AuroraTwinkle commented on code in PR #22861:
URL: https://github.com/apache/pulsar/pull/22861#discussion_r1634455525
##########
pulsar-client-api/src/main/java/org/apache/pulsar/client/api/ConsumerBuilder.java:
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@@ -283,6 +283,21 @@ public interface ConsumerBuilder<T> extends Cloneable {
*/
ConsumerBuilder<T> messageListener(MessageListener<T> messageListener);
+ /**
+ * Set the {@link ThreadPoolProvider} to be used for message listeners of
<b>current consumer</b>.
+ * <i>(default: use executor from PulsarClient,
+ * {@link
org.apache.pulsar.client.impl.PulsarClientImpl#externalExecutorProvider})</i>.
+ *
+ * <p>The listener thread pool is exclusively owned by current consumer
+ * that are using a "listener" model to get messages. For a given internal
consumer,
+ * the listener will always be invoked from the same thread, to ensure
ordering.
+ *
+ * <p> The user need to shut down the thread pool after closing the
consumer to avoid leaks.
+ * @param listenerThreadsProvider the threads provider of the consumer
message listener
+ * @return the consumer builder instance
+ */
+ ConsumerBuilder<T> listenerThreadsProvider(ThreadPoolProvider
listenerThreadsProvider);
Review Comment:
> It's possible that `java.util.concurrent.Executor` isn't optimal.
>
> Pulsar client executes Key_Shared subscriptions on different threads:
>
>
https://github.com/apache/pulsar/blob/fb80007a47deaadb82d0b1b1e4fcd6ca04c05c9c/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerBase.java#L1129-L1136
>
> I guess that's the reason why you have added the `ThreadPoolProvider`. To
simplify, I guess one possibility is to have an interface with an execute
method that provides the `Message` and the `Runnable`.
yeah, in the current Pulsar client versions, we needs to ensure that each
consumer's message listener is executed in the same thread to avoid lock
contention and ensure message order , so it cannot simply use
java.util.concurrent.Executor. And, I will simplify the interface later. Thanks
for your idea!
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