Issue

The JMX statistic PendingQueueSize, when applied to a durable subscription, records the number of messages that a durable subscriber is eligible to receive, but has not yet received. If no messages are being published, and the durable subscriber has read and acknowledged all the messages that were published, then PendingQueueSize should be zero.

However, if the broker is forcibly shut down under load, PendingQueueSize may show a non-zero value, and will never drop to zero, even if the broker and all clients are restarted, and JMX statistics are reset. A forcible shutdown includes, of course, an operating-system "kill -KILL" operation performed by the administrator; but the ordinary management utilities may resort to a forcible shutdown if the broker does not shut down cleanly within a certain time.