Prometheus metrics about kellnr HOT 2 OPEN

Prometheus metrics (or metrics at all) are on my mental to-do list, but not more a.t.m. I'll use this issue as a feature request to get it on the backlog.

What are metrics you would expect? Some I can think of are

• Number of crates (kellnr or cached)
• Uploads / Downloads of crates
• Used storage size

If you have more, feel free to add them here as a comment, such that I have a list of what people expect.

Btw. if you deployed Kellnr with the Postgres backend, you can use Prometheus with SQL queries to create whatever metric you like from the database already.

from kellnr.

This crate appears promising for easily setting up a Prometheus exporter in Axum: https://crates.io/crates/axum-prometheus .

However, it's still a good question which Kellner-related metrics would be beneficial to expose on this endpoint, without duplicating those that a potential Postgres exporter might cover.

from kellnr.