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https://issues.apache.org/jira/browse/HDFS-5096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13795681#comment-13795681
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Chris Nauroth commented on HDFS-5096:
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Regarding those comments, it looks to me like the logic is correct, but the
comments have inverted the phrases "too few" and "too many". The first path is
for {{neededCached <= numCached}}, but its comment says "too few" cached
replicas. The second path is for {{neededCached >= numCached}}, but its
comment says "too many" cached replicas.
Thanks for addressing the feedback, Colin. At this point, I've looked at all
of the main code, so I expect this is the last of my feedback on that. I
haven't looked at test code yet. I'll take a look at that when the next patch
version gets posted.
> Automatically cache new data added to a cached path
> ---------------------------------------------------
>
> Key: HDFS-5096
> URL: https://issues.apache.org/jira/browse/HDFS-5096
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, namenode
> Reporter: Andrew Wang
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-5096-caching.005.patch,
> HDFS-5096-caching.006.patch, HDFS-5096-caching.009.patch
>
>
> For some applications, it's convenient to specify a path to cache, and have
> HDFS automatically cache new data added to the path without sending a new
> caching request or a manual refresh command.
> One example is new data appended to a cached file. It would be nice to
> re-cache a block at the new appended length, and cache new blocks added to
> the file.
> Another example is a cached Hive partition directory, where a user can drop
> new files directly into the partition. It would be nice if these new files
> were cached.
> In both cases, this automatic caching would happen after the file is closed,
> i.e. block replica is finalized.
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