Merge pull request #127 from PashaPash/stale-connection-fix

Azure stale connection detection

StackExchange.Redis.Tests/ConnectingFailDetection.cs

@@ -8,7 +8,7 @@ namespace StackExchange.Redis.Tests
     public class ConnectingFailDetection : TestBase
     {
 #if DEBUG
-        [TestCase]
+        [Test]
         public void FastNoticesFailOnConnectingSync()
         {
             try
@@ -34,16 +34,15 @@ public void FastNoticesFailOnConnectingSync()
 
                     Assert.IsTrue(muxer.IsConnected);
                 }
-
-                ClearAmbientFailures();
             }
             finally 
             {
                 SocketManager.ConnectCompletionType = CompletionType.Any;
+                ClearAmbientFailures();
             }
         }
 
-        [TestCase]
+        [Test]
         public void ConnectsWhenBeginConnectCompletesSynchronously()
         {
             try
@@ -57,16 +56,15 @@ public void ConnectsWhenBeginConnectCompletesSynchronously()
 
                     Assert.IsTrue(muxer.IsConnected);
                 }
-
-                ClearAmbientFailures();
             }
             finally
             {
                 SocketManager.ConnectCompletionType = CompletionType.Any;
+                ClearAmbientFailures();
             }
         }
 
-        [TestCase]
+        [Test]
         public void FastNoticesFailOnConnectingAsync()
         {
             try
@@ -92,15 +90,43 @@ public void FastNoticesFailOnConnectingAsync()
                     Thread.Sleep(2000);
 
                     Assert.IsTrue(muxer.IsConnected);
-                    ClearAmbientFailures();
-
                 }
             }
             finally
             {
                 SocketManager.ConnectCompletionType = CompletionType.Any;
+                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 firstUnansweredWrite)
+        {
+            if (emulateStaleConnection)
+            {
+                firstUnansweredWrite = Environment.TickCount - 100000;
+            }
+        }
     }
 #endif
 

StackExchange.Redis/StackExchange/Redis/PhysicalBridge.cs

@@ -679,23 +679,6 @@ private bool ChangeState(State oldState, State newState)
             return result;
         }
 
-        private void Flush()
-        {
-            var tmp = physical;
-            if (tmp != null)
-            {
-                try
-                {
-                    Trace(connectionType + " flushed");
-                    tmp.Flush();
-                }
-                catch (Exception ex)
-                {
-                    OnInternalError(ex);
-                }
-            }
-        }
-
         private PhysicalConnection GetConnection()
         {
             if (state == (int)State.Disconnected)

StackExchange.Redis/StackExchange/Redis/PhysicalConnection.cs

@@ -64,6 +64,7 @@ private static readonly Message
         int ioBufferBytes = 0;
 
         int lastWriteTickCount, lastReadTickCount, lastBeatTickCount;
+        int firstUnansweredWriteTickCount;
 
         private Stream netStream, outStream;
 
@@ -85,6 +86,7 @@ public PhysicalConnection(PhysicalBridge bridge)
 
         public void BeginConnect()
         {
+            Thread.VolatileWrite(ref firstUnansweredWriteTickCount, 0);
             var endpoint = this.bridge.ServerEndPoint.EndPoint;
 
             multiplexer.Trace("Connecting...", physicalName);
@@ -164,14 +166,15 @@ public void RecordConnectionFailed(ConnectionFailureType failureType, Exception
 
             if (isCurrent && Interlocked.CompareExchange(ref failureReported, 1, 0) == 0)
             {
-                //try
-                //{
                 int now = Environment.TickCount, lastRead = Thread.VolatileRead(ref lastReadTickCount), lastWrite = Thread.VolatileRead(ref lastWriteTickCount),
                     lastBeat = Thread.VolatileRead(ref lastBeatTickCount);
+                int unansweredRead = Thread.VolatileRead(ref firstUnansweredWriteTickCount);
 
                 string message = failureType + " on " + Format.ToString(bridge.ServerEndPoint.EndPoint) + "/" + connectionType
                     + ", input-buffer: " + ioBufferBytes + ", outstanding: " + GetSentAwaitingResponseCount()
-                    + ", last-read: " + unchecked(now - lastRead) / 1000 + "s ago, last-write: " + unchecked(now - lastWrite) / 1000 + "s ago, keep-alive: " + bridge.ServerEndPoint.WriteEverySeconds + "s, pending: "
+                    + ", last-read: " + unchecked(now - lastRead) / 1000 + "s ago, last-write: " + unchecked(now - lastWrite) / 1000 + "s ago"
+                    + ", unanswered-write: " + unchecked(now - unansweredRead) / 1000 + "s ago"
+                    + ", keep-alive: " + bridge.ServerEndPoint.WriteEverySeconds + "s, pending: "
                     + bridge.GetPendingCount() + ", state: " + oldState + ", last-heartbeat: " + (lastBeat == 0 ? "never" : (unchecked(now - lastBeat) / 1000 + "s ago"))
                     + (bridge.IsBeating ? " (mid-beat)" : "") + ", last-mbeat: " + multiplexer.LastHeartbeatSecondsAgo + "s ago, global: "
                     + ConnectionMultiplexer.LastGlobalHeartbeatSecondsAgo + "s ago";
@@ -181,13 +184,6 @@ public void RecordConnectionFailed(ConnectionFailureType failureType, Exception
                     : new RedisConnectionException(failureType, message, innerException);
 
                 bridge.OnConnectionFailed(this, failureType, ex);
-                //    throw ex;
-                //}
-                //catch (Exception caught)
-                //{
-                //    bridge.OnConnectionFailed(this, failureType, caught);
-                //}
-
             }
 
             // cleanup
@@ -390,6 +386,10 @@ internal void WriteHeader(RedisCommand command, int arguments)
                 throw ExceptionFactory.CommandDisabled(multiplexer.IncludeDetailInExceptions, command, null, bridge.ServerEndPoint);
             }
             outStream.WriteByte((byte)'*');
+
+            // remember the time of the first write that still not followed by read
+            Interlocked.CompareExchange(ref firstUnansweredWriteTickCount, Environment.TickCount, 0);
+
             WriteRaw(outStream, arguments + 1);
             WriteUnified(outStream, commandBytes);
         }
@@ -825,6 +825,10 @@ private bool ProcessReadBytes(int bytesRead)
             }
 
             Interlocked.Exchange(ref lastReadTickCount, Environment.TickCount);
+
+            // reset unanswered write timestamp
+            Thread.VolatileWrite(ref firstUnansweredWriteTickCount, 0);
+
             ioBufferBytes += bytesRead;
             multiplexer.Trace("More bytes available: " + bytesRead + " (" + ioBufferBytes + ")", physicalName);
             int offset = 0, count = ioBufferBytes;
@@ -962,5 +966,22 @@ RawResult TryParseResult(byte[] buffer, ref int offset, ref int count)
                     throw new InvalidOperationException("Unexpected response prefix: " + (char)resultType);
             }
         }
+
+        partial void DebugEmulateStaleConnection(ref int firstUnansweredWrite);
+
+        public void CheckForStaleConnection()
+        {
+            int firstUnansweredWrite;
+            firstUnansweredWrite = Thread.VolatileRead(ref firstUnansweredWriteTickCount);
+
+            DebugEmulateStaleConnection(ref firstUnansweredWrite);
+
+            int now = Environment.TickCount;
+
+            if (firstUnansweredWrite != 0 && (now - firstUnansweredWrite) > 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