[GitHub] [pulsar] eolivelli commented on a diff in pull request #16603: [enh] Broker - Shared subscription: run filters in a separate (per-subscription) thread (dispatcherDispatchMessagesInSubscriptionThread)

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

eolivelli commented on code in PR #16603:
URL: https://github.com/apache/pulsar/pull/16603#discussion_r921151871


##########
pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java:
##########
@@ -520,10 +521,19 @@ public synchronized void readEntriesComplete(List<Entry> entries, Object ctx) {
             log.debug("[{}] Distributing {} messages to {} consumers", name, entries.size(), consumerList.size());
         }
 
-        sendMessagesToConsumers(readType, entries);
+        if (serviceConfig.isDispatcherDispatchMessagesInSubscriptionThread()) {
+            // dispatch messages to a separate thread, but still in order for this subscription
+            // sendMessagesToConsumers is responsible for running broker-side filters
+            // that may be quite expensive
+            topic.getBrokerService().getTopicOrderedExecutor()
+                    .executeOrdered(name,
+                            safeRun(() -> sendMessagesToConsumers(readType, entries)));
+        } else {
+            sendMessagesToConsumers(readType, entries);
+        }
     }
 
-    protected void sendMessagesToConsumers(ReadType readType, List<Entry> entries) {
+    protected synchronized void sendMessagesToConsumers(ReadType readType, List<Entry> entries) {

Review Comment:
   sendMessagesToConsumers is usually called by readEntriesComplete, that is already  `synchronized`
   https://github.com/apache/pulsar/blob/019493dbcf8e86c9caff71a88adc03aed5b1fbc8/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java#L492
   
   the JVM is smart enough to understand that there is no need for extra work for `synchronized`



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