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Date: Wed, 21 Nov 2007 06:05:27 -0800 (PST)
From: "Rainer Klute (JIRA)" <jira@apache.org>
To: dev@activemq.apache.org
Subject: [jira] Commented: (AMQ-1490) Deadlocks (with JUnit tests)
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    [ https://issues.apache.org/activemq/browse/AMQ-1490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_40677 ] 

Rainer Klute commented on AMQ-1490:
-----------------------------------

Just tried the stuff with a TCP transport instead of a VM transport: No substantial change except for the places where the deadlocks occur.

> Deadlocks (with JUnit tests)
> ----------------------------
>
>                 Key: AMQ-1490
>                 URL: https://issues.apache.org/activemq/browse/AMQ-1490
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 5.0.0
>         Environment: Linux
>            Reporter: Rainer Klute
>            Assignee: Rob Davies
>             Fix For: 5.0.0
>
>         Attachments: ActiveMQ_Testcases.jar, ActiveMQ_Testcases.jar, ActiveMQ_Testcases.jar
>
>
> For some time now there have been various bug reports about ActiveMQ "blocking", "not receiving messages", "running into a deadlock" etc. Since I encoutered such deadlocks now and then, too, I eventually wrote up a JUnit testing scenario for this stuff. I found out that deadlocks can be quite easily reproduced. The symptoms are that the producer thread is sending or committing while the consumer thread is receiving or committing - and none of them can advance. One of the threads is always stuck in a blocking queue.
> Here's a sample output of my testing class:
>  An ActiveMQ deadlock has been discovered. The following threads seem to be involved:
>  Thread "producer" is inactive since 16 seconds after 358719 status changes. The current status is COMMITTING
>  sun.misc.Unsafe.park(Native Method)
>  java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)
>   java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:1889)
>  java.util.concurrent.ArrayBlockingQueue.take(ArrayBlockingQueue.java:317)
>  org.apache.activemq.transport.FutureResponse.getResult(FutureResponse.java:40)
>  org.apache.activemq.transport.ResponseCorrelator.request(ResponseCorrelator.java:76)
>  org.apache.activemq.ActiveMQConnection.syncSendPacket(ActiveMQConnection.java:1172)
>  org.apache.activemq.TransactionContext.commit(TransactionContext.java:259)
>  org.apache.activemq.ActiveMQSession.commit(ActiveMQSession.java:494)
>  de.rainer_klute.activemq.ProducerThread.run(ProducerThread.java:162)
>  Thread "consumer" is inactive since 16 seconds after 1807 status changes. The current status is RECEIVING
>  java.lang.Object.wait(Native Method)
>  java.lang.Object.wait(Object.java:485)
>  org.apache.activemq.MessageDispatchChannel.dequeue(MessageDispatchChannel.java:75)
>  org.apache.activemq.ActiveMQMessageConsumer.dequeue(ActiveMQMessageConsumer.java:404)
>  org.apache.activemq.ActiveMQMessageConsumer.receive(ActiveMQMessageConsumer.java:452)
>  org.apache.activemq.ActiveMQMessageConsumer.receive(ActiveMQMessageConsumer.java:504)
>  de.rainer_klute.activemq.ConsumerThread.run(ConsumerThread.java:183)
> The following factors seem to increase the probability of a deadlock:
> * small values for memoryUsage
> * working transacted in the consumer (not always necessary but "helps")
> * many messages in the persistence store (to be achieved via a long delay before the consumer starts to read messages)

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