clients属性里。

三.接着调用ClientOperationService的getPublishInfo()方法
将请求中的instance实例信息封装为InstancePublishInfo对象。

四.然后调用IpPortBasedClient对象的addServiceInstance()方法
往IpPortBasedClient对象里添加Service对象 -> InstancePublishInfo对象。

由于IpPortBasedClient继承自实现了Client接口的AbstractClient抽象类，所以实际是调用AbstractClient的addServiceInstance()方法添加服务实例。

在AbstractClient抽象类中，有一个名为publishers的属性。它是一个ConcurrentHashMap，用于存储客户端服务注册请求中的Instance信息。就是记录该客户端提供的服务和服务实例，一个客户端可提供多个服务，当然这些信息已经被封装为InstancePublishInfo对象了。所以AbstractClient.publishers属性的key为已注册的Service，value是根据请求中的Instance实例信息封装的InstancePublishInfo对象。

在AbstractClient的addServiceInstance()方法中，首先往publishers放入这次要注册的Service对象和客户端Instance实例，然后发布客户端改变事件ClientChangedEvent，用来同步集群间的数据。

五.最后发布客户端注册服务实例事件和服务实例元数据事件
客户端注册服务实例事件是ClientRegisterServiceEvent，服务实例元数据事件是InstanceMetadataEvent。

//Instance request handler.
@Component
public class InstanceRequestHandler extends RequestHandler<InstanceRequest, InstanceResponse> {
private final EphemeralClientOperationServiceImpl clientOperationService;
public InstanceRequestHandler(EphemeralClientOperationServiceImpl clientOperationService) {
this.clientOperationService = clientOperationService;
}
@Override
@Secured(action = ActionTypes.WRITE)
public InstanceResponse handle(InstanceRequest request, RequestMeta meta) throws NacosException {
//根据请求信息创建一个Service对象，里面包含了：命名空间、分组名、服务名
Service service = Service.newService(request.getNamespace(), request.getGroupName(), request.getServiceName(), true);
switch (request.getType()) {
case NamingRemoteConstants.REGISTER_INSTANCE:
//注册实例
return registerInstance(service, request, meta);
case NamingRemoteConstants.DE_REGISTER_INSTANCE:
//注销实例
return deregisterInstance(service, request, meta);
default:
throw new NacosException(NacosException.INVALID_PARAM, String.format("Unsupported request type %s", request.getType()));
}
}
private InstanceResponse registerInstance(Service service, InstanceRequest request, RequestMeta meta) {
//调用EphemeralClientOperationServiceImpl的注册方法registerInstance()，这里需要注意如下参数；
//参数service：根据请求信息创建的一个Service对象，里面有命名空间、分组名、服务名
//参数request.getInstance()：这个参数就对应了客户端的实例对象，里面包含IP、端口等信息
//参数meta.getConnectionId()：这个参数很关键，它是连接ID
clientOperationService.registerInstance(service, request.getInstance(), meta.getConnectionId());
return new InstanceResponse(NamingRemoteConstants.REGISTER_INSTANCE);
}
private InstanceResponse deregisterInstance(Service service, InstanceRequest request, RequestMeta meta) {
//调用EphemeralClientOperationServiceImpl的注销方法deregisterInstance()
clientOperationService.deregisterInstance(service, request.getInstance(), meta.getConnectionId());
return new InstanceResponse(NamingRemoteConstants.DE_REGISTER_INSTANCE);
}
}
//Operation service for ephemeral clients and services.
@Component("ephemeralClientOperationService")
public class EphemeralClientOperationServiceImpl implements ClientOperationService {
private final ClientManager clientManager;
public EphemeralClientOperationServiceImpl(ClientManagerDelegate clientManager) {
this.clientManager = clientManager;
}
@Override
public void registerInstance(Service service, Instance instance, String clientId) {
//1.从ServiceManager中根据由请求信息创建的Service对象获取一个已注册的Service对象
Service singleton = ServiceManager.getInstance().getSingleton(service);
if (!singleton.isEphemeral()) {
throw new NacosRuntimeException(NacosException.INVALID_PARAM, String.format("Current service %s is persistent service, can't register ephemeral instance.", singleton.getGroupedServiceName()));
}
//2.从ClientManagerDelegate中根据请求参数中的connectionId获取一个Client对象，即IpPortBasedClient对象
Client client = clientManager.getClient(clientId);
if (!clientIsLegal(client, clientId)) {
return;
}
//3.将请求中的instance实例信息封装为InstancePublishInfo对象
InstancePublishInfo instanceInfo = getPublishInfo(instance);
//4.往Client对象里添加已注册的服务对象Service，调用的是IpPortBasedClient对象的父类AbstractClient的addServiceInstance()方法
client.addServiceInstance(singleton, instanceInfo);
//设置IpPortBasedClient对象的lastUpdatedTime属性为最新时间
client.setLastUpdatedTime();
//5.发布客户端注册服务实例的事件
NotifyCenter.publishEvent(new ClientOperationEvent.ClientRegisterServiceEvent(singleton, clientId));
//5.发布服务实例元数据的事件
NotifyCenter.publishEvent(new MetadataEvent.InstanceMetadataEvent(singleton, instanceInfo.getMetadataId(), false));
}
...
}
public interface ClientOperationService {
...
//get publish info.
default InstancePublishInfo getPublishInfo(Instance instance) {
InstancePublishInfo result = new InstancePublishInfo(instance.getIp(), instance.getPort());
Map<String, Object> extendDatum = result.getExtendDatum();
if (null != instance.getMetadata() && !instance.getMetadata().isEmpty()) {
extendDatum.putAll(instance.getMetadata());
}
if (StringUtils.isNotEmpty(instance.getInstanceId())) {
extendDatum.put(Constants.CUSTOM_INSTANCE_ID, instance.getInstanceId());
}
if (Constants.DEFAULT_INSTANCE_WEIGHT != instance.getWeight()) {
extendDatum.put(Constants.PUBLISH_INSTANCE_WEIGHT, instance.getWeight());
}
if (!instance.isEnabled()) {
extendDatum.put(Constants.PUBLISH_INSTANCE_ENABLE, instance.isEnabled());
}
String clusterName = StringUtils.isBlank(instance.getClusterName()) ? UtilsAndCommons.DEFAULT_CLUSTER_NAME : instance.getClusterName();
result.setHealthy(instance.isHealthy());
result.setCluster(clusterName);
return result;
}
}
//Nacos service manager for v2.
public class ServiceManager {
private static final ServiceManager INSTANCE = new ServiceManager();
//key是根据请求参数创建的Service对象，value是已经注册的Service对象
private final ConcurrentHashMap<Service, Service> singletonRepository;
//key是命名空间，value是相同命名空间的已注册的Service对象集合
private final ConcurrentHashMap<String, Set<Service>> namespaceSingletonMaps;
private ServiceManager() {
singletonRepository = new ConcurrentHashMap<>(1 << 10);
namespaceSingletonMaps = new ConcurrentHashMap<>(1 << 2);
}
public static ServiceManager getInstance() {
return INSTANCE;
}
public Set<Service> getSingletons(String namespace) {
return namespaceSingletonMaps.getOrDefault(namespace, new HashSet<>(1));
}
//Get singleton service. Put to manager if no singleton.
//@param service new service
//@return if service is exist, return exist service, otherwise return new service
public Service getSingleton(Service service) {
//往singletonRepository这个ConcurrentHashMap中添加一个Service对象，如果存在就不添加
singletonRepository.putIfAbsent(service, service);
//从这个ConcurrentHashMap中把已注册的Service对象取出来
Service result = singletonRepository.get(service);
//将已注册的Service对象添加到namespaceSingletonMaps中
//由于namespaceSingletonMaps会按命名空间对已注册的Service对象进行分类
//所以namespaceSingletonMaps的key是命名空间，value是相同命名空间的已注册的Service对象集合
namespaceSingletonMaps.computeIfAbsent(result.getNamespace(), (namespace) -> new ConcurrentHashSet<>());
namespaceSingletonMaps.get(result.getNamespace()).add(result);
return result;
}
...
}
//Client manager delegate.
@Component("clientManager")
public class ClientManagerDelegate implements ClientManager {
private final ConnectionBasedClientManager connectionBasedClientManager;
private final EphemeralIpPortClientManager ephemeralIpPortClientManager;
private final PersistentIpPortClientManager persistentIpPortClientManager;
public ClientManagerDelegate(ConnectionBasedClientManager connectionBasedClientManager, EphemeralIpPortClientManager ephemeralIpPortClientManager, PersistentIpPortClientManager persistentIpPortClientManager) {
this.connectionBasedClientManager = connectionBasedClientManager;
this.ephemeralIpPortClientManager = ephemeralIpPortClientManager;
this.persistentIpPortClientManager = persistentIpPortClientManager;
}
...
@Override
public Client getClient(String clientId) {
//通过请求参数中的connectionId获取一个Client对象，比如调用EphemeralIpPortClientManager.getClient()方法
return getClientManagerById(clientId).getClient(clientId);
}
private ClientManager getClientManagerById(String clientId) {
if (isConnectionBasedClient(clientId)) {
return connectionBasedClientManager;
}
return clientId.endsWith(ClientConstants.PERSISTENT_SUFFIX) ? persistentIpPortClientManager : ephemeralIpPortClientManager;
}
...
}
//The manager of {@code IpPortBasedClient} and ephemeral.
@Component("ephemeralIpPortClientManager")
public class EphemeralIpPortClientManager implements ClientManager {
//key是请求参数中的connectionId即clientId，value是一个继承了实现Client接口的AbstractClient的IpPortBasedClient对象
private final ConcurrentMap<String, IpPortBasedClient> clients = new ConcurrentHashMap<>();
private final DistroMapper distroMapper;
private final ClientFactory<IpPortBasedClient> clientFactory;
public EphemeralIpPortClientManager(DistroMapper distroMapper, SwitchDomain switchDomain) {
this.distroMapper = distroMapper;
GlobalExecutor.scheduleExpiredClientCleaner(new ExpiredClientCleaner(this, switchDomain), 0, Constants.DEFAULT_HEART_BEAT_INTERVAL, TimeUnit.MILLISECONDS);
clientFactory = ClientFactoryHolder.getInstance().findClientFactory(ClientConstants.EPHEMERAL_IP_PORT);
}
@Override
public boolean clientConnected(String clientId, ClientAttributes attributes) {
return clientConnected(clientFactory.newClient(clientId, attributes));
}
@Override
public boolean clientConnected(final Client client) {
clients.computeIfAbsent(client.getClientId(), s -> {
Loggers.SRV_LOG.info("Client connection {} connect", client.getClientId());
IpPortBasedClient ipPortBasedClient = (IpPortBasedClient) client;
ipPortBasedClient.init();
return ipPortBasedClient;
});
return true;
}
@Override
public boolean syncClientConnected(String clientId, ClientAttributes attributes) {
return clientConnected(clientFactory.newSyncedClient(clientId, attributes));
}
@Override
public Client getClient(String clientId) {
//客户端和服务端建立长连接时，就会通过EphemeralIpPortClientManager.clientConnected()方法将clientId放入到clients
return clients.get(clientId);
}
...
}
public class IpPortBasedClient extends AbstractClient {
...
...
}
public abstract class AbstractClient implements Client {
//publishers其实就是记录该客户端提供的服务和服务实例，一个客户端可提供多个服务；
//存储客户端发送过来的请求中的Instance信息，当然这些信息已封装为InstancePublishInfo对象
//key为已注册的Service，value是根据请求中的Instance实例信息封装的InstancePublishInfo对象
protected final ConcurrentHashMap<Service, InstancePublishInfo> publishers = new ConcurrentHashMap<>(16, 0.75f, 1);
...
@Override
public boolean addServiceInstance(Service service, InstancePublishInfo instancePublishInfo) {
//服务注册时，如果是第一次put进去Service对象，会返回null
if (null == publishers.put(service, instancePublishInfo)) {
//监视器记录
MetricsMonitor.incrementInstanceCount();
}
//发布客户端改变事件ClientChangedEvent，用于处理集群间的数据同步
NotifyCenter.publishEvent(new ClientEvent.ClientChangedEvent(this));
Loggers.SRV_LOG.info("Client change for service {}, {}", service, getClientId());
return true;
}
...
}

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(2)服务端对客户端注册事件的处理源码
一.服务端处理客户端的服务注册请求时的主要工作
往三个ConcurrentHashMap里放入内容 + 发布三个事件。

三个ConcurrentHashMap分别是：第一个是ServiceManager中的，key是根据请求参数创建的Service对象，value是已经注册的Service对象。第二个是ServiceManager中的，key是命名空间，value是相同命名空间的已注册的Service对象集合。第三个是AbstractClient中的，key是注册的Service服务对象，value是根据请求中的Instance实例封装的InstancePublishInfo对象。

三个事件分别是：第一个是在AbstractClient的addServiceInstance()方法中，发布的ClientChangedEvent客户端改变事件。第二个是在EphemeralClientOperationService的registerInstance()方法中，发布的ClientRegisterServiceEvent客户端注册事件。第三个是在EphemeralClientOperationService的registerInstance()方法中，发布的InstanceMetadataEvent服务实例元数据事件。

二.服务端对客户端注册事件ClientRegisterServiceEvent的处理
当执行EphemeralClientOperationService的registerInstance()方法，发布一个ClientRegisterServiceEvent客户端注册事件时，便会触发执行ClientServiceIndexesManager的onEvent()方法，然后执行ClientServiceIndexesManager的handleClientOperation()方法，最终调用ClientServiceIndexesManager的addPublisherIndexes()方法。

其中addPublisherIndexes()方法会把clientId放入到publisherIndexes中。publisherIndexes是一个ConcurrentMap，它的key是要注册的服务实例所属的服务Service对象，它的value是某服务Service对象下的所有clientId即connectionId。由于connectionId代表了一个Client对象，也就是一个客户端，所以publisherIndexes的value可理解为服务Service下的所有客户端实例。

//Client and service index manager.
@Component
public class ClientServiceIndexesManager extends SmartSubscriber {
//注册表(服务提供者)，一个Service服务对象，对应多个服务实例的clientId
private final ConcurrentMap<Service, Set<String>> publisherIndexes = new ConcurrentHashMap<>();
...
//可以处理客户端注册事件ClientRegisterServiceEvent
@Override
public void onEvent(Event event) {
if (event instanceof ClientEvent.ClientDisconnectEvent) {
handleClientDisconnect((ClientEvent.ClientDisconnectEvent) event);
} else if (event instanceof ClientOperationEvent) {
handleClientOperation((ClientOperationEvent) event);
}
}
private void handleClientOperation(ClientOperationEvent event) {
Service service = event.getService();
String clientId = event.getClientId();
if (event instanceof ClientOperationEvent.ClientRegisterServiceEvent) {
//处理客户端注册事件ClientRegisterServiceEvent
addPublisherIndexes(service, clientId);
} else if (event instanceof ClientOperationEvent.ClientDeregisterServiceEvent) {
//处理客户端注销事件ClientDeregisterServiceEvent
removePublisherIndexes(service, clientId);
} else if (event instanceof ClientOperationEvent.ClientSubscribeServiceEvent) {
//处理客户端订阅服务事件ClientSubscribeServiceEvent
addSubscriberIndexes(service, clientId);
} else if (event instanceof ClientOperationEvent.ClientUnsubscribeServiceEvent) {
//处理客户端取消订阅事件ClientUnsubscribeServiceEvent
removeSubscriberIndexes(service, clientId);
}
}
private void addPublisherIndexes(Service service, String clientId) {
//判断注册表是否存在该Service，不存在则创建一个空的ConcurrentHashSet
publisherIndexes.computeIfAbsent(service, (key) -> new ConcurrentHashSet<>());
//把clientId放入到对应的Service中
publisherIndexes.get(service).add(clientId);
//发布服务改变事件
NotifyCenter.publishEvent(new ServiceEvent.ServiceChangedEvent(service, true));
}
...
}

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(3)总结
服务端处理服务实例注册时，会使用多个Map来存储微服务实例的信息。在注册表也就是ClientServiceIndexesManager.publisherIndexes属性中，只是简单记录每个Service服务对象下包含的clientId字符串集合。通过clientId可以在clients属性中获取到IpPortBasedClient对象，IpPortBasedClient的父类AbstractClient会存储对应的Instance实例信息，所以这样的注册表是可记录每个Service服务包含的所有Instance实例的。

4.客户端服务发现和服务端处理服务订阅的源码分析
(1)Nacos客户端进行服务发现的源码
(2)Nacos服务端处理服务订阅请求的源码

(1)Nacos客户端进行服务发现的源码
一.nacos-discovery引入Ribbon实现服务调用时的负载均衡
二.nacos-discovery如何整合Ribbon实现服务调用时的负载均衡
三.nacos-client如何进行服务发现

一.nacos-discovery引入Ribbon实现服务调用时的负载均衡
Nacos客户端就是引入了nacos-discovery + nacos-client依赖的项目。由于nacos-discovery整合了Ribbon，所以Ribbon可以调用Nacos服务端的服务实例查询列表接口。于是Nacos客户端便借助Ribbon实现了服务调用时的负载均衡，即Ribbon会从服务实例列表中选择一个服务实例给客户端进行服务调用。

在nacos-discovery的pom.xml中，可以看到它引入了Ribbon依赖：

二.nacos-discovery如何整合Ribbon实现服务调用时的负载均衡
在Ribbon中会有一个ServerList接口，如下所示：ServerList就是一个扩展接口，这个接口的作用就是获取Server列表。然后nacos-discovery会针对这个接口进行实现，从而整合Ribbon。

从引入的包来看，loadbalancer是属于Ribbon源码包下的。而LoadBalancer则是Ribbon中的负载均衡器。负载均衡器会结合IRule负载均衡策略，从服务实例列表中选择一个实例。

package com.netflix.loadbalancer;
import java.util.List;
//Interface that defines the methods sed to obtain the List of Servers
public interface ServerList<T extends Server> {
public List<T> getInitialListOfServers();
//Return updated list of servers. This is called say every 30 secs
public List<T> getUpdatedListOfServers();
}

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当Nacos客户端进行微服务调用时，会通过Ribbon来选出一个服务实例，此时Ribbon会调用NacosServerList的getUpdatedListOfServers()方法获取服务实例列表。

nacos-discovery的NacosServerList类继承了AbstractServerList类，而且实现了Ribbon的ServerList接口的两个方法，如下所示：

public abstract class AbstractServerList<T extends Server> implements ServerList<T>, IClientConfigAware {
...
...
}
public class NacosServerList extends AbstractServerList<NacosServer> {
private NacosDiscoveryProperties discoveryProperties;
private String serviceId;
public NacosServerList(NacosDiscoveryProperties discoveryProperties) {
this.discoveryProperties = discoveryProperties;
}
@Override
public List<NacosServer> getInitialListOfServers() {
return getServers();
}
@Override
public List<NacosServer> getUpdatedListOfServers() {
return getServers();
}
private List<NacosServer> getServers() {
try {
//读取分组
String group = discoveryProperties.getGroup();
//通过服务名称、分组、true(表示只需要健康实例)，
//调用NacosNamingService.selectInstances()方法来查询服务实例列表
List<Instance> instances = discoveryProperties.namingServiceInstance().selectInstances(serviceId, group, true);
//把Instance转换成NacosServer类型
return instancesToServerList(instances);
} catch (Exception e) {
throw new IllegalStateException("Can not get service instances from nacos, serviceId=" + serviceId, e);
}
}
private List<NacosServer> instancesToServerList(List<Instance> instances) {
List<NacosServer> result = new ArrayList<>();
if (CollectionUtils.isEmpty(instances)) {
return result;
}
for (Instance instance : instances) {
result.add(new NacosServer(instance));
}
return result;
}
public String getServiceId() {
return serviceId;
}
@Override
public void initWithNiwsConfig(IClientConfig iClientConfig) {
this.serviceId = iClientConfig.getClientName();
}
}

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NacosServerList的核心方法是getServers()，因为nacos-discovery实现Ribbon的两个接口都调用到了该方法。

在nacos-discovery的NacosServerList的getServers()方法中，会调用nacos-client的NacosNamingService的selectInstances()方法，来获取服务实例列表。

三.nacos-client如何进行服务发现
在nacos-client的NacosNamingService的selectInstances()方法中，首先会调用ServiceInfoHolder的getServiceInfo()方法从本地缓存获取数据。ServiceInfoHolder的serviceInfoMap中的value是一个ServiceInfo对象，在ServiceInfo对象中会有一个Listhosts属性来存放实例数据。

如果ServiceInfoHolder中的本地缓存没有对应的ServiceInfo对象，那么就会调用NamingClientProxyDelegate的subscribe()方法。该方法首先会开启一个查询服务实例列表的延时执行的任务，然后通过Client对象发送订阅请求，去服务端实时获取服务实例数据。

具体来说就是先调用ServiceInfoUpdateService的scheduleUpdateIfAbsent()方法，开启一个延迟执行查询服务实例列表的UpdateTask任务，然后再次调用ServiceInfoHolder的getServiceInfoMap()方法查询本地缓存。如果本地缓存为空，则向服务端发起gRPC请求获取服务实例数据，也就是通过调用NamingGrpcClientProxy的subscribe()方法，触发调用NamingGrpcClientProxy的doSubscribe()方法，再触发调用NamingGrpcClientProxy的requestToServer()方法，接着调用RpcClient的request()方法发送gRPC请求给服务端，最后调用ServiceInfoHolder的processServiceInfo()方法更新本地缓存。

public class NacosNamingService implements NamingService {
private ServiceInfoHolder serviceInfoHolder;
private NamingClientProxy clientProxy;
...
private void init(Properties properties) throws NacosException {
...
this.serviceInfoHolder = new ServiceInfoHolder(namespace, properties);
this.clientProxy = new NamingClientProxyDelegate(this.namespace, serviceInfoHolder, properties, changeNotifier);
}
@Override
public List<Instance> selectInstances(String serviceName, String groupName, List<String> clusters, boolean healthy, boolean subscribe) throws NacosException {
ServiceInfo serviceInfo;
String clusterString = StringUtils.join(clusters, ",");
//判断是否需要订阅，默认为true
if (subscribe) {
//查询Nacos本地缓存数据
serviceInfo = serviceInfoHolder.getServiceInfo(serviceName, groupName, clusterString);
if (null == serviceInfo) {
//如果本地缓存数据为空，则调用Client代理NamingClientProxyDelegate的订阅方法subscribe()，通过Client对象请求服务端获取数据
serviceInfo = clientProxy.subscribe(serviceName, groupName, clusterString);
}
} else {
serviceInfo = clientProxy.queryInstancesOfService(serviceName, groupName, clusterString, 0, false);
}
//返回数据
return selectInstances(serviceInfo, healthy);
}
...
}
//Naming client service information holder.
public class ServiceInfoHolder implements Closeable {
private final ConcurrentMap<String, ServiceInfo> serviceInfoMap;
...
public ServiceInfo getServiceInfo(final String serviceName, final String groupName, final String clusters) {
NAMING_LOGGER.debug("failover-mode: {}", failoverReactor.isFailoverSwitch());
//获取key
String groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName);
String key = ServiceInfo.getKey(groupedServiceName, clusters);
if (failoverReactor.isFailoverSwitch()) {
return failoverReactor.getService(key);
}
//通过key从本地缓存中获取数据
return serviceInfoMap.get(key);
}
...
}
public class NamingClientProxyDelegate implements NamingClientProxy {
private final ServiceInfoUpdateService serviceInfoUpdateService;
private final ServiceInfoHolder serviceInfoHolder;
private final NamingGrpcClientProxy grpcClientProxy;
...
public NamingClientProxyDelegate(String namespace, ServiceInfoHolder serviceInfoHolder, Properties properties, InstancesChangeNotifier changeNotifier) throws NacosException {
...
this.serviceInfoUpdateService = new ServiceInfoUpdateService(properties, serviceInfoHolder, this, changeNotifier);
this.serviceInfoHolder = serviceInfoHolder;
this.grpcClientProxy = new NamingGrpcClientProxy(namespace, securityProxy, serverListManager, properties, serviceInfoHolder);
}
...
@Override
public ServiceInfo subscribe(String serviceName, String groupName, String clusters) throws NacosException {
NAMING_LOGGER.info("[SUBSCRIBE-SERVICE] service:{}, group:{}, clusters:{} ", serviceName, groupName, clusters);
String serviceNameWithGroup = NamingUtils.getGroupedName(serviceName, groupName);
String serviceKey = ServiceInfo.getKey(serviceNameWithGroup, clusters);
//1.调用ServiceInfoUpdateService.scheduleUpdateIfAbsent()方法开启一个查询服务实例列表的定时任务
serviceInfoUpdateService.scheduleUpdateIfAbsent(serviceName, groupName, clusters);
//再次查询本地的缓存数据
ServiceInfo result = serviceInfoHolder.getServiceInfoMap().get(serviceKey);
if (null == result || !isSubscribed(serviceName, groupName, clusters)) {
//2.如果本地缓存还是为空，则使用gRPC来请求服务端，也就是调用NamingGrpcClientProxy.subscribe()方法
result = grpcClientProxy.subscribe(serviceName, groupName, clusters);
}
//更新本地缓存
serviceInfoHolder.processServiceInfo(result);
return result;
}
...
}
public class NamingGrpcClientProxy extends AbstractNamingClientProxy {
...
private final RpcClient rpcClient;
private final NamingGrpcRedoService redoService;
public NamingGrpcClientProxy(String namespaceId, SecurityProxy securityProxy, ServerListFactory serverListFactory, Properties properties, ServiceInfoHolder serviceInfoHolder) throws NacosException {
...
//通过RpcClientFactory.createClient()方法创建一个GrpcSdkClient对象实例，然后赋值给rpcClient属性
this.rpcClient = RpcClientFactory.createClient(uuid, ConnectionType.GRPC, labels);
this.redoService = new NamingGrpcRedoService(this);
start(serverListFactory, serviceInfoHolder);
}
private void start(ServerListFactory serverListFactory, ServiceInfoHolder serviceInfoHolder) throws NacosException {
rpcClient.serverListFactory(serverListFactory);
rpcClient.registerConnectionListener(redoService);
rpcClient.registerServerRequestHandler(new NamingPushRequestHandler(serviceInfoHolder));
rpcClient.start();
NotifyCenter.registerSubscriber(this);
}
...
@Override
public ServiceInfo subscribe(String serviceName, String groupName, String clusters) throws NacosException {
if (NAMING_LOGGER.isDebugEnabled()) {
NAMING_LOGGER.debug("[GRPC-SUBSCRIBE] service:{}, group:{}, cluster:{} ", serviceName, groupName, clusters);
}
redoService.cacheSubscriberForRedo(serviceName, groupName, clusters);
//执行订阅
return doSubscribe(serviceName, groupName, clusters);
}
//Execute subscribe operation.
public ServiceInfo doSubscribe(String serviceName, String groupName, String clusters) throws NacosException {
//构建订阅服务请求——SubscribeServiceRequest对象
SubscribeServiceRequest request = new SubscribeServiceRequest(namespaceId, groupName, serviceName, clusters, true);
//向服务端发送SubscribeServiceRequest类型的请求
SubscribeServiceResponse response = requestToServer(request, SubscribeServiceResponse.class);
redoService.subscriberRegistered(serviceName, groupName, clusters);
return response.getServiceInfo();
}
private <T extends Response> T requestToServer(AbstractNamingRequest request, Class<T> responseClass) throws NacosException {
try {
request.putAllHeader(getSecurityHeaders(request.getNamespace(), request.getGroupName(), request.getServiceName()));
//实际会调用RpcClient.request()方法发起gRPC请求
Response response = requestTimeout < 0 ? rpcClient.request(request) : rpcClient.request(request, requestTimeout);
if (ResponseCode.SUCCESS.getCode() != response.getResultCode()) {
throw new NacosException(response.getErrorCode(), response.getMessage());
}
if (responseClass.isAssignableFrom(response.getClass())) {
return (T) response;
}
NAMING_LOGGER.error("Server return unexpected response '{}', expected response should be '{}'", response.getClass().getName(), responseClass.getName());
} catch (Exception e) {
throw new NacosException(NacosException.SERVER_ERROR, "Request nacos server failed: ", e);
}
throw new NacosException(NacosException.SERVER_ERROR, "Server return invalid response");
}
...
}

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其中UpdateTask任务的run()方法会先调用NamingClientProxy.queryInstancesOfService()方法，然后调用ServiceInfoHolder的processServiceInfo()方法向服务端查询服务实例列表以及更新本地服务实例缓存。当该任务执行完毕时，会继续向调度线程池提交一个延迟6s执行的任务，从而实现不断更新本地缓存的服务实例列表。

在ServiceInfoHolder的processServiceInfo()方法更新本地服务实例缓存中，会判断服务实例是否发生改变。如果有改变，那么客户端会先发布一个服务实例改变事件InstancesChangeEvent，然后把新的服务实例数据写入本地磁盘。

public class ServiceInfoUpdateService implements Closeable {
private final NamingClientProxy namingClientProxy;
private final Map<String, ScheduledFuture<?>> futureMap = new HashMap<String, ScheduledFuture<?>>();
...
//Schedule update if absent.
public void scheduleUpdateIfAbsent(String serviceName, String groupName, String clusters) {
//生成一个serverKey
String serviceKey = ServiceInfo.getKey(NamingUtils.getGroupedName(serviceName, groupName), clusters);
//判断当前serviceKey是否已经开启了对应的定时任务，如果已经开启就不开启了
if (futureMap.get(serviceKey) != null) {
return;
}
//加一把同步锁，避免并发冲突
synchronized (futureMap) {
//加锁之后再进行一次判断，双重检测Double Check
if (futureMap.get(serviceKey) != null) {
return;
}
//添加UpdateTask任务到executor延迟执行
ScheduledFuture<?> future = addTask(new UpdateTask(serviceName, groupName, clusters));
futureMap.put(serviceKey, future);
}
}
private synchronized ScheduledFuture<?> addTask(UpdateTask task) {
return executor.schedule(task, DEFAULT_DELAY, TimeUnit.MILLISECONDS);
}
...
public class UpdateTask implements Runnable {
long lastRefTime = Long.MAX_VALUE;
private boolean isCancel;
private final String serviceName;
private final String groupName;
private final String clusters;
private final String groupedServiceName;
private final String serviceKey;
//the fail situation. 1:can't connect to server 2:serviceInfo's hosts is empty
private int failCount = 0;
public UpdateTask(String serviceName, String groupName, String clusters) {
this.serviceName = serviceName;
this.groupName = groupName;
this.clusters = clusters;
this.groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName);
this.serviceKey = ServiceInfo.getKey(groupedServiceName, clusters);
}
@Override
public void run() {
long delayTime = DEFAULT_DELAY;
try {
if (!changeNotifier.isSubscribed(groupName, serviceName, clusters) && !futureMap.containsKey(serviceKey)) {
NAMING_LOGGER.info("update task is stopped, service:{}, clusters:{}", groupedServiceName, clusters);
isCancel = true;
return;
}
//获取本地缓存
ServiceInfo serviceObj = serviceInfoHolder.getServiceInfoMap().get(serviceKey);
if (serviceObj == null) {
//如果本地缓存为空，则通过gRPC去查询服务端的服务实例数据
serviceObj = namingClientProxy.queryInstancesOfService(serviceName, groupName, clusters, 0, false);
//更新本地缓存
serviceInfoHolder.processServiceInfo(serviceObj);
//更新UpdateTask的lastRefTime属性，即更新UpdateTask任务的数据获取时间
lastRefTime = serviceObj.getLastRefTime();
return;
}
//如果本地缓存不为空，则判断本地缓存最后一次刷新时间是否小于等于最后一次UpdateTask任务的数据获取时间
if (serviceObj.getLastRefTime() <= lastRefTime) {
//如果小于等于，则重新查询服务端的服务实例数据
serviceObj = namingClientProxy.queryInstancesOfService(serviceName, groupName, clusters, 0, false);
//更新本地缓存
serviceInfoHolder.processServiceInfo(serviceObj);
}
lastRefTime = serviceObj.getLastRefTime();
if (CollectionUtils.isEmpty(serviceObj.getHosts())) {
incFailCount();
return;
}
//TODO multiple time can be configured.
//计算下一次定时任务执行的时间，这个时间默认是6s
delayTime = serviceObj.getCacheMillis() * DEFAULT_UPDATE_CACHE_TIME_MULTIPLE;
//请求成功后，重置错误次数为0
resetFailCount();
} catch (Throwable e) {
//记录请求失败的次数
incFailCount();
NAMING_LOGGER.warn("[NA] failed to update serviceName: {}", groupedServiceName, e);
} finally {
if (!isCancel) {
//根据请求失败的次数，动态调整重新提交的UpdateTask定时任务的执行时间
executor.schedule(this, Math.min(delayTime << failCount, DEFAULT_DELAY * 60), TimeUnit.MILLISECONDS);
}
}
}
private void incFailCount() {
int limit = 6;
if (failCount == limit) {
return;
}
failCount++;
}
private void resetFailCount() {
failCount = 0;
}
}
...
}
//Naming client service information holder.
public class ServiceInfoHolder implements Closeable {
private final ConcurrentMap<String, ServiceInfo> serviceInfoMap;
...
//Process service info.
public ServiceInfo processServiceInfo(ServiceInfo serviceInfo) {
String serviceKey = serviceInfo.getKey();
if (serviceKey == null) {
return null;
}
//获取本地缓存中的服务实例
ServiceInfo oldService = serviceInfoMap.get(serviceInfo.getKey());
if (isEmptyOrErrorPush(serviceInfo)) {
return oldService;
}
//更新本地缓存中的服务实例
serviceInfoMap.put(serviceInfo.getKey(), serviceInfo);
//判断服务实例是否有改变
boolean changed = isChangedServiceInfo(oldService, serviceInfo);
if (StringUtils.isBlank(serviceInfo.getJsonFromServer())) {
serviceInfo.setJsonFromServer(JacksonUtils.toJson(serviceInfo));
}
MetricsMonitor.getServiceInfoMapSizeMonitor().set(serviceInfoMap.size());
if (changed) {
NAMING_LOGGER.info("current ips:({}) service: {} -> {}", serviceInfo.ipCount(), serviceInfo.getKey(), JacksonUtils.toJson(serviceInfo.getHosts()));
//发布服务实例改变事件
NotifyCenter.publishEvent(new InstancesChangeEvent(serviceInfo.getName(), serviceInfo.getGroupName(), serviceInfo.getClusters(), serviceInfo.getHosts()));
//将服务实例信息写入本地磁盘
DiskCache.write(serviceInfo, cacheDir);
}
return serviceInfo;
}
...
}

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ServiceStorage的getData()方法在读取缓存时，获取要查询的Service服务对象下的全部Instance实例会分三步：一是从注册表中获取要查询的Service对象下的全部clientId，二是根据clientId获取对应的Client对象，三是根据Client对象获取对应的Instance信息。

//Handler to handle subscribe service.
@Component
public class SubscribeServiceRequestHandler extends RequestHandler<SubscribeServiceRequest, SubscribeServiceResponse> {
private final ServiceStorage serviceStorage;
private final EphemeralClientOperationServiceImpl clientOperationService;
...
//假设order-service需要调用stock-service的接口，那么order-service(Nacos客户端)就要向服务端订阅stock-service服务
//也就是order-service需要从服务端获取到(查询出)stock-service的所有服务实例
@Override
@Secured(action = ActionTypes.READ)
public SubscribeServiceResponse handle(SubscribeServiceRequest request, RequestMeta meta) throws NacosException {
String namespaceId = request.getNamespace();
String serviceName = request.getServiceName();
String groupName = request.getGroupName();
String app = request.getHeader("app", "unknown");
String groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName);
//构建要查询的Service服务对象，对应的是stock-serivce
Service service = Service.newService(namespaceId, groupName, serviceName, true);
//构建要订阅Service服务的订阅者，对应的是order-service
Subscriber subscriber = new Subscriber(meta.getClientIp(), meta.getClientVersion(), app, meta.getClientIp(), namespaceId, groupedServiceName, 0, request.getClusters());
//1.调用ServiceStorage.getData()方法读取缓存
ServiceInfo serviceInfo = ServiceUtil.selectInstancesWithHealthyProtection(serviceStorage.getData(service), metadataManager.getServiceMetadata(service).orElse(null), subscriber);
if (request.isSubscribe()) {
//2.添加订阅者，如果订阅的服务有变动，则需要通知订阅者
clientOperationService.subscribeService(service, subscriber, meta.getConnectionId());
} else {
clientOperationService.unsubscribeService(service, subscriber, meta.getConnectionId());
}
return new SubscribeServiceResponse(ResponseCode.SUCCESS.getCode(), "success", serviceInfo);
}
}

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二.添加订阅者即Subscriber对象
调用的方法是EphemeralClientOperationServiceImpl.subscribeService()，添加订阅者其实就是先根据clientId找出对应的客户端Client对象，然后往AbstractClient.subscribers属性放入服务对象和对应的订阅者对象，最后再发布一个客户端订阅服务事件ClientSubscribeServiceEvent。

这个事件会被ClientServiceIndexesManager的onEvent()方法处理，即调用ClientServiceIndexesManager的addSubscriberIndexes()方法，该方法会继续发布一个服务订阅事件ServiceSubscribedEvent。

-> serviceDataIndexes.get()
-> ServiceStorage.getPushData()方法
-> ServiceStorage.emptyServiceInfo()方法
-> ServiceStorage.getAllInstancesFromIndex()方法
-> ClientServiceIndexesManager.getAllClientsRegisteredService()方法
-> ServiceStorage.getInstanceInfo()方法根据clientId获取Instance对象
-> EphemeralIpPortClientManager.getClient()方法
-> AbstractClient.getInstancePublishInfo()方法
-> ServiceStorage.parseInstance()方法
-> serviceDataIndexes.put() + serviceClusterIndex.put()

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(3)总结

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Nacos源码—6.Nacos升级gRPC分析一

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