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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6268) Better sorting in NetworkTopology#pseudoSortByDistance when no local node is found
Date Tue, 13 May 2014 02:00:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6268?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13995942#comment-13995942
] 

Andrew Wang commented on HDFS-6268:
-----------------------------------

Manually triggered Jenkins, dunno why it didn't run.

> Better sorting in NetworkTopology#pseudoSortByDistance when no local node is found
> ----------------------------------------------------------------------------------
>
>                 Key: HDFS-6268
>                 URL: https://issues.apache.org/jira/browse/HDFS-6268
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 2.4.0
>            Reporter: Andrew Wang
>            Assignee: Andrew Wang
>            Priority: Minor
>         Attachments: hdfs-6268-1.patch, hdfs-6268-2.patch, hdfs-6268-3.patch, hdfs-6268-4.patch
>
>
> In NetworkTopology#pseudoSortByDistance, if no local node is found, it will always place
the first rack local node in the list in front.
> This became an issue when a dataset was loaded from a single datanode. This datanode
ended up being the first replica for all the blocks in the dataset. When running an Impala
query, the non-local reads when reading past a block boundary were all hitting this node,
meaning massive load skew.



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