Summary:
Formerly, we were updating the metrics every 15 seconds. We were facing a couple of issues doing it manually:
- Outdated metrics in case of a one-time crash
- Metrics getting exposed for deleted PVs
Instead of fixing the bugs, I preferred to do it the right way. As per `python-prometheus` docs:
> Sometimes it is not possible to directly instrument code, as it is not in your control. This requires you to proxy metrics from other systems. To do so you need to create a custom collector...
Test Plan:
- Deploy on a cluster with existing rawfile PVs
- Send request to `:9100/metrics` and assert that metrics are exposed
- Delete a PV, and assert that its metrics disappear
Reviewers: h.marvi, bghadiri, sina_rad, mhyousefi
Reviewed By: h.marvi, bghadiri, sina_rad
Differential Revision: https://phab.hamravesh.ir/D815
