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From Gary Tully <>
Subject Re: Zero Prefetch Not Working in 5.3.0
Date Thu, 14 Jan 2010 14:14:18 GMT
can you open an issue for this, I just gave it a whirl (on trunk) and get
similar but non deterministic results. The second consumer got 6 and 7 on
two runs.
PrefetchSubscription and prefetchExtension on a deliveryAck in a transaction
are areas that you need to look into to resolve this. Great that you have a
simple junit test case.

2010/1/14 Rudolf Janz <>

> Hello,
> I have problems using a prefetch of Zero. The consumer starts prefetching
> messages after some receives.
> Our use case is, that we have a large computation which is split into
> smaller sub jobs. These jobs are sent via ActiveMQ to some processing nodes
> on different machines. The duration of jobs differs very much (10s to some
> minutes). The jobs are sent by decreasing estimated computation time. If one
> of the consumers which receives a large job prefetches some other jobs,
> these will be processed later. In the meantime the remaining consumers are
> idle, and the total computation time is much longer than necessary.
> I have modified the existing ZeroPrefetchConsumerTest to test for the
> problem (I have removed the other test methods).
> Two consumers (C1  and C2) are instantiated. These messages are sent:
> 1,2,3,4,5,6,7,8,9
> C1 reads 4 times, receives 1,2,3,4 -> this is correct
> now C2 reads, it receives 8 not 5, which is the next message in the queue.
> The reason is, that C1 prefetched 5, 6, 7, that should not have
> happened.(sometimes C1 only prefetches 5,6)
> The problem can be seen in the JMX Console as well, after a while, the
> first consumer has more than one dispatched message and the queue has an
> InflightCount of 3, although there are only two consumers!
> I have tried debugging in the ActiveMQConsumer code, but did not get far.
> If somebody can give me a pointer where to look, I might give it another
> try.
>   Regards
>   Rudolf Janz


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