Dubbo cloud native

dubbo-registry/dubbo-registry-api/src/main/java/org/apache/dubbo/registry/client/ServiceDiscovery.java

@@ -23,6 +23,7 @@
 import org.apache.dubbo.common.utils.StringUtils;
 import org.apache.dubbo.event.EventDispatcher;
 import org.apache.dubbo.event.EventListener;
+import org.apache.dubbo.registry.NotifyListener;
 import org.apache.dubbo.registry.client.event.ServiceInstancesChangedEvent;
 import org.apache.dubbo.registry.client.event.listener.ServiceInstancesChangedListener;
 
@@ -198,16 +199,22 @@ default Map<String, Page<ServiceInstance>> getInstances(Iterable<String> service
     /**
      * Add an instance of {@link ServiceInstancesChangedListener} for specified service
      * <p>
-     * Default, the ServiceInstancesChangedListener will be {@link EventDispatcher#addEventListener(EventListener) added}
-     * into {@link EventDispatcher}
+     * Default, Current method will be invoked by {@link ServiceDiscoveryRegistry#subscribe(URL, NotifyListener)
+     * the ServiceDiscoveryRegistry on the subscription}, and it's mandatory to
+     * {@link EventDispatcher#addEventListener(EventListener) add} the {@link ServiceInstancesChangedListener} argument
+     * into {@link EventDispatcher} whether the subclass implements same approach or not, thus this method is used to
+     * trigger or adapt the vendor's change notification mechanism typically, like Zookeeper Watcher,
+     * Nacos EventListener. If the registry observes the change, It's suggested that the implementation could invoke
+     * {@link #dispatchServiceInstancesChangedEvent(String)} method or variants
      *
      * @param listener an instance of {@link ServiceInstancesChangedListener}
      * @throws NullPointerException
      * @throws IllegalArgumentException
+     * @see EventPublishingServiceDiscovery
+     * @see EventDispatcher
      */
     default void addServiceInstancesChangedListener(ServiceInstancesChangedListener listener)
             throws NullPointerException, IllegalArgumentException {
-        getDefaultExtension().addEventListener(listener);
     }
 
     /**

dubbo-registry/dubbo-registry-api/src/main/java/org/apache/dubbo/registry/client/ServiceDiscoveryRegistry.java

@@ -105,7 +105,7 @@ public class ServiceDiscoveryRegistry extends FailbackRegistry {
 
     private final WritableMetadataService writableMetadataService;
 
-    private final Set<String> listenedServices = new LinkedHashSet<>();
+    private final Set<String> registeredListeners = new LinkedHashSet<>();
 
     public ServiceDiscoveryRegistry(URL registryURL) {
         super(registryURL);
@@ -287,7 +287,7 @@ protected void subscribeURLs(URL url, NotifyListener listener, String serviceNam
         subscribeURLs(url, listener, serviceName, serviceInstances);
 
         // register ServiceInstancesChangedListener
-        registerServiceInstancesChangedListener(new ServiceInstancesChangedListener(serviceName) {
+        registerServiceInstancesChangedListener(url, new ServiceInstancesChangedListener(serviceName) {
 
             @Override
             public void onEvent(ServiceInstancesChangedEvent event) {
@@ -299,14 +299,20 @@ public void onEvent(ServiceInstancesChangedEvent event) {
     /**
      * Register the {@link ServiceInstancesChangedListener} If absent
      *
+     * @param url      {@link URL}
      * @param listener the {@link ServiceInstancesChangedListener}
      */
-    private void registerServiceInstancesChangedListener(ServiceInstancesChangedListener listener) {
-        if (listenedServices.add(listener.getServiceName())) {
+    private void registerServiceInstancesChangedListener(URL url, ServiceInstancesChangedListener listener) {
+        String listenerId = createListenerId(url, listener);
+        if (registeredListeners.add(listenerId)) {
             serviceDiscovery.addServiceInstancesChangedListener(listener);
         }
     }
 
+    private String createListenerId(URL url, ServiceInstancesChangedListener listener) {
+        return listener.getServiceName() + ":" + url.toString(VERSION_KEY, GROUP_KEY, PROTOCOL_KEY);
+    }
+
     protected void subscribeURLs(URL subscribedURL, NotifyListener listener, String serviceName,
                                  Collection<ServiceInstance> serviceInstances) {
 

dubbo-registry/dubbo-registry-api/src/main/java/org/apache/dubbo/registry/client/metadata/CompositeMetadataServiceURLBuilder.java

@@ -19,7 +19,6 @@
 import org.apache.dubbo.common.URL;
 import org.apache.dubbo.metadata.MetadataService;
 import org.apache.dubbo.registry.client.ServiceInstance;
-import org.apache.dubbo.registry.client.metadata.proxy.MetadataServiceProxy;
 
 import java.util.Iterator;
 import java.util.LinkedList;
@@ -34,10 +33,9 @@
 /**
  * The implementation of {@link MetadataServiceURLBuilder} composites the multiple {@link MetadataServiceURLBuilder}
  * instances are loaded by Java standard {@link ServiceLoader} will aggregate {@link URL URLs} for
- * {@link MetadataServiceProxy}
+ * {@link MetadataService}
  *
  * @see MetadataServiceURLBuilder
- * @see MetadataServiceProxy
  * @see MetadataService
  * @see URL
  * @see ServiceLoader