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https://issues.apache.org/jira/browse/HADOOP-13169?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rajesh Balamohan updated HADOOP-13169:
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Attachment: HADOOP-13169-branch-2-009.patch
Thank you [~cnauroth].
Changes in the latest patch:
1. Changed LinkedList to ArrayList in SimpleCopyListing
2. For the test, I thought of having guava's {{Ordering.arbitrary()}} which
relies on {{System.identityHashCode}}, but that is also prone to collisions
(http://bugs.java.com/bugdatabase/view_bug.do?bug_id=6809470). Instead, using
{{setSeedForRandomListing(long seed)}} with "@VisibleForTesting" for testing
purpose.
> Randomize file list in SimpleCopyListing
> ----------------------------------------
>
> Key: HADOOP-13169
> URL: https://issues.apache.org/jira/browse/HADOOP-13169
> Project: Hadoop Common
> Issue Type: Improvement
> Components: tools/distcp
> Reporter: Rajesh Balamohan
> Assignee: Rajesh Balamohan
> Priority: Minor
> Attachments: HADOOP-13169-branch-2-001.patch,
> HADOOP-13169-branch-2-002.patch, HADOOP-13169-branch-2-003.patch,
> HADOOP-13169-branch-2-004.patch, HADOOP-13169-branch-2-005.patch,
> HADOOP-13169-branch-2-006.patch, HADOOP-13169-branch-2-007.patch,
> HADOOP-13169-branch-2-008.patch, HADOOP-13169-branch-2-009.patch
>
>
> When copying files to S3, based on file listing some mappers can get into S3
> partition hotspots. This would be more visible, when data is copied from hive
> warehouse with lots of partitions (e.g date partitions). In such cases, some
> of the tasks would tend to be a lot more slower than others. It would be good
> to randomize the file paths which are written out in SimpleCopyListing to
> avoid this issue.
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