[jira] Created: (HDFS-1325) DFSClient(DFSInputStream) release the persistent connection with datanode when no data have been read for a long time

["jinglong.liujl (JIRA)" <ji...@apache.org>]

DFSClient(DFSInputStream) release the persistent connection with datanode when no data have been read for a long time
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                 Key: HDFS-1325
                 URL: https://issues.apache.org/jira/browse/HDFS-1325
             Project: Hadoop HDFS
          Issue Type: Improvement
          Components: hdfs client
            Reporter: jinglong.liujl
             Fix For: 0.20.3
         Attachments: dfsclient.patch

When you use Hbase over hadoop. We found during scanning over a large table ( which has many regions and each region has many store files), there're too many connections has been kept between regionserver (act as DFSClient) and datanode.  Even if the store file has been complete to scanning, the connections can not be closed.
In our cluster, too many extra connections cause too many system resource has been wasted, which cause system cpu on region server reach to a high level, then bring this region server down.
After investigating, we found the number of active connection is very small, and the most connection is idle. We add a timeout checker thread into DFSClient, to close this connection.




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