Tracing SDK

[armanbilge]

Towards #199 🚀

Tracing API spec: https://opentelemetry.io/docs/specs/otel/trace/api/
Tracing SDK spec: https://opentelemetry.io/docs/specs/otel/trace/sdk/

There are obviously quite a lot of things in there to fully implement the spec 😅 so below I've attempted to carve out some tractable steps that brings us to a minimum viable implementation: something that can build spans, trace effects, and send them to an OTLP endpoint. I can't promise these are the precise and exact steps needed, so we may edit as we go along 😝 but it should be a rough sketch.

• add otel4s-sdk-trace module to build.sbt New modules + span context maybe?  #236
• implement SpanContext New modules + span context maybe?  #236
• implement Span via Span.Backend + builders
• add SpanExporter interface
• implement Tracer + builder/provider
• add otel4s-exporter-otlp module to build.sbt and configure http4s-grpc source generator¹
• implement SpanExporter interface with gRPC
• setup an integration test e.g. against Jaeger 🎉
• begin iterating, to add features and fully implement the spec

I've create a branch that @sherriesyt can target with a series of small PRs. Then we can merge that branch into main.
https://github.com/typelevel/otel4s/tree/tracing-sdk

Thoughts and input very appreciated 🙏

Footnotes

1. @kovstas will need this too, for their work on the metrics SDK. so whoever gets to it first can do the setup :) ↩

[sherriesyt]

Thanks @armanbilge :) I can also use this issue as a space for discussion if we realize along the way that steps may change, be reordered, etc.

[kovstas]

@armanbilge What do you think about having a common branch for Tracing & Metrics API? We will definitely have a otel4s-sdk-common module, at least for Resource (https://opentelemetry.io/docs/specs/otel/resource/sdk/) class and other entities like Attributes or InstrumentalScopeInfo. In addition, I noticed that TracerProvider & MetricsProvider will have a lot in common, such as providing a registry for objects related to them. For example, in Java SDK it is ComponentRegistry.

Originally, I was going to make a PR with the otel4s-sdk-common module, but if we keep everything under a feature branch, then keeping everything related under a single branch makes sense to me.

[armanbilge]

Good point, thanks! Ok sure, so then I created an sdk branch which you can both target :)

https://github.com/typelevel/otel4s/tree/sdk

[iRevive]

https://opentelemetry.io/docs/specs/otel/context/api-propagators/#propagators-distribution

Required propagators:

• B3
• W3C tracestate
• W3C baggage
• Jaeger

[iRevive]

The tracing SDK has been released. Only gRPC exporter is not implemented from the original scope.

I will close this task and make a new one for the gRPC exporter.