Nacos源码—7.Nacos升级gRPC分析三

大纲

5.服务变动时如何通知订阅的客户端

6.微服务实例信息如何同步集群节点

5.服务变动时如何通知订阅的客户端

(1)服务注册和服务订阅时发布的客户端注册和订阅事件的处理

(2)延迟任务的执行引擎源码

(3)处理客户端注册和订阅事件时发布的服务变动和服务订阅事件的处理

(1)服务注册和服务订阅时发布的客户端注册和订阅事件的处理

一.服务注册

Nacos客户端注册服务实例时，Nacos服务端会发布ClientRegisterServiceEvent客户端注册服务实例事件。Nacos服务端在处理客户端注册服务实例事件时，会把clientId写入到注册表，然后接着发布ServiceChangedEvent服务改变事件。

//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) {
        //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()));
        }
        //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;
        }
        //将请求中的instance实例信息封装为InstancePublishInfo对象
        InstancePublishInfo instanceInfo = getPublishInfo(instance);
        //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();
        //发布客户端注册服务实例的事件
        NotifyCenter.publishEvent(new ClientOperationEvent.ClientRegisterServiceEvent(singleton, clientId));
        //发布服务实例元数据的事件
        NotifyCenter.publishEvent(new MetadataEvent.InstanceMetadataEvent(singleton, instanceInfo.getMetadataId(), false));
    }
    ...
}

//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<>();
    ...
    //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));
    }
    ...
}

二.服务订阅

客户端查询微服务实例列表进行服务发现时，调用的是订阅接口。服务端处理客户端的订阅请求时会发布ClientSubscribeServiceEvent事件，这个事件的处理逻辑是先向订阅表添加clientId到所订阅服务对应的集合中，如果第一次添加clientId则发布一个ServiceSubscribedEvent服务订阅事件。

//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,