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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-6268) Better sorting in NetworkTopology#pseudoSortByDistance when no local node is found
Date Tue, 22 Apr 2014 02:44:15 GMT
Andrew Wang created HDFS-6268:
---------------------------------

             Summary: 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


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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