[GitHub] [dubbo] zrlw commented on a change in pull request #8701: [3.0] fix urlInvokerMap concurrent access issue

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

zrlw commented on a change in pull request #8701:
URL: https://github.com/apache/dubbo/pull/8701#discussion_r712651258



##########
File path: dubbo-registry/dubbo-registry-api/src/main/java/org/apache/dubbo/registry/integration/RegistryDirectory.java
##########
@@ -222,7 +223,14 @@ private void refreshInvoker(List<URL> invokerUrls) {
             if (invokerUrls.isEmpty()) {
                 return;
             }
-            Map<URL, Invoker<T>> newUrlInvokerMap = toInvokers(invokerUrls);// Translate url list to Invoker map
+            
+            // can't use local reference because this.urlInvokerMap might be accessed at isAvailable() by main thread concurrently.
+            Map<URL, Invoker<T>> oldUrlInvokerMap = null;
+            if (this.urlInvokerMap != null) {
+                oldUrlInvokerMap = new LinkedHashMap<>(this.urlInvokerMap.size());

Review comment:
       do you mean setting the initial capacity greater than the maximum number of entries divided by the load factor (default: 0.75) to avoid rehash operations?




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