Metric for number of remote_read queries in-flight

[gouthamve]

We have a metric that shows the number in-flight queries on the promql engine: prometheus_engine_queries, with the introduction of the concurrency limits #4656, a similar metric should be added for in-flight remote-read queries.

[tariq1890]

I can take this up

[tariq1890]

Hi @gouthamve . To continue the discussion, I had created the other PR based on how other metrics were tracked in the prometheus codebase.

If I understand correctly, We want a remote read metric at the api module level regardless of the underlying remote storage implementation used. Please correct me If I am wrong.

[simonpasquier]

@tariq1890 this metric applies to the /api/v1/read endpoint which can be used by external systems to read samples from Prometheus. One use case is described here: https://www.robustperception.io/accessing-data-from-prometheus-1-x-in-prometheus-2-0