Fix memory leak potential by not calling op.cancel()

transcoder.go

@@ -59,11 +59,12 @@ type Transcoder struct {
 // services and transcoding protocols and message encoding as needed.
 func (t *Transcoder) ServeHTTP(writer http.ResponseWriter, request *http.Request) {
 	op := t.newOperation(writer, request)
+	defer op.cancel()
 	err := op.validate(t)
 
 	if t.unknownHandler != nil && errors.Is(err, errNotFound) {
-		request.Header = op.originalHeaders // restore headers, just in case initialization removed keys
-		t.unknownHandler.ServeHTTP(writer, request)
+		op.request.Header = op.originalHeaders // restore headers, just in case initialization removed keys
+		t.unknownHandler.ServeHTTP(writer, op.request)
 		return
 	}
 
@@ -77,8 +78,8 @@ func (t *Transcoder) ServeHTTP(writer http.ResponseWriter, request *http.Request
 		op.client.reqCompression.Name() == op.server.reqCompression.Name() {
 		// No transformation needed. But we do need to restore the original headers first
 		// since extracting request metadata may have removed keys.
-		request.Header = op.originalHeaders
-		op.methodConf.handler.ServeHTTP(writer, request)
+		op.request.Header = op.originalHeaders
+		op.methodConf.handler.ServeHTTP(writer, op.request)
 		return
 	}
 

transcoder_test.go

@@ -1740,3 +1740,61 @@ func rot13(data []byte) {
 		data[index] = char
 	}
 }
+
+func TestTranscoder_ContextLeak(t *testing.T) {
+	t.Parallel()
+
+	t.Run("success_pass_through", func(t *testing.T) {
+		t.Parallel()
+		ctxChan := make(chan context.Context, 1)
+		rpcHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			ctxChan <- r.Context()
+			w.WriteHeader(http.StatusOK)
+		})
+		services := []*Service{
+			NewService(testv1connect.LibraryServiceName, rpcHandler),
+		}
+		handler, err := NewTranscoder(services)
+		require.NoError(t, err)
+
+		req := httptest.NewRequest(http.MethodPost, "/vanguard.test.v1.LibraryService/GetBook", nil)
+		req.ProtoMajor = 2
+		req.ProtoMinor = 0
+		req.Header.Set("Content-Type", "application/grpc")
+		rec := httptest.NewRecorder()
+
+		handler.ServeHTTP(rec, req)
+
+		var handlerCtx context.Context
+		select {
+		case handlerCtx = <-ctxChan:
+		default:
+		}
+		require.NotNil(t, handlerCtx)
+		assert.ErrorIs(t, handlerCtx.Err(), context.Canceled)
+	})
+
+	t.Run("not_found_unknown_handler", func(t *testing.T) {
+		t.Parallel()
+		ctxChan := make(chan context.Context, 1)
+		unknownHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			ctxChan <- r.Context()
+			w.WriteHeader(http.StatusNotFound)
+		})
+		handler, err := NewTranscoder(nil, WithUnknownHandler(unknownHandler))
+		require.NoError(t, err)
+
+		req := httptest.NewRequest(http.MethodGet, "/unknown/path", nil)
+		rec := httptest.NewRecorder()
+
+		handler.ServeHTTP(rec, req)
+
+		var unknownCtx context.Context
+		select {
+		case unknownCtx = <-ctxChan:
+		default:
+		}
+		require.NotNil(t, unknownCtx)
+		assert.ErrorIs(t, unknownCtx.Err(), context.Canceled)
+	})
+}