add brief description of enhancements

README.md

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+This is a repository for the flume source code we are using inside our company.
+It is forked from Cloudera's 0.9.3-cdh3u0 distribution (Flume-OG).
+
+Two major enhancements:
+
+1) Masterless Ack:
+This enhancement aims to increase the reliability and throughput of the whole distributed collecting system.
+Flume provides End-to-End delivery mode to guarantee the data delivery; an acknowledgement message (ACK) is sent back to original node to confirm the successful delivery of a group of messages. However, the ACKs are sent back through master, which could be a single-point-of-failure or bottle neck of the whole system.
+Therefore, I re-designed the ACKs system to let the ACK go back via the route of Event.
+
+You can also get some information here https://issues.apache.org/jira/browse/FLUME-640
+This enhancement was supposed to be merged into 0.10 if Flume was not upgraded to NG; 
+
+2) Append to HDFS with new file rotation method.
+Use HDFS append() and change the file rotation mechanism to create large HDFS files, which could increase the performance of Map/Reduce program when using these files as input, and reduce the number of block mapping entries in Hadoop NameNode.
+
+This modified version has been heavily used inside our company, with single collector receiving more than 300GB data per day.
+
+Contact me:
+yongkun at gmail.com
+
+https://github.com/yongkun/flume-0.9.3-cdh3u0