feat(otel): add OpenTelemetry SpanProcessor, Propagator, Extractor

[lcian]

Creates a new crate sentry-opentelemetry for integration with OTEL.

The implementation is based on a SpanProcessor that creates and finishes Sentry spans on OTEL span start/end.
There's also a Propagator/Extractor that injects the metadata (e.g. HTTP headers) required for distributed tracing to work.
It's based on our implementation for JS and other SDKs (https://develop.sentry.dev/sdk/telemetry/traces/opentelemetry/).

The goal with this initial version is:

• support OTEL <> Sentry span conversion and capturing
• capture OTEL span attributes
• link any messages/errors captured through the Sentry API to the correct spans, assuming that only the OTEL API is used to manage spans

Feedback appreciated on:

• SPAN_MAP, general Rust stuff, additions to performance API (@Swatinem)
• OTEL/SDKs things (@adinauer & @sl0thentr0py)

There are some todo items which will be addressed in follow-up PRs (not necessarily in this release).

[lcian]

Seems like Windows CI is getting stuck on test_captures_transaction for some reason. I'll stop it for now.

[adinauer]

Just gave this a quick glance and left some comments on what I noticed so far.

[lcian]

Just gave this a quick glance and left some comments on what I noticed so far.

Thank you!

[lcian]

Apparently we need to put each test in a different file or they will get stuck on Windows.

[Swatinem]

this looks reasonable to me.
Its a bit unfortunate how the lack of "onlyspans" means that you have to still deal with needing access to a TransactionOrSpan object instead of just being able to push finished spans with opaque parent ids into a global span sink.

[Swatinem]

lgtm

[sl0thentr0py]

@lcian what is the end user experience of using this? I see you're adding stuff on the opentelemetry::{global} reference but how does a user configure their instrumentation along with this?

EDIT: nvm that's a docstring, ignore 🤦

[sl0thentr0py]

wonderful, ship it

[lcian]

@lcian what is the end user experience of using this? I see you're adding stuff on the opentelemetry::{global} reference but how does a user configure their instrumentation along with this?

EDIT: nvm that's a docstring, ignore 🤦

Yeah this is the snippet to set it up
https://github.com/getsentry/sentry-rust/blob/lcian/feat/sentry-opentelemetry/sentry-opentelemetry/src/lib.rs#L18-43
Then they can just use OTEL APIs as normal (quite verbose unfortunately, I'm not sure if the UX is the same on other platforms).

[adinauer]

LGTM, great work!