feat: option to emit event to bus upon message sent

waku/v2/api/publish/message_sender.go

@@ -6,6 +6,8 @@ import (
 	"time"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/libp2p/go-libp2p/core/event"
+	"github.com/libp2p/go-libp2p/core/host"
 	"github.com/libp2p/go-libp2p/core/peer"
 	"github.com/waku-org/go-waku/waku/v2/protocol"
 	"github.com/waku-org/go-waku/waku/v2/protocol/pb"
@@ -53,6 +55,12 @@ type MessageSender struct {
 	messageSentCheck ISentCheck
 	rateLimiter      *PublishRateLimiter
 	logger           *zap.Logger
+	evtMessageSent   event.Emitter
+}
+
+type MessageSent struct {
+	Size      uint32 // Size of payload in bytes
+	Timestamp int64
 }
 
 type Request struct {
@@ -96,6 +104,15 @@ func (ms *MessageSender) WithRateLimiting(rateLimiter *PublishRateLimiter) *Mess
 	return ms
 }
 
+func (ms *MessageSender) WithMessageSentEmitter(host host.Host) *MessageSender {
+	evtMessageSent, err := host.EventBus().Emitter(new(MessageSent))
+	if err != nil {
+		ms.logger.Error("failed to create message sent emitter", zap.Error(err))
+	}
+	ms.evtMessageSent = evtMessageSent
+	return ms
+}
+
 func (ms *MessageSender) Send(req *Request) error {
 	logger := ms.logger.With(
 		zap.Stringer("envelopeHash", req.envelope.Hash()),
@@ -149,6 +166,16 @@ func (ms *MessageSender) Send(req *Request) error {
 		)
 	}
 
+	if ms.evtMessageSent != nil {
+		err := ms.evtMessageSent.Emit(MessageSent{
+			Size:      uint32(len(req.envelope.Message().Payload)),
+			Timestamp: req.envelope.Message().GetTimestamp(),
+		})
+		if err != nil {
+			logger.Error("failed to emit message sent event", zap.Error(err))
+		}
+	}
+
 	return nil
 }
 

waku/v2/api/publish/message_sender_test.go

@@ -3,6 +3,7 @@ package publish
 import (
 	"context"
 	"crypto/rand"
+	"sync"
 	"testing"
 	"time"
 
@@ -129,3 +130,45 @@ func createRelayNode(t *testing.T) (host.Host, *relay.WakuRelay) {
 
 	return host, relay
 }
+
+func TestMessageSentEmitter(t *testing.T) {
+	host, relayNode := createRelayNode(t)
+	err := relayNode.Start(context.Background())
+	require.Nil(t, err)
+	defer relayNode.Stop()
+
+	_, err = relayNode.Subscribe(context.Background(), protocol.NewContentFilter("test-pubsub-topic"))
+	require.Nil(t, err)
+	publisher := NewDefaultPublisher(nil, relayNode)
+	sender, err := NewMessageSender(Relay, publisher, utils.Logger())
+	require.Nil(t, err)
+
+	check := &MockMessageSentCheck{Messages: make(map[string]map[common.Hash]uint32)}
+	sender.WithMessageSentCheck(check)
+	sender.WithMessageSentEmitter(host)
+
+	msg := &pb.WakuMessage{
+		Payload:      []byte{1, 2, 3},
+		Timestamp:    utils.GetUnixEpoch(),
+		ContentTopic: "test-content-topic",
+	}
+	envelope := protocol.NewEnvelope(msg, *utils.GetUnixEpoch(), "test-pubsub-topic")
+	req := NewRequest(context.TODO(), envelope)
+
+	wg := sync.WaitGroup{}
+	wg.Add(1)
+	sub, err := host.EventBus().Subscribe(new(MessageSent))
+	require.Nil(t, err)
+	go func() {
+		for msgSentEvt := range sub.Out() {
+			msgSent := msgSentEvt.(MessageSent)
+			require.Equal(t, uint32(len(msg.Payload)), msgSent.Size)
+			require.Equal(t, msg.Timestamp, msgSent.Timestamp)
+			wg.Done()
+		}
+	}()
+
+	err = sender.Send(req)
+	require.Nil(t, err)
+	go wg.Wait()
+}