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https://issues.apache.org/jira/browse/HDFS-7597?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15332800#comment-15332800
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Xiao Chen commented on HDFS-7597:
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Looks the test failures are related. I attached a patch to try to fix the test
failure with minimum change, and following the above discussions to have a
clean up after this.
(Assigned to myself so I can attached a patch. Failed to assign back to Daryn
because I can't seem to find him in the user list...)
> DNs should not open new NN connections when webhdfs clients seek
> ----------------------------------------------------------------
>
> Key: HDFS-7597
> URL: https://issues.apache.org/jira/browse/HDFS-7597
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: webhdfs
> Affects Versions: 2.0.0-alpha
> Reporter: Daryn Sharp
> Priority: Critical
> Labels: BB2015-05-TBR
> Attachments: HDFS-7597.01.patch, HDFS-7597.patch, HDFS-7597.patch,
> HDFS-7597.patch
>
>
> Webhdfs seeks involve closing the current connection, and reissuing a new
> open request with the new offset. The RPC layer caches connections so the DN
> keeps a lingering connection open to the NN. Connection caching is in part
> based on UGI. Although the client used the same token for the new offset
> request, the UGI is different which forces the DN to open another unnecessary
> connection to the NN.
> A job that performs many seeks will easily crash the NN due to fd exhaustion.
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