[GitHub] [pulsar] massakam commented on a change in pull request #10696: [broker] Fix issue where StackOverflowError occurs when trying to redeliver a large number of already acked messages

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massakam commented on a change in pull request #10696:
URL: https://github.com/apache/pulsar/pull/10696#discussion_r638971507



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File path: pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java
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@@ -248,7 +249,9 @@ public synchronized void readMoreEntries() {
                 // next entries as readCompletedEntries-callback was never called
                 if ((messagesToReplayNow.size() - deletedMessages.size()) == 0) {
                     havePendingReplayRead = false;
-                    readMoreEntries();
+                    // We should not call readMoreEntries() recursively in the same thread
+                    // as there is a risk of StackOverflowError
+                    topic.getBrokerService().executor().execute(() -> readMoreEntries());

Review comment:
       @eolivelli Those are difficult questions...
   
   Even now, if the message dispatch rate reaches the threshold, another thread can execute `readMoreEntries()` recursively after a certain period of time, so it seems to me that this change doesn't break the behavior of the dispatcher. However, there is no clear evidence for it.
   
   If anyone has any knowledge, I would like to hear opinions.
   
   https://github.com/apache/pulsar/blob/a6aed551026825ef2de6b1ac5916d17daf1af5c3/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java#L225
   https://github.com/apache/pulsar/blob/a6aed551026825ef2de6b1ac5916d17daf1af5c3/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java#L275-L308




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