Make serializer a little more forgiving when keys collide.

Source/EasyGelf.Core/GelfMessageSerializer.cs

@@ -10,23 +10,40 @@ public interface IGelfMessageSerializer
 
     public sealed class GelfMessageSerializer : IGelfMessageSerializer
     {
+        private readonly IEasyGelfLogger _logger;
+
+        public GelfMessageSerializer(IEasyGelfLogger logger)
+        {
+            _logger = logger;
+        }
+
         public byte[] Serialize(GelfMessage message)
         {
             var duration = message.Timestamp.ToUniversalTime() - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
             var result = new JsonObject
-                {
-                    {"version", message.Version},
-                    {"host", message.Host},
-                    {"short_message", message.ShortMessage},
-                    {"full_message", message.FullMessage},
-                    {"timestamp", Math.Round(duration.TotalSeconds, 3, MidpointRounding.AwayFromZero)},
-                    {"level", (int)message.Level}
-                };
+            {
+                {"version", message.Version},
+                {"host", message.Host},
+                {"short_message", message.ShortMessage},
+                {"full_message", message.FullMessage},
+                {"timestamp", Math.Round(duration.TotalSeconds, 3, MidpointRounding.AwayFromZero)},
+                {"level", (int) message.Level}
+            };
             foreach (var additionalField in message.AdditionalFields)
             {
                 var key = additionalField.Key;
                 var value = additionalField.Value;
-                result.Add(key.StartsWith("_") ? key : "_" + key, value);
+                var prefixedKey = key.StartsWith("_") ? key : "_" + key;
+                if (!result.ContainsKey(prefixedKey))
+                {
+                    result.Add(prefixedKey, value);
+                }
+                else
+                {
+                    _logger.Debug(string.Format(
+                        "Duplicate key {0} found.  Key collisions are resolved by favoring the first key-value to be added.",
+                        prefixedKey));
+                }
             }
             return Encoding.UTF8.GetBytes(result.ToString());
         }

Source/EasyGelf.Core/Transports/Tcp/TcpTransportFactory.cs

@@ -9,16 +9,11 @@ namespace EasyGelf.Core.Transports.Tcp
 {
     public class TcpTransportFactory
     {
-        public static ITransport Produce(TcpTransportConfiguration configuration)
+        public static ITransport Produce(TcpTransportConfiguration configuration, IEasyGelfLogger logger)
         {
-            if (configuration.Ssl)
-            {
-                return new TcpTransport(configuration, new GelfMessageSerializer(), () => new TcpSslConnection(configuration));
-            }
-            else
-            {
-                return new TcpTransport(configuration, new GelfMessageSerializer(), () => new TcpConnection(configuration));
-            }
+            return configuration.Ssl
+                ? new TcpTransport(configuration, new GelfMessageSerializer(logger), () => new TcpSslConnection(configuration))
+                : new TcpTransport(configuration, new GelfMessageSerializer(logger), () => new TcpConnection(configuration));
         }
     }
 }

Source/EasyGelf.Log4Net/GelfAmqpAppender.cs

@@ -44,7 +44,7 @@ protected override ITransport InitializeTransport(IEasyGelfLogger logger)
                     Persistent = Persistent,
                 };
             var encoder = new CompositeEncoder(new GZipEncoder(), new ChunkingEncoder(new MessageBasedIdGenerator(), MessageSize));
-            return new AmqpTransport(configuration, encoder, new GelfMessageSerializer());
+            return new AmqpTransport(configuration, encoder, new GelfMessageSerializer(logger));
         }
     }
 }

Source/EasyGelf.Log4Net/GelfTcpAppender.cs

@@ -36,7 +36,7 @@ protected override ITransport InitializeTransport(IEasyGelfLogger logger)
                 Timeout = Timeout
             };
 
-            return TcpTransportFactory.Produce(configuration);
+            return TcpTransportFactory.Produce(configuration, logger);
         }
     }
 }

Source/EasyGelf.Log4Net/GelfUdpAppender.cs

@@ -29,7 +29,7 @@ protected override ITransport InitializeTransport(IEasyGelfLogger logger)
                     RemoteAddress = RemoteAddress,
                     RemotePort = RemotePort
                 };
-            return new UdpTransport(configuration, encoder, new GelfMessageSerializer());
+            return new UdpTransport(configuration, encoder, new GelfMessageSerializer(logger));
         }
     }
 }

Source/EasyGelf.NLog.Example/EntryPoint.cs

@@ -22,7 +22,7 @@ public static void Main()
                 }
                 catch (Exception ex)
                 {
-                    Log.Error("Descriptive message example", ex);
+                    Log.Error(ex, "Descriptive message example");
                 }
 
                 Thread.Sleep(TimeSpan.FromSeconds(0.5));

Source/EasyGelf.NLog/GelfAmqpTarget.cs

@@ -46,7 +46,7 @@ protected override ITransport InitializeTransport(IEasyGelfLogger logger)
                     RoutingKey = RoutingKey,
                     Persistent = Persistent
                 };
-            return new AmqpTransport(configuration, encoder, new GelfMessageSerializer());
+            return new AmqpTransport(configuration, encoder, new GelfMessageSerializer(logger));
         }
     }
 }

Source/EasyGelf.NLog/GelfHttpTarget.cs

@@ -34,7 +34,7 @@ protected override ITransport InitializeTransport(IEasyGelfLogger logger)
                 Port = RemotePort
             };
 
-            return new HttpTransport(configuration, new GelfMessageSerializer());
+            return new HttpTransport(configuration, new GelfMessageSerializer(logger));
         }
     }
 }

Source/EasyGelf.NLog/GelfTcpTarget.cs

@@ -38,7 +38,7 @@ protected override ITransport InitializeTransport(IEasyGelfLogger logger)
                 Timeout = Timeout
             };
 
-            return TcpTransportFactory.Produce(configuration);
+            return TcpTransportFactory.Produce(configuration, logger);
         }
     }
 }

Source/EasyGelf.NLog/GelfUdpTarget.cs

@@ -31,7 +31,7 @@ protected override ITransport InitializeTransport(IEasyGelfLogger logger)
                     RemoteAddress = RemoteAddress,
                     RemotePort = RemotePort
                 };
-            return new UdpTransport(configuration, encoder, new GelfMessageSerializer());
+            return new UdpTransport(configuration, encoder, new GelfMessageSerializer(logger));
         }
     }
 }

Source/EasyGelf.Tests/Core/GelfMessageSerializerTests.cs

@@ -13,7 +13,7 @@ public class GelfMessageSerializerTests
         [SetUp]
         public void SetUp()
         {
-            serializer = new GelfMessageSerializer();
+            serializer = new GelfMessageSerializer(new SilentLogger());
         }
 
         [Test]