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https://issues.apache.org/jira/browse/AMQ-4196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13509923#comment-13509923
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Christian Posta commented on AMQ-4196:
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@Arthur
{quote}
Only 1 dispatch thread for all Topics? Then what were all those leaked threads
we came across as one of the consequences of this consumer leak? We had threads
for every temporary topic and for every advisory destination.
{quote}
Yes, that's correct. There is a thread for the topic, but it's used for
dispatching messages that were set aside because of producer flow control when
sent with a producer window or sent synchronous. That's the only purpose for
that thread. It does not dispatch the messages in normal cases. Even in the PFC
case, it will not race because the Usage#usageMutex would allow the messages
waiting for space to fire first before any new messages are sent.
However, I agree to the extent that consumers to temporary destinations should
be tied to the life of the temporary destination (whether a network sub or real
sub). In other words, if somehow there is a consumer for a temp dest around
when the temp dest is being removed, then that consumer too should be removed.
I think Gary's patch will enforce this at the bridge level, but further
assurances should be fine.
> Race condition between removal of subscriptions and removal of destinations
> in a network of brokers
> ---------------------------------------------------------------------------------------------------
>
> Key: AMQ-4196
> URL: https://issues.apache.org/jira/browse/AMQ-4196
> Project: ActiveMQ
> Issue Type: Bug
> Components: Broker, Connector
> Affects Versions: 5.6.0, 5.7.0
> Reporter: Gary Tully
> Assignee: Gary Tully
> Labels: Temp, networkBridge
> Fix For: 5.8.0
>
>
> n a broker network like this: A <--> B <---> C
> Scenario:
> A producer to BrokerA creates a message, sets its replyTo header to a temp
> destination that it creates and listens on, then sends the message off to
> broker A. The message is demand forwarded to BrokerC because there is a
> consumer there that consumes the message and replies to the temp dest in the
> replyTo header.
> As the number of concurrent producers on BrokerA sending these messages
> increases, the subscription to the temp destination that was demand forwarded
> will not be cleaned up properly on BrokerC. The reason for this is the
> DemandForwardingBridge runs the remove consumer code in a separate thread.
> But if a "remove destination" advisory messages comes in, it will remove the
> destination from the AdvisoryBroker's destination map. So if this happens
> before the code for removeConsumer runs (in AdvisoryBroker), then the
> destination will not be in the destination map and the advisory for
> removeConsumer will not fire.
> The net result is a subscription leak in the network bridge on B & C
> The junit test shows two issues:
> 1) the subscriptions leaked when concurrent producers using request/reply and
> correctly closing the consumer and connection
> 2) all subscriptions leaked when using a single producer with request/reply
> and closing only the connection, and not the consumer explicitly
> Issue 2 is related to temp destinations only and is compounded by
> https://issues.apache.org/jira/browse/AMQ-3879
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