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Posted to dev@activemq.apache.org by "Gary Tully (JIRA)" <ji...@apache.org> on 2013/02/28 14:39:13 UTC
[jira] [Commented] (AMQ-4351) Deadlock when unsubscribing durable
subscriber
[ https://issues.apache.org/jira/browse/AMQ-4351?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13589535#comment-13589535 ]
Gary Tully commented on AMQ-4351:
---------------------------------
@Tim, thanks for the report and patch. Is there any chance you could provide a unit test that can demonstrate so that we can protect the change?
My suspicion is that the cleanup safety should not come down to sync on the consumers list, but should be handled at a higher level.
> 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: 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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