feat(http/transport): allow passing a function to customize trace propagation

unitelhttp/transport.go

@@ -24,12 +24,28 @@ func WithLogger(l logr.Logger) HTTPTransportOpt {
 	}
 }
 
+type TracePropagator = func(r *http.Request) bool
+
+func WithTracePropagation(propagator TracePropagator) HTTPTransportOpt {
+	return func(t *HTTPTransport) {
+		t.tracePropagator = propagator
+	}
+}
+
+func PropagateAllTraces(req *http.Request) bool {
+	return true
+}
+
+func PropagateNoTraces(req *http.Request) bool {
+	return false
+}
+
 type HTTPTransport struct {
 	logger    logr.Logger
 	telemetry *unitel.Telemetry
 	transport http.RoundTripper
 
-	forwardTrace bool
+	tracePropagator TracePropagator
 
 	tracedRequestHeaders  []string
 	tracedResponseHeaders []string
@@ -37,13 +53,13 @@ type HTTPTransport struct {
 	tracer trace.Tracer
 }
 
-func NewTracedTransport(t *unitel.Telemetry, inner http.RoundTripper, forwardTrace bool, tracedRequestHeaders []string, tracedResponseHeaders []string, opts ...HTTPTransportOpt) *HTTPTransport {
+func NewTracedTransport(t *unitel.Telemetry, inner http.RoundTripper, tracedRequestHeaders []string, tracedResponseHeaders []string, opts ...HTTPTransportOpt) *HTTPTransport {
 	transport := &HTTPTransport{
 		logger:    logr.Discard(),
 		telemetry: t,
 		transport: inner,
 
-		forwardTrace: forwardTrace,
+		tracePropagator: PropagateNoTraces,
 
 		tracedRequestHeaders:  tracedRequestHeaders,
 		tracedResponseHeaders: tracedResponseHeaders,
@@ -69,7 +85,7 @@ func (t *HTTPTransport) RoundTrip(req *http.Request) (*http.Response, error) {
 	ctx := s.Context()
 	req = req.WithContext(ctx)
 
-	if t.forwardTrace {
+	if t.tracePropagator(req) {
 		t.telemetry.InjectIntoHeaders(ctx, req.Header)
 	}