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From "Chris Nauroth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9208) Disabling atime may fail clients like distCp
Date Mon, 19 Oct 2015 15:57:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9208?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14963503#comment-14963503
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Chris Nauroth commented on HDFS-9208:
-------------------------------------

[~kihwal], thank you for the patch.  I am +1 for making this change.

The test failures look unrelated, and I can't repro them locally.  I also manually tested
{{hdfs dfs -copyFromLocal -p}} and {{hadoop distcp -pt}} with a NameNode that has atime disabled.
 You can remove the now-unused import of {{DFS_NAMENODE_ACCESSTIME_PRECISION_KEY}} to fix
the Checkstyle warning.  After that, I think the patch will be ready.


> Disabling atime may fail clients like distCp
> --------------------------------------------
>
>                 Key: HDFS-9208
>                 URL: https://issues.apache.org/jira/browse/HDFS-9208
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>         Attachments: HDFS-9208.patch
>
>
> When atime is disabled, {{setTimes()}} throws an exception if the passed-in atime is
not -1.  But since atime is not -1, distCp fails when it tries to set the mtime and atime.

> There are several options:
> 1) make distCp check for 0 atime and call {{setTimes()}} with -1. I am not very enthusiastic
about it.
> 2) make NN also accept 0 atime in addition to -1, when the atime support is disabled.
> 3) support setting mtime & atime regardless of the atime support.  The main reason
why atime is disabled is to avoid edit logging/syncing during {{getBlockLocations()}} read
calls. Explicit setting can be allowed.



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