Return missing sampled and traceparent headers

e2e/sink/internal/handler/handler.go

@@ -12,21 +12,25 @@ import (
 	cev2http "github.com/cloudevents/sdk-go/v2/protocol/http"
 )
 
+const (
+	SampledHeader     = "X-B3-Sampled"
+	TraceparentHeader = "Traceparent"
+)
+
 // Handler interface for the SinkHandler.
 type Handler interface {
 	Start() error
 }
 
 type SinkHandler struct {
 	logger *zap.Logger
-	events map[string]*cev2event.Event
-	cache  map[string]*cev2event.Event
+	events map[string]*sinkEvent
 }
 
 func NewSinkHandler(logger *zap.Logger) *SinkHandler {
 	return &SinkHandler{
 		logger: logger,
-		events: make(map[string]*cev2event.Event),
+		events: make(map[string]*sinkEvent),
 	}
 }
 
@@ -38,6 +42,12 @@ func (h *SinkHandler) Start() error {
 	return http.ListenAndServe(":8080", router)
 }
 
+type sinkEvent struct {
+	// Header stores the non CE events, e.g. X-B3-Sampled and Traceparent
+	http.Header
+	cev2event.Event
+}
+
 func (h *SinkHandler) StoreEvent(w http.ResponseWriter, r *http.Request) {
 	event, err := extractCloudEventFromRequest(r)
 	if err != nil {
@@ -49,7 +59,15 @@ func (h *SinkHandler) StoreEvent(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	h.events[event.ID()] = event
+	// store the event in memory
+	h.events[event.ID()] = &sinkEvent{
+		Header: http.Header{
+			SampledHeader:     r.Header[SampledHeader],
+			TraceparentHeader: r.Header[TraceparentHeader],
+		},
+		Event: *event,
+	}
+
 	err = writeResponse(w, http.StatusNoContent, []byte(""))
 	if err != nil {
 		h.namedLogger().Error("failed to write response", zap.Error(err))
@@ -78,6 +96,10 @@ func (h *SinkHandler) GetEvent(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// fill the non CE headers
+	w.Header().Set(SampledHeader, event.Header.Get(SampledHeader))
+	w.Header().Set(TraceparentHeader, event.Header.Get(TraceparentHeader))
+	w.Header().Set("Content-Type", "application/json")
 	err = writeResponse(w, http.StatusOK, respBody)
 	if err != nil {
 		h.namedLogger().Error("failed to write response", zap.Error(err))