What makes an AMQ queue's pending message number negative？

Question

After I purged the message of a queue (not a topic), the pending message number of this queue in Active MQ Admin console changed to negative.

I assumed the pending message number of any queue ought to be positive. Is it issue of purging? Or is it a bug of activemq?

Answer 1

It seems to be a bug in ActiveMQ. I've personally witnessed this bug on numerous occasions when purging a queue. It does not seem to affect actual message delivery however.

There are a number of open issues in the ActiveMQ issue tracker related to this problem. You can vote them up if you want:

https://issues.apache.org/jira/browse/AMQ-3472

https://issues.apache.org/jira/browse/AMQ-3111

Answer 2

This problem is solved in ActiveMQ 5.8 :

https://issues.apache.org/jira/browse/AMQ-4598