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https://issues.apache.org/jira/browse/AMQ-6775?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Fabian González updated AMQ-6775:
---------------------------------
Description:
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 queued 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 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 back in the consumer is redelivered *after* another
message in the session consumer (which was enqueued after the former message).
was:
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 queued 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 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 back in the consumer is redelivered *after* another
message in the session consumer (which was enqueued after the former message).
> 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 queued 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 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 back in the consumer is redelivered *after* another
> message in the session consumer (which was enqueued after the former message).
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