Setting trace ID based on X-Amzn-Trace-Id

[bbhoss]

I didn't see anywhere in here that you have a plug to parse the X-Amzn-Trace-Id header field and set the trace id in the context from it. I found opentelemetry_xray_propagator and it seems like it could handle it, but it's not clear how to use it.

[bbhoss]

Update: It seems like potentially this should just be working out of the box, but it's not. I think it's related to Bandit (vs Cowboy) downcasing the headers, it doesn't match the case from opentelemetry_xray_propagator. Not sure what the best fix is or if that's even the issue.

[patmaddox]

I haven't tried working with this example application, but we found that the config key is now text_map_propagators. So the config would be:

config :opentelemetry,
  text_map_propagators: [:opentelemetry_xray_propagator, :baggage]

The header case doesn't matter, otel library does the right thing.

The other line that needs to be called somewhere as part of the request is:

:otel_propagator_text_map.extract(conn.req_headers)

which happens as a side effect of OpentelemetryPhoenix.setup. If one of the other libraries isn't calling it, you'll need to add it in a plug.