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https://issues.apache.org/jira/browse/HADOOP-3799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12708460#action_12708460
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Jingkei Ly commented on HADOOP-3799:
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> However, in this patch, I would like to expose the name of the file via the
> BlockPlacement policy interface. Any ideas here?
I think having two versions of BlockPlacementInterface#chooseTarget() would be
the most efficient - one that accepts the filename (to be called from
FSNamesystem#getAdditionalBlock()) and another that accepts the INode (to be
called from FSNamesystem#computeReplicationWorkForBlock()). As you said, it
does make the interface rather inelegant, though.
An alternative is to pass the Block object to chooseTarget() and let the
plugin-code look up the INode itself in the FSNamesystem map - not particularly
efficient, but perhaps plugin-code could cache INodes to filenames to mitigate
it a bit.
> Design a pluggable interface to place replicas of blocks in HDFS
> ----------------------------------------------------------------
>
> Key: HADOOP-3799
> URL: https://issues.apache.org/jira/browse/HADOOP-3799
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Attachments: BlockPlacementPluggable.txt
>
>
> The current HDFS code typically places one replica on local rack, the second
> replica on remote random rack and the third replica on a random node of that
> remote rack. This algorithm is baked in the NameNode's code. It would be nice
> to make the block placement algorithm a pluggable interface. This will allow
> experimentation of different placement algorithms based on workloads,
> availability guarantees and failure models.
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