Declaring a classic priority queue leads to strange "queue storage version"

[walro]

Describe the bug

Declaring a priority queue leads to weird values being presented in the management UI (and via rabbitmqadmin), see screenshots.

Here I would expect it to be 1 rather than 11:

and here to be 2 rather than 22:

Reproduction steps

1. Create two queues:
   1. rabbitmqadmin declare queue name=priority-bug1 arguments='{"x-max-priority":10,"x-queue-version":1}'
   2. rabbitmqadmin declare queue name=priority-bug2 arguments='{"x-max-priority":10,"x-queue-version":2}'
2. List the queues:
   1. rabbitmqadmin --vhost / list queues name backing_queue_status.version
3. See the output not having the expected values:

+---------------+------------------------------+
|     name      | backing_queue_status.version |
+---------------+------------------------------+
| priority-bug1 | 11                           |
| priority-bug2 | 22                           |
+---------------+------------------------------+

It seems like the value becomes something like (1 + max_priority) * queue_version?

Expected behavior

To see versions correspond to the queue version number.

Additional context

Tried this on 3.12.4, but have observed on 3.12.1 too.

[michaelklishin]

Every priority queue is N queues under the hood, so my guess is that the metric tries to aggregate version numbers as it would, say, counters like the number of messages in a certain state.

It should instead just pick the storage version of the first internal queue since they will never differ.