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From "Ohad Raviv (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-14600) LocatedFileStatus constructor forces RawLocalFS to exec a process to get the permissions
Date Fri, 24 Nov 2017 18:36:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-14600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16265476#comment-16265476
] 

Ohad Raviv commented on HADOOP-14600:
-------------------------------------

I'm not sure I was clear enough in the above comment.
I totaly agree with your current patch, but I'm saying that the initiator of all this mess
from SPARK-21137 is org.apache.hadoop.mapred.FileInputFormat with the following code:
{code}
for (FileStatus globStat: matches) {
  if (globStat.isDirectory()) {
    RemoteIterator<LocatedFileStatus> iter =
        fs.listLocatedStatus(globStat.getPath());
    while (iter.hasNext()) {
      LocatedFileStatus stat = iter.next();
      if (inputFilter.accept(stat.getPath())) {
        if (recursive && stat.isDirectory()) {
          addInputPathRecursively(result, fs, stat.getPath(),
              inputFilter);
        } else {
          result.add(stat);
        }
      }
    }
  } else {
    result.add(globStat);
  }
}
{code}
All I'm suggesting is to replace `listLocatedStatus` call with `listStatusIterator` because
it returns FileStatus rather than LocatedFileStatus and that doesn't trigger all the getPermission()
mess at all.
testing that localy (on Mac) caused the test to run in less than a second instead of about
30 seconds for about 10000 files.

> LocatedFileStatus constructor forces RawLocalFS to exec a process to get the permissions
> ----------------------------------------------------------------------------------------
>
>                 Key: HADOOP-14600
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14600
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>    Affects Versions: 2.7.3
>         Environment: file:// in a dir with many files
>            Reporter: Steve Loughran
>            Assignee: Ping Liu
>         Attachments: HADOOP-14600.001.patch, HADOOP-14600.002.patch, HADOOP-14600.003.patch,
HADOOP-14600.004.patch, HADOOP-14600.005.patch, HADOOP-14600.006.patch, HADOOP-14600.007.patch,
HADOOP-14600.008.patch, HADOOP-14600.009.patch, TestRawLocalFileSystemContract.java
>
>
> Reported in SPARK-21137. a {{FileSystem.listStatus}} call really craws against the local
FS, because {{FileStatus.getPemissions}} call forces  {{DeprecatedRawLocalFileStatus}} tp
spawn a process to read the real UGI values.
> That is: for every other FS, what's a field lookup or even a no-op, on the local FS it's
a process exec/spawn, with all the costs. This gets expensive if you have many files.



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