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From Stefanic <>
Subject Re: Consumers hanging on a queue although there are messages in it
Date Fri, 02 Feb 2018 07:05:39 GMT
Hi Tim,

There are no selectors, so there are no messages left behind.
We have seen this three times now in production and every time when the
queue is empty (after about 30 minutes of refreshing) the problem goes away.

Threads behavior is rather strange, when the blocking issue is on-going we
see 1 thread constantly running (100%) in visualvm, and all other threads
(31 in our case) almost seem synchronized on the same object because all of
them start running at the same time and go into timed_waiting state at the
same time.
That results in 33% running of all other threads and that is not enough to
keep our queue empty.

Reproducing this behavior is nearly impossible for us, it occurs randomly
within about a week.

Here are the things we tried so far:
- Downgraded ActiveMQ broker from 5.15.2 to our previous version 5.11.1 but
the problem occurred again on that version so we assume it is not the
- Yesterday we downgraded both ActiveMQ and Camel client libraries: ActiveMQ
down to 5.14.5 and Camel from 2.20.1 down to 2.19.4 (I would have rather
only downgraded 1 at a time but it's our production environment so cannot
play around too much)

I will reply here if we experience the blocked state again.

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