expose per process metrics in fpm status

[cdaguerre]

#9494

[bukka]

You should add a test for this as full is not currently used. It might need some tweaking in the tester to make it nicely work by the look of it.

[bukka]

I think we might pre-format those labels and then have a single string to add there multiple times.

[cdaguerre]

@bukka I took a different approach...
According to the openmetrics specification, metric values can not be "interleaved", meaning that valid format can not be achieved by iterating over processes and then metrics. You have to iterate over each process for each metric...
While this works it's probably pretty ugly C because it's the first time I get anywhere near C ;)
Some guidance on how I could clean this up would be much appreciated.

[bukka]

Agreed it's getting quite ugly. Honestly it was already quite bad but with more logic like this, it's becoming even worse. So I think it might require some deeper refactoring so we don't duplicate things and it's more manageable. I just prioritised status related issues on my TODO list and try to fix some bugs first so merging is less painful later (we are merging up from lower branches so if it changes, we have to deal with conflicts). I will think about better structure and then let you know when I have got something.

I think it's fine if you just concentrate on the functionality (fine to keep it ugly for now) and adding some test. Then we could take it from there.

[cdaguerre]

Closed in favor of #9646