chore: Add metrics that shows the current height of approvals

[kostekIV]

fixes #7846
I have labelled this as chore, but I am not sure if it is an appropriate label.

[nikurt]

Thank you @kostekIV for picking up that issue!
Do you know why shouldn't we export largest_final_height? Would it be the same as last_final_block_height (in info.rs)?
I'd prefer to also export largest_final_height for completeness.

The code in the PR is fine.
My only suggestion is to replace assignments with setter methods. That way, we'll never forget to update the metrics when the values are changed.

[kostekIV]

Thank you @kostekIV for picking up that issue! Do you know why shouldn't we export largest_final_height? Would it be the same as last_final_block_height (in info.rs)? I'd prefer to also export largest_final_height for completeness.

The code in the PR is fine. My only suggestion is to replace assignments with setter methods. That way, we'll never forget to update the metrics when the values are changed.

Setters sounds nice. Im not sure why largest_final_height was not mentioned in the issue, I think I will just add it.

[kostekIV]

So I have ended up adding TrackableBlockHeightValue which guards values and sets appropriate gauge on every change to the inner value. It may be overkill tho. Added also largest_final_height. Should I also mention somewhere new metrics?

[nikurt]

Thank you, looks good!

[nikurt]

The setters interface looks good.

mention new metrics

Please add a line to non-protocol changes in CHANGELOG.md, and then I'll press the "merge" the PR.

[kostekIV]

The setters interface looks good.

mention new metrics

Please add a line to non-protocol changes in CHANGELOG.md, and then I'll press the "merge" the PR.

Done