add new highcardmetrics pkg to grpcmetrics

[agnaite]

Context

We want to add two new options to the grpc server, which allows us to collect metrics using attributes.

The new highcardmetrics pkg provides high cardinality unary and stream server interceptors. The interceptors take an explicit bool arg, which makes the histogram type configurable. Passing in true will create explicit histograms with a default 5s distribution.

Usage

To initialize a grpc server with high cardinality unary and stream servers using explicit histograms:

gSrv, hSrv := grpcserver.NewStandardH2C(
  apiSrv,
  // high cardinality interceptors using explicit histograms
  grpcserver.HighCardInterceptors(
     highcardmetrics.NewUnaryServerInterceptor(o.metricsProvider, true), 
     highcardmetrics.NewStreamServerInterceptor(o.metricsProvider, true),
   ),
)

[voidlock]

Yup, this is exactly what I was thinking.

[voidlock]

Will this service conflict (or be confused) with the existing service* columns?

[agnaite]

very true. how do you feel about grpc.service and grpc.method? Or any other suggestions welcome!

[voidlock]

It's like you can read my mind, I love those choices!

In fact, I was wondering about changing ours in the httpmetrics middleware to use http.method, http.path, http.response-status.

[voidlock]

There is a much easier way to do this now https://pkg.go.dev/time#Duration.Milliseconds

[agnaite]

good catch! just a copy/paste from the other code.

[voidlock]

These labels will need to get tweaked as well.

[voidlock]

Looks great!