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Date: Thu, 10 Jan 2013 15:22:59 +0100
From: Karel Gardas <karel.gardas@centrum.cz>
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To: users@activemq.apache.org
Subject: Subscriber losing messages (from topic)
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Hello,

I'm playing a bit with ActiveMQ 5.7.0 and found that under some 
circumstances my subscriber looks like losing messages which are 
delivered to him from the broker. Honestly speaking I don't know if to 
blame subscriber or broker in this case but while looking into web 
console of the broker, the broker claims the messages are delivered, but 
I don't see them on subscriber. It took me some time to duplicate this 
issue on as simple as possible example, but finally I've been able to a 
bit hack activemq's own demo to duplicate it.

If you'd like to see the same effect as I see now, just go to 
activemq/example/src and add:

try {
Thread.sleep(1);
}
catch (Exception ex) {
ex.printStackTrace();
}

into ConsumerTool.java's onMessage method. This will ensure that 
onMessage on consumer will run a little bit slower than producer is able 
to send messages and you will see the effect.

Once done, just run consumer with:

ant consumer -Dtopic=true -Dverbose=false -Dmax=1000000 -Dsubject=TRM

and producer with:

ant producer -Dtopic=true -Dverbose=false -Dmax=1000000 -Dsubject=TRM

if everything is working well, then both consumer and producer should 
end once delivering 1000000 messages. The problem is that consumer does 
not end due to losing some of the messages somewhere. If this does not 
happen on your box, please increase number of milliseconds on 
Thread.sleep to make onMessage even slower. I'm running this on Solaris 
11/JDK 1.7 on Xeon E5 2.0 GHz here.

Now, I do have following questions:

- am I right assuming the example above should really deliver all the 
messages to the consumer onMessage method?

- is this already known issue or shall I report it properly to 
ActiveMQ's bug tracking system?

Just to make sure, I've also tried running consumer with ant consumer 
-Dtopic=true -Dverbose=false -Dmax=1000000 -Dsubject=TRM 
-Durl="tcp://localhost:61616?jms.prefetchPolicy.queuePrefetch=0" -- but 
it neither helps. At least I've thought pre-fetching might cause this so 
I tried...

BTW: I've seen the same issue but not on demo, but on our own 
application also while running subscriber on top of 5.6.0 and 5.5.0 
releases. I always used 5.7.0 release for broker and producer though. 
I've not seen it on demo as I've not tested this with older releases but 
I would guess the issue will be there too.


Thanks a lot for any idea about what's going wrong here.

Karel