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https://issues.apache.org/jira/browse/HDFS-5304?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13788626#comment-13788626
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Colin Patrick McCabe commented on HDFS-5304:
--------------------------------------------
An array of booleans in {{LocatedBlock}} seems kind of clunky. You have to
check all of them to find out if any are true. And then you have to match
them up with the corresponding element in the {{locs}} array. Can we have
something like this instead?
{code}
DatanodeInfo[] cachedLocs;
{code}
Obviously, these would just be pointers to the same DatanodeInfo objects stored
in {{locs}}, not copies. This way:
* it's easy to iterate over all cached locations, or check if there are any
(just do {{location.getCachedLocations.isEmpty()}}).
* this can be mapped to a statically declared empty array most of the time,
saving memory
The RPC changes themselves are fine, I think.
> Expose if a block replica is cached in getFileBlockLocations
> ------------------------------------------------------------
>
> Key: HDFS-5304
> URL: https://issues.apache.org/jira/browse/HDFS-5304
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Affects Versions: HDFS-4949
> Reporter: Andrew Wang
> Assignee: Andrew Wang
> Attachments: hdfs-5304-1.patch
>
>
> We need to expose which replicas of a block are cached so applications can
> place their tasks for memory-locality.
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