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From "Gary Tully (JIRA)" <j...@apache.org>
Subject [jira] [Created] (AMQ-4196) Race condition between removal of subscriptions and removal of destinations in a network of brokers
Date Thu, 29 Nov 2012 13:16:58 GMT
Gary Tully created AMQ-4196:
-------------------------------

             Summary: 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: 5.7.0, 5.6.0
            Reporter: Gary Tully
            Assignee: Gary Tully
             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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