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From "Ping Liu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-14600) LocatedFileStatus constructor forces RawLocalFS to exec a process to get the permissions
Date Sat, 30 Sep 2017 04:07:02 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-14600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16186875#comment-16186875
] 

Ping Liu commented on HADOOP-14600:
-----------------------------------

[~stevel@apache.org]

Thanks for your detailed code review!  Really appreciate it.

I just finished making recommended changes and attached *HADOOP-14600.003.patch*.

Following are details.

{{Helper.java (new class):}}

For better supporting unit test, I added some more testing mechanism and moved the logic into
a new class called Helper.java.  Now I can not only check permission but also change permission.
I didn't find a place where we can put the utilities.  So just add this one.  In case, if
one want to added other common utility method.  Helper class can be the place.

{{TestRawLocalFileSystemContract.java:}}

With this addition, I can improve test by adding testPermission() into TestRawLocalFileSystemContract
where now both loadPermissionInfoByNativeIO() and loadPermissionInfoByNonNativeIO() can be
directly tested as you suggested. I can test it on Linux.  But on Windows, sticky bit change
doesn't take effect.  I guess Windows probably doesn't have sticky bit feature.

{{TestNativeIO.java:}}

Similarly, doStatTest() was simplified by calling the Helper method.

Also improved testStatOnError() by using LambdaTestUtils, improved testMultiThreadedStat()
by using ExecutorService and Future, also adding testMultiThreadedStatOnError().

{{RawLocalFileSystem.java:}}

A minor issue found (loadPermissionInfo()) is that domain returned with group in Windows.
 So we need remove domain.  This is the same as removing domain from domain/user in existing
code.

Lastly, for {{NativeIO.c}}, FindFileOwnerAndPermission is not a MSDN function.  I found it
defined at Line 811 in hadoop-common/src/main/winutils/libwinutils.c.

> 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,
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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