Support PAPI for custom metrics

[jippi]

Describe the feature you would like to see.

Being able to use PAPI values for custom metrics

I'm using https://www.spigotmc.org/resources/view-distance-tweaks-1-14-1-18.75164/ on my servers and would love to see the render/simulation distance over time vs MSPT

I'm sure there would be other great values in PAPI once I would start digging into them.

How would you like to see this implemented?

I think where this might be more complicated than I initially thought is around some PAPI values being "per world" or "per X" - and likely wanting to either support a list that gets enumerated and emitted together, or some other way to provide different PAPI keys, but emit them as a single metric with tags

e.g. given %viewdistancetweaks_simulation_distance_<world>% it could possibly be satisfied with custom config like this:

name: viewdistancetweaks_simulation_distance
papi: viewdistancetweaks_simulation_distance_<world>
values: 
  world: [world,world_the_end,world_nether]
tags:
  world: <world>

Where it would basically be

// compute all permutations of key/value combinations within the `values` dict
// iterate each of these and read PAPI value, generate metric, emit tags
// replacing `<world>` with each possible value in `values.world`  across `papi` and `tags`

Note

Maybe a v1 would just support a single permutation (e.g. world) to keep it simple, and likely to satisfy 90%+ of the PAPI idea s I have