My Queue Length is zero but Queue Size isn't, are messages stuck.

Question

When looking at my Queues in the Portal, they all have a Queue Length of zero. At the moment my producers are offline so that makes sense to me and is re-enforced by the fact that my consumers aren't receiving any messages.

With that said, in a few instances the Queue Size is not zero. This seems like a discrepency to me and makes me think there really are messages on the queue. Can someone explain what this means? If there are messages on the queue, how can I get to them given the normal channels don't appear to be working.

For additional context... If I start the producers again messages will flow, but the mysterious chunk reflected in the Queue Size will not go down. Also, I have not enabled the Dead Letter options or the Duplicate Detection options. 

Answer 1

When viewing the Queue Length in the portal; or by getting an instance of QueueDescription; I can see there are 5581 messages waiting in my Azure Service Bus queue (Queue Size is 6.8 MB). But when I spin up a QueueClient to receive them I don't get anything. Even more mysterious... If I start my producers again I'll receive messages through the same queue, but they don't seem to relate to the 5581... The count always seems to stop at this number.

I've observed similar situations on a couple other queues, although the numbers are different. I am not using any dead letter features and messages shouldn't expire. Lock durations are set for one minute.

Can anyone shed some light on this?

  

Answer 2

I take you're using Service Bus queue, not storage queue. The number reported on the portal may not be very accurate. Try to do a test: Send 100 messages from the producer. Then close the producer. On the receiver side, check if it receives 100 messages.

Answer 3

I put a ticket in to Microsoft about this and they have confirmed that in some cases the "Size" may not be zero (+ or -) when the "length" is zero. They said it is a bug and will be resolved at some point. Thanks for the help MS.