Prometheus Metrics

[codello]

What feature do you want to propose?

The API server should expose metrics in a prometheus compatible format.

Why does Karman need this feature?

Prometheus metrics are a standardized way for applications to provide observability. The /healthz endpoint does not provide an adequate level of detail.

How do users access the feature?

Server admins should be able to decide whether to run the metrics on the same port as the API or a different port. By default the metrics should be available on :9090/metrics. The /metrics path should probably be configurable as well.

Additional context

• The asynq library provides an example how to implement some metrics.
• There are probably metrics packages for pgx
• Karman should also provide custom metrics about the library.

Implementation Considerations

This issue does not affect the frontend.