Add a second argument to callbacks for grpc streams with metadata

Change updates the grpc stream callbacks to all receivers to be passed
a meta data object that includes the timestamp of the original event.
This change facilitates being able to accurately check the time when a
message was recevied by a client stream.

js/modules/k6/grpc/listeners.go

@@ -27,7 +27,7 @@ type eventListener struct {
 
 	// this return sobek.value *and* error in order to return error on exception instead of panic
 	// https://pkg.go.dev/github.com/dop251/goja#hdr-Functions
-	list []func(sobek.Value) (sobek.Value, error)
+	list []func(sobek.Value, sobek.Value) (sobek.Value, error)
 }
 
 // newListener creates a new listener of a certain type
@@ -38,7 +38,7 @@ func newListener(eventType string) *eventListener {
 }
 
 // add adds a listener to the listener list
-func (l *eventListener) add(fn func(sobek.Value) (sobek.Value, error)) {
+func (l *eventListener) add(fn func(sobek.Value, sobek.Value) (sobek.Value, error)) {
 	l.list = append(l.list, fn)
 }
 
@@ -59,7 +59,7 @@ func (l *eventListeners) getType(t string) *eventListener {
 }
 
 // add adds a listener to the listeners
-func (l *eventListeners) add(t string, f func(sobek.Value) (sobek.Value, error)) error {
+func (l *eventListeners) add(t string, f func(sobek.Value, sobek.Value) (sobek.Value, error)) error {
 	list := l.getType(t)
 
 	if list == nil {
@@ -72,11 +72,11 @@ func (l *eventListeners) add(t string, f func(sobek.Value) (sobek.Value, error))
 }
 
 // all returns all possible listeners for a certain event type or an empty array
-func (l *eventListeners) all(t string) []func(sobek.Value) (sobek.Value, error) {
+func (l *eventListeners) all(t string) []func(sobek.Value, sobek.Value) (sobek.Value, error) {
 	list := l.getType(t)
 
 	if list == nil {
-		return []func(sobek.Value) (sobek.Value, error){}
+		return []func(sobek.Value, sobek.Value) (sobek.Value, error){}
 	}
 
 	return list.list

js/modules/k6/grpc/stream.go

@@ -33,6 +33,10 @@ const (
 	closed
 )
 
+const (
+	timestampMetadata = "ts"
+)
+
 type stream struct {
 	vu     modules.VU
 	client *Client
@@ -143,12 +147,13 @@ func (s *stream) loop() {
 }
 
 func (s *stream) queueMessage(msg interface{}) {
+	now := time.Now()
 	metrics.PushIfNotDone(s.vu.Context(), s.vu.State().Samples, metrics.Sample{
 		TimeSeries: metrics.TimeSeries{
 			Metric: s.instanceMetrics.StreamsMessagesReceived,
 			Tags:   s.tagsAndMeta.Tags,
 		},
-		Time:     time.Now(),
+		Time:     now,
 		Metadata: s.tagsAndMeta.Metadata,
 		Value:    1,
 	})
@@ -157,8 +162,14 @@ func (s *stream) queueMessage(msg interface{}) {
 		rt := s.vu.Runtime()
 		listeners := s.eventListeners.all(eventData)
 
+		metadataObj := rt.NewObject()
+		err := metadataObj.Set(timestampMetadata, rt.ToValue(now.Unix()))
+		if err != nil {
+			return err
+		}
+
 		for _, messageListener := range listeners {
-			if _, err := messageListener(rt.ToValue(msg)); err != nil {
+			if _, err := messageListener(rt.ToValue(msg), metadataObj); err != nil {
 				// TODO(olegbespalov) consider logging the error
 				_ = s.closeWithError(err)
 
@@ -294,7 +305,7 @@ func (s *stream) processSendError(err error) {
 }
 
 // on registers a handler for a certain event type
-func (s *stream) on(event string, handler func(sobek.Value) (sobek.Value, error)) {
+func (s *stream) on(event string, handler func(sobek.Value, sobek.Value) (sobek.Value, error)) {
 	if handler == nil {
 		common.Throw(s.vu.Runtime(), fmt.Errorf("handler for %q event isn't a callable function", event))
 	}
@@ -384,8 +395,15 @@ func (s *stream) callErrorListeners(e error) error {
 		s.logger.Warnf("no handlers for error registered, but an error happened: %s", e)
 	}
 
+	now := time.Now()
+	metadataObj := rt.NewObject()
+	err := metadataObj.Set(timestampMetadata, rt.ToValue(now.Unix()))
+	if err != nil {
+		return err
+	}
+
 	for _, errorListener := range list {
-		if _, err := errorListener(rt.ToValue(obj)); err != nil {
+		if _, err := errorListener(rt.ToValue(obj), metadataObj); err != nil {
 			return err
 		}
 	}
@@ -426,10 +444,16 @@ func extractError(e error) grpcError {
 }
 
 func (s *stream) callEventListeners(eventType string) error {
+	now := time.Now()
 	rt := s.vu.Runtime()
 
+	metadataObj := rt.NewObject()
+	err := metadataObj.Set(timestampMetadata, rt.ToValue(now.Unix()))
+	if err != nil {
+		return err
+	}
 	for _, listener := range s.eventListeners.all(eventType) {
-		if _, err := listener(rt.ToValue(struct{}{})); err != nil {
+		if _, err := listener(rt.ToValue(struct{}{}), metadataObj); err != nil {
 			return err
 		}
 	}

js/modules/k6/grpc/stream_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"io"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -271,6 +272,92 @@ func TestStream_ReceiveAllServerResponsesAfterEnd(t *testing.T) {
 	)
 }
 
+func TestStream_ReceiveMetadata(t *testing.T) {
+	t.Parallel()
+
+	ts := newTestState(t)
+
+	stub := &featureExplorerStub{}
+
+	savedFeatures := []*grpcservice.Feature{
+		{
+			Name: "foo",
+			Location: &grpcservice.Point{
+				Latitude:  1,
+				Longitude: 2,
+			},
+		},
+		{
+			Name: "bar",
+			Location: &grpcservice.Point{
+				Latitude:  3,
+				Longitude: 4,
+			},
+		},
+	}
+
+	stub.listFeatures = func(_ *grpcservice.Rectangle, stream grpcservice.FeatureExplorer_ListFeaturesServer) error {
+		for _, feature := range savedFeatures {
+			// adding a delay to make server response "slower"
+			time.Sleep(200 * time.Millisecond)
+
+			if err := stream.Send(feature); err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}
+
+	grpcservice.RegisterFeatureExplorerServer(ts.httpBin.ServerGRPC, stub)
+
+	initString := codeBlock{
+		code: `
+		var client = new grpc.Client();
+		client.load([], "../../../../lib/testutils/grpcservice/route_guide.proto");`,
+	}
+	vuString := codeBlock{
+		code: `
+		client.connect("GRPCBIN_ADDR");
+		let stream = new grpc.Stream(client, "main.FeatureExplorer/ListFeatures")
+		stream.on('data', function (data, meta) {
+			call(meta.ts);
+		});
+		stream.on('end', function (_, meta) {
+			call(meta.ts);
+		});
+
+		stream.write({
+			lo: {
+			  latitude: 1,
+			  longitude: 2,
+			},
+			hi: {
+			  latitude: 1,
+			  longitude: 2,
+			},
+		});
+		stream.end();
+		`,
+	}
+
+	val, err := ts.Run(initString.code)
+	assertResponse(t, initString, err, val, ts)
+
+	ts.ToVUContext()
+
+	val, err = ts.RunOnEventLoop(vuString.code)
+
+	assertResponse(t, vuString, err, val, ts)
+
+	for _, call := range ts.callRecorder.Recorded() {
+		seconds, err := strconv.ParseInt(call, 10, 64)
+		assert.NoError(t, err)
+		metaTS := time.Unix(seconds, 0)
+		assert.WithinDuration(t, time.Now(), metaTS, 1*time.Minute)
+	}
+}
+
 // featureExplorerStub is a stub for FeatureExplorerServer
 // it has ability to override methods
 type featureExplorerStub struct {