Module propagation 

W3C traceparent propagation across the connectrpc boundary.

Pairs with crate::observability::init (which installs the global TraceContextPropagator). Together they close the OTel cross-process story: a turn started on the control plane carries its trace context into the harness’s connect span, so a single user request stitches into one trace tree across the control-plane → harness hop.

Direction

• Outgoing: inject_current_span_into writes the current tracing::Span’s OTel context into an http::HeaderMap using the globally-installed propagator. Callers attach the headers to a connectrpc::client::CallOptions (per-call) or connectrpc::client::ClientConfig (per-client default).
• Incoming: extract_parent_into_current_span reads traceparent (and any other propagator-registered fields) off a borrowed http::HeaderMap and re-parents the current tracing::Span so the server-side span shares the dialer’s trace id.

Design

The Injector/Extractor adapters are intentionally trivial — they exist because opentelemetry’s trait surface is carrier-agnostic and http::HeaderMap is not. Keeping them in polyc-runtime means the control plane, the harness, and any future server share one implementation; per-call sites only pick which side (inject vs extract) they need.

Structs

HttpHeaderExtractor

Adapter that lets the global OTel propagator read traceparent (and any other fields) off an http::HeaderMap.

HttpHeaderInjector

Adapter that injects propagator fields into an http::HeaderMap.

Functions

extract_context_from

Extract a parent Context from headers using the globally-installed propagator. Lower-level than extract_parent_into_current_span.

extract_parent_into_current_span

Extract the parent OTel context from headers and attach it to the current tracing::Span, so server-side spans share the dialer’s trace id.

inject_context_into

Inject a specific Context into headers. Lower-level than inject_current_span_into; prefer that for production call sites.

inject_current_span_into

Inject the current tracing::Span’s OTel context into headers.