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https://issues.apache.org/jira/browse/HDFS-1605?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13847100#comment-13847100
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Liang Xie commented on HDFS-1605:
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bq. waitFor(4000);
totally agreed with your point, it should have a different configurable value
for online app like HBase , or offline app processing app.
I can file a minor jira for this, thanks [~stack].
> Convert DFSInputStream synchronized sections to a ReadWrite lock
> ----------------------------------------------------------------
>
> Key: HDFS-1605
> URL: https://issues.apache.org/jira/browse/HDFS-1605
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: DFSClientRWlock.1.txt, DFSClientRWlock.3.txt,
> HDFS-1605.txt
>
>
> Hbase does concurrent preads from multiple threads to different blocks of the
> same hdfs file. Each of these pread calls invoke
> DFSInputStream.getFileLength() and DFSInputStream.getBlockAt(). These methods
> are "synchronized", thus causing all the concurrent threads to serialize. It
> would help performance to convert this to a Read/Write lock
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