Opentelemetry-java: Add Jaeger propagator

[pavolloffay]

Similar to https://github.com/open-telemetry/opentelemetry-java/issues/853 but for Jaeger clients.

• https://www.jaegertracing.io/docs/1.17/client-libraries/#propagation-format
• https://github.com/jaegertracing/jaeger-client-java/blob/master/jaeger-core/src/main/java/io/jaegertracing/internal/propagation/TextMapCodec.java

Does OTEL client support exporting/injecting of TraceContext/SpanContext into two formats? At the same time use W3C TraceContext and Jaeger? The use case is to allow gradual migration of existing deployments using Jaeger prop. format to W3C.

[Oberon00]

Related #718 "No way to change HttpTextFormat"

[jarebudev]

Hi, I can take a look into this if nobody is already working on it

[pavolloffay]

Go ahead @jarebudev

[carlosalberto]

We need to support baggage in the Jaeger format to close this one.

[jarebudev]

i can take a look at this, should have a bit more spare time to help out

[jarebudev]

I should have a PR ready this week time permitting.
To confirm - is this for inject only, or both inject and extract?

[jkwatson]

Unless there's some reason I don't understand, I think we'd want both inject and extract.

[jarebudev]

Unless there's some reason I don't understand, I think we'd want both inject and extract.

Finally got back to this.. :)

I have made changes so that JaegerPropagator injects baggage items and is ready for a PR.

For extracting baggage from Jaeger, unless I've missed something, I was wondering how we'd extract a baggage item when the HTTP headers uberctx-{baggage-key} passed to the propagator are not fixed and we can only get 'known' headers (e.g. uber-trace-id) using the HttpTextFormat.Getter.get() method? Do we need an additional method on the Getter interface to return all keys?

[carlosalberto]

@jarebudev

We need to support iteration of keys in the Getter - see this (on my queue, and it's also marked as "required-for-ga"). Hope to work on that next week, and once that is done, you will be able to complete this task ;)

[carlosalberto]

Assigning this to me as this will be part of the over all updates for Getter.Keys(). Hope that is fine @jarebudev 😅