Added a field replica concept so the appender can be configured with …

…the same value in two fields for the case when you are migrating from one field name to another.

Made the additional static setup use one method for passing the new settings down.

src/log4net.ElasticSearch.Tests/UnitTests/UnitTestContext.cs

@@ -42,9 +42,16 @@ public static UnitTestContext Create(int bufferSize = BufferSize, bool? failSend
             };
 
             appender.AddFieldNameOverride(new FieldNameOverride
+                {
+                    Original = "timetamp",
+                    Replacement = "timestamp"
+                }
+            );
+
+            appender.AddFieldValueReplica(new FieldValueReplica
                 {
                     Original = "timeStamp",
-                    Replacement = "@timestamp"
+                    Replica = "@timestamp"
                 }
             );
 

src/log4net.ElasticSearch.Tests/logConfig.xml

@@ -12,8 +12,12 @@
       <lossy value="false" />
       <fieldNameOverride type="log4net.ElasticSearch.FieldNameOverride, log4net.ElasticSearch">
         <original value="timeStamp" />
-        <replacement value="@timestamp" />
+        <replacement value="timestamp" />
       </fieldNameOverride>
+      <fieldValueReplica type="log4net.ElasticSearch.FieldValueReplica, log4net.ElasticSearch">
+        <original value="timeStamp" />
+        <replica value="@timestamp" />
+      </fieldValueReplica>
       <rollingIndexNameDateFormat value="yyyy-MM-dd" />
       <evaluator type="log4net.Core.LevelEvaluator">
         <threshold value="ALL" />

src/log4net.ElasticSearch/CustomDataContractResolver.cs

@@ -10,6 +10,7 @@ namespace log4net.ElasticSearch
     public class CustomDataContractResolver : DefaultContractResolver
     {
         public Dictionary<string, string> FieldNameChanges { get; set; }
+        public List<FieldValueReplica> FieldValueReplica { get; set; }
 
         protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
         {
@@ -21,5 +22,5 @@ protected override JsonProperty CreateProperty(MemberInfo member, MemberSerializ
 
             return property;
         }
-    }
+   }
 }

src/log4net.ElasticSearch/ElasticSearchAppender.cs

@@ -17,9 +17,10 @@ public class ElasticSearchAppender : BufferingAppenderSkeleton
         const int DefaultOnCloseTimeout = 30000;
         readonly ManualResetEvent workQueueEmptyEvent;
 
-        int queuedCallbackCount;
         IRepository repository;
+        int queuedCallbackCount;
         List<FieldNameOverride> fieldNameOverrides = new List<FieldNameOverride>();
+        List<FieldValueReplica> fieldValueReplicas = new List<FieldValueReplica>();
 
         public ElasticSearchAppender()
         {
@@ -62,6 +63,11 @@ public void AddFieldNameOverride(FieldNameOverride fieldNameOverride)
             fieldNameOverrides.Add(fieldNameOverride);
         }
 
+        public void AddFieldValueReplica(FieldValueReplica fieldValueReplica)
+        {
+            fieldValueReplicas.Add(fieldValueReplica);
+        }
+
         protected override void SendBuffer(LoggingEvent[] events)
         {
             BeginAsyncSend();
@@ -83,7 +89,11 @@ protected virtual IRepository CreateRepository(string connectionString)
             log4net.ElasticSearch.Models.Uri.Init(RollingIndexNameDateFormat, IndexTypeName);
 
             var overrides = fieldNameOverrides.ToDictionary(x => x.Original, x => x.Replacement);
-            var resolver = new CustomDataContractResolver { FieldNameChanges = overrides };
+            var resolver = new CustomDataContractResolver
+            {
+                FieldNameChanges = overrides,
+                FieldValueReplica = fieldValueReplicas,
+            };
             return Repository.Create(connectionString, resolver);
         }
 
@@ -149,7 +159,7 @@ static void Validate(string connectionString)
             }
         }
     }
-    
+
     public class FieldNameOverride : IOptionHandler
     {
         public string Original {get; set;}
@@ -160,4 +170,15 @@ public void ActivateOptions()
         {
         }
     }
+
+    public class FieldValueReplica : IOptionHandler
+    {
+        public string Original {get; set;}
+
+        public string Replica {get; set;}
+
+        public void ActivateOptions()
+        {
+        }
+    }
 }

src/log4net.ElasticSearch/ExtensionMethods.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Data.Common;
+using System.Dynamic;
 using System.Linq;
 using log4net.Core;
 using log4net.ElasticSearch.Infrastructure;
@@ -32,7 +33,20 @@ public static IEnumerable<KeyValuePair<string, string>> Properties(this LoggingE
 
         public static string ToJson<T>(this T self, CustomDataContractResolver resolver)
         {
-            return JsonConvert.SerializeObject(self, new JsonSerializerSettings { ContractResolver = resolver });
+            var json = JsonConvert.SerializeObject(self, new JsonSerializerSettings { ContractResolver = resolver });
+
+            if (resolver.FieldValueReplica != null && resolver.FieldValueReplica.Count > 0)
+            {
+                resolver.FieldValueReplica.ForEach(x =>
+                {
+                    var originalValue = self.GetType().GetProperty(x.Original)?.GetValue(self, null);
+                    var obj = JsonConvert.DeserializeObject<ExpandoObject>(json) as IDictionary<string, Object>;
+                    obj.Add(x.Replica, originalValue);
+                    json = JsonConvert.SerializeObject(obj);
+                });
+            }
+
+            return json;
         }
 
         public static bool Contains(this StringDictionary self, string key)