1) Fix log loss scenario during rebalance, 2) use api version 0 instead of

1, 3) Some minor performance improvement and bug fixes

Author: Som Sahu

src/KafkaNET.Library/Consumers/ConsumerIterator.cs

@@ -247,7 +247,7 @@ private TData MakeNext()
                 currentTopicInfo = currentDataChunk.TopicInfo;
                 Logger.DebugFormat("CurrentTopicInfo: ConsumedOffset({0}), FetchOffset({1})",
                                     currentTopicInfo.ConsumeOffset, currentTopicInfo.FetchOffset);
-                if (currentTopicInfo.ConsumeOffset != currentDataChunk.FetchOffset)
+                if (currentTopicInfo.FetchOffset < currentDataChunk.FetchOffset)
                 {
                     Logger.ErrorFormat("consumed offset: {0} doesn't match fetch offset: {1} for {2}; consumer may lose data",
                         currentTopicInfo.ConsumeOffset,

src/KafkaNET.Library/Consumers/PartitionTopicInfo.cs

@@ -232,8 +232,8 @@ public int Add(BufferedMessageSet messages)
 
                 Logger.InfoFormat("{2} : Updating fetch offset = {0} with value = {1}", this.fetchedOffset, offset, this.PartitionId);
                 this.chunkQueue.Add(new FetchedDataChunk(messages, this, this.fetchedOffset));
-                long newOffset = Interlocked.Exchange(ref this.fetchedOffset, offset);
-                Logger.Debug("Updated fetch offset of " + this + " to " + newOffset);
+                Interlocked.Exchange(ref this.fetchedOffset, offset);
+                Logger.Debug("Updated fetch offset of " + this + " to " + offset);
             }
 
             return size;

src/KafkaNET.Library/Messages/BufferedMessageSet.cs

@@ -316,7 +316,7 @@ private MessageAndOffset MakeNextOuter()
                 return AllDone();
             }
 
-            Message newMessage = this.Messages.ToList()[topIterPosition];
+            Message newMessage = this.Messages.ElementAt(topIterPosition);
             lastMessageSize = newMessage.Size;
             topIterPosition++;
             switch (newMessage.CompressionCodec)

src/KafkaNET.Library/Requests/FetchRequest.cs

@@ -56,7 +56,7 @@ public class FetchRequest : AbstractRequest, IWritable
         public const byte DefaultMinBytesSize = 4;
         public const byte DefaultOffsetInfoSizeSize = 4;
 
-        public const short CurrentVersion = 1;
+        public const short CurrentVersion = 0;
 
         public FetchRequest(int correlationId, string clientId, int maxWait, int minBytes, Dictionary<string, List<PartitionFetchInfo>> fetchInfos)
         {

src/KafkaNET.Library/ZooKeeperIntegration/Listeners/ZKRebalancerListener.cs

@@ -496,34 +496,19 @@ private void AddPartitionTopicInfo(ZKGroupTopicDirs topicDirs, string partition,
             }
             var leader = leaderOpt.Value;
             var znode = topicDirs.ConsumerOffsetDir + "/" + partition;
-            var offsetString = this.zkClient.ReadData<string>(znode, true);
+
+            var offsetCommitedString = this.zkClient.ReadData<string>(znode, true);
 
             //if first time starting a consumer, set the initial offset based on the config
-            long offset = 0;
-            long offsetCommited = 0;
-            if (offsetString == null)
-            {
-                switch (config.AutoOffsetReset)
-                {
-                    case OffsetRequest.SmallestTime:
-                        offset = this.EarliestOrLatestOffset(topic, leader, partitionId, OffsetRequest.EarliestTime);
-                        break;
-                    case OffsetRequest.LargestTime:
-                        offset = this.EarliestOrLatestOffset(topic, leader, partitionId, OffsetRequest.LatestTime);
-                        break;
-                    default:
-                        throw new ConfigurationErrorsException("Wrong value in autoOffsetReset in ConsumerConfig");
-                }
-                offsetCommited = Math.Max(offset - 1, 0);
-            }
-            else
+            long offset = -1;
+            long offsetCommited = -1;
+            if (offsetCommitedString != null)
             {
-                offsetCommited = long.Parse(offsetString);
-                long latestOffset = this.EarliestOrLatestOffset(topic, leader, partitionId, OffsetRequest.LatestTime);
-                offset = Math.Min(offsetCommited + 1, latestOffset);
-                Logger.InfoFormat("Final offset {0} for topic {1} partition {2} OffsetCommited {3} latestOffset {4}"
-                    , offset, topic, partition, offsetCommited, latestOffset);
+                offsetCommited = long.Parse(offsetCommitedString);
+                offset = offsetCommited + 1;
             }
+            Logger.InfoFormat("Final offset {0} for topic {1} partition {2} OffsetCommited {3}"
+                    , offset, topic, partition, offsetCommited);
 
             var queue = this.queues[new Tuple<string, string>(topic, consumerThreadId)];
             var partTopicInfo = new PartitionTopicInfo(
@@ -540,32 +525,6 @@ private void AddPartitionTopicInfo(ZKGroupTopicDirs topicDirs, string partition,
             Logger.InfoFormat("{0} selected new offset {1}", partTopicInfo, offset);
         }
 
-        private long EarliestOrLatestOffset(string topic, int brokerId, int partitionId, long earliestIoLatest)
-        {
-            Consumer consumer = null;
-            long producedOffset = -1;
-            try
-            {
-                var cluster = new Cluster(this.zkClient);
-                var broker = cluster.GetBroker(brokerId);
-                if (broker == null)
-                {
-                    throw new IllegalStateException(string.Format("Broker {0} is unavailable. Cannot issue GetOffsetsBefore request", brokerId));
-                }
-                consumer = new Consumer(this.config, broker.Host, broker.Port);
-                var requestInfos = new Dictionary<string, List<PartitionOffsetRequestInfo>>();
-                requestInfos[topic] = new List<PartitionOffsetRequestInfo>() { new PartitionOffsetRequestInfo(partitionId, earliestIoLatest, 1) };
-                var offsets = consumer.GetOffsetsBefore(new OffsetRequest(requestInfos));
-
-                producedOffset = offsets.ResponseMap[topic].First().Offsets[0];
-            }
-            catch (Exception ex)
-            {
-                Logger.ErrorFormat("error in EarliestOrLatestOffset() : {0}", ex.FormatException());
-            }
-            return producedOffset;
-        }
-
         private void ReleasePartitionOwnership(IDictionary<string, IList<string>> topicThreadIdsMap)
         {