Zero Prefetch not working
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Key: AMQ-2567
URL: https://issues.apache.org/activemq/browse/AMQ-2567
Project: ActiveMQ
Issue Type: Bug
Components: Broker
Affects Versions: 5.3.0
Environment: Unix/Windows, Java 1.6
Reporter: Rudolf Janz
I have problems using the zero prefetch. 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!
The last version that we used was 4.1.1, that worked.
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