fshttp: add prometheus metrics for HTTP status code

Browse Source

This patch adds rclone_http_status_code counter vector labeled by

* host,
* method,
* code.

It allows to see HTTP errors, backoffs etc.

The Metrics struct is designed for extensibility.
Adding new metrics is a matter of adding them to Metrics struct and including them in the response handling.

This feature has been discussed in the forum [1].

[1] https://forum.rclone.org/t/prometheus-metrics/14484

...

This commit is contained in:

500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f