[ openjms-Bugs-1214292 ] topicSubscriber.close() hangs

Bugs item #1214292, was opened at 2005-06-04 00:13
Message generated for change (Comment added) made by tanderson
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Category: client
Group: v0.7.6.1
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: ssp (surjitinlondon)
Assigned to: Tim Anderson (tanderson)
Summary: topicSubscriber.close() hangs

Initial Comment:
Hi

We have cleanup code as shown below :

topicConnection.stop();
topicSubscriber.close();  <-- hangs here
topicSession.close();
topicConnection.close();

which ocassionaly hangs when executing 
topicSubscriber.close();

Any ideas ?

Thanks



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>Comment By: Tim Anderson (tanderson)
Date: 2005-12-03 00:10

Message:
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Fixed in CVS. Fix will be available in 0.7.7-alpha-2.

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Comment By: Tim Anderson (tanderson)
Date: 2005-07-23 23:48

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Using the attached  SRTest, I can reproduce the problem in 
0.7.6.1. 
In 0.7.7-alpha-1, it also periodically deadlocks, but for a different 
reason - the no. of pooled threads allocated to handle ORB 
invocations is too small (10).
In the 0.7.7 CVS version, the deadlock for lack of threads doesn't 
occur as the pooling strategy has changed.


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Comment By: Tim Anderson (tanderson)
Date: 2005-07-23 23:34

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The attached code can be used to reproduce the problem.
It starts 20 asynchronous subscribers, publishes 200 messages, 
and tries to close each subscriber after they have handled >= 
100 messages.

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Comment By: Russ (russellperry)
Date: 2005-06-10 20:37

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I get this hang whenever I call topicSubscriebr.close() in the way 
shown above.  I'm using version 0.7.6.1.

This occurs whenever the Subscriber is trying to close() at the 
same time that a message is being delivered by one of the JMS 
RMI Threads.  

Looking at the code it seems to be possible for a deadlock to 
occur (possibly in multiple ways).  This is because both the close
() and onMessage(~) methods on the TopicSubscriber use 
synchronized and also the TopicSession uses synchronized on 
the methods removeSubscriber(~) and execute(~).

I think what's happening is the close() method gets called by the 
application thread, which internally calls removeSubscriber() on 
the TopicSession.  This grabs the TopicSession Lock as well as 
the TopicSubscriber Locks.

At the same time, a JMS RMI thread tries to deliver a message.  
This blocks on the TopicSession execute() method because it 
can't get the TopicSession lock.  It seems the application thread 
eventually blocks on the 
RemoteJmsServerSessionIfc.deleteSubscriber(long) call.  I think 
this is because a message delivery is in progress?

I think , there are other combinations of dealock that occur.  For 
example if close() is called by the app thread (grabs 
TopicSubscriber Lock).  A JMS-RMI thread inside the 
TopicSession execute(~) method blocks trying to deliver a 
message to the consumer using onMessage(~); it can't get the 
TopicSubscriber lock.  The app thread also blocks when calling  
removeSubscriber(~) because it can' the TopicSession lock 
currently held by the JMS RMI Thread.  

Hope this helps.  







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Comment By: Tim Anderson (tanderson)
Date: 2005-06-08 14:58

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Can you attach a client and server stack trace?
See http://openjms.sourceforge.net/faq.html if you don't now how 
to generate these.
Also update the group field to include the openjms version you 
are using.

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