baggage headers not propagating

[cchawn]

Current behaviour

baggage (and ot-baggage-*) headers are not being propagated through the system.

Expected behaviour

Based on the Trace Context Propagation documentation, the baggage headers should be automatically propagated?

Baggage propagation through OpenTelemetry’s W3C-compatible headers is enabled by default.

Perhaps I'm missing something ... but based on the documentation, it seems like this should "just work" 😅

Steps to reproduce

1. Make a request to a service with DataDog tracing enabled
2. Include a baggage or ot-baggage-* HTTP header in the request
3. Notice that these headers do not get propagated to the rest of the system

Environment

• datadog version: 2.4.0
• Ruby version: 3.3.5

---

Additional context

It looks like at one point these headers were being propagated, see:

dd-trace-rb/lib/datadog/opentracer/rack_propagator.rb

Lines 12 to 13 in 426ae56

	BAGGAGE_PREFIX = 'ot-baggage-'.freeze
	BAGGAGE_PREFIX_FORMATTED = 'HTTP_OT_BAGGAGE_'.freeze

However, I can no longer find any references to "baggage" in the latest version.

Looking at other language libraries, they still include functionality to propagate these headers, for example: dd-trace-js

[ZStriker19]

Hi @cchawn ,

Thanks for reaching out. At the moment the Ruby tracer supports neither an OpenTracing or OpenTelemetry implementation of baggage. I think we previously removed the OpenTracing implementation since it's EOL. We do have plans to implement OpenTelemetry's baggage for Ruby as we are doing across other tracers, which is why you saw it in the docs, however it looks like we merged that docs update a bit too early as it's still in the works (we will fix this).

I'll update here as soon as baggage support is merged into the Ruby tracer.