Realm modifications should occur on concurrent queue

ios/App/Shared/player/AudioPlayer.swift

@@ -18,8 +18,6 @@ enum PlayMethod:Int {
 }
 
 class AudioPlayer: NSObject {
-    private let audioPlayerQueue = DispatchQueue(label: "ABSAudioPlayerQueue")
-    
     // enums and @objc are not compatible
     @objc dynamic var status: Int
     @objc dynamic var rate: Float
@@ -143,7 +141,7 @@ class AudioPlayer: NSObject {
         // Rate will be different depending on playback speed, aim for 2 observations/sec
         let seconds = 0.5 * (self.rate > 0 ? self.rate : 1.0)
         let time = CMTime(seconds: Double(seconds), preferredTimescale: timeScale)
-        self.timeObserverToken = self.audioPlayer.addPeriodicTimeObserver(forInterval: time, queue: audioPlayerQueue) { [weak self] time in
+        self.timeObserverToken = self.audioPlayer.addPeriodicTimeObserver(forInterval: time, queue: PlayerProgress.queue) { [weak self] time in
             let sleepTimeStopAt = self?.sleepTimeStopAt
             Task {
                 // Let the player update the current playback positions
@@ -207,7 +205,7 @@ class AudioPlayer: NSObject {
     
     private func startPausedTimer() {
         guard self.pausedTimer == nil else { return }
-        audioPlayerQueue.async {
+        PlayerProgress.queue.async {
             self.pausedTimer = Timer.scheduledTimer(withTimeInterval: 10, repeats: true) { timer in
                 NSLog("PAUSE TIMER: Syncing from server")
                 Task { await PlayerProgress.shared.syncFromServer() }
@@ -400,7 +398,7 @@ class AudioPlayer: NSObject {
         var times = [NSValue]()
         times.append(NSValue(time: sleepTime))
         
-        sleepTimeToken = self.audioPlayer.addBoundaryTimeObserver(forTimes: times, queue: audioPlayerQueue) { [weak self] in
+        sleepTimeToken = self.audioPlayer.addBoundaryTimeObserver(forTimes: times, queue: PlayerProgress.queue) { [weak self] in
             NSLog("SLEEP TIMER: Pausing audio")
             self?.pause()
             self?.removeSleepTimer()

ios/App/Shared/player/PlayerProgress.swift

@@ -10,8 +10,8 @@ import UIKit
 import RealmSwift
 
 class PlayerProgress {
-    
     public static let shared = PlayerProgress()
+    public static let queue = DispatchQueue(label: "ABSPlayerProgressQueue")
     
     private static let TIME_BETWEEN_SESSION_SYNC_IN_SECONDS = 10.0
     
@@ -22,7 +22,7 @@ class PlayerProgress {
     
     public func syncFromPlayer(currentTime: Double, includesPlayProgress: Bool, isStopping: Bool) async {
         let backgroundToken = await UIApplication.shared.beginBackgroundTask(withName: "ABS:syncFromPlayer")
-        let session = await updateLocalSessionFromPlayer(currentTime: currentTime, includesPlayProgress: includesPlayProgress)
+        let session = updateLocalSessionFromPlayer(currentTime: currentTime, includesPlayProgress: includesPlayProgress)
         updateLocalMediaProgressFromLocalSession()
         if let session = session {
             await updateServerSessionFromLocalSession(session, rateLimitSync: !isStopping)
@@ -45,7 +45,8 @@ class PlayerProgress {
     
     // MARK: - SYNC LOGIC
     
-    private func updateLocalSessionFromPlayer(currentTime: Double, includesPlayProgress: Bool) async -> PlaybackSession? {
+    private func updateLocalSessionFromPlayer(currentTime: Double, includesPlayProgress: Bool) -> PlaybackSession? {
+        PlayerProgress.queue.sync {
             guard let session = PlayerHandler.getPlaybackSession() else { return nil }
             guard !currentTime.isNaN else { return nil } // Prevent bad data on player stop
             
@@ -68,8 +69,10 @@ class PlayerProgress {
             
             return session.freeze()
         }
+    }
     
     private func updateLocalMediaProgressFromLocalSession() {
+        PlayerProgress.queue.sync {
             guard let session = PlayerHandler.getPlaybackSession() else { return }
             guard session.isLocal else { return }
             
@@ -88,6 +91,7 @@ class PlayerProgress {
             // Send the local progress back to front-end
             NotificationCenter.default.post(name: NSNotification.Name(PlayerEvents.localProgress.rawValue), object: nil)
         }
+    }
     
     private func updateAllServerSessionFromLocalSession() async {
         await withTaskGroup(of: Void.self) { [self] group in
@@ -102,8 +106,9 @@ class PlayerProgress {
     }
     
     private func updateServerSessionFromLocalSession(_ session: PlaybackSession, rateLimitSync: Bool = false) async {
-        guard var session = session.thaw() else { return }
+        PlayerProgress.queue.sync {
             var safeToSync = true
+            guard var session = session.thaw() else { return }
             
             // We need to update and check the server time in a transaction for thread-safety
             session.update {
@@ -125,8 +130,8 @@ class PlayerProgress {
                 session.serverUpdatedAt = nowInMilliseconds
             }
             session = session.freeze()
-        
             guard safeToSync else { return }
+        }
         
         NSLog("Sending sessionId(\(session.id)) to server")
         
@@ -138,13 +143,16 @@ class PlayerProgress {
             success = await ApiClient.reportPlaybackProgress(report: playbackReport, sessionId: session.id)
         }
         
+        
         // Remove old sessions after they synced with the server
         if success && !session.isActiveSession {
+            PlayerProgress.queue.sync {
                 if let session = session.thaw() {
                     session.delete()
                 }
             }
         }
+    }
     
     private func updateLocalSessionFromServerMediaProgress() async {
         NSLog("updateLocalSessionFromServerMediaProgress: Checking if local media progress was updated on server")
@@ -176,6 +184,7 @@ class PlayerProgress {
         
         // Update the session, if needed
         if serverIsNewerThanLocal && currentTimeIsDifferent {
+            PlayerProgress.queue.sync {
                 NSLog("updateLocalSessionFromServerMediaProgress: Server has newer time than local serverLastUpdate=\(serverLastUpdate) localLastUpdate=\(localLastUpdate)")
                 guard let session = session.thaw() else { return }
                 session.update {
@@ -184,6 +193,7 @@ class PlayerProgress {
                 }
                 NSLog("updateLocalSessionFromServerMediaProgress: Updated session currentTime newCurrentTime=\(serverCurrentTime) previousCurrentTime=\(localCurrentTime)")
                 PlayerHandler.seek(amount: session.currentTime)
+            }
         } else {
             NSLog("updateLocalSessionFromServerMediaProgress: Local session does not need updating; local has latest progress")
         }