Andrew Wang created HDFS-6268:
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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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