Add separate modules for metrics and tracing wrappers

[brancz]

The specific libraries and mechanisms used for metrics and tracing can be quite opinionated and a library meant as an abstraction for object storage providers should not force a dependency of one or the other system onto downstream users. As such I think that the:

• prometheus wrapper (already exists)
• opentracing wrapper (already exists)
• opentelemetry wrapper (does not exist yet)

Should be served by separate modules.

[bwplotka]

Agree, there is a simpler idea, though: Just abstract away the metrics and opentracing as much as possible - but maybe overkill.

[bboreham]

OpenTracing has been deprecated for nearly a year; why wouldn't you just switch to OpenTelemetry?
Adding abstractions over abstractions seems like an antipattern to me.

There is a bridge for anyone who needs OpenTracing.

[brancz]

I agree I wouldn’t want yet another abstraction, but for me it was important people choose to adopt the dependency, not us force it onto people.

[bboreham]

Maybe if you include "no dependency" as an option that becomes clearer?
I.e. the abstraction would include a no-op tracer.

[brancz]

I'm not exactly sure what you're proposing.