Experiment: Schematized Metrics

[tombrk]

Uses tooling from OTel (https://github.com/open-telemetry/weaver) to strongly schematize all metrics of blackbox_exporter.

This gives:

• Type-safe client_golang constructors for all metrics that make are:
  • hard to mis-use (e.g. each label is a different type, to prevent ordering mismatch using the type system)
  • discoverable (IDE auto-complete, godoc)
• Documentation (internal/metrics/metrics.md) that lists all metrics, labels and their respective possible values

I chose blackbox_exporter as a sufficiently simple target to try this approach and serve as a ground for future discussions around schematizing Prometheus metrics.

Templates for codegen are at https://github.com/sh0rez/promconv/tree/main/templates/registry/go

[bwplotka]

You didn't get any warning from Weaver? This is not the correct Otel unit type I think (just curious)

[tombrk]

It is a valid unit!

Instruments for utilization metrics (that measure the fraction out of a total) are dimensionless and SHOULD use the default unit 1 (the unity).
https://opentelemetry.io/docs/specs/semconv/general/metrics/#instrument-units

However, I still think its the wrong unit here, as it should be seconds lol

[bwplotka]

Looks good!

One thing I would ensure is to embed/import the generation in the Makefile and CI of this project, so those yamls and Go files don't diverge.

[bwplotka]

NOTE: Current schema model is not great for changes later on without open-telemetry/opentelemetry-specification#4492 -- so we might want to be careful with committing to a certain yaml model.