Use new track id for republishing (#3020)

* Use new track id for republishing

Always generates new track id for track publishing
to make the behavior more consistent. A republishing of
clien track will be considered as a new track publication
and always trigger trackUnpublished & trackPublished event
on subscriber side.

* remove test

pkg/rtc/participant.go

@@ -207,9 +207,6 @@ type ParticipantImpl struct {
 
 	icQueue [2]atomic.Pointer[webrtc.ICECandidate]
 
-	// keeps track of unpublished tracks in order to reuse trackID
-	unpublishedTracks []*livekit.TrackInfo
-
 	requireBroadcast bool
 	// queued participant updates before join response is sent
 	// guarded by updateLock
@@ -1913,7 +1910,7 @@ func (p *ParticipantImpl) addPendingTrackLocked(req *livekit.AddTrackRequest) *l
 	if ti.Stream == "" {
 		ti.Stream = StreamFromTrackSource(ti.Source)
 	}
-	p.setStableTrackID(req.Cid, ti)
+	p.setTrackID(req.Cid, ti)
 
 	if len(req.SimulcastCodecs) == 0 {
 		if req.Type == livekit.TrackType_VIDEO {
@@ -2268,8 +2265,6 @@ func (p *ParticipantImpl) addMediaTrack(signalCid string, sdpCid string, ti *liv
 		if pti := p.pendingTracks[signalCid]; pti != nil {
 			p.sendTrackPublished(signalCid, pti.trackInfos[0])
 			pti.queued = false
-		} else {
-			p.unpublishedTracks = append(p.unpublishedTracks, ti)
 		}
 		p.pendingTracksLock.Unlock()
 		p.handlePendingRemoteTracks()
@@ -2368,9 +2363,8 @@ func (p *ParticipantImpl) getPendingTrack(clientId string, kind livekit.TrackTyp
 	return signalCid, pendingInfo.trackInfos[0], pendingInfo.migrated, pendingInfo.createdAt
 }
 
-// setStableTrackID either generates a new TrackID or reuses a previously used one
-// for
-func (p *ParticipantImpl) setStableTrackID(cid string, info *livekit.TrackInfo) {
+// setTrackID either generates a new TrackID for an AddTrackRequest
+func (p *ParticipantImpl) setTrackID(cid string, info *livekit.TrackInfo) {
 	var trackID string
 	// if already pending, use the same SID
 	// should not happen as this means multiple `AddTrack` requests have been called, but check anyway
@@ -2378,31 +2372,6 @@ func (p *ParticipantImpl) setStableTrackID(cid string, info *livekit.TrackInfo)
 		trackID = pti.trackInfos[0].Sid
 	}
 
-	// check against published tracks as re-publish could be happening
-	if trackID == "" {
-		if pt := p.getPublishedTrackBySignalCid(cid); pt != nil {
-			ti := pt.ToProto()
-			if ti.Type == info.Type && ti.Source == info.Source && ti.Name == info.Name {
-				trackID = ti.Sid
-			}
-		}
-	}
-
-	if trackID == "" {
-		// check a previously published matching track
-		for i, ti := range p.unpublishedTracks {
-			if ti.Type == info.Type && ti.Source == info.Source && ti.Name == info.Name {
-				trackID = ti.Sid
-				if i < len(p.unpublishedTracks)-1 {
-					p.unpublishedTracks = append(p.unpublishedTracks[:i], p.unpublishedTracks[i+1:]...)
-				} else {
-					p.unpublishedTracks = p.unpublishedTracks[:i]
-				}
-				break
-			}
-		}
-	}
-
 	// otherwise generate
 	if trackID == "" {
 		trackPrefix := utils.TrackPrefix

pkg/rtc/participant_internal_test.go

@@ -332,77 +332,6 @@ func TestSubscriberAsPrimary(t *testing.T) {
 	})
 }
 
-func TestSetStableTrackID(t *testing.T) {
-	testCases := []struct {
-		name                 string
-		trackInfo            *livekit.TrackInfo
-		unpublished          []*livekit.TrackInfo
-		cid                  string
-		prefix               string
-		remainingUnpublished int
-	}{
-		{
-			name: "first track, generates new ID",
-			trackInfo: &livekit.TrackInfo{
-				Type:   livekit.TrackType_VIDEO,
-				Source: livekit.TrackSource_CAMERA,
-			},
-			prefix: "TR_VC",
-		},
-		{
-			name: "re-using existing ID",
-			trackInfo: &livekit.TrackInfo{
-				Type:   livekit.TrackType_VIDEO,
-				Source: livekit.TrackSource_CAMERA,
-			},
-			unpublished: []*livekit.TrackInfo{
-				{
-					Type:   livekit.TrackType_VIDEO,
-					Source: livekit.TrackSource_SCREEN_SHARE,
-					Sid:    "TR_VC1234",
-				},
-				{
-					Type:   livekit.TrackType_VIDEO,
-					Source: livekit.TrackSource_CAMERA,
-					Sid:    "TR_VC1235",
-				},
-			},
-			cid:                  "TR_VC1235",
-			prefix:               "TR_VC1235",
-			remainingUnpublished: 1,
-		},
-		{
-			name: "mismatch name for reuse",
-			trackInfo: &livekit.TrackInfo{
-				Type:   livekit.TrackType_VIDEO,
-				Source: livekit.TrackSource_CAMERA,
-				Name:   "new_name",
-			},
-			unpublished: []*livekit.TrackInfo{
-				{
-					Type:   livekit.TrackType_VIDEO,
-					Source: livekit.TrackSource_CAMERA,
-					Sid:    "TR_NotUsed",
-				},
-			},
-			prefix:               "TR_VC",
-			remainingUnpublished: 1,
-		},
-	}
-
-	for _, tc := range testCases {
-		t.Run(tc.name, func(t *testing.T) {
-			p := newParticipantForTest("test")
-			p.unpublishedTracks = tc.unpublished
-
-			ti := tc.trackInfo
-			p.setStableTrackID(tc.cid, ti)
-			require.Contains(t, ti.Sid, tc.prefix)
-			require.Len(t, p.unpublishedTracks, tc.remainingUnpublished)
-		})
-	}
-}
-
 func TestDisableCodecs(t *testing.T) {
 	participant := newParticipantForTestWithOpts("123", &participantOpts{
 		publisher: false,