[GitHub] [pulsar] Jason918 commented on a change in pull request #14641: fix: fix ArrayIndexOutOfBoundsException when concurrent

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

Jason918 commented on a change in pull request #14641:
URL: https://github.com/apache/pulsar/pull/14641#discussion_r834899169



##########
File path: pulsar-broker/src/main/java/org/apache/pulsar/broker/service/AbstractDispatcherMultipleConsumers.java
##########
@@ -36,7 +37,7 @@
 
     protected final CopyOnWriteArrayList<Consumer> consumerList = new CopyOnWriteArrayList<>();
     protected final ObjectSet<Consumer> consumerSet = new ObjectHashSet<>();
-    protected volatile int currentConsumerRoundRobinIndex = 0;
+    protected volatile AtomicInteger currentConsumerRoundRobinIndex = new AtomicInteger(0);

Review comment:
       ```suggestion
       protected AtomicInteger currentConsumerRoundRobinIndex = new AtomicInteger(0);
   ```

##########
File path: pulsar-broker/src/main/java/org/apache/pulsar/broker/service/AbstractDispatcherMultipleConsumers.java
##########
@@ -119,26 +120,30 @@ public Consumer getNextConsumer() {
             return null;
         }
 
-        if (currentConsumerRoundRobinIndex >= consumerList.size()) {
-            currentConsumerRoundRobinIndex = 0;
+        // other thread will change consumerList
+        if (currentConsumerRoundRobinIndex.get() >= consumerList.size()) {
+            currentConsumerRoundRobinIndex.set(0);
         }
 
-        int currentRoundRobinConsumerPriority = consumerList.get(currentConsumerRoundRobinIndex).getPriorityLevel();
+        int currentRoundRobinConsumerPriority = consumerList.get(currentConsumerRoundRobinIndex.get())

Review comment:
       Still, there is race condition between Line 124 and Line 128, if `consumerList.size` decreases.




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