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From "Haohui Mai (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7597) Clients seeking over webhdfs may crash the NN
Date Thu, 19 Mar 2015 21:22:40 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7597?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14370136#comment-14370136
] 

Haohui Mai commented on HDFS-7597:
----------------------------------

[~daryn], can you please change the title and the description to match the intent of the patch?

> Clients seeking over webhdfs may crash the NN
> ---------------------------------------------
>
>                 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
>            Assignee: Daryn Sharp
>            Priority: Critical
>         Attachments: 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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