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https://issues.apache.org/jira/browse/HDFS-5096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13796308#comment-13796308
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Colin Patrick McCabe commented on HDFS-5096:
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bq. In DatanodeManager, we pop commands off of the pending lists when we send
them. This means the NN no longer knows what's in-flight on the cluster,
potentially leading to a few issues if there are lost/delayed messages...
good point. I'm going to file a follow-up for these. There's a bunch of
issues that we need to address there. We're also going to need a lot of unit
tests for that area.
bq. It'd also be nice to re-introduce some edge triggering via an incremental
#kick() taking a set of PBCEntries or Paths since we could sprinkle it around
FSN to improve our reaction time.
Yeah, we should do that. I think it's for down the road, though...
bq. I think scan and cur need to be reversed here:
fixed
bq. Right below that, I think we can move setting scanTimeMs and mark out of
the synchronized block
OK.
bq. Maybe rename {{TestPathBasedCacheRequests}} to {{TestCacheManager}} ? It
deserves a more generic name now.
I guess my thinking here is that if we add LRU caching, we'd have a different
file. Right now, everything we're testing pertains to
{{PathBasedCacheRequests}}, so {{TestPathBasedCacheRequests}} seems logical
here.
> 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,
> HDFS-5096-caching.010.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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