[GitHub] [dubbo] wuwen5 edited a comment on pull request #8907: Nacos unsub support and RegistryDirectory destroy

[GitBox <gi...@apache.org>]

wuwen5 edited a comment on pull request #8907:
URL: https://github.com/apache/dubbo/pull/8907#issuecomment-958703542


   NacosRegistry 存在一个严重的内存泄露问题，在dubbo admin中出现，经过分析发现被这个pr解决了，建议2.7.x尽早发布一个release版本.
   
   ```
   private void subscribeEventListener(String serviceName, final URL url, final NotifyListener listener)
               throws NacosException {
           EventListener eventListener = event -> {
               if (event instanceof NamingEvent) {
                   NamingEvent e = (NamingEvent) event;
                   List<Instance> instances = e.getInstances();
   
   
                   if (isServiceNamesWithCompatibleMode(url)) {
                       /**
                        * Get all instances with corresponding serviceNames to avoid instance overwrite and but with empty instance mentioned
                        * in https://github.com/apache/dubbo/issues/5885 and https://github.com/apache/dubbo/issues/5899
                        */
                       NacosInstanceManageUtil.initOrRefreshServiceInstanceList(serviceName, instances);
                       instances = NacosInstanceManageUtil.getAllCorrespondingServiceInstanceList(serviceName);
                   }
   
                   notifySubscriber(url, listener, instances);
               }
           };
           namingService.subscribe(serviceName,
                   getUrl().getParameter(GROUP_KEY, Constants.DEFAULT_GROUP),
                   eventListener);
       }
   ```
   ```EventListener eventListener```实例会无限制存储到 nacos ```InstancesChangeNotifier#listenerMap```的ConcurrentHashSet中
   
   ```
   public class InstancesChangeNotifier extends Subscriber<InstancesChangeEvent> {
       
       private final Map<String, ConcurrentHashSet<EventListener>> listenerMap = new ConcurrentHashMap<String, ConcurrentHashSet<EventListener>>();
       
       private final Object lock = new Object();
       
       /**
        * register listener.
        *
        * @param serviceName combineServiceName, such as 'xxx@@xxx'
        * @param clusters    clusters, concat by ','. such as 'xxx,yyy'
        * @param listener    custom listener
        */
       public void registerListener(String serviceName, String clusters, EventListener listener) {
           String key = ServiceInfo.getKey(serviceName, clusters);
           ConcurrentHashSet<EventListener> eventListeners = listenerMap.get(key);
           if (eventListeners == null) {
               synchronized (lock) {
                   eventListeners = listenerMap.get(key);
                   if (eventListeners == null) {
                       eventListeners = new ConcurrentHashSet<EventListener>();
                       listenerMap.put(key, eventListeners);
                   }
               }
           }
           eventListeners.add(listener);
       }
   ...
   }
   ```
   
   ![E1E5323A-BF00-4F1D-96D3-E2A07374244B](https://user-images.githubusercontent.com/5037807/140021563-46587435-41d5-40b8-b8b5-fc49306d1242.png)
   
   ![884E8D77-67AB-417E-ABC4-7873057DDC74](https://user-images.githubusercontent.com/5037807/140021627-36c1e46a-386d-43d1-be2d-de08377567a9.png)
   
   ```
   One instance of "com.alibaba.nacos.client.naming.event.InstancesChangeNotifier" loaded by "org.springframework.boot.loader.LaunchedURLClassLoader @ 0x80000000" occupies 1,828,304,624 (94.09%) bytes. The memory is accumulated in one instance of "java.util.concurrent.ConcurrentHashMap$Node[]" loaded by "<system class loader>".
   
   Keywords
   java.util.concurrent.ConcurrentHashMap$Node[]
   com.alibaba.nacos.client.naming.event.InstancesChangeNotifier
   org.springframework.boot.loader.LaunchedURLClassLoader @ 0x80000000
   ```


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