Move to OpenTelemetry for metrics

[guseggert]

Checklist

• My issue is specific & actionable.
• I am not suggesting a protocol enhancement.
• I have searched on the issue tracker for my issue.

Description

go-ipfs should migrate to OpenTelemetry for metrics, now that the Metrics API is stable (and the Go implementation is imminently stable), and we are using it for tracing. OpenCensus is on life support as most industry resources have moved to developing OpenTelemetry. There are also places in our code that are Prometheus-specific, which should be changed to use OpenTelemetry.

There are some options here, as there is an OpenCensus -> OpenTelemetry bridge that would ease such a migration, but it has limitations and caveats (I don't know the specifics). We should try out the bridge first and see if it works, so that we can turn on the OTLP exporter. We should also keep a Prometheus exporter by default, for backwards compatibility with the /debug/metrics/prometheus endpoint, but it should be on a deprecation path as OTLP is implementation-agnostic.

[guseggert]

We should be careful about performance here based on learnings from libp2p, see eg libp2p/go-libp2p#1955. That issue is specifically about OpenCensus, not OTel, but I don't know what the perf characteristics of OTel are. Prometheus is very performant.

[BigLep]

@Jorropo : did I understand correctly that you did this work recently?

[Jorropo]

Not really, I updated opentelemetry but it's rather not falling behind, the work I did (ipfs/boxo#532) only fixes our tracing code.

[Jorropo]

It's unclear to me the value of this issue except consolidation, our current metrics code work for better or worst. It has rough edges in some places but I don't see any issue that would be fixed by doing this.

[BigLep]

Thanks @Jorropo . In that case, I'll close for now as "not planned". We can reopen if there's a compelling reason.