In our environment in one of the regional hub the number of messages in queued state for the queue prediction_engine.QOS_MESSAGE queue is keep on increasing and it is not getting transferred to sent state. As per our observation in all the other queues for the same hub data flow is fine except this one.
The queue that was piling up on the regional hub was an attach queue with a subject of "QOS_MESSAGE".
There was no "get" queue on another hub to pull from this regional hub queue.
As a result, the regional hub queue was piling up.
Ensure you do not have a duplicate queue listening to the same subject.
Ensure that for every attach queue on your regional hub, that there is an "attach" queue on another hub.
Please reference the documentation on hub queues found here: