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From "Chris Nauroth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5096) Automatically cache new data added to a cached path
Date Mon, 14 Oct 2013 22:57:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13794601#comment-13794601
] 

Chris Nauroth commented on HDFS-5096:
-------------------------------------

bq. Let me know if you think the comments in the code could be improved.

I think some version of what Andrew just said would do the job nicely, i.e.:

{code}
        if (mark != ocblock.getMark()) {
          // Mark hasn't been set in this scan, so update replication and mark.
          ocblock.setReplicationAndMark(pce.getReplication(), mark);
        } else {
          // Mark already set in this scan.  Set replication to highest value in
          // any PathBasedCacheEntry that covers this file.
          ocblock.setReplicationAndMark((short)Math.max(
              pce.getReplication(), ocblock.getReplication()), mark);
        }
{code}

bq. thanks for your patience, both of you

No problem, thanks for your code.  :-)

> 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
>
>
> 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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