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https://issues.apache.org/jira/browse/HDFS-5096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13797270#comment-13797270
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Andrew Wang commented on HDFS-5096:
-----------------------------------
I'm +1 pending some nitty things. It's mostly just rolling through my previous
comments. Great work Colin!
CachedBlock
* Add a little more to the {{CachedBlock#triplets}} javadoc that specifies
{{element, prev, next}}. You could even just copy the javadoc from
{{BlockInfo}}.
* getDatanodes javadoc should mention pending uncached blocks too
* Class javadoc explaining the use of the GSet and IntrusiveCollection
* A short is 16 bits, the comment on {{replicationAndMark}} indicates it's 8
bits.
CacheReplicationMonitor
* I think this should be a {{>=}}:
{code}
if (numCached > neededCached) {
{code}
Follow-on work (some might just be part of HDFS-5366):
* Refactor out a separate {{CacheReplicationPolicy}} class with more smarts (is
this HDFS-5366?)
* Take into account DN decomissioning status when doing caching/uncaching, this
should be easy to fix as part of HDFS-5366
* Incremental kicking of the CRMon on PBCE changes
* Kicking on a DN failure
> 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.002.patch,
> HDFS-5096-caching.005.patch, HDFS-5096-caching.006.patch,
> HDFS-5096-caching.009.patch, HDFS-5096-caching.010.patch,
> HDFS-5096-caching.011.patch, HDFS-5096-caching.012.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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