fix for #124 - Azure timeouts/disconnection detection

StackExchange.Redis.Tests/ConnectingFailDetection.cs

@@ -98,6 +98,35 @@ public void FastNoticesFailOnConnectingAsync()
                 ClearAmbientFailures();
             }
         }
+
+        [Test]
+        public void ReconnectsOnStaleConnection()
+        {
+            try
+            {
+                using (var muxer = Create(keepAlive: 1, connectTimeout: 3000))
+                {
+                    var conn = muxer.GetDatabase();
+                    conn.Ping();
+
+                    Assert.IsTrue(muxer.IsConnected);
+
+                    PhysicalConnection.EmulateStaleConnection = true;
+                    Thread.Sleep(500);
+                    Assert.IsFalse(muxer.IsConnected);
+
+                    PhysicalConnection.EmulateStaleConnection = false;
+                    Thread.Sleep(1000);
+                    Assert.IsTrue(muxer.IsConnected);
+                }
+            }
+            finally
+            {
+                PhysicalConnection.EmulateStaleConnection = false;
+                ClearAmbientFailures();
+            }
+        }
+
 #endif
     }
 }

StackExchange.Redis/StackExchange/Redis/DebuggingAids.cs

@@ -260,6 +260,26 @@ bool ISocketCallback.IgnoreConnect
         {
             get { return multiplexer.IgnoreConnect; }
         }
+
+        private volatile static bool emulateStaleConnection;
+        public static bool EmulateStaleConnection 
+        { get
+            {
+                return emulateStaleConnection;
+            }
+            set
+            {
+                emulateStaleConnection = value;
+            }
+        }
+
+        partial void DebugEmulateStaleConnection(ref int lastRead)
+        {
+            if (emulateStaleConnection)
+            {
+                lastRead -= 100500;
+            }
+        }
     }
 #endif
 

StackExchange.Redis/StackExchange/Redis/PhysicalConnection.cs

@@ -953,5 +953,21 @@ RawResult TryParseResult(byte[] buffer, ref int offset, ref int count)
                     throw new InvalidOperationException("Unexpected response prefix: " + (char)resultType);
             }
         }
+
+        partial void DebugEmulateStaleConnection(ref int lastWrite);
+
+        public void CheckForStaleConnection()
+        {
+            int lastRead, lastWrite;
+            lastRead = Thread.VolatileRead(ref this.lastReadTickCount);
+            lastWrite = Thread.VolatileRead(ref this.lastWriteTickCount);
+
+            DebugEmulateStaleConnection(ref lastRead);
+
+            if ((lastWrite - lastRead) > this.multiplexer.RawConfig.SyncTimeout)
+            {
+                this.RecordConnectionFailed(ConnectionFailureType.SocketFailure, origin: "CheckForStaleConnection");
+            }
+        }
     }
 }

StackExchange.Redis/StackExchange/Redis/SocketManager.Poll.cs

@@ -178,6 +178,7 @@ internal ManagerState State
         private void ReadImpl()
         {
             List<IntPtr> dead = null, active = new List<IntPtr>();
+            List<ISocketCallback> activeCallbacks = new List<ISocketCallback>();
             IntPtr[] readSockets = EmptyPointers, errorSockets = EmptyPointers;
             long lastHeartbeat = Environment.TickCount;
             SocketPair[] allSocketPairs = null;
@@ -185,6 +186,7 @@ private void ReadImpl()
             {
                 managerState = ManagerState.CheckForHeartbeat;
                 active.Clear();
+                activeCallbacks.Clear();
                 if (dead != null) dead.Clear();
 
                 // this check is actually a pace-maker; sometimes the Timer callback stalls for
@@ -227,6 +229,7 @@ private void ReadImpl()
                             if (pair.Value.Socket.Connected)
                             {
                                 active.Add(pair.Key);
+                                activeCallbacks.Add(pair.Value.Callback);
                             }
                             else
                             {
@@ -267,6 +270,13 @@ private void ReadImpl()
                     ready = select(0, readSockets, null, errorSockets, ref timeout);
                     if (ready <= 0)
                     {
+                        if (ready == 0)
+                        {
+                            foreach (var s in activeCallbacks)
+                            {
+                                s.CheckForStaleConnection();
+                            }
+                        }
                         continue; // -ve typically means a socket was disposed just before; just retry
                     }
 

StackExchange.Redis/StackExchange/Redis/SocketManager.cs

@@ -39,6 +39,9 @@ internal partial interface ISocketCallback
         /// Indicates that we cannot know whether data is available, and that the consume should commence reading asynchronously
         /// </summary>
         void StartReading();
+
+        // check for write-read timeout
+        void CheckForStaleConnection();
     }
 
     internal struct SocketToken