Add discardResponseMessage option for gRPC client

js/modules/k6/grpc/client.go

@@ -365,12 +365,13 @@ func (c *Client) buildInvokeRequest(
 	p.SetSystemTags(state, c.addr, method)
 
 	return grpcext.InvokeRequest{
-		Method:           method,
-		MethodDescriptor: methodDesc,
-		Timeout:          p.Timeout,
-		Message:          b,
-		TagsAndMeta:      &p.TagsAndMeta,
-		Metadata:         p.Metadata,
+		Method:                 method,
+		MethodDescriptor:       methodDesc,
+		Timeout:                p.Timeout,
+		DiscardResponseMessage: p.DiscardResponseMessage,
+		Message:                b,
+		TagsAndMeta:            &p.TagsAndMeta,
+		Metadata:               p.Metadata,
 	}, nil
 }
 

js/modules/k6/grpc/client_test.go

@@ -310,6 +310,19 @@ func TestClient(t *testing.T) {
 				client.invoke("grpc.testing.TestService/EmptyCall", {}, { timeout: 2000 })`,
 			},
 		},
+		{
+			name: "InvokeDiscardResponseMessage",
+			initString: codeBlock{
+				code: `
+				var client = new grpc.Client();
+				client.load([], "../../../../lib/testutils/httpmultibin/grpc_testing/test.proto");`,
+			},
+			vuString: codeBlock{
+				code: `
+				client.connect("GRPCBIN_ADDR");
+				client.invoke("grpc.testing.TestService/EmptyCall", {}, { discardResponseMessage: true })`,
+			},
+		},
 		{
 			name: "Invoke",
 			initString: codeBlock{code: `
@@ -333,6 +346,32 @@ func TestClient(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "InvokeDiscardResponseMessage",
+			initString: codeBlock{code: `
+				var client = new grpc.Client();
+				client.load([], "../../../../lib/testutils/httpmultibin/grpc_testing/test.proto");`},
+			setup: func(tb *httpmultibin.HTTPMultiBin) {
+				tb.GRPCStub.EmptyCallFunc = func(context.Context, *grpc_testing.Empty) (*grpc_testing.Empty, error) {
+					return &grpc_testing.Empty{}, nil
+				}
+			},
+			vuString: codeBlock{
+				code: `
+				client.connect("GRPCBIN_ADDR");
+				var resp = client.invoke("grpc.testing.TestService/EmptyCall", {}, { discardResponseMessage: true })
+				if (resp.status !== grpc.StatusOK) {
+					throw new Error("unexpected error: " + JSON.stringify(resp.error) + "or status: " + resp.status)
+				}
+				if (resp.message !== null) {
+					throw new Error("unexpected message: " + JSON.stringify(resp.message))
+				}`,
+				asserts: func(t *testing.T, rb *httpmultibin.HTTPMultiBin, samples chan metrics.SampleContainer, _ error) {
+					samplesBuf := metrics.GetBufferedSamples(samples)
+					assertMetricEmitted(t, metrics.GRPCReqDurationName, samplesBuf, rb.Replacer.Replace("GRPCBIN_ADDR/grpc.testing.TestService/EmptyCall"))
+				},
+			},
+		},
 		{
 			name: "AsyncInvoke",
 			initString: codeBlock{code: `
@@ -360,6 +399,36 @@ func TestClient(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "AsyncInvokeDiscardResponseMessage",
+			initString: codeBlock{code: `
+				var client = new grpc.Client();
+				client.load([], "../../../../lib/testutils/httpmultibin/grpc_testing/test.proto");`},
+			setup: func(tb *httpmultibin.HTTPMultiBin) {
+				tb.GRPCStub.EmptyCallFunc = func(context.Context, *grpc_testing.Empty) (*grpc_testing.Empty, error) {
+					return &grpc_testing.Empty{}, nil
+				}
+			},
+			vuString: codeBlock{
+				code: `
+				client.connect("GRPCBIN_ADDR");
+				client.asyncInvoke("grpc.testing.TestService/EmptyCall", {}, { discardResponseMessage: true }).then(function(resp) {
+					if (resp.status !== grpc.StatusOK) {
+						throw new Error("unexpected error: " + JSON.stringify(resp.error) + "or status: " + resp.status)
+					}
+					if (resp.message !== null) {
+						throw new Error("unexpected message: " + JSON.stringify(resp.message))
+					}
+				}, (err) => {
+					throw new Error("unexpected error: " + err)
+				})
+				`,
+				asserts: func(t *testing.T, rb *httpmultibin.HTTPMultiBin, samples chan metrics.SampleContainer, _ error) {
+					samplesBuf := metrics.GetBufferedSamples(samples)
+					assertMetricEmitted(t, metrics.GRPCReqDurationName, samplesBuf, rb.Replacer.Replace("GRPCBIN_ADDR/grpc.testing.TestService/EmptyCall"))
+				},
+			},
+		},
 		{
 			name: "InvokeAnyProto",
 			initString: codeBlock{code: `

js/modules/k6/grpc/params.go

@@ -18,9 +18,10 @@ import (
 // callParams is the parameters that can be passed to a gRPC calls
 // like invoke or newStream.
 type callParams struct {
-	Metadata    metadata.MD
-	TagsAndMeta metrics.TagsAndMeta
-	Timeout     time.Duration
+	Metadata               metadata.MD
+	TagsAndMeta            metrics.TagsAndMeta
+	Timeout                time.Duration
+	DiscardResponseMessage bool
 }
 
 // newCallParams constructs the call parameters from the input value.
@@ -58,6 +59,8 @@ func newCallParams(vu modules.VU, input sobek.Value) (*callParams, error) {
 			if err != nil {
 				return result, fmt.Errorf("invalid timeout value: %w", err)
 			}
+		case "discardResponseMessage":
+			result.DiscardResponseMessage = params.Get(k).ToBoolean()
 		default:
 			return result, fmt.Errorf("unknown param: %q", k)
 		}

js/modules/k6/grpc/params_test.go

@@ -139,6 +139,47 @@ func TestCallParamsTimeOutParse(t *testing.T) {
 	}
 }
 
+func TestCallParamsDiscardResponseMessageParse(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		Name                   string
+		JSON                   string
+		DiscardResponseMessage bool
+	}{
+		{
+			Name:                   "Empty",
+			JSON:                   `{}`,
+			DiscardResponseMessage: false,
+		},
+		{
+			Name:                   "DiscardResponseMessageFalse",
+			JSON:                   `{ discardResponseMessage: false }`,
+			DiscardResponseMessage: false,
+		},
+		{
+			Name:                   "DiscardResponseMessageTrue",
+			JSON:                   `{ discardResponseMessage: true }`,
+			DiscardResponseMessage: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+
+		t.Run(tc.Name, func(t *testing.T) {
+			t.Parallel()
+
+			testRuntime, params := newParamsTestRuntime(t, tc.JSON)
+
+			p, err := newCallParams(testRuntime.VU, params)
+			require.NoError(t, err)
+
+			assert.Equal(t, tc.DiscardResponseMessage, p.DiscardResponseMessage)
+		})
+	}
+}
+
 // newParamsTestRuntime creates a new test runtime
 // that could be used to test the params
 // it also moves to the VU context and creates the params

lib/netext/grpcext/conn.go

@@ -26,16 +26,20 @@ import (
 	"google.golang.org/protobuf/reflect/protoreflect"
 	"google.golang.org/protobuf/types/descriptorpb"
 	"google.golang.org/protobuf/types/dynamicpb"
+	"google.golang.org/protobuf/types/known/emptypb"
 )
 
+var emptyDescriptor = (&emptypb.Empty{}).ProtoReflect().Descriptor() //nolint:gochecknoglobals
+
 // InvokeRequest represents a unary gRPC request.
 type InvokeRequest struct {
-	Method           string
-	MethodDescriptor protoreflect.MethodDescriptor
-	Timeout          time.Duration
-	TagsAndMeta      *metrics.TagsAndMeta
-	Message          []byte
-	Metadata         metadata.MD
+	Method                 string
+	MethodDescriptor       protoreflect.MethodDescriptor
+	Timeout                time.Duration
+	TagsAndMeta            *metrics.TagsAndMeta
+	DiscardResponseMessage bool
+	Message                []byte
+	Metadata               metadata.MD
 }
 
 // InvokeResponse represents a gRPC response.
@@ -133,7 +137,13 @@ func (c *Conn) Invoke(
 
 	ctx = withRPCState(ctx, &rpcState{tagsAndMeta: req.TagsAndMeta})
 
-	resp := dynamicpb.NewMessage(req.MethodDescriptor.Output())
+	var resp *dynamicpb.Message
+	if req.DiscardResponseMessage {
+		resp = dynamicpb.NewMessage(emptyDescriptor)
+	} else {
+		resp = dynamicpb.NewMessage(req.MethodDescriptor.Output())
+	}
+
 	header, trailer := metadata.New(nil), metadata.New(nil)
 
 	copts := make([]grpc.CallOption, 0, len(opts)+2)
@@ -165,7 +175,7 @@ func (c *Conn) Invoke(
 		response.Error = errMsg
 	}
 
-	if resp != nil {
+	if resp != nil && !req.DiscardResponseMessage {
 		msg, err := convert(marshaler, resp)
 		if err != nil {
 			return nil, fmt.Errorf("unable to convert response object to JSON: %w", err)

lib/netext/grpcext/conn_test.go

@@ -64,6 +64,28 @@ func TestInvokeWithCallOptions(t *testing.T) {
 	assert.NotNil(t, res)
 }
 
+func TestInvokeWithDiscardResponseMessage(t *testing.T) {
+	t.Parallel()
+
+	reply := func(_, _ *dynamicpb.Message, opts ...grpc.CallOption) error {
+		assert.Len(t, opts, 3) // two by default plus one injected
+		return nil
+	}
+
+	c := Conn{raw: invokemock(reply)}
+	r := InvokeRequest{
+		Method:                 "/hello.HelloService/NoOp",
+		MethodDescriptor:       methodFromProto("NoOp"),
+		DiscardResponseMessage: true,
+		Message:                []byte(`{}`),
+		Metadata:               metadata.New(nil),
+	}
+	res, err := c.Invoke(context.Background(), r, grpc.UseCompressor("fakeone"))
+	require.NoError(t, err)
+	assert.NotNil(t, res)
+	assert.Nil(t, res.Message)
+}
+
 func TestInvokeReturnError(t *testing.T) {
 	t.Parallel()