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https://issues.apache.org/activemq/browse/AMQ-1490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_40672
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Rainer Klute commented on AMQ-1490:
-----------------------------------
I did some further investigation and changed by JUnit test to use a
configurable number of producers and consumers. The good news is that it
demonstrates a bug with a very small amount of messages already. I one of the
test scenarios I have 2 producers. Each one sends 2 messages to a topic. The
single consumer should receive 4 messages. However, this fails depending on the
combination of whether the producers or the consumers or both operate
transacted or not. Increase the number of messages and other combinations fail.
(I'll check in the JUnit test soon.)
> 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
>
>
> 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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