Where to contribute a propagator for the gRPC plugin?

[nkelly75]

• This only affects the JavaScript OpenTelemetry library

While using the grpc plugin in a node service I was able to successfully export spans (to two tracing back-ends I was testing). However, the spans didn’t take their context from incoming gRPC calls as expected (leading to new "shallow" traces being created). Having discussed with @austinlparker we realized a propagator was required that would use the grpc-trace-bin gRPC header. I have an initial working implementation (inspired by previous OpenCensus work) and would like to contribute to the appropriate OpenTelemetry repo.

Looks like options include:

• opentelemetry-js repo under packages/opentelemetry-core/src/context/propagation
• opentelemetry-js repo under packages/opentelemetry-plugin-grpc
• opentelemetry-js-contrib repo under propagators

Please advise on the best location for the propagator and I will work to get a pull request in place.

[mayurkale22]

We had implemented binary propagator, but removed it with respect to open-telemetry/opentelemetry-specification#426 in #762 and #804.

I am not sure current status of specs, @dyladan any idea?

[dyladan]

Binary propagator comes up periodically on spec calls. Afaik it is something they consider a requirement before GA but isn't the highest priority thing right now

[nkelly75]

Some extra context. While learning more about OpenTelemetry following observe2020 I had started with a fork of the microservices-demo (originally instrumented using OpenCensus) where spans were exported to a local OpenTelemetry Collector which then exported to the two backends. Then I wanted to learn more about direct OTel instrumentation in code and chose to modify the PaymentService (node) so it was instrumented using OpenTelemetry (rather than OpenCensus). I added OTel “attributes” on spans to generate some currency tags for demo purposes. The incoming gRPC calls (from CheckoutService, still instrumented with OpenCensus) had the grpc-trace-bin headers. Without the binary propagator the end-to-end demo wasn’t effective.

I wasn’t aware that a binary propagator had existed previously. Just learned today that it was removed as part of #804. I now see also that the binary format was removed from the Propagators section of the OTel Spec (as part of #426).

Looks like there are good reasons for these removals in the long term. However, in order to have interoperability with existing OpenCensus-instrumented services, is there an argument for having a binary “CensusPropagator” (working off the grpc-trace-bin header) in the contrib repo?

[dyladan]

is there an argument for having a binary “CensusPropagator” (working off the grpc-trace-bin header) in the contrib repo

That sounds like a great idea 👍

[mayurkale22]

I think we agree on this one, can we close issue?

[dyladan]

Created a new issue in the contrib repo. @nkelly75 you have to comment on the new issue if you want me to assign it to you.