(Asking on behalf of someone else so doing my best to parlay the question)
It looks like Android supports W3C Trace Context propagation via its OkHttp and Volley wrappers, which is great. Unfortunately, we don't see this same support in the iOS SDK. We're relying on the traceparent header for sampling decision propagation, so this lack of support means API requests coming from our iOS client often go untraced in APM. Is this a known issue or something that we've missed as a configuration option? We've explored the iOS SDK repository thoroughly but weren't able to figure it out.
To clarify, both Android and iOS SDK successfully read the Server-Timing header from an API call's response and associate it with the client-side spans. The issue is that iOS doesn't include the traceparent header on the request, which is what tells the server to trace the operation in the first place. We would expect that to work since it's core to how OpenTelemetry is supposed to work and does work on the web and Android.
Standardized context propagation via W3C Trace Context, which includes the sampling decision, is one of the main advantages of using OpenTelemetry. We would need to update all of our backend services with custom logic to understand a novel propagation system, which is a non-starter.
