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https://issues.apache.org/jira/browse/HDFS-12809?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16263324#comment-16263324
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Virajith Jalaparti commented on HDFS-12809:
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[~elgoiri], the existing tests ensure that there are enough locations but don't
really make sure that the distribution is random.
> [READ] Fix the randomized selection of locations in {{ProvidedBlocksBuilder}}.
> ------------------------------------------------------------------------------
>
> Key: HDFS-12809
> URL: https://issues.apache.org/jira/browse/HDFS-12809
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Virajith Jalaparti
> Assignee: Virajith Jalaparti
> Attachments: HDFS-12809-HDFS-9806.001.patch
>
>
> Calling {{getBlockLocations}} on files that have a PROVIDED replica, results
> in the datanode locations being selected at random. Currently, this
> randomization uses the datanode uuids to pick a node at random
> ({{ProvidedDescriptor#choose}}, {{ProvidedDescriptor#chooseRandom}}).
> Depending on the distribution of the datanode UUIDs, this can lead to large
> number of iterations (which may not terminate) before a location is chosen.
> This JIRA aims to replace this with a more efficient randomization strategy.
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