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From "Akira AJISAKA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8989) hadoop dfs -find feature
Date Tue, 17 Jun 2014 22:23:16 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14034491#comment-14034491
] 

Akira AJISAKA commented on HADOOP-8989:
---------------------------------------

Thanks for updating the patch! Mostly looks good. I verified -print0 option and the following
command worked well.
{code}
# hdfs dfs -find /user/root/ -name "file*" -print0 | xargs -0 hdfs dfs -rm
{code}

Minor comment:
{code}
  private static String[] HELP =
      { "Finds all files that match the specified expression and "
          + "applies selected actions to them." };
{code}
Would you change the code like other commands? i.e.
{code}
  private static String[] HELP =
      { "Finds all files that match the specified expression and",
        "applies selected actions to them." };
{code}

In addition, can you please include a document in the patch for keeping consistency between
source code and document? (i.e. Would you split HADOOP-10580?)

[~umamaheswararao], do you have any comments on this patch? I'll appreciate your reviews.

> hadoop dfs -find feature
> ------------------------
>
>                 Key: HADOOP-8989
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8989
>             Project: Hadoop Common
>          Issue Type: New Feature
>            Reporter: Marco Nicosia
>            Assignee: Jonathan Allen
>         Attachments: HADOOP-8989.patch, HADOOP-8989.patch, HADOOP-8989.patch, HADOOP-8989.patch,
HADOOP-8989.patch, HADOOP-8989.patch, HADOOP-8989.patch, HADOOP-8989.patch, HADOOP-8989.patch,
HADOOP-8989.patch, HADOOP-8989.patch, HADOOP-8989.patch, HADOOP-8989.patch, HADOOP-8989.patch,
HADOOP-8989.patch, HADOOP-8989.patch
>
>
> Both sysadmins and users make frequent use of the unix 'find' command, but Hadoop has
no correlate. Without this, users are writing scripts which make heavy use of hadoop dfs -lsr,
and implementing find one-offs. I think hdfs -lsr is somewhat taxing on the NameNode, and
a really slow experience on the client side. Possibly an in-NameNode find operation would
be only a bit more taxing on the NameNode, but significantly faster from the client's point
of view?
> The minimum set of options I can think of which would make a Hadoop find command generally
useful is (in priority order):
> * -type (file or directory, for now)
> * -atime/-ctime-mtime (... and -creationtime?) (both + and - arguments)
> * -print0 (for piping to xargs -0)
> * -depth
> * -owner/-group (and -nouser/-nogroup)
> * -name (allowing for shell pattern, or even regex?)
> * -perm
> * -size
> One possible special case, but could possibly be really cool if it ran from within the
NameNode:
> * -delete
> The "hadoop dfs -lsr | hadoop dfs -rm" cycle is really, really slow.
> Lower priority, some people do use operators, mostly to execute -or searches such as:
> * find / \(-nouser -or -nogroup\)
> Finally, I thought I'd include a link to the [Posix spec for find|http://www.opengroup.org/onlinepubs/009695399/utilities/find.html]



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