Queue shows spike at the hour every hour

[Peter]

Hi,

We are experiencing something odd that we can't seem to explain from the available logs. One of the more active queues in RMQ is showing a relatively huge spike on the number of queued messages at the hour every hour. 

The queue is part of a shovel between this instance and another. This other instance doesn't show any spikes however. The queue shows a consistent processing of messages. 

There is no indication whatsoever of messages "hanging" on either this instance or the source instance. We've been going through the logs over and over, but it doesn't show anything that can explain this behaviour.

Our configuration is pretty basic. We are running RMQ 3.9.14 / Erlang 23.3.4.11 and RMQ 3.8.8 / Erlang 22.0.7 on the source instance. The only plugin used is the shovel plugin on the instance showing these strange spikes.

Any thoughts on what could cause this? Thanks!

Cheers,

Peter

N.B. Posted this in users group as well. Didn't know best group to post.