Function extractTrace

tracing/tracing.go:258–283

extractTrace attempts to check for a cf-trace-id from a request and return the trace context with the provided http.Request.

(req *http.Request)

// extractTrace attempts to check for a cf-trace-id from a request and return the
// trace context with the provided http.Request.
func extractTrace(req *http.Request) (context.Context, bool) {
	// Only add tracing for requests with appropriately tagged headers
	remoteTraces := req.Header.Values(TracerContextName)
	if len(remoteTraces) <= 0 {
		// Strip the cf-trace-id header
		req.Header.Del(TracerContextName)
		return nil, false
	}

	traceHeader := map[string]string{}
	for _, t := range remoteTraces {
		// Override the 'cf-trace-id' as 'uber-trace-id' so the jaeger propagator can extract it.
		// Last entry wins if multiple provided
		traceHeader[TracerContextNameOverride] = t
	}

	// Strip the cf-trace-id header
	req.Header.Del(TracerContextName)

	if traceHeader[TracerContextNameOverride] == "" {
		return nil, false
	}

	remoteCtx := otel.GetTextMapPropagator().Extract(req.Context(), propagation.MapCarrier(traceHeader))
	return remoteCtx, true
}

func NewNoopSpan() trace.Span {
	return trace.SpanFromContext(nil)