From cf06c236cb197b4a2ae99012c8ff83b46c11a050 Mon Sep 17 00:00:00 2001
From: David Zhao <dz@livekit.io>
Date: Mon, 24 Feb 2025 19:41:41 -0800
Subject: [PATCH] fix: race that causes LocalParticipant to show up as
 RemoteParticipant (#619)

* fix: race that causes LocalParticipant to show up as RemoteParticipant

RTCEngine.JoinContext starts SignalClient's dispatch loop. If there's an
update to the local participant (in the form of ParticipantUpdate) before
PeerConnection is established, then we would incorrectly categorize the
LocalParticipant as a RemoteParticipant.

* actually call it

* fix staticcheck
---
 engine.go            |  5 +++++
 regionurlprovider.go |  9 +++++++--
 room.go              | 46 ++++++++++++++++++++++++--------------------
 3 files changed, 37 insertions(+), 23 deletions(-)

diff --git a/engine.go b/engine.go
index e7f722a7..b1d96fa0 100644
--- a/engine.go
+++ b/engine.go
@@ -83,6 +83,7 @@ type RTCEngine struct {
 	OnResuming              func()
 	OnResumed               func()
 	OnTranscription         func(*livekit.Transcription)
+	OnSignalClientConnected func(*livekit.JoinResponse)
 
 	// callbacks to get data
 	CbGetLocalParticipantSID func() string
@@ -160,6 +161,10 @@ func (e *RTCEngine) JoinContext(ctx context.Context, url string, token string, p
 		return nil, err
 	}
 
+	if e.OnSignalClientConnected != nil {
+		e.OnSignalClientConnected(res)
+	}
+
 	e.client.Start()
 
 	// send offer
diff --git a/regionurlprovider.go b/regionurlprovider.go
index 415ba810..b804919d 100644
--- a/regionurlprovider.go
+++ b/regionurlprovider.go
@@ -78,14 +78,19 @@ func (r *regionURLProvider) RefreshRegionSettings(cloudHostname, token string) e
 		return errors.New("refreshRegionSettings failed to decode region settings: " + err.Error())
 	}
 
-	r.mutex.Lock()
-	r.hostnameSettingsCache[cloudHostname] = &hostnameSettingsCacheItem{
+	item := &hostnameSettingsCacheItem{
 		regionSettings:    regions,
 		updatedAt:         time.Now(),
 		regionURLAttempts: map[string]int{},
 	}
+	r.mutex.Lock()
+	r.hostnameSettingsCache[cloudHostname] = item
 	r.mutex.Unlock()
 
+	if len(item.regionSettings.Regions) == 0 {
+		logger.Warnw("no regions returned", nil, "cloudHostname", cloudHostname)
+	}
+
 	return nil
 }
 
diff --git a/room.go b/room.go
index d4177114..d8a6f3a5 100644
--- a/room.go
+++ b/room.go
@@ -189,6 +189,7 @@ func NewRoom(callback *RoomCallback) *Room {
 	r.LocalParticipant = newLocalParticipant(engine, r.callback)
 
 	// callbacks from engine
+	engine.OnSignalClientConnected = r.handleSignalClientConnected
 	engine.OnMediaTrack = r.handleMediaTrack
 	engine.OnDisconnected = r.handleDisconnect
 	engine.OnParticipantUpdate = r.handleParticipantUpdate
@@ -328,6 +329,7 @@ func (r *Room) JoinWithToken(url, token string, opts ...ConnectOption) error {
 					d := time.Duration(1<<min(tries, 6)) * time.Second // max 64 seconds
 					logger.Errorw("failed to join room", err,
 						"retrying in", d,
+						"url", bestURL,
 					)
 					time.Sleep(d)
 					continue
@@ -338,32 +340,12 @@ func (r *Room) JoinWithToken(url, token string, opts ...ConnectOption) error {
 
 	if joinRes == nil {
 		var err error
-		joinRes, err = r.engine.JoinContext(ctx, url, token, params)
+		_, err = r.engine.JoinContext(ctx, url, token, params)
 		if err != nil {
 			return err
 		}
 	}
 
-	r.lock.Lock()
-	r.name = joinRes.Room.Name
-	r.metadata = joinRes.Room.Metadata
-	r.serverInfo = joinRes.ServerInfo
-	r.connectionState = ConnectionStateConnected
-	r.sifTrailer = make([]byte, len(joinRes.SifTrailer))
-	copy(r.sifTrailer, joinRes.SifTrailer)
-	r.lock.Unlock()
-
-	r.setSid(joinRes.Room.Sid, false)
-
-	r.LocalParticipant.updateInfo(joinRes.Participant)
-	r.LocalParticipant.updateSubscriptionPermission()
-
-	for _, pi := range joinRes.OtherParticipants {
-		rp := r.addRemoteParticipant(pi, true)
-		r.clearParticipantDefers(livekit.ParticipantID(pi.Sid), pi)
-		r.runParticipantDefers(livekit.ParticipantID(pi.Sid), rp)
-	}
-
 	return nil
 }
 
@@ -552,6 +534,28 @@ func (r *Room) handleMediaTrack(track *webrtc.TrackRemote, receiver *webrtc.RTPR
 	r.runParticipantDefers(livekit.ParticipantID(participantID), rp)
 }
 
+func (r *Room) handleSignalClientConnected(joinRes *livekit.JoinResponse) {
+	r.lock.Lock()
+	r.name = joinRes.Room.Name
+	r.metadata = joinRes.Room.Metadata
+	r.serverInfo = joinRes.ServerInfo
+	r.connectionState = ConnectionStateConnected
+	r.sifTrailer = make([]byte, len(joinRes.SifTrailer))
+	copy(r.sifTrailer, joinRes.SifTrailer)
+	r.lock.Unlock()
+
+	r.setSid(joinRes.Room.Sid, false)
+
+	r.LocalParticipant.updateInfo(joinRes.Participant)
+	r.LocalParticipant.updateSubscriptionPermission()
+
+	for _, pi := range joinRes.OtherParticipants {
+		r.addRemoteParticipant(pi, true)
+		r.clearParticipantDefers(livekit.ParticipantID(pi.Sid), pi)
+		// no need to run participant defers here, since we are connected for the first time
+	}
+}
+
 func (r *Room) handleDisconnect(reason DisconnectionReason) {
 	r.callback.OnDisconnected()
 	r.callback.OnDisconnectedWithReason(reason)