在同一个进程的多个NamingService的发布-订阅没有相互隔离

[liqipeng]

Describe the bug
nacos-client版本：1.4.3
在使用Dubbo框架进行注册中心迁移处理从一个nacos-server迁移至另一个nacos-server时，服务的消费方采用了双订阅的方式进行迁移，但是在迁移的过程中两个Registry会相互影响。
分析发现由于nacos-client的事件通知在不同NamingService实例之间没有隔离，如下场景的两个订阅会相互影响：

String serviceName = "serviceName1";
NamingService namingService1 = NamingFactory.createNamingService("nacos-server1");
NamingService namingService2 = NamingFactory.createNamingService("nacos-server2");

namingService1.subscribe(serviceName, new EventListener() {
    @Override
    public void onEvent(Event event) {

    }
});
namingService2.subscribe(serviceName, new EventListener() {
    @Override
    public void onEvent(Event event) {

    }
});
// 当两个server任意一边有通知时，这两个订阅都会收到通知

nacos-client源码：

    public HostReactor(NamingProxy serverProxy, BeatReactor beatReactor, String cacheDir, boolean loadCacheAtStart,
            boolean pushEmptyProtection, int pollingThreadCount) {
        // ..........
        NotifyCenter.registerToPublisher(InstancesChangeEvent.class, 16384);
        NotifyCenter.registerSubscriber(notifier);
    }

可以看到HostReactor里的发布订阅并没有处理不同 HostReactor 的隔离。

[liqipeng]

bug复现：（详见测试subscribeSameServiceForTwoNamingService : liqipeng@64dc1de ）

        naming1.subscribe(serviceName, new EventListener() {
            @Override
            public void onEvent(Event event) {
                System.out.println("Event from naming1: " + ((NamingEvent) event).getServiceName());
                System.out.println("Event from naming1: " + ((NamingEvent) event).getInstances());
                instances = ((NamingEvent) event).getInstances();
            }
        });
        naming2.subscribe(serviceName, new EventListener() {
            @Override
            public void onEvent(Event event) {
                System.out.println("Event from naming2: " + ((NamingEvent) event).getServiceName());
                System.out.println("Event from naming2: " + ((NamingEvent) event).getInstances());
                atomicInteger.incrementAndGet();
            }
        });
    
        naming1.registerInstance(serviceName, "1.1.1.1", TEST_PORT, "c1");

输出日志：

Event from naming1: DEFAULT_GROUP@@jinhanT06Yu.eRoX3.net
Event from naming1: [Instance{instanceId='1.1.1.1#8080#c1#DEFAULT_GROUP@@jinhanT06Yu.eRoX3.net', ip='1.1.1.1', port=8080, weight=1.0, healthy=true, enabled=true, ephemeral=true, clusterName='c1', serviceName='DEFAULT_GROUP@@jinhanT06Yu.eRoX3.net', metadata={}}]
Event from naming2: DEFAULT_GROUP@@jinhanT06Yu.eRoX3.net
Event from naming2: [Instance{instanceId='1.1.1.1#8080#c1#DEFAULT_GROUP@@jinhanT06Yu.eRoX3.net', ip='1.1.1.1', port=8080, weight=1.0, healthy=true, enabled=true, ephemeral=true, clusterName='c1', serviceName='DEFAULT_GROUP@@jinhanT06Yu.eRoX3.net', metadata={}}]

通过日志可以看到，只有一个变更，但是两个NamingService都接收到了变更事件。

[KomachiSion]

Should we add an UUID to identity one Client(NamingService) ?

[liqipeng]

Should we add an UUID to identity one Client(NamingService) ?

在 #8433 进行了说明。