[GitHub] [pulsar] merlimat commented on a change in pull request #10180: Use AtomicIntegerFieldUpdater to mutate volatile int totalAvailablePermits in PersistentDispatcherMultipleConsumers class

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merlimat commented on a change in pull request #10180:
URL: https://github.com/apache/pulsar/pull/10180#discussion_r610736439



##########
File path: pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java
##########
@@ -184,7 +184,7 @@ public synchronized void removeConsumer(Consumer consumer) throws BrokerServiceE
                     messagesToRedeliver.add(ledgerId, entryId);
                     redeliveryTracker.addIfAbsent(PositionImpl.get(ledgerId, entryId));
                 });
-                totalAvailablePermits -= consumer.getAvailablePermits();
+                TOTAL_AVAILABLE_PERMITS_UPDATER.addAndGet(this, -consumer.getAvailablePermits());

Review comment:
       The increments/decrement on the `totalAvailablePermits` should already be safe because they're all done while holding the mutex on the dispatcher object.

##########
File path: pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentDispatcherMultipleConsumers.java
##########
@@ -175,7 +175,7 @@ public synchronized void removeConsumer(Consumer consumer) throws BrokerServiceE
                     log.info("[{}] All consumers removed. Subscription is disconnected", name);
                     closeFuture.complete(null);
                 }
-                totalAvailablePermits = 0;
+                TOTAL_AVAILABLE_PERMITS_UPDATER.set(this, 0);

Review comment:
       This would be equivalent to `totalAvailablePermits = 0` 




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