[GitHub] [dubbo] FinalVersion commented on a change in pull request #8899: [master] Fix-#8506 MultipleRegistry remove duplicate URL

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

FinalVersion commented on a change in pull request #8899:
URL: https://github.com/apache/dubbo/pull/8899#discussion_r719005623



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File path: dubbo-registry/dubbo-registry-multiple/src/main/java/org/apache/dubbo/registry/multiple/MultipleRegistry.java
##########
@@ -205,14 +206,14 @@ public void unsubscribe(URL url, NotifyListener listener) {
 
     @Override
     public List<URL> lookup(URL url) {
-        List<URL> urls = new ArrayList<URL>();
+        List<URL> urls = new ArrayList<>();
         for (Registry registry : referenceRegistries.values()) {
             List<URL> tmpUrls = registry.lookup(url);
             if (!CollectionUtils.isEmpty(tmpUrls)) {
                 urls.addAll(tmpUrls);
             }
         }
-        return urls;
+        return urls.stream().distinct().collect(Collectors.toList());

Review comment:
       @wangchengming666 @AlbumenJ @pinxiong 
   这个实现可能有两个问题：
   1. 同一个实例在不同注册中心上的url可能有部分parameter是不同的，比如我们测试下来，同时注册nacos和zookeeper时，nacos比zookeeper的url多`path`，`protocol`，`category`三个parameter。用URL#equals比较仍然会有重复实例。
   2. 通过notify变更通知的时候也需要处理重复实例问题。
   
   https://github.com/apache/dubbo/pull/8508 已经处理了这两个问题，不过采用什么标准来判断两个url是否为同一个实例可能需要斟酌一下




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