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https://issues.apache.org/jira/browse/HADOOP-3799?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12721805#action_12721805
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Tom White commented on HADOOP-3799:
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Hi Dhruba,
A couple more comments:
> BlockPlacementInterface#chooseTarget(). Make excludedNodes a
> List<DatanodeDescriptor>. Implementations may choose to turn it into a map if
> they need to, but for the interface, it should just be a list, shouldn't it?
I think you missed this change.
I'm not convinced that ReplicationPolicyChooser is needed. Couldn't we add a
static method (e.g. getInstance()) to BlockPlacementPolicy to construct a
BlockPlacementPolicy from the dfs.block.replicator.classname property? We can
add an overloaded chooseTarget() method to BlockPlacementPolicy which doesn't
take a chosenNodes argument (BTW this is misspelt as "choosenNodes" in
BlockPlacementPolicy).
> 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, BlockPlacementPluggable2.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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