include the origin of timeouts

src/StackExchange.Redis/ConnectionMultiplexer.cs

@@ -2152,7 +2152,7 @@ private static async Task<T> ExecuteAsyncImpl_Awaited<T>(ConnectionMultiplexer @
             return tcs == null ? default(T) : await tcs.Task.ForAwait();
         }
 
-        internal Exception GetException(WriteResult result, Message message, ServerEndPoint server)
+        internal Exception GetException(WriteResult result, Message message, ServerEndPoint server, [CallerMemberName] string caller = null)
         {
             switch (result)
             {
@@ -2160,7 +2160,7 @@ internal Exception GetException(WriteResult result, Message message, ServerEndPo
                 case WriteResult.NoConnectionAvailable:
                     return ExceptionFactory.NoConnectionAvailable(IncludeDetailInExceptions, IncludePerformanceCountersInExceptions, message.Command, message, server, GetServerSnapshot());
                 case WriteResult.TimeoutBeforeWrite:
-                    return ExceptionFactory.Timeout(this, "The timeout was reached before the message could be written to the output buffer, and it was not sent", message, server, result);
+                    return ExceptionFactory.Timeout(this, "The timeout was reached before the message could be written to the output buffer, and it was not sent", message, server, result, caller: caller);
                 case WriteResult.WriteFailure:
                 default:
                     return ExceptionFactory.ConnectionFailure(IncludeDetailInExceptions, ConnectionFailureType.ProtocolFailure, "An unknown error occurred when writing the message", server);

src/StackExchange.Redis/ExceptionFactory.cs

@@ -181,7 +181,7 @@ internal static string GetLibVersion()
             }
             return _libVersion;
         }
-        internal static Exception Timeout(ConnectionMultiplexer mutiplexer, string baseErrorMessage, Message message, ServerEndPoint server, WriteResult? result = null)
+        internal static Exception Timeout(ConnectionMultiplexer mutiplexer, string baseErrorMessage, Message message, ServerEndPoint server, WriteResult? result = null, string origin = null)
         {
             List<Tuple<string, string>> data = new List<Tuple<string, string>> { Tuple.Create("Message", message.CommandAndKey) };
             var sb = new StringBuilder();
@@ -198,11 +198,13 @@ void add(string lk, string sk, string v)
             {
                 if (v != null)
                 {
-                    data.Add(Tuple.Create(lk, v));
-                    sb.Append(", ").Append(sk).Append(": ").Append(v);
+                    if (lk != null) data.Add(Tuple.Create(lk, v));
+                    if (sk != null) sb.Append(", ").Append(sk).Append(": ").Append(v);
                 }
             }
 
+            if (!string.IsNullOrWhiteSpace(origin)) add("Origin", null, origin);
+
             // Add timeout data, if we have it
             if (result == WriteResult.TimeoutBeforeWrite)
             {