`rabbitmq_queue_messages_bytes` metric for stream queues in Prometheus plugin

[mdecalf]

Is your feature request related to a problem? Please describe.

The Prometheus metric rabbitmq_queue_messages_bytes, exposed by the rabbitmq_prometheus plugin, does not report the size in bytes of messages for stream queues. It works as expected for classic queues, but for stream queues the metric is missing.

Describe the solution you'd like

Having the metric rabbitmq_queue_messages_bytes which report the size of messages in byte for stream queues

Describe alternatives you've considered

du -sh /.../stream/* but what a solution ...

Additional context

I guess I already now the answer by looking atdeps/rabbitmq_prometheus/src/collectors/prometheus_rabbitmq_core_metrics_collector.erl. Metrics are collected from ETS tables that do not expose stream queue stats the same way as classic queues, something like that?

If this is a known limitation, can we document it in the metric reference (maybe I missed a reference somewhere)? Could we imagine a solution? I was not able to find an issue or discussion regarding that

[michaelklishin]

This metric was never added because no one has asked for it, until today.

[mdecalf]

Oh. I was not expected that answer but great! It would be awesome to have it