Fixed: Multiple SignalR Improvements

Support for serverSentEvents, connection optimizations

Co-Authored-By: taloth <taloth@users.noreply.github.com>

frontend/src/Components/SignalRConnector.js

@@ -84,7 +84,7 @@ class SignalRConnector extends Component {
   constructor(props, context) {
     super(props, context);
 
-    this.signalRconnectionOptions = { transport: ['webSockets', 'longPolling'] };
+    this.signalRconnectionOptions = { transport: ['webSockets', 'serverSentEvents', 'longPolling'] };
     this.signalRconnection = null;
     this.retryInterval = 1;
     this.retryTimeoutId = null;

src/Lidarr.Http/LidarrRestModuleWithSignalR.cs

@@ -25,6 +25,8 @@ namespace Lidarr.Http
 
         public void Handle(ModelEvent<TModel> message)
         {
+            if (!_signalRBroadcaster.IsConnected) return;
+
             if (message.Action == ModelAction.Deleted || message.Action == ModelAction.Sync)
             {
                 BroadcastResourceChange(message.Action);
@@ -35,6 +37,8 @@ namespace Lidarr.Http
 
         protected void BroadcastResourceChange(ModelAction action, int id)
         {
+            if (!_signalRBroadcaster.IsConnected) return;
+
             if (action == ModelAction.Deleted)
             {
                 BroadcastResourceChange(action, new TResource { Id = id });
@@ -48,6 +52,8 @@ namespace Lidarr.Http
 
         protected void BroadcastResourceChange(ModelAction action, TResource resource)
         {
+            if (!_signalRBroadcaster.IsConnected) return;
+
             if (GetType().Namespace.Contains("V1"))
             {
                 var signalRMessage = new SignalRMessage
@@ -64,6 +70,8 @@ namespace Lidarr.Http
 
         protected void BroadcastResourceChange(ModelAction action)
         {
+            if (!_signalRBroadcaster.IsConnected) return;
+
             if (GetType().Namespace.Contains("V1"))
             {
                 var signalRMessage = new SignalRMessage

src/NzbDrone.Host/Owin/MiddleWare/SignalRMiddleWare.cs

@@ -16,9 +16,14 @@ namespace NzbDrone.Host.Owin.MiddleWare
             SignalRDependencyResolver.Register(container);
             SignalRJsonSerializer.Register();
 
-            // Half the default time (110s) to get under nginx's default 60 proxy_read_timeout
-            GlobalHost.Configuration.ConnectionTimeout = TimeSpan.FromSeconds(55);
-            GlobalHost.Configuration.DisconnectTimeout = TimeSpan.FromMinutes(3);
+            // Note there are some important timeouts involved here:
+            // nginx has a default 60 sec proxy_read_timeout, this means the connection will be terminated if the server doesn't send anything within that time.
+            // Previously we lowered the ConnectionTimeout from 110s to 55s to remedy that, however all we should've done is set an appropriate KeepAlive.
+            // By default KeepAlive is 1/3rd of the DisconnectTimeout, which we set incredibly high 5 years ago, resulting in KeepAlive being 1 minute.
+            // So when adjusting these values in the future, please keep that all in mind.
+            GlobalHost.Configuration.ConnectionTimeout = TimeSpan.FromSeconds(110);
+            GlobalHost.Configuration.DisconnectTimeout = TimeSpan.FromSeconds(180);
+            GlobalHost.Configuration.KeepAlive = TimeSpan.FromSeconds(30);
         }
 
         public void Attach(IAppBuilder appBuilder)

src/NzbDrone.SignalR/NzbDronePersistentConnection.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using Microsoft.AspNet.SignalR;
 using Microsoft.AspNet.SignalR.Infrastructure;
@@ -12,6 +12,7 @@ namespace NzbDrone.SignalR
 {
     public interface IBroadcastSignalRMessage
     {
+        bool IsConnected { get; }
         void BroadcastMessage(SignalRMessage message);
     }
 
@@ -20,7 +21,8 @@ namespace NzbDrone.SignalR
         private IPersistentConnectionContext Context => ((ConnectionManager)GlobalHost.ConnectionManager).GetConnection(GetType());
 
         private static string API_KEY;
-        private readonly Dictionary<string, string> _messageHistory; 
+        private readonly Dictionary<string, string> _messageHistory;
+        private HashSet<string> _connections = new HashSet<string>();
 
         public NzbDronePersistentConnection(IConfigFileProvider configFileProvider)
         {
@@ -28,6 +30,16 @@ namespace NzbDrone.SignalR
             _messageHistory = new Dictionary<string, string>();
         }
 
+        public bool IsConnected
+        {
+            get
+            {
+                lock (_connections)
+                {
+                    return _connections.Count != 0;
+                }
+            }
+        }
 
         public void BroadcastMessage(SignalRMessage message)
         {
@@ -59,14 +71,34 @@ namespace NzbDrone.SignalR
 
         protected override Task OnConnected(IRequest request, string connectionId)
         {
+            lock (_connections)
+            {
+                _connections.Add(connectionId);
+            }
+
             return SendVersion(connectionId);
         }
 
         protected override Task OnReconnected(IRequest request, string connectionId)
         {
+            lock (_connections)
+            {
+                _connections.Add(connectionId);
+            }
+
             return SendVersion(connectionId);
         }
 
+        protected override Task OnDisconnected(IRequest request, string connectionId, bool stopCalled)
+        {
+            lock (_connections)
+            {
+                _connections.Remove(connectionId);
+            }
+
+            return base.OnDisconnected(request, connectionId, stopCalled);
+        }
+
         private Task SendVersion(string connectionId)
         {
             return Context.Connection.Send(connectionId, new SignalRMessage
@@ -79,4 +111,4 @@ namespace NzbDrone.SignalR
             });
         }        
     }
-}
+}

src/NzbDrone.SignalR/SignalRJsonSerializer.cs

@@ -13,6 +13,7 @@ namespace NzbDrone.SignalR
         {
             _serializerSettings = Json.GetSerializerSettings();
             _serializerSettings.ContractResolver = new SignalRContractResolver();
+            _serializerSettings.Formatting = Formatting.None; // ServerSentEvents doesn't like newlines
 
             _serializer = JsonSerializer.Create(_serializerSettings);