Deadlock when unsubscribing durable subscriber

[ouwenbelg <fr...@gmail.com>]

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)




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Re: Deadlock when unsubscribing durable subscriber

[tlammens <ti...@gmail.com>]

I've created an issue for this with a patch attached:
https://issues.apache.org/jira/browse/AMQ-4351



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