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https://issues.apache.org/jira/browse/HDFS-3672?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andrew Wang updated HDFS-3672:
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Attachment: hdfs-3672-2.patch
Newer version of the patch, addressing Todd and Tom's comments.
One unfortunate bit is that to split the NN and DN RPCs, I needed to add a
subclass of {{BlockLocation}} that hides a corresponding {{LocatedBlock}}. An
array of these {{HdfsBlockLocation}} is now returned by
{{DFS#getFileBlockLocations}}, and downcasted in
{{DFSClient#getDiskBlockLocations}} to retrieve the {{LocatedBlock}}.
I took Todd's advice about {{Integer.MAX_VALUE}} for denoting invalid blocks,
but turn it a boolean accessible via {{DiskId#isValid}} before it's shown to
consumers of {{FileSystem}}.
Finally, I already renamed things to {{DiskBlockLocation}} based on Tom's
comment, and reused the name {{HdfsBlockLocation}} for my {{LocatedBlock}}
wrapper class. I can re-rename both of these if we don't like them.
> Expose disk-location information for blocks to enable better scheduling
> -----------------------------------------------------------------------
>
> Key: HDFS-3672
> URL: https://issues.apache.org/jira/browse/HDFS-3672
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.0.0-alpha
> Reporter: Andrew Wang
> Assignee: Andrew Wang
> Attachments: hdfs-3672-1.patch, hdfs-3672-2.patch
>
>
> Currently, HDFS exposes on which datanodes a block resides, which allows
> clients to make scheduling decisions for locality and load balancing.
> Extending this to also expose on which disk on a datanode a block resides
> would enable even better scheduling, on a per-disk rather than coarse
> per-datanode basis.
> This API would likely look similar to Filesystem#getFileBlockLocations, but
> also involve a series of RPCs to the responsible datanodes to determine disk
> ids.
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