feat: add metrics middleware

[frekw]

Since ZIO 2.0 ships with integrated metrics support, I think it makes sense to include middleware for some standard metrics into zio-http.

[codecov-commenter]

Codecov Report

Merging #1394 (7c99571) into main (3dd64d8) will increase coverage by 0.34%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1394      +/-   ##
==========================================
+ Coverage   57.54%   57.88%   +0.34%     
==========================================
  Files          97       98       +1     
  Lines        3196     3222      +26     
  Branches       89       91       +2     
==========================================
+ Hits         1839     1865      +26     
  Misses       1357     1357              

Impacted Files	Coverage Δ
...-http/src/main/scala/zio/http/middleware/Web.scala	72.05% <ø> (ø)
...p/src/main/scala/zio/http/middleware/Metrics.scala	100.00% <100.00%> (ø)

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[tusharmath]

@frekw This would be a great addition to the ZIO Http ecosystem. I think it would better to maintain it as separate project, in the same repo.

[frekw]

@frekw This would be a great addition to the ZIO Http ecosystem. I think it would better to maintain it as separate project, in the same repo.

Definitely! What do you think is a good project structure in this case? Should we add an extras folder or something similar or should we just add metrics to the top level?

[987Nabil]

@frekw I would highly recommend to make metric names configurable. Orgs might have naming schemas that a team has to stick to. We have this and I know others as well. And I think making names configurable should not be too complicated.

[jdegoes]

@frekw If you want this to become #1459, I can help shepherd this through to merging. The functionality is most-welcome!

[frekw]

@jdegoes now that Gauge.increment/decrement is in core I'd love to take another stab at it 👍

[frekw]

@jdegoes I've pushed an updated version that uses the new Gauge.increment/decrement. Temporarily changed the dependency to the snapshot version of ZIO to get access to them but should hold off merging until there's a proper release. It gets a bit repetitive to handle all cases (sucess / error / defect) but nothing too bad.

What I'm struggling a bit with is writing tests that aren't dependent on global state (and execution order) – but I guess that's an issue with testing any logic around metrics, or is there a way to create a scoped, fresh metrics registry solely for testing?

[adamgfraser]

@frekw I think you can do this with tags.

[frekw]

@adamgfraser ah, by accepting something like extraTags: Set[MetricLabel] = Set.empty? Clever!

I'll look at that in the morning, need to jump to bed now! 😴

[frekw]

Ok, I think this is good to go @adamgfraser @jdegoes

[swoogles]

Great work here! 👍

[jdegoes]

@swoogles Since you also did some work, can you work with @frekw to get this one through?

[swoogles]

@swoogles Since you also did some work, can you work with @frekw to get this one through?

Yep, I've already submitted a PR against his branch with a few small additions. Otherwise I think he nailed it.

[frekw]

Sorry @swoogles I didn't have notifications turned on for my fork so I had missed it. Merged now ✅

[frekw]

Ok, I've rebased based on the latest changes to main and updated the test accordingly. CI should pass now. 👍

[frekw]

@jdegoes I noticed master is now using a ZIO snapshot so I've rebased. This should be good to merge now.

[frekw]

Whoops, I spoke too early, looks like the Middleware API has changed. I'll adjust.

[jdegoes]

Thank you!