#201 - give specific message when too many arguments are involved

StackExchange.Redis/StackExchange/Redis/ExceptionFactory.cs

 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Text;
 
 namespace StackExchange.Redis
@@ -30,6 +31,13 @@ internal static Exception CommandDisabled(bool includeDetail, RedisCommand comma
             if (includeDetail) AddDetail(ex, message, server, s);
             return ex;
         }
+        internal static Exception TooManyArgs(bool includeDetail, string command, Message message, ServerEndPoint server, int required)
+        {
+            string s = GetLabel(includeDetail, command, message);
+            var ex = new RedisCommandException($"This operation would involve too many arguments ({required} vs the redis limit of {PhysicalConnection.REDIS_MAX_ARGS}): {s}");
+            if (includeDetail) AddDetail(ex, message, server, s);
+            return ex;
+        }
         internal static Exception CommandDisabled(bool includeDetail, string command, Message message, ServerEndPoint server)
         {
             string s = GetLabel(includeDetail, command, message);

StackExchange.Redis/StackExchange/Redis/PhysicalConnection.cs

@@ -474,8 +474,14 @@ internal void WriteHeader(RedisCommand command, int arguments)
             WriteRaw(outStream, arguments + 1);
             WriteUnified(outStream, commandBytes);
         }
+        internal const int REDIS_MAX_ARGS = 1024 * 1024; // there is a <= 1024*1024 max constraint inside redis itself: https://github.com/antirez/redis/blob/6c60526db91e23fb2d666fc52facc9a11780a2a3/src/networking.c#L1024
+
         internal void WriteHeader(string command, int arguments)
         {
+            if(arguments >= REDIS_MAX_ARGS) // using >= here because we will be adding 1 for the command itself (which is an arg for the purposes of the multi-bulk protocol)
+            {
+                throw ExceptionFactory.TooManyArgs(Multiplexer.IncludeDetailInExceptions, command, null, Bridge.ServerEndPoint, arguments + 1);
+            }
             var commandBytes = Multiplexer.CommandMap.GetBytes(command);
             if (commandBytes == null)
             {