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https://issues.apache.org/jira/browse/HDFS-1325?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12895149#action_12895149
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jinglong.liujl commented on HDFS-1325:
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    Thanks for your reply. 
    I think hbase client (In fact, it's region server) should use HDFS as 
general file system, It holds HDFS input stream like a simple file 
handle.Network connection between DFSClient and DataNode should be transparent 
to them. 
    As a platform,  we should handle these resources to make platform more 
robust,  right ? 
    From another point, HBase client should close file handle (input stream) in 
the right time.

> DFSClient(DFSInputStream) release the persistent connection with datanode 
> when no data have been read for a long time
> ---------------------------------------------------------------------------------------------------------------------
>
>                 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, toomanyconnction.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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