From 356e05e3af7702b7dfefbba6e936d602c3638055 Mon Sep 17 00:00:00 2001
From: Bond-009 <bond.009@outlook.com>
Date: Wed, 17 Apr 2024 18:44:39 +0200
Subject: Changes SessionWebSocketListener to (re)use a timer (#11358)

---
 .../Session/SessionWebSocketListener.cs            | 114 ++++++---------------
 1 file changed, 31 insertions(+), 83 deletions(-)

(limited to 'Emby.Server.Implementations/Session')

diff --git a/Emby.Server.Implementations/Session/SessionWebSocketListener.cs b/Emby.Server.Implementations/Session/SessionWebSocketListener.cs
index b3c93a904a..aba51de8f5 100644
--- a/Emby.Server.Implementations/Session/SessionWebSocketListener.cs
+++ b/Emby.Server.Implementations/Session/SessionWebSocketListener.cs
@@ -33,11 +33,6 @@ namespace Emby.Server.Implementations.Session
         /// </summary>
         private const float ForceKeepAliveFactor = 0.75f;
 
-        /// <summary>
-        /// Lock used for accessing the KeepAlive cancellation token.
-        /// </summary>
-        private readonly object _keepAliveLock = new object();
-
         /// <summary>
         /// The WebSocket watchlist.
         /// </summary>
@@ -55,7 +50,7 @@ namespace Emby.Server.Implementations.Session
         /// <summary>
         /// The KeepAlive cancellation token.
         /// </summary>
-        private CancellationTokenSource? _keepAliveCancellationToken;
+        private System.Timers.Timer _keepAlive;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="SessionWebSocketListener" /> class.
@@ -71,12 +66,34 @@ namespace Emby.Server.Implementations.Session
             _logger = logger;
             _sessionManager = sessionManager;
             _loggerFactory = loggerFactory;
+            _keepAlive = new System.Timers.Timer(TimeSpan.FromSeconds(WebSocketLostTimeout * IntervalFactor))
+            {
+                AutoReset = true,
+                Enabled = false
+            };
+            _keepAlive.Elapsed += KeepAliveSockets;
         }
 
         /// <inheritdoc />
         public void Dispose()
         {
-            StopKeepAlive();
+            if (_keepAlive is not null)
+            {
+                _keepAlive.Stop();
+                _keepAlive.Elapsed -= KeepAliveSockets;
+                _keepAlive.Dispose();
+                _keepAlive = null!;
+            }
+
+            lock (_webSocketsLock)
+            {
+                foreach (var webSocket in _webSockets)
+                {
+                    webSocket.Closed -= OnWebSocketClosed;
+                }
+
+                _webSockets.Clear();
+            }
         }
 
         /// <summary>
@@ -164,7 +181,7 @@ namespace Emby.Server.Implementations.Session
                 webSocket.Closed += OnWebSocketClosed;
                 webSocket.LastKeepAliveDate = DateTime.UtcNow;
 
-                StartKeepAlive();
+                _keepAlive.Start();
             }
 
             // Notify WebSocket about timeout
@@ -186,66 +203,26 @@ namespace Emby.Server.Implementations.Session
         {
             lock (_webSocketsLock)
             {
-                if (!_webSockets.Remove(webSocket))
-                {
-                    _logger.LogWarning("WebSocket {0} not on watchlist.", webSocket);
-                }
-                else
+                if (_webSockets.Remove(webSocket))
                 {
                     webSocket.Closed -= OnWebSocketClosed;
                 }
-            }
-        }
-
-        /// <summary>
-        /// Starts the KeepAlive watcher.
-        /// </summary>
-        private void StartKeepAlive()
-        {
-            lock (_keepAliveLock)
-            {
-                if (_keepAliveCancellationToken is null)
-                {
-                    _keepAliveCancellationToken = new CancellationTokenSource();
-                    // Start KeepAlive watcher
-                    _ = RepeatAsyncCallbackEvery(
-                        KeepAliveSockets,
-                        TimeSpan.FromSeconds(WebSocketLostTimeout * IntervalFactor),
-                        _keepAliveCancellationToken.Token);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Stops the KeepAlive watcher.
-        /// </summary>
-        private void StopKeepAlive()
-        {
-            lock (_keepAliveLock)
-            {
-                if (_keepAliveCancellationToken is not null)
+                else
                 {
-                    _keepAliveCancellationToken.Cancel();
-                    _keepAliveCancellationToken.Dispose();
-                    _keepAliveCancellationToken = null;
+                    _logger.LogWarning("WebSocket {0} not on watchlist.", webSocket);
                 }
-            }
 
-            lock (_webSocketsLock)
-            {
-                foreach (var webSocket in _webSockets)
+                if (_webSockets.Count == 0)
                 {
-                    webSocket.Closed -= OnWebSocketClosed;
+                    _keepAlive.Stop();
                 }
-
-                _webSockets.Clear();
             }
         }
 
         /// <summary>
         /// Checks status of KeepAlive of WebSockets.
         /// </summary>
-        private async Task KeepAliveSockets()
+        private async void KeepAliveSockets(object? o, EventArgs? e)
         {
             List<IWebSocketConnection> inactive;
             List<IWebSocketConnection> lost;
@@ -291,11 +268,6 @@ namespace Emby.Server.Implementations.Session
                         RemoveWebSocket(webSocket);
                     }
                 }
-
-                if (_webSockets.Count == 0)
-                {
-                    StopKeepAlive();
-                }
             }
         }
 
@@ -310,29 +282,5 @@ namespace Emby.Server.Implementations.Session
                 new ForceKeepAliveMessage(WebSocketLostTimeout),
                 CancellationToken.None);
         }
-
-        /// <summary>
-        /// Runs a given async callback once every specified interval time, until cancelled.
-        /// </summary>
-        /// <param name="callback">The async callback.</param>
-        /// <param name="interval">The interval time.</param>
-        /// <param name="cancellationToken">The cancellation token.</param>
-        /// <returns>Task.</returns>
-        private async Task RepeatAsyncCallbackEvery(Func<Task> callback, TimeSpan interval, CancellationToken cancellationToken)
-        {
-            while (!cancellationToken.IsCancellationRequested)
-            {
-                await callback().ConfigureAwait(false);
-
-                try
-                {
-                    await Task.Delay(interval, cancellationToken).ConfigureAwait(false);
-                }
-                catch (TaskCanceledException)
-                {
-                    return;
-                }
-            }
-        }
     }
 }
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