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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 resolved HDFS-1351.
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Resolution: Invalid
Sorry, after talking with Hairong I realized that it will not be possible to
make the fix this easy. The reason return value cannot be null is that at this
point NameNode knows it has to delete extra replica of the block. If we skip
this deletion it will not know the block has extra replicas until the next time
it does full rescan (on restart). So this jira is itself invalid.
> 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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