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From "SuoNayi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AMQ-4351) Deadlock when unsubscribing durable subscriber
Date Fri, 01 Mar 2013 03:55:13 GMT

    [ https://issues.apache.org/jira/browse/AMQ-4351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13590217#comment-13590217
] 

SuoNayi commented on AMQ-4351:
------------------------------

I'm interesting in the issue.It seems the thread stack does not reveal the deadlock threads
and the test is not an unit test as there are many special objects rather than pure AMQ objects.

                
> Deadlock when unsubscribing durable subscriber
> ----------------------------------------------
>
>                 Key: AMQ-4351
>                 URL: https://issues.apache.org/jira/browse/AMQ-4351
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 5.7.0, 5.8.0
>         Environment: Setup: 
> Active MQ 5.7.0 with master/slave using JDBC store 
> Approx 3 - 5 concurrent durable subscribers 
> Approx 5 messages / sec 
>            Reporter: Tim Lammens
>              Labels: patch
>         Attachments: ActiveMQUnsubscribeTest.java, dispatcher.patch
>
>
> We started using durable subscribers a week ago, and after the 4th durable subscriber
unsubscribed (due to 1 hour inactivity), the system deadlocked. If the "Durable Subscriber
Cleanup Timer" goes of at the wrong time, your entire server locks up. 
> Setup: 
> Active MQ 5.7.0 with master/slave using JDBC store 
> Approx 3 - 5 concurrent durable subscribers 
> Approx 5 messages / sec 
> Active MQ checks every 1 minute for subscribers which have been offline for 1 hour. 
> Locked threads: 
> "ActiveMQ Transport: tcp:///79.125.71.104:48082@8090": 
>         at org.apache.activemq.broker.region.Topic.doMessageSend(Topic.java:446) 
>         - waiting to lock <0x00000000c6228480> (a org.apache.activemq.broker.region.Topic)

>         at org.apache.activemq.broker.region.Topic.send(Topic.java:427) 
>         at org.apache.activemq.broker.region.AbstractRegion.send(AbstractRegion.java:407)

>         at org.apache.activemq.broker.region.RegionBroker.send(RegionBroker.java:503)

> "ActiveMQ Transport: tcp:///79.125.71.104:47590@8090": 
>         at org.apache.activemq.broker.region.PrefetchSubscription.add(PrefetchSubscription.java:142)

>         - waiting to lock <0x00000000c66ba050> (a java.lang.Object) 
>         at org.apache.activemq.broker.region.DurableTopicSubscription.add(DurableTopicSubscription.java:243)

>         at org.apache.activemq.broker.region.policy.StrictOrderDispatchPolicy.dispatch(StrictOrderDispatchPolicy.java:58)

> "ActiveMQ Durable Subscriber Cleanup Timer": 
>         at org.apache.activemq.broker.region.Topic.deactivate(Topic.java:288) 
>         - waiting to lock <0x00000000c6250670> (a java.util.concurrent.CopyOnWriteArrayList)

>         at org.apache.activemq.broker.region.DurableTopicSubscription.deactivate(DurableTopicSubscription.java:184)

>         - locked <0x00000000c66ba060> (a java.lang.Object) 
>         - locked <0x00000000c66ba050> (a java.lang.Object) 
>         at org.apache.activemq.broker.region.Topic.deleteSubscription(Topic.java:195)

>         at org.apache.activemq.broker.region.TopicRegion.removeSubscription(TopicRegion.java:199)

>         at org.apache.activemq.broker.region.TopicRegion.doCleanup(TopicRegion.java:99)

> I have attached a patch which fixes the problem.
> Since there is only one dispatch policy per Topic, synchronisation can happen on the
DispatchPolicy instead of on the consumers object which causes the deadlock.

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