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https://issues.apache.org/jira/browse/HDFS-1351?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dmytro Molkov updated HDFS-1351:
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Attachment: HDFS-1351.patch
Please have a look at the patch.
The only point of concern here is changing the order of choosing the replica to
be deleted. Instead of taking the hint first we check with the
BlockPlacementPolicy and if we get null - return immediately since we are not
deleting anything. However if we can follow the hint we do so.
> Make it possible for BlockPlacementPolicy to return null
> --------------------------------------------------------
>
> Key: HDFS-1351
> URL: https://issues.apache.org/jira/browse/HDFS-1351
> Project: Hadoop HDFS
> Issue Type: Test
> Components: name-node
> Affects Versions: 0.22.0
> Reporter: Dmytro Molkov
> Assignee: Dmytro Molkov
> Attachments: HDFS-1351.patch
>
>
> The idea is to modify FSNamesystem.chooseExcessReplicates code, so it can
> accept a null return from chooseReplicaToDelete which will indicate that
> NameNode should not be deleting extra replicas.
> One possible usecase - if there are nodes being added to the cluster that
> might have corrupt replicas on them you do not want to delete other replicas
> until the block scanner finished scanning every block on the datanode.
> This will require additional work on the implementation of the
> BlockPlacementPolicy, but with this JIRA I just wanted to create a basis for
> future improvements.
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