[core] Checkin opentelemetry C++ sdk dependency

[dentiny]

opencensus has been archived for ~2 years, we should upgrade to opentelemetry which is the somewhat an "improved" and maintained version.

[edoakes]

Looks fine, but let's check it in with the code that uses it?

[aslonnie]

Looks fine, but let's check it in with the code that uses it?

+1, maybe use it at least for once? otherwise it is hard to tell if the import works.

[dentiny]

Looks fine, but let's check it in with the code that uses it?

I thought about that, the most ideal way is to have a basic replacement implementation for metrics class that we have, but checking the codebase there're much work to do.

One concern is the compatibility between opencensus vs opentelemetry, like the default endpoint.

But I think your argument makes sense; I add a simple "test script" to show dependency checkin has no problem.

[MengjinYan]

Thanks for taking this on! Just to confirm, this is just to add the open telemetry dependency and there will be followup PRs to fix the breaking changes (https://opentelemetry.io/docs/specs/otel/compatibility/opencensus/) between the OpenCensus and OPTL, is that correct?

[dentiny]

Thanks for taking this on! Just to confirm, this is just to add the open telemetry dependency and there will be followup PRs to fix the breaking changes (https://opentelemetry.io/docs/specs/otel/compatibility/opencensus/) between the OpenCensus and OPTL, is that correct?

Yes, my plan is to implement a compatible metrics class, which is a counterpart for existing class, later on migrate metrics usage one by one.

[MengjinYan]

Thanks for taking this on! Just to confirm, this is just to add the open telemetry dependency and there will be followup PRs to fix the breaking changes (https://opentelemetry.io/docs/specs/otel/compatibility/opencensus/) between the OpenCensus and OPTL, is that correct?

Yes, my plan is to implement a compatible metrics class, which is a counterpart for existing class, later on migrate metrics usage one by one.

I'm wondering other than the metrics classes, whether the metrics collectors and exporters needs to be updated as well.