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From "Dmytro Molkov (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HDFS-1351) Make it possible for BlockPlacementPolicy to return null
Date Tue, 24 Aug 2010 08:41:16 GMT

     [ https://issues.apache.org/jira/browse/HDFS-1351?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Dmytro Molkov updated HDFS-1351:

    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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