[
https://issues.apache.org/jira/browse/AMQ-6775?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Fabian González updated AMQ-6775:
---------------------------------
Summary: Race condition makes messages queued in the session be delivered
before messages queued in consumers (was: Race condition makes messages queued
in the session be delivered before messages queued in )
> Race condition makes messages queued in the session be delivered before
> messages queued in consumers
> -----------------------------------------------------------------------------------------------------
>
> Key: AMQ-6775
> URL: https://issues.apache.org/jira/browse/AMQ-6775
> Project: ActiveMQ
> Issue Type: Bug
> Components: JMS client
> Affects Versions: 5.14.3, 5.16.0
> Reporter: Fabian González
> Labels: client
>
> I found this situacion in org.apache.activemq.ActiveMQSessionExecutor.iterate:
> As I understand, the idea is that if there are messages queued on the
> consumers they are delivered to the listeners and if that is not the case,
> you should dispatch the messages in the session:
> {code:java}
> public boolean iterate() {
> // Deliver any messages queued on the consumer to their listeners.
> for (ActiveMQMessageConsumer consumer : this.session.consumers) {
> if (consumer.iterate()) {
> return true;
> }
> }
> // No messages left queued on the listeners.. so now dispatch messages
> // queued on the session
> MessageDispatch message = messageQueue.dequeueNoWait();
> if (message == null) {
> return false;
> } else {
> dispatch(message);
> return !messageQueue.isEmpty();
> }
> }
> {code}
> Now I the following race condition arises:
> 1) thread A (ActiveMQ Session Task) invokes .ActiveMQSessionExecutor
> 2) When this part of the code is executed:
> {code:java}
> for (ActiveMQMessageConsumer consumer : this.session.consumers) {
> if (consumer.iterate()) {
> return true;
> }
> }
> {code}
> ActiveMQMessageConsumer.iterate is invoked. There are messages unconsumed in
> the consumer, but as unconsumedMessages is not started, a null is returned as
> if there were no messages queued.
> 3) Thread A is interrupted
> 4) Thread B (ActiveMQConnection[xx]Scheduler) invokes
> ActiveMQMessageConsumer.start, unconsumed messages are started.
> 5) Thread A continues to deliver the messages queued in the session (*notice
> that if thread B starts unconsumed messages before thread A which happens
> most of times the messages in the consumer queue would have been dispatched*
> 6) Thread A dispatch a message from the session when there are messages from
> the consumer pending.
> This race condition makes makes that in some cases a message which has been
> rollbacked and get queued in the consumer queued is processed *after* another
> message in the session consumer (which was enqueued after the former message).
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
