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From ConstantChange <>
Subject Question @ the insiders about concurrent consumers and high watermark
Date Wed, 22 Aug 2007 08:58:58 GMT


I have a question about the concurrency of consumers. I understood that the
property "concurrentConsumers" of the container actually says/defines how
many concurrent requests are handled by the consumer. Now just out of
curiousity I tested a bit arround, and found that having 1 consumer ends up
in 4 concurrent threads running the consumer code, if I have set 2
consumers, its about 9 and so on...the consumers are all the same object
(have the same objectId within the vm). 
Following you can see the results of that test, I sent 75 messages within
about a second, and this is what came out: (copy paste of the log)

When sending 75 workers to the queue within a very few seconds, and having…
1 consumer  set: never exceeds 4 concurrent requests.
2 consumers set: never exceeds 6 concurrent requests
3 consumers set: never exceeds 9 concurrent requests
5 consumers set: never exceeds 14 concurrent requests
10 consumers set: never exceeds 24 concurrent requests
20 consumers: never exceeds 41 concurrent requests
30 consumers: never exceeds 53 concurrent requests
50 consumers: never exceeds 56 concurrent requests

Can somebody explain that to me?? I tried to think of it, but these figures
did not make me understand what the concurrentConsumers property means...

The second question I have is about High Watermarks. Do you know if one can
set something like "high water mark", on the queue or container, meaning
that if a certain amount of messages is reached in the queue, new messages
are immediatly rejected...!?

Thanks everybody, if I could i'd throw a round of pints here... ;)
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