Changes from PR feedback

Signed-off-by: Drew Robbins <drew@drewby.com>

bindings/http/http.go

@@ -38,12 +38,14 @@ import (
 )
 
 const (
-	MTLSEnable        = "MTLSEnable"
-	MTLSRootCA        = "MTLSRootCA"
-	MTLSClientCert    = "MTLSClientCert"
-	MTLSClientKey     = "MTLSClientKey"
-	traceparentHeader = "traceparent"
-	tracestateHeader  = "tracestate"
+	MTLSEnable     = "MTLSEnable"
+	MTLSRootCA     = "MTLSRootCA"
+	MTLSClientCert = "MTLSClientCert"
+	MTLSClientKey  = "MTLSClientKey"
+
+	TraceparentHeaderKey = "traceparent"
+	TracestateHeaderKey  = "tracestate"
+	TraceMetadataKey     = "traceHeaders"
 )
 
 // HTTPSource is a binding for an http url endpoint invocation
@@ -107,12 +109,7 @@ func (h *HTTPSource) Init(metadata bindings.Metadata) error {
 		h.errorIfNot2XX = true
 	}
 
-	if val, ok := metadata.Properties["traceHeaders"]; ok {
-		h.traceHeaders = utils.IsTruthy(val)
-	} else {
-		// Default behavior
-		h.traceHeaders = false
-	}
+	h.traceHeaders = utils.IsTruthy(metadata.Properties[TraceMetadataKey])
 
 	return nil
 }
@@ -196,7 +193,6 @@ func (h *HTTPSource) Operations() []bindings.OperationKind {
 func (h *HTTPSource) Invoke(ctx context.Context, req *bindings.InvokeRequest) (*bindings.InvokeResponse, error) {
 	u := h.metadata.URL
 
-	traceHeaders := h.traceHeaders
 	errorIfNot2XX := h.errorIfNot2XX // Default to the component config (default is true)
 
 	if req.Metadata != nil {
@@ -246,12 +242,12 @@ func (h *HTTPSource) Invoke(ctx context.Context, req *bindings.InvokeRequest) (*
 	}
 
 	// HTTP binding needs to inject traceparent header for proper tracing stack.
-	if traceHeaders {
-		if tp, ok := req.Metadata[traceparentHeader]; ok {
-			request.Header.Set(traceparentHeader, tp)
+	if h.traceHeaders {
+		if tp, ok := req.Metadata[TraceparentHeaderKey]; ok && tp != "" {
+			request.Header.Set(TraceparentHeaderKey, tp)
 		}
-		if ts, ok := req.Metadata[tracestateHeader]; ok {
-			request.Header.Set(tracestateHeader, ts)
+		if ts, ok := req.Metadata[TracestateHeaderKey]; ok && ts != "" {
+			request.Header.Set(TracestateHeaderKey, ts)
 		}
 	}
 

bindings/http/http_test.go

@@ -177,15 +177,17 @@ func TestTraceHeadersForwarded(t *testing.T) {
 		req := TestCase{
 			input:      "GET",
 			operation:  "get",
-			metadata:   map[string]string{"path": "/somewhere", "traceparent": "12345", "tracestate": "67890"},
-			path:       "/somewhere",
+			metadata:   map[string]string{"path": "/", "traceparent": "12345", "tracestate": "67890"},
+			path:       "/",
 			err:        "",
 			statusCode: 200,
 		}.ToInvokeRequest()
 		_, err = hs.Invoke(context.Background(), &req)
 		assert.NoError(t, err)
-		assert.Empty(t, handler.Headers["Traceparent"])
-		assert.Empty(t, handler.Headers["Tracestate"])
+		_, traceParentExists := handler.Headers["Traceparent"]
+		assert.False(t, traceParentExists)
+		_, traceStateExists := handler.Headers["Traceparent"]
+		assert.False(t, traceStateExists)
 	})
 
 	hs, err = InitBinding(s, map[string]string{"traceHeaders": "true"})
@@ -195,8 +197,8 @@ func TestTraceHeadersForwarded(t *testing.T) {
 		req := TestCase{
 			input:      "GET",
 			operation:  "get",
-			metadata:   map[string]string{"path": "/somewhere", "traceparent": "12345", "tracestate": "67890"},
-			path:       "/somewhere",
+			metadata:   map[string]string{"path": "/", "traceparent": "12345", "tracestate": "67890"},
+			path:       "/",
 			err:        "",
 			statusCode: 200,
 		}.ToInvokeRequest()
@@ -205,6 +207,23 @@ func TestTraceHeadersForwarded(t *testing.T) {
 		assert.Equal(t, "12345", handler.Headers["Traceparent"])
 		assert.Equal(t, "67890", handler.Headers["Tracestate"])
 	})
+
+	t.Run("trace headers should not be forwarded if empty", func(t *testing.T) {
+		req := TestCase{
+			input:      "GET",
+			operation:  "get",
+			metadata:   map[string]string{"path": "/", "traceparent": "", "tracestate": ""},
+			path:       "/",
+			err:        "",
+			statusCode: 200,
+		}.ToInvokeRequest()
+		_, err = hs.Invoke(context.Background(), &req)
+		assert.NoError(t, err)
+		_, traceParentExists := handler.Headers["Traceparent"]
+		assert.False(t, traceParentExists)
+		_, traceStateExists := handler.Headers["Traceparent"]
+		assert.False(t, traceStateExists)
+	})
 }
 
 func InitBindingForHTTPS(s *httptest.Server, extraProps map[string]string) (bindings.OutputBinding, error) {