Justin Reock created AMQ-6231:
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Summary: AbortSlowConsumer Strategy Inaccurate at default Sampling
Rate
Key: AMQ-6231
URL: https://issues.apache.org/jira/browse/AMQ-6231
Project: ActiveMQ
Issue Type: Bug
Components: JMS client
Affects Versions: 5.13.2
Environment: Any
Reporter: Justin Reock
Priority: Minor
The default period check for the AbortSlowConsumer strategy is set to 30
seconds, however, the check itself is rather simple. It checks the the number
of messages in the prefetch buffer, and if that number is the same on the next
check, that consumer is considered slow and is evicted.
This can be inaccurate though, because there is no check that actually looks at
whether the messages in the prefetch buffer are the same messages as before.
In other words, if the consumer processes all the messages in prefetch, and
prefetch is refilled to the same number as the previous check, the consumer
will be considered slow.
You can reproduce this issue by starting with a queue with 5000 messages in it,
and a prefetch of 1000. Attach a consumer, and enable the Logger Plugin with
logAll=true. Set the AbortSlowConsumer strategy with default options. After
30 seconds, even though the consumer has been reasonably processing messages,
the Strategy will abort the consumer anyway, and you'll see a report from the
Logger plugin that the consumer was slow.
Then, repeat the same test, but set the AbortSlowConsumer checkPeriod down to a
very small value, like 5 milliseconds. The Consumer will never be considered
slow.
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