Listen directly to connectionState changes instead of polling

livekit-android-sdk/src/main/java/io/livekit/android/room/PublisherTransportObserver.kt

@@ -16,7 +16,10 @@
 
 package io.livekit.android.room
 
+import io.livekit.android.room.util.PeerConnectionStateObservable
+import io.livekit.android.util.FlowObservable
 import io.livekit.android.util.LKLog
+import io.livekit.android.util.flowDelegate
 import io.livekit.android.webrtc.peerconnection.executeOnRTCThread
 import livekit.LivekitRtc
 import livekit.org.webrtc.CandidatePairChangeEvent
@@ -31,9 +34,14 @@ import livekit.org.webrtc.SessionDescription
 internal class PublisherTransportObserver(
     private val engine: RTCEngine,
     private val client: SignalClient,
-) : PeerConnection.Observer, PeerConnectionTransport.Listener {
+) : PeerConnection.Observer, PeerConnectionTransport.Listener, PeerConnectionStateObservable {
 
-    var connectionChangeListener: ((newState: PeerConnection.PeerConnectionState) -> Unit)? = null
+    var connectionChangeListener: PeerConnectionStateListener? = null
+
+    @FlowObservable
+    @get:FlowObservable
+    override var connectionState by flowDelegate(PeerConnection.PeerConnectionState.NEW)
+        private set
 
     override fun onIceCandidate(iceCandidate: IceCandidate?) {
         executeOnRTCThread {
@@ -66,6 +74,7 @@ internal class PublisherTransportObserver(
         executeOnRTCThread {
             LKLog.v { "onConnection new state: $newState" }
             connectionChangeListener?.invoke(newState)
+            connectionState = newState
         }
     }
 

livekit-android-sdk/src/main/java/io/livekit/android/room/RTCEngine.kt

@@ -29,6 +29,7 @@ import io.livekit.android.room.track.TrackException
 import io.livekit.android.room.util.MediaConstraintKeys
 import io.livekit.android.room.util.createAnswer
 import io.livekit.android.room.util.setLocalDescription
+import io.livekit.android.room.util.waitUntilConnected
 import io.livekit.android.util.CloseableCoroutineScope
 import io.livekit.android.util.Either
 import io.livekit.android.util.FlowObservable
@@ -49,10 +50,12 @@ import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.ensureActive
+import kotlinx.coroutines.joinAll
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
+import kotlinx.coroutines.withTimeoutOrNull
 import kotlinx.coroutines.yield
 import livekit.LivekitModels
 import livekit.LivekitModels.AudioTrackFeature
@@ -66,6 +69,7 @@ import livekit.org.webrtc.MediaConstraints
 import livekit.org.webrtc.MediaStream
 import livekit.org.webrtc.MediaStreamTrack
 import livekit.org.webrtc.PeerConnection
+import livekit.org.webrtc.PeerConnection.PeerConnectionState
 import livekit.org.webrtc.PeerConnection.RTCConfiguration
 import livekit.org.webrtc.RTCStatsCollectorCallback
 import livekit.org.webrtc.RTCStatsReport
@@ -246,7 +250,7 @@ internal constructor(
                     null,
                 )
 
-                val connectionStateListener: (PeerConnection.PeerConnectionState) -> Unit = { newState ->
+                val connectionStateListener: PeerConnectionStateListener = { newState ->
                     LKLog.v { "onIceConnection new state: $newState" }
                     if (newState.isConnected()) {
                         connectionState = ConnectionState.CONNECTED
@@ -528,31 +532,21 @@ internal constructor(
                 }
 
                 // wait until publisher ICE connected
-                val endTime = SystemClock.elapsedRealtime() + MAX_ICE_CONNECT_TIMEOUT_MS
+                var publisherWaitJob: Job? = null
                 if (hasPublished) {
-                    while (SystemClock.elapsedRealtime() < endTime) {
-                        if (publisher?.isConnected() == true) {
-                            LKLog.v { "publisher reconnected to ICE" }
-                            break
-                        }
-                        delay(100)
+                    publisherWaitJob = launch {
+                        publisherObserver.waitUntilConnected()
                     }
                 }
 
-                ensureActive()
-                if (isClosed) {
-                    LKLog.v { "RTCEngine closed, aborting reconnection" }
-                    break
+                // wait until subscriber ICE connected
+                val subscriberWaitJob = launch {
+                    subscriberObserver.waitUntilConnected()
                 }
 
-                // wait until subscriber ICE connected
-                while (SystemClock.elapsedRealtime() < endTime) {
-                    if (subscriber?.isConnected() == true) {
-                        LKLog.v { "reconnected to ICE" }
-                        connectionState = ConnectionState.CONNECTED
-                        break
-                    }
-                    delay(100)
+                withTimeoutOrNull(MAX_ICE_CONNECT_TIMEOUT_MS.toLong()) {
+                    listOfNotNull(publisherWaitJob, subscriberWaitJob)
+                        .joinAll()
                 }
 
                 ensureActive()
@@ -1160,3 +1154,5 @@ fun LivekitRtc.ICEServer.toWebrtc(): PeerConnection.IceServer = PeerConnection.I
     .setTlsAlpnProtocols(emptyList())
     .setTlsEllipticCurves(emptyList())
     .createIceServer()
+
+typealias PeerConnectionStateListener = (PeerConnectionState) -> Unit

livekit-android-sdk/src/main/java/io/livekit/android/room/SubscriberTransportObserver.kt

@@ -16,7 +16,10 @@
 
 package io.livekit.android.room
 
+import io.livekit.android.room.util.PeerConnectionStateObservable
+import io.livekit.android.util.FlowObservable
 import io.livekit.android.util.LKLog
+import io.livekit.android.util.flowDelegate
 import io.livekit.android.webrtc.peerconnection.executeOnRTCThread
 import livekit.LivekitRtc
 import livekit.org.webrtc.CandidatePairChangeEvent
@@ -34,10 +37,15 @@ import livekit.org.webrtc.RtpTransceiver
 class SubscriberTransportObserver(
     private val engine: RTCEngine,
     private val client: SignalClient,
-) : PeerConnection.Observer {
+) : PeerConnection.Observer, PeerConnectionStateObservable {
 
     var dataChannelListener: ((DataChannel) -> Unit)? = null
-    var connectionChangeListener: ((PeerConnection.PeerConnectionState) -> Unit)? = null
+    var connectionChangeListener: PeerConnectionStateListener? = null
+
+    @FlowObservable
+    @get:FlowObservable
+    override var connectionState by flowDelegate(PeerConnection.PeerConnectionState.NEW)
+        private set
 
     override fun onIceCandidate(candidate: IceCandidate) {
         executeOnRTCThread {
@@ -75,6 +83,7 @@ class SubscriberTransportObserver(
         executeOnRTCThread {
             LKLog.v { "onConnectionChange new state: $newState" }
             connectionChangeListener?.invoke(newState)
+            connectionState = newState
         }
     }
 

livekit-android-sdk/src/main/java/io/livekit/android/room/util/PeerConnectionStateObservable.kt

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2024 LiveKit, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.livekit.android.room.util
+
+import io.livekit.android.util.FlowObservable
+import io.livekit.android.util.flow
+import io.livekit.android.webrtc.isConnected
+import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.flow.takeWhile
+import livekit.org.webrtc.PeerConnection.PeerConnectionState
+
+internal interface PeerConnectionStateObservable {
+    @FlowObservable
+    @get:FlowObservable
+    val connectionState: PeerConnectionState
+}
+
+/**
+ * Waits until the connection state [PeerConnectionState.isConnected].
+ */
+internal suspend fun PeerConnectionStateObservable.waitUntilConnected() {
+    this::connectionState.flow
+        .takeWhile {
+            !it.isConnected()
+        }
+        .collect()
+}