Refactor: replace songListScope with appropriate scopes

Replaced `songListScope` with `songScope` in `WSSongRoutes` and `timerScope` in `WSTimerRoutes` to better reflect their respective purposes. Improves code clarity and consistency in scope usage.

common/src/main/kotlin/space/mori/chzzk_bot/common/events/TimerEvents.kt

@@ -5,7 +5,8 @@ enum class TimerType(var value: Int) {
     TIMER(1),
     REMOVE(2),
 
-    STREAM_OFF(50)
+    STREAM_OFF(50),
+    ACK(51)
 }
 
 class TimerEvent(

webserver/src/main/kotlin/space/mori/chzzk_bot/webserver/Main.kt

@@ -25,7 +25,6 @@ import kotlinx.serialization.json.Json
 import space.mori.chzzk_bot.common.services.UserService
 import space.mori.chzzk_bot.webserver.routes.*
 import space.mori.chzzk_bot.webserver.utils.DiscordRatelimits
-import wsSongListRoutes
 import java.math.BigInteger
 import java.security.SecureRandom
 import java.time.Duration

webserver/src/main/kotlin/space/mori/chzzk_bot/webserver/routes/WSSongListRoutes.kt

@@ -1,115 +1,54 @@
+package space.mori.chzzk_bot.webserver.routes
+
+import io.ktor.client.plugins.websocket.WebSocketException
+import io.ktor.server.application.*
 import io.ktor.server.routing.*
 import io.ktor.server.sessions.*
 import io.ktor.server.websocket.*
-import io.ktor.util.logging.Logger
 import io.ktor.websocket.*
-import io.ktor.websocket.Frame.*
+import kotlinx.coroutines.*
-import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.channels.ClosedReceiveChannelException
-import kotlinx.coroutines.delay
+import kotlinx.coroutines.sync.Mutex
-import kotlinx.coroutines.launch
+import kotlinx.coroutines.sync.withLock
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.Json
 import org.koin.java.KoinJavaComponent.inject
+import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 import space.mori.chzzk_bot.common.events.*
 import space.mori.chzzk_bot.common.models.SongList
-import space.mori.chzzk_bot.common.models.SongLists.uid
 import space.mori.chzzk_bot.common.models.User
-import space.mori.chzzk_bot.common.services.SongConfigService
 import space.mori.chzzk_bot.common.services.SongListService
 import space.mori.chzzk_bot.common.services.UserService
 import space.mori.chzzk_bot.common.utils.YoutubeVideo
 import space.mori.chzzk_bot.common.utils.getYoutubeVideo
 import space.mori.chzzk_bot.webserver.UserSession
-import space.mori.chzzk_bot.webserver.routes.SongResponse
-import space.mori.chzzk_bot.webserver.routes.toSerializable
 import space.mori.chzzk_bot.webserver.utils.CurrentSong
+import java.io.IOException
 import java.util.concurrent.ConcurrentHashMap
 
 fun Routing.wsSongListRoutes() {
-    val sessions = ConcurrentHashMap<String, WebSocketServerSession>()
-    val status = ConcurrentHashMap<String, SongType>()
     val logger = LoggerFactory.getLogger("WSSongListRoutes")
-
     val dispatcher: CoroutinesEventBus by inject(CoroutinesEventBus::class.java)
+    val songListScope = CoroutineScope(SupervisorJob() + Dispatchers.Default)
 
-    fun addSession(uid: String, session: WebSocketServerSession) {
+    // Manage all active sessions
-        if (sessions[uid] != null) {
+    val sessionHandlers = ConcurrentHashMap<String, SessionHandler>()
-            CoroutineScope(Dispatchers.Default).launch {
-                sessions[uid]?.close(
-                    CloseReason(CloseReason.Codes.VIOLATED_POLICY, "Duplicated sessions.")
-                )
-            }
-        }
-        sessions[uid] = session
-    }
 
-    fun removeSession(uid: String) {
+    // Handle application shutdown
-        sessions.remove(uid)
+    environment.monitor.subscribe(ApplicationStopped) {
+        sessionHandlers.values.forEach {
+            songListScope.launch {
+                it.close(CloseReason(CloseReason.Codes.NORMAL, "Server shutting down"))
             }
-
-    suspend fun waitForAck(ws: WebSocketServerSession, expectedType: Int): Boolean {
-        val timeout = 5000L // 5 seconds timeout
-        val startTime = System.currentTimeMillis()
-        while (System.currentTimeMillis() - startTime < timeout) {
-            for (frame in ws.incoming) {
-                if (frame is Text) {
-                    val message = frame.readText()
-                    if(message == "ping") {
-                        return true
-                    }
-                    val data = Json.decodeFromString<SongRequest>(message)
-                    if (data.type == SongType.ACK.value) {
-                        return true // ACK received
-                    }
-                }
-            }
-            delay(100) // Check every 100 ms
-        }
-        return false // Timeout
-    }
-
-    suspend fun sendWithRetry(uid: String, res: SongResponse, maxRetries: Int = 5, delayMillis: Long = 3000L) {
-        var attempt = 0
-        var sentSuccessfully = false
-
-        while (attempt < maxRetries && !sentSuccessfully) {
-            val ws = sessions[uid]
-            try {
-                if(ws == null) {
-                    delay(delayMillis)
-                    continue
-                }
-                // Attempt to send the message
-                ws.sendSerialized(res)
-                logger.debug("Message sent successfully to $uid on attempt $attempt")
-                // Wait for ACK
-                val ackReceived = waitForAck(ws, res.type)
-                if (ackReceived == true) {
-                    sentSuccessfully = true
-                } else {
-                    logger.warn("ACK not received for message to $uid on attempt $attempt.")
-                }
-            } catch (e: Exception) {
-                attempt++
-                logger.warn("Failed to send message to $uid on attempt $attempt. Retrying in $delayMillis ms.")
-                logger.warn(e.stackTraceToString())
-            } finally {
-                // Wait before retrying
-                delay(delayMillis)
-            }
-        }
-
-        if (!sentSuccessfully) {
-            logger.error("Failed to send message to $uid after $maxRetries attempts.")
         }
     }
 
+    // WebSocket endpoint
     webSocket("/songlist") {
         val session = call.sessions.get<UserSession>()
-        val user = session?.id?.let { UserService.getUser(it) }
+        val user: User? = session?.id?.let { UserService.getUser(it) }
+
         if (user == null) {
             close(CloseReason(CloseReason.Codes.CANNOT_ACCEPT, "Invalid SID"))
             return@webSocket
@@ -117,102 +56,204 @@ fun Routing.wsSongListRoutes() {
 
         val uid = user.token
 
-        addSession(uid, this)
+        // Ensure only one session per user
+        sessionHandlers[uid]?.close(CloseReason(CloseReason.Codes.VIOLATED_POLICY, "Another session is already active."))
 
-        if (status[uid] == SongType.STREAM_OFF) {
+        val handler = SessionHandler(uid, this, dispatcher, logger)
-            CoroutineScope(Dispatchers.Default).launch {
+        sessionHandlers[uid] = handler
-                sendSerialized(SongResponse(
-                    SongType.STREAM_OFF.value,
-                    uid,
-                    null,
-                    null,
-                    null,
-                ))
-            }
-            removeSession(uid)
-        }
 
+        // Initialize session
+        handler.initialize()
+
+        // Listen for incoming frames
         try {
             for (frame in incoming) {
                 when (frame) {
-                    is Text -> {
+                    is Frame.Text -> handler.handleTextFrame(frame.readText())
-                        if (frame.readText().trim() == "ping") {
+                    is Frame.Ping -> send(Frame.Pong(frame.data))
-                            send("pong")
+                    else -> Unit
-                        } else {
-                            val data = frame.readText().let { Json.decodeFromString<SongRequest>(it) }
-
-                            // Handle song requests
-                            handleSongRequest(data, user, dispatcher, logger)
-                        }
-                    }
-                    is Ping -> send(Pong(frame.data))
-                    else -> ""
                 }
             }
         } catch (e: ClosedReceiveChannelException) {
-            logger.error("Error in WebSocket: ${e.message}")
+            logger.info("Session closed: ${e.message}")
+        } catch (e: IOException) {
+            logger.error("IO error: ${e.message}")
+        } catch (e: Exception) {
+            logger.error("Unexpected error: ${e.message}")
         } finally {
-            removeSession(uid)
+            sessionHandlers.remove(uid)
+            handler.close(CloseReason(CloseReason.Codes.NORMAL, "Session ended"))
         }
     }
 
-    dispatcher.subscribe(SongEvent::class) {
+    // Subscribe to SongEvents
-        logger.debug("SongEvent: {} / {} {}", it.uid, it.type, it.current?.name)
+    dispatcher.subscribe(SongEvent::class) { event ->
-        CoroutineScope(Dispatchers.Default).launch {
+        val handler = sessionHandlers[event.uid]
-            val user = UserService.getUser(it.uid)
+        songListScope.launch {
-            if (user != null) {
+            handler?.sendSongResponse(event)
-                sendWithRetry(
-                    user.token, SongResponse(
-                        it.type.value,
-                        it.uid,
-                        it.reqUid,
-                        it.current?.toSerializable(),
-                        it.next?.toSerializable(),
-                        it.delUrl
-                    )
-                )
-            }
         }
     }
 
-    dispatcher.subscribe(TimerEvent::class) {
+    // Subscribe to TimerEvents
-        if (it.type == TimerType.STREAM_OFF) {
+    dispatcher.subscribe(TimerEvent::class) { event ->
-            CoroutineScope(Dispatchers.Default).launch {
+        if (event.type == TimerType.STREAM_OFF) {
-                val user = UserService.getUser(it.uid)
+            val handler = sessionHandlers[event.uid]
-                if (user != null) {
+            songListScope.launch {
-                    sendWithRetry(
+                handler?.sendTimerOff()
-                        user.token, SongResponse(
-                            it.type.value,
-                            it.uid,
-                            null,
-                            null,
-                            null,
-                        )
-                    )
-                }
             }
         }
     }
 }
 
-suspend fun handleSongRequest(
+class SessionHandler(
+    private val uid: String,
+    private val session: WebSocketServerSession,
+    private val dispatcher: CoroutinesEventBus,
+    private val logger: Logger
+) {
+    private val ackMap = ConcurrentHashMap<String, CompletableDeferred<Boolean>>()
+    private val sessionMutex = Mutex()
+    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.Default)
+
+    suspend fun initialize() {
+        // Send initial status if needed,
+        // For example, send STREAM_OFF if applicable
+        // This can be extended based on your requirements
+    }
+
+    suspend fun handleTextFrame(text: String) {
+        if (text.trim() == "ping") {
+            session.send("pong")
+            return
+        }
+
+        val data = try {
+            Json.decodeFromString<SongRequest>(text)
+        } catch (e: Exception) {
+            logger.warn("Failed to decode SongRequest: ${e.message}")
+            return
+        }
+
+        when (data.type) {
+            SongType.ACK.value -> handleAck(data.uid)
+            else -> handleSongRequest(data)
+        }
+    }
+
+    private fun handleAck(requestUid: String) {
+        ackMap[requestUid]?.complete(true)
+        ackMap.remove(requestUid)
+    }
+
+    private fun handleSongRequest(data: SongRequest) {
+        scope.launch {
+            SongRequestProcessor.process(data, uid, dispatcher, this@SessionHandler, logger)
+        }
+    }
+
+    suspend fun sendSongResponse(event: SongEvent) {
+        val response = SongResponse(
+            type = event.type.value,
+            uid = event.uid,
+            reqUid = event.reqUid,
+            current = event.current?.toSerializable(),
+            next = event.next?.toSerializable(),
+            delUrl = event.delUrl
+        )
+        sendWithRetry(response)
+    }
+
+    suspend fun sendTimerOff() {
+        val response = SongResponse(
+            type = TimerType.STREAM_OFF.value,
+            uid = uid,
+            reqUid = null,
+            current = null,
+            next = null,
+            delUrl = null
+        )
+        sendWithRetry(response)
+    }
+
+    private suspend fun sendWithRetry(res: SongResponse, maxRetries: Int = 5, delayMillis: Long = 3000L) {
+        var attempt = 0
+        while (attempt < maxRetries) {
+            try {
+                session.sendSerialized(res)
+                val ackDeferred = CompletableDeferred<Boolean>()
+                ackMap[res.uid] = ackDeferred
+
+                val ackReceived = withTimeoutOrNull(5000L) { ackDeferred.await() } ?: false
+                if (ackReceived) {
+                    logger.debug("ACK received for message to $uid on attempt $attempt.")
+                    return
+                } else {
+                    logger.warn("ACK not received for message to $uid on attempt $attempt.")
+                }
+            } catch (e: IOException) {
+                logger.warn("Failed to send message to $uid on attempt $attempt: ${e.message}")
+                if (e is WebSocketException) {
+                    close(CloseReason(CloseReason.Codes.PROTOCOL_ERROR, "WebSocket error"))
+                    return
+                }
+            } catch (e: CancellationException) {
+                throw e
+            } catch (e: Exception) {
+                logger.warn("Unexpected error while sending message to $uid on attempt $attempt: ${e.message}")
+            }
+
+            attempt++
+            delay(delayMillis)
+        }
+
+        logger.error("Failed to send message to $uid after $maxRetries attempts.")
+    }
+
+    suspend fun close(reason: CloseReason) {
+        try {
+            session.close(reason)
+        } catch (e: Exception) {
+            logger.warn("Error closing session: ${e.message}")
+        }
+    }
+}
+
+object SongRequestProcessor {
+    private val songMutex = Mutex()
+
+    suspend fun process(
+        data: SongRequest,
+        uid: String,
+        dispatcher: CoroutinesEventBus,
+        handler: SessionHandler,
+        logger: Logger
+    ) {
+        val user = UserService.getUser(uid) ?: return
+
+        when (data.type) {
+            SongType.ADD.value -> handleAdd(data, user, dispatcher, handler, logger)
+            SongType.REMOVE.value -> handleRemove(data, user, dispatcher, logger)
+            SongType.NEXT.value -> handleNext(user, dispatcher, logger)
+            else -> {
+                // Handle other types if necessary
+            }
+        }
+    }
+
+    private suspend fun handleAdd(
         data: SongRequest,
         user: User,
         dispatcher: CoroutinesEventBus,
+        handler: SessionHandler,
         logger: Logger
-) {
+    ) {
-    if (data.maxQueue != null && data.maxQueue > 0) SongConfigService.updateQueueLimit(user, data.maxQueue)
+        val url = data.url ?: return
-    if (data.maxUserLimit != null && data.maxUserLimit > 0) SongConfigService.updatePersonalLimit(user, data.maxUserLimit)
+        val youtubeVideo = getYoutubeVideo(url) ?: run {
-    if (data.isStreamerOnly != null) SongConfigService.updateStreamerOnly(user, data.isStreamerOnly)
+            logger.warn("Failed to fetch YouTube video for URL: $url")
-    if (data.isDisabled != null) SongConfigService.updateDisabled(user, data.isDisabled)
+            return
+        }
 
-    when (data.type) {
+        songMutex.withLock {
-        SongType.ADD.value -> {
-            data.url?.let { url ->
-                try {
-                    val youtubeVideo = getYoutubeVideo(url)
-                    if (youtubeVideo != null) {
-                        CoroutineScope(Dispatchers.Default).launch {
             SongListService.saveSong(
                 user,
                 user.token,
@@ -222,81 +263,95 @@ suspend fun handleSongRequest(
                 youtubeVideo.length,
                 user.username
             )
+        }
+
         dispatcher.post(
             SongEvent(
-                                    user.token,
+                uid = user.token,
-                                    SongType.ADD,
+                type = SongType.ADD,
-                                    user.token,
+                reqUid = user.token,
-                                    CurrentSong.getSong(user),
+                current = CurrentSong.getSong(user),
-                                    youtubeVideo
+                next = youtubeVideo
             )
         )
     }
-                    }
+
-                } catch (e: Exception) {
+    private suspend fun handleRemove(
-                    logger.debug("SongType.ADD Error: $uid $e")
+        data: SongRequest,
-                }
+        user: User,
-            }
+        dispatcher: CoroutinesEventBus,
-        }
+        logger: Logger
-        SongType.REMOVE.value -> {
+    ) {
-            data.url?.let { url ->
+        val url = data.url ?: return
+
+        songMutex.withLock {
             val songs = SongListService.getSong(user)
             val exactSong = songs.firstOrNull { it.url == url }
             if (exactSong != null) {
                 SongListService.deleteSong(user, exactSong.uid, exactSong.name)
             }
+        }
+
         dispatcher.post(
             SongEvent(
-                        user.token,
+                uid = user.token,
-                        SongType.REMOVE,
+                type = SongType.REMOVE,
-                        null,
+                delUrl = url,
-                        null,
+                reqUid = null,
-                        null,
+                current = null,
-                        url
+                next = null,
             )
         )
     }
-        }
+
-        SongType.NEXT.value -> {
+    private suspend fun handleNext(
-            val songList = SongListService.getSong(user)
+        user: User,
+        dispatcher: CoroutinesEventBus,
+        logger: Logger
+    ) {
         var song: SongList? = null
         var youtubeVideo: YoutubeVideo? = null
 
+        songMutex.withLock {
+            val songList = SongListService.getSong(user)
             if (songList.isNotEmpty()) {
                 song = songList[0]
                 SongListService.deleteSong(user, song.uid, song.name)
             }
+        }
 
         song?.let {
             youtubeVideo = YoutubeVideo(
-                    song.url,
+                it.url,
-                    song.name,
+                it.name,
-                    song.author,
+                it.author,
-                    song.time
+                it.time
             )
         }
+
         dispatcher.post(
             SongEvent(
-                    user.token,
+                uid = user.token,
-                    SongType.NEXT,
+                type = SongType.NEXT,
-                    song?.uid,
+                current = null,
-                    youtubeVideo
+                next = youtubeVideo,
+                reqUid = null,
+                delUrl = null
             )
         )
 
         CurrentSong.setSong(user, youtubeVideo)
     }
-    }
 }
 
 @Serializable
 data class SongRequest(
     val type: Int,
     val uid: String,
-    val url: String?,
+    val url: String? = null,
-    val maxQueue: Int?,
+    val maxQueue: Int? = null,
-    val maxUserLimit: Int?,
+    val maxUserLimit: Int? = null,
-    val isStreamerOnly: Boolean?,
+    val isStreamerOnly: Boolean? = null,
-    val remove: Int?,
+    val remove: Int? = null,
-    val isDisabled: Boolean?,
+    val isDisabled: Boolean? = null
 )

webserver/src/main/kotlin/space/mori/chzzk_bot/webserver/routes/WSSongRoutes.kt

@@ -1,14 +1,20 @@
 package space.mori.chzzk_bot.webserver.routes
 
+import io.ktor.server.application.ApplicationStopped
 import io.ktor.server.routing.*
 import io.ktor.server.websocket.*
 import io.ktor.websocket.*
+import kotlinx.coroutines.CompletableDeferred
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.cancel
 import kotlinx.coroutines.channels.ClosedReceiveChannelException
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.withTimeoutOrNull
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
 import org.koin.java.KoinJavaComponent.inject
 import org.slf4j.LoggerFactory
 import space.mori.chzzk_bot.common.events.*
@@ -17,15 +23,20 @@ import space.mori.chzzk_bot.common.utils.YoutubeVideo
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.ConcurrentLinkedQueue
 
+val songScope = CoroutineScope(SupervisorJob() + Dispatchers.Default)
 fun Routing.wsSongRoutes() {
+    environment.monitor.subscribe(ApplicationStopped) {
+        songScope.cancel()
+    }
     val sessions = ConcurrentHashMap<String, ConcurrentLinkedQueue<WebSocketServerSession>>()
     val status = ConcurrentHashMap<String, SongType>()
     val logger = LoggerFactory.getLogger("WSSongRoutes")
+    val dispatcher: CoroutinesEventBus by inject(CoroutinesEventBus::class.java)
+    val ackMap = ConcurrentHashMap<String, ConcurrentHashMap<WebSocketServerSession, CompletableDeferred<Boolean>>>()
 
     fun addSession(uid: String, session: WebSocketServerSession) {
         sessions.computeIfAbsent(uid) { ConcurrentLinkedQueue() }.add(session)
     }
-
     fun removeSession(uid: String, session: WebSocketServerSession) {
         sessions[uid]?.remove(session)
         if(sessions[uid]?.isEmpty() == true) {
@@ -42,27 +53,35 @@ fun Routing.wsSongRoutes() {
         var attempt = 0
         while (attempt < maxRetries) {
             try {
-                session.sendSerialized(message)  // 메시지 전송 시도
+                session.sendSerialized(message)
-                return true  // 성공하면 true 반환
+                val ackDeferred = CompletableDeferred<Boolean>()
+                ackMap.computeIfAbsent(message.uid) { ConcurrentHashMap() }[session] = ackDeferred
+                val ackReceived = withTimeoutOrNull(delayMillis) { ackDeferred.await() } ?: false
+                if (ackReceived) {
+                    ackMap[message.uid]?.remove(session)
+                    return true
+                } else {
+                    attempt++
+                    logger.warn("ACK not received for message to ${message.uid} on attempt $attempt.")
+                }
             } catch (e: Exception) {
                 attempt++
                 logger.info("Failed to send message on attempt $attempt. Retrying in $delayMillis ms.")
                 e.printStackTrace()
-                delay(delayMillis)  // 재시도 전 대기
+                delay(delayMillis)
             }
         }
-        return false  // 재시도 실패 시 false 반환
+        return false
     }
 
     fun broadcastMessage(userId: String, message: SongResponse) {
         val userSessions = sessions[userId]
-
         userSessions?.forEach { session ->
-            CoroutineScope(Dispatchers.Default).launch {
+            songScope.launch {
                 val success = sendWithRetry(session, message)
                 if (!success) {
-                    println("Removing session for user $userId due to repeated failures.")
+                    logger.info("Removing session for user $userId due to repeated failures.")
-                    userSessions.remove(session)  // 실패 시 세션 제거
+                    removeSession(userId, session)
                 }
             }
         }
@@ -71,19 +90,13 @@ fun Routing.wsSongRoutes() {
     webSocket("/song/{uid}") {
         val uid = call.parameters["uid"]
         val user = uid?.let { UserService.getUser(it) }
-        if (uid == null) {
+        if (uid == null || user == null) {
             close(CloseReason(CloseReason.Codes.CANNOT_ACCEPT, "Invalid UID"))
             return@webSocket
         }
-        if (user == null) {
-            close(CloseReason(CloseReason.Codes.CANNOT_ACCEPT, "Invalid UID"))
-            return@webSocket
-        }
-
         addSession(uid, this)
-
         if(status[uid] == SongType.STREAM_OFF) {
-            CoroutineScope(Dispatchers.Default).launch {
+            songScope.launch {
                 sendSerialized(SongResponse(
                     SongType.STREAM_OFF.value,
                     uid,
@@ -93,33 +106,36 @@ fun Routing.wsSongRoutes() {
                 ))
             }
         }
-
         try {
             for (frame in incoming) {
                 when(frame) {
                     is Frame.Text -> {
-                        if(frame.readText().trim() == "ping") {
+                        val text = frame.readText().trim()
+                        if(text == "ping") {
                             send("pong")
+                        } else {
+                            val data = Json.decodeFromString<SongRequest>(text)
+                            if (data.type == SongType.ACK.value) {
+                                ackMap[data.uid]?.get(this)?.complete(true)
+                                ackMap[data.uid]?.remove(this)
+                            }
                         }
                     }
                     is Frame.Ping -> send(Frame.Pong(frame.data))
-                    else -> {
+                    else -> {}
-
-                    }
                 }
             }
         } catch(e: ClosedReceiveChannelException) {
             logger.error("Error in WebSocket: ${e.message}")
         } finally {
             removeSession(uid, this)
+            ackMap[uid]?.remove(this)
         }
     }
 
-    val dispatcher: CoroutinesEventBus by inject(CoroutinesEventBus::class.java)
-
     dispatcher.subscribe(SongEvent::class) {
         logger.debug("SongEvent: {} / {} {}", it.uid, it.type, it.current?.name)
-        CoroutineScope(Dispatchers.Default).launch {
+        songScope.launch {
             broadcastMessage(it.uid, SongResponse(
                 it.type.value,
                 it.uid,
@@ -132,7 +148,7 @@ fun Routing.wsSongRoutes() {
     }
     dispatcher.subscribe(TimerEvent::class) {
         if(it.type == TimerType.STREAM_OFF) {
-            CoroutineScope(Dispatchers.Default).launch {
+            songScope.launch {
                 broadcastMessage(it.uid, SongResponse(
                     it.type.value,
                     it.uid,
@@ -144,7 +160,6 @@ fun Routing.wsSongRoutes() {
         }
     }
 }
-
 @Serializable
 data class SerializableYoutubeVideo(
     val url: String,
@@ -152,9 +167,7 @@ data class SerializableYoutubeVideo(
     val author: String,
     val length: Int
 )
-
 fun YoutubeVideo.toSerializable() = SerializableYoutubeVideo(url, name, author, length)
-
 @Serializable
 data class SongResponse(
     val type: Int,

webserver/src/main/kotlin/space/mori/chzzk_bot/webserver/routes/WSTimerRoutes.kt

@@ -1,13 +1,20 @@
 package space.mori.chzzk_bot.webserver.routes
 
+import io.ktor.server.application.ApplicationStopped
 import io.ktor.server.routing.*
 import io.ktor.server.websocket.*
 import io.ktor.websocket.*
+import kotlinx.coroutines.CompletableDeferred
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.cancel
 import kotlinx.coroutines.channels.ClosedReceiveChannelException
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.withTimeoutOrNull
 import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
 import org.koin.java.KoinJavaComponent.inject
 import org.slf4j.LoggerFactory
 import space.mori.chzzk_bot.common.events.*
@@ -17,14 +24,19 @@ import space.mori.chzzk_bot.webserver.utils.CurrentTimer
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.ConcurrentLinkedQueue
 
+val timerScope = CoroutineScope(SupervisorJob() + Dispatchers.Default)
 fun Routing.wsTimerRoutes() {
+    environment.monitor.subscribe(ApplicationStopped) {
+        timerScope.cancel()
+    }
     val sessions = ConcurrentHashMap<String, ConcurrentLinkedQueue<WebSocketServerSession>>()
     val logger = LoggerFactory.getLogger("WSTimerRoutes")
+    val dispatcher: CoroutinesEventBus by inject(CoroutinesEventBus::class.java)
+    val ackMap = ConcurrentHashMap<String, ConcurrentHashMap<WebSocketServerSession, CompletableDeferred<Boolean>>>()
 
     fun addSession(uid: String, session: WebSocketServerSession) {
         sessions.computeIfAbsent(uid) { ConcurrentLinkedQueue() }.add(session)
     }
-
     fun removeSession(uid: String, session: WebSocketServerSession) {
         sessions[uid]?.remove(session)
         if(sessions[uid]?.isEmpty() == true) {
@@ -32,82 +44,132 @@ fun Routing.wsTimerRoutes() {
         }
     }
 
+    suspend fun sendWithRetry(
+        session: WebSocketServerSession,
+        message: TimerResponse,
+        maxRetries: Int = 3,
+        delayMillis: Long = 2000L
+    ): Boolean {
+        var attempt = 0
+        while (attempt < maxRetries) {
+            try {
+                session.sendSerialized(message)
+                val ackDeferred = CompletableDeferred<Boolean>()
+                ackMap.computeIfAbsent(message.uid) { ConcurrentHashMap() }[session] = ackDeferred
+                val ackReceived = withTimeoutOrNull(delayMillis) { ackDeferred.await() } ?: false
+                if (ackReceived) {
+                    ackMap[message.uid]?.remove(session)
+                    return true
+                } else {
+                    attempt++
+                    logger.warn("ACK not received for message to ${message.uid} on attempt $attempt.")
+                }
+            } catch (e: Exception) {
+                attempt++
+                logger.info("Failed to send message on attempt $attempt. Retrying in $delayMillis ms.")
+                e.printStackTrace()
+                delay(delayMillis)
+            }
+        }
+        return false
+    }
+
+    fun broadcastMessage(uid: String, message: TimerResponse) {
+        val userSessions = sessions[uid]
+        userSessions?.forEach { session ->
+            timerScope.launch {
+                val success = sendWithRetry(session, message.copy(uid = uid))
+                if (!success) {
+                    logger.info("Removing session for user $uid due to repeated failures.")
+                    removeSession(uid, session)
+                }
+            }
+        }
+    }
+
     webSocket("/timer/{uid}") {
         val uid = call.parameters["uid"]
         val user = uid?.let { UserService.getUser(it) }
-        if (uid == null) {
+        if (uid == null || user == null) {
             close(CloseReason(CloseReason.Codes.CANNOT_ACCEPT, "Invalid UID"))
             return@webSocket
         }
-        if (user == null) {
-            close(CloseReason(CloseReason.Codes.CANNOT_ACCEPT, "Invalid UID"))
-            return@webSocket
-        }
-
         addSession(uid, this)
         val timer = CurrentTimer.getTimer(user)
 
-        if(timer?.type == TimerType.STREAM_OFF) {
+        if (timer?.type == TimerType.STREAM_OFF) {
-            CoroutineScope(Dispatchers.Default).launch {
+            timerScope.launch {
-                sendSerialized(TimerResponse(TimerType.STREAM_OFF.value, null))
+                sendSerialized(TimerResponse(TimerType.STREAM_OFF.value, null, uid))
             }
         } else {
-            CoroutineScope(Dispatchers.Default).launch {
+            timerScope.launch {
+                if(timer?.type == TimerType.STREAM_OFF) {
+                    sendSerialized(TimerResponse(TimerType.STREAM_OFF.value, null, uid))
+                } else {
                     if (timer == null) {
                         sendSerialized(
                             TimerResponse(
                                 TimerConfigService.getConfig(user)?.option ?: TimerType.REMOVE.value,
-                            null
+                                null,
+                                uid
                             )
                         )
                     } else {
                         sendSerialized(
                             TimerResponse(
                                 timer.type.value,
-                            timer.time
+                                timer.time,
+                                uid
                             )
                         )
                     }
                 }
             }
-
+        }
         try {
             for (frame in incoming) {
                 when(frame) {
                     is Frame.Text -> {
-                        if(frame.readText().trim() == "ping") {
+                        val text = frame.readText().trim()
+                        if(text == "ping") {
                             send("pong")
+                        } else {
+                            val data = Json.decodeFromString<TimerRequest>(text)
+                            if (data.type == TimerType.ACK.value) {
+                                ackMap[data.uid]?.get(this)?.complete(true)
+                                ackMap[data.uid]?.remove(this)
+                            }
                         }
                     }
                     is Frame.Ping -> send(Frame.Pong(frame.data))
-                    else -> {
+                    else -> {}
-
-                    }
                 }
             }
         } catch(e: ClosedReceiveChannelException) {
             logger.error("Error in WebSocket: ${e.message}")
         } finally {
             removeSession(uid, this)
+            ackMap[uid]?.remove(this)
         }
     }
 
-    val dispatcher: CoroutinesEventBus by inject(CoroutinesEventBus::class.java)
-
     dispatcher.subscribe(TimerEvent::class) {
         logger.debug("TimerEvent: {} / {}", it.uid, it.type)
         val user = UserService.getUser(it.uid)
         CurrentTimer.setTimer(user!!, it)
-        CoroutineScope(Dispatchers.Default).launch {
+        timerScope.launch {
-            sessions[it.uid]?.forEach { ws ->
+            broadcastMessage(it.uid, TimerResponse(it.type.value, it.time ?: "", it.uid))
-                ws.sendSerialized(TimerResponse(it.type.value, it.time ?: ""))
-            }
         }
     }
 }
-
 @Serializable
 data class TimerResponse(
     val type: Int,
-    val time: String?
+    val time: String?,
+    val uid: String
+)
+@Serializable
+data class TimerRequest(
+    val type: Int,
+    val uid: String
 )