MSMQ console showing message count but no messages for private queue

Question

I have a transactional private message queue (among other message queues on which I have not seen this problem) on a Windows Server 2008 R2 server.

This particular queue has a recurring problem happening every few weeks where the console shows a nonzero count of messages in the queue, but it does not have any messages in the queue itself or any subqueue. Queue Explorer shows the same thing. Performance counters indicate there are messages like the count in the built-in msmq console and queue explorer.

I cannot find any messages. I understand that I could see a situation like this for outgoing queues with dead letter tracking such that it may have been delivered to a remote machine but not yet processed. This is not an outgoing queue, though. Messages are sourced from remote machines and have landed here on this machine.

Also, I am certain that the count I'm seeing are not journal messages or subqueues.

Does this make any sense? Is there a logical explanation for this and under some circumstance this is expected? If so, what is it?

EDIT: Removed info about purging queue removing the count - that was incorrect. Purging actually does nothing and leaves me in the same state as before with a count reflected, but no messages showing.

Answer 1

As you noted, you can see a message count on an outgoing queue if source journaling is in use. The invisible messages are there in case they need to be moved to the DLQ.

I would expect your problem to be similar - there should be a visible message in the outgoing queue and an invisible message in the destination queue because delivery hasn't completed. I assume a handshaking or storage acknowledgement has been lost along the way. Or maybe the message has been processed and removed from the queue but MSMQ couldn't update the sender of the fact.

Check the outgoing queues on the remote machines sending TO this queue.