Add Google Trace propagator

[lucacasonato]

Should this be added to opentelemetry or opentelemetry-contrib? Unless anyone else wants to implement this, I will do it.

Go implementation for opencensus: https://github.com/census-instrumentation/opencensus-go/blob/v0.22.5/exporter/stackdriver/propagation/http.go

[jtescher]

I think @djc was moving some of https://github.com/vivint-smarthome/opentelemetry-stackdriver over, could work out what the best path forward is for that. I think either way the contrib crate is probably the best place for it currently.

[TommyCpp]

I think https://github.com/vivint-smarthome/opentelemetry-stackdriver only have exporter. If that's the case, then I don't know anyone else is working on the propagator.

[jtescher]

@TommyCpp good point, can be done separately if they only have an exporter. Looks like contrib is still the right place for the propagator either way according to the propagators distribution spec.

[djc]

@jtescher I still don't like the idea of throwing a bunch of otherwise unrelated code in a single contrib crate; it would probably need complex feature combinations to make sure dependencies match your particular needs at any time. What's the argument against doing a top-level opentelemetry-google-cloud-ops crate (to be bikeshedded) containing both an exporter, a propagater, and whatever else makes sense for that particular environment?

(Alternatively, why aren't opentelemetry-jaeger, opentelemetry-zipkin etc all in the contrib crate?)

[jtescher]

@djc I think having a top level crate works as well for common exporters like aws/gcp, having more niche exporters like newrelic/datadog at the top level could become a maintenance burden. Was mentioning contrib for propagator-only additions where a full crate is a bit heavy, but as this will likely end up having both, a new crate makes sense.

[hdost]

We've discussed recently in the SIG open-telemetry/opentelemetry-rust#841 and the current idea is that for now we can accept things into the repo, though likely in a separate crate for things like these extensions. Once stable we'd definitely move into a contrib.

Specifically this could be a:
opentelemetry-extensions-gcp or something like that.

[djc]

@hdost, I'm confused, this is effectively what opentelemetry-stackdriver provides today.

Edit: ahh, this is specifically about a propagator.

[hdost]

@hdost, I'm confused, this is effectively what opentelemetry-stackdriver provides today.

Edit: ahh, this is specifically about a propagator.

Indeed but it seems feasible that it could be a feature of the stackdriver crate but it's conceivable you wouldn't want both parts.

[cijothomas]

Closed via #25