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From "Christopher L. Shannon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (AMQ-5712) Broker can deadlock when using queues while producers wait on disk space
Date Mon, 13 Apr 2015 18:17:12 GMT

    [ https://issues.apache.org/jira/browse/AMQ-5712?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14492775#comment-14492775
] 

Christopher L. Shannon commented on AMQ-5712:
---------------------------------------------

Great, thanks for your help and for taking a look this issue in detail as it is very important
to us and it is causing us a lot of problems.  I suspected my patch may not be the best solution
and would need some rework because when the tryAdd method times out with my patch nothing
is actually done with that message.  After returning false it just continues on and the message
gets lost as you pointed out.  However, I figured submitting something that at least demonstrated
the issue as well as a unit test where it is consistently reproducible would help get things
started towards finding the best solution to fix the issue permanently.

Chris

> Broker can deadlock when using queues while producers wait on disk space
> ------------------------------------------------------------------------
>
>                 Key: AMQ-5712
>                 URL: https://issues.apache.org/jira/browse/AMQ-5712
>             Project: ActiveMQ
>          Issue Type: Bug
>          Components: Broker
>    Affects Versions: 5.11.1
>            Reporter: Christopher L. Shannon
>
> I am experiencing a deadlock when using a Queue with non-persistent messages.  The queue
has a cursor high memory water mark set (right now at 70%).  When a producer is producing
messages quickly to the queue and that limit gets hit, the broker can deadlock.   I have tried
setting producerWindowSize and alwaysSyncSend which did not seem to help. When the broker
hits that limit, I am unable to do things like purge the queue.  Consumers can also deadlock
as well. 
> Note that this appears to be the same issue as described in this ticket here: AMQ-2475
.  The difference is that I am using a Queue and not a Topic and the fix for this appears
to only have been for Topics.
> The problem appears to be in the Queue class on line 1852 inside the {{cursorAdd}} method.
 The method being called is {{return messages.addMessageLast(msg);}} which will block indefinitely
if there is no space available, which in turn ties up the {{messagesLock}} from being used
by any other threads.  We have seen a deadlock where consumers can't consume because they
are waiting on this lock.   It looks like in AMQ-2475 part of the fix was to replace {{messages.addMessageLast(msg)}}
with {{messages.tryAddMessageLast(msg, 10)}}.  I also noticed that not all of the message
cursors support {{tryAddMessageLast}}, which could be a problem.  {{FilePendingMessageCursor}}
implements it but the rest of the cursors (notably {{StoreQueueCursor}}) simply delegate back
to {{addMessageLast}} in the parent class.  So part of this fix may require implementing {{tryAddMessageLast}}
across more cursors.
> Here is part of the thread dump showing the stuck producer:
> {code}
> "ActiveMQ Transport: ssl:///192.168.3.142:38589" daemon prio=10 tid=0x00007fb46c006000
nid=0x3b1a runnable [0x00007fb4b8a0d000]
>    java.lang.Thread.State: TIMED_WAITING (parking)
>         at sun.misc.Unsafe.park(Native Method)
>         - parking to wait for  <0x00000000cfb13cd0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
>         at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:226)
>         at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2176)
>         at org.apache.activemq.usage.Usage.waitForSpace(Usage.java:103)
>         at org.apache.activemq.usage.Usage.waitForSpace(Usage.java:90)
>         at org.apache.activemq.usage.Usage.waitForSpace(Usage.java:80)
>         at org.apache.activemq.broker.region.cursors.FilePendingMessageCursor.tryAddMessageLast(FilePendingMessageCursor.java:235)
>         - locked <0x00000000d2015ee0> (a org.apache.activemq.broker.region.cursors.FilePendingMessageCursor)
>         at org.apache.activemq.broker.region.cursors.FilePendingMessageCursor.addMessageLast(FilePendingMessageCursor.java:207)
>         - locked <0x00000000d2015ee0> (a org.apache.activemq.broker.region.cursors.FilePendingMessageCursor)
>         at org.apache.activemq.broker.region.cursors.StoreQueueCursor.addMessageLast(StoreQueueCursor.java:97)
>         - locked <0x00000000d1f20908> (a org.apache.activemq.broker.region.cursors.StoreQueueCursor)
> {code}



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