supporting status for being able to retry, if command was never sent over the wire.

StackExchange.Redis.Tests/ConnectionFailedErrors.cs

@@ -64,6 +64,7 @@ public void AuthenticationFailureError()
                 };
                 var ex = Assert.Throws<RedisConnectionException>(() => muxer.GetDatabase().Ping());
                 var rde = (RedisConnectionException)ex.InnerException;
+                Assert.That(ex.CommandStatus, Is.EqualTo(CommandStatus.WaitingToBeSent));
                 Assert.That(rde.FailureType, Is.EqualTo(ConnectionFailureType.AuthenticationFailure));
                 Assert.That(rde.InnerException.Message, Is.EqualTo("Error: NOAUTH Authentication required. Verify if the Redis password provided is correct."));
                 //wait for a second  for connectionfailed event to fire

StackExchange.Redis/StackExchange/Redis/CommandStatus.cs

+namespace StackExchange.Redis
+{
+    /// <summary>
+    /// track status of a command while communicating with Redis
+    /// </summary>
+    public enum CommandStatus
+    {
+        /// <summary>
+        /// command status unknown
+        /// </summary>
+        Unknown,
+        /// <summary>
+        /// ConnectionMultiplexer has not yet started writing this command to redis 
+        /// </summary>
+        WaitingToBeSent,
+        /// <summary>
+        /// command has been sent to Redis
+        /// </summary>
+        Sent,
+    }
+}

StackExchange.Redis/StackExchange/Redis/ExceptionFactory.cs

@@ -12,7 +12,8 @@ internal static class ExceptionFactory
             DataServerEndpoint = "server-endpoint",
             DataConnectionState = "connection-state",
             DataLastFailure = "last-failure",
-            DataLastInnerException = "last-innerexception";
+            DataLastInnerException = "last-innerexception",
+            DataSentStatusKey = "request-sent-status";
 
 
         internal static Exception AdminModeNotEnabled(bool includeDetail, RedisCommand command, Message message, ServerEndPoint server)
@@ -118,7 +119,7 @@ internal static Exception NoConnectionAvailable(bool includeDetail, RedisCommand
             }
 #endif
 
-            var ex = new RedisConnectionException(ConnectionFailureType.UnableToResolvePhysicalConnection, exceptionmessage.ToString(), innerException);
+            var ex = new RedisConnectionException(ConnectionFailureType.UnableToResolvePhysicalConnection, exceptionmessage.ToString(), innerException, message?.Status ?? CommandStatus.Unknown);
             
             if (includeDetail)
             {
@@ -173,7 +174,7 @@ internal static Exception NoCursor(RedisCommand command)
 
         internal static Exception Timeout(bool includeDetail, string errorMessage, Message message, ServerEndPoint server)
         {
-            var ex = new TimeoutException(errorMessage);
+            var ex = new RedisTimeoutException(errorMessage, message?.Status ?? CommandStatus.Unknown);
             if (includeDetail) AddDetail(ex, message, server, null);
             return ex;
         }
@@ -182,7 +183,11 @@ private static void AddDetail(Exception exception, Message message, ServerEndPoi
         {
             if (exception != null)
             {
-                if (message != null) exception.Data.Add(DataCommandKey, message.CommandAndKey);
+                if (message != null)
+                {
+                    exception.Data.Add(DataCommandKey, message.CommandAndKey);
+                    exception.Data.Add(DataSentStatusKey, message.Status);
+                }
                 else if (label != null) exception.Data.Add(DataCommandKey, label);
 
                 if (server != null) exception.Data.Add(DataServerKey, Format.ToString(server.EndPoint));

StackExchange.Redis/StackExchange/Redis/Message.cs

@@ -27,6 +27,40 @@ public sealed class RedisCommandException : Exception
     }
 
 
+/// <summary>
+/// Indicates the time allotted for a command or operation has expired.
+/// </summary>
+#if FEATURE_SERIALIZATION
+    [Serializable]
+#endif
+    public sealed class RedisTimeoutException : TimeoutException
+    {
+#if FEATURE_SERIALIZATION
+        private RedisTimeoutException(SerializationInfo info, StreamingContext ctx) : base(info, ctx)
+        {
+             Commandstatus = (CommandStatus) info.GetValue("commandStatus", typeof(CommandStatus));
+        }
+        /// <summary>
+        /// Serialization implementation; not intended for general usage
+        /// </summary>
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("commandStatus", Commandstatus);
+        }
+#endif
+        internal RedisTimeoutException(string message, CommandStatus commandStatus) : base(message)
+        {
+            Commandstatus = commandStatus;
+        }
+
+        /// <summary>
+        /// status of the command while communicating with Redis
+        /// </summary>
+        public CommandStatus Commandstatus { get; }
+    }
+
+
 
     /// <summary>
     /// Indicates a connection fault when communicating with redis
@@ -40,6 +74,7 @@ public sealed class RedisConnectionException : RedisException
         private RedisConnectionException(SerializationInfo info, StreamingContext ctx) : base(info, ctx)
         {
             FailureType = (ConnectionFailureType)info.GetInt32("failureType");
+            CommandStatus = (CommandStatus)info.GetValue("commandStatus", typeof(CommandStatus));
         }
         /// <summary>
         /// Serialization implementation; not intended for general usage
@@ -48,22 +83,33 @@ public override void GetObjectData(SerializationInfo info, StreamingContext cont
         {
             base.GetObjectData(info, context);
             info.AddValue("failureType", (int)FailureType);
+            info.AddValue("commandStatus", CommandStatus);
         }
 #endif
 
-        internal RedisConnectionException(ConnectionFailureType failureType, string message) : base(message)
+        internal RedisConnectionException(ConnectionFailureType failureType, string message) : this(failureType, message, null, CommandStatus.Unknown)
         {
-            FailureType = failureType;
         }
-        internal RedisConnectionException(ConnectionFailureType failureType, string message, Exception innerException) : base(message, innerException)
+
+        internal RedisConnectionException(ConnectionFailureType failureType, string message, Exception innerException) : this(failureType, message, innerException, CommandStatus.Unknown)
+        {
+        }
+
+        internal RedisConnectionException(ConnectionFailureType failureType, string message, Exception innerException, CommandStatus commandStatus) : base(message, innerException)
         {
             FailureType = failureType;
+            CommandStatus = commandStatus;
         }
 
         /// <summary>
         /// The type of connection failure
         /// </summary>
         public ConnectionFailureType FailureType { get; }
+
+        /// <summary>
+        /// status of the command while communicating with Redis
+        /// </summary>
+        public CommandStatus CommandStatus { get; }
     }
 
     /// <summary>
@@ -193,6 +239,7 @@ protected Message(int db, CommandFlags flags, RedisCommand command)
 
             createdDateTime = DateTime.UtcNow;
             createdTimestamp = System.Diagnostics.Stopwatch.GetTimestamp();
+            Status = CommandStatus.WaitingToBeSent;
         }
 
         internal void SetMasterOnly()
@@ -231,8 +278,11 @@ internal void PrepareToResend(ServerEndPoint resendTo, bool isMoved)
             createdTimestamp = System.Diagnostics.Stopwatch.GetTimestamp();
             performance = ProfileStorage.NewAttachedToSameContext(oldPerformance, resendTo, isMoved);
             performance.SetMessage(this);
+            Status = CommandStatus.WaitingToBeSent;
         }
 
+        internal CommandStatus Status { get; private set; }
+
         public RedisCommand Command => command;
 
         public virtual string CommandAndKey => Command.ToString();
@@ -678,6 +728,7 @@ internal void SetEnqueued()
 
         internal void SetRequestSent()
         {
+            Status = CommandStatus.Sent;
             performance?.SetRequestSent();
         }