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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-10942) Globbing optimizations and regression fix
Date Tue, 12 Aug 2014 00:16:11 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-10942?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14093535#comment-14093535
] 

Colin Patrick McCabe commented on HADOOP-10942:
-----------------------------------------------

It seems like there's a bunch of things going on here:

* The globber will sometimes erroneously return a permission denied exception when there is
a non-terminal wildcard.  For example, when listing {{/a*/b}}, if there is a file named /alpha,
the glob will fail.  This bug does *not* occur for superusers, which is why the existing tests
and casual testing didn't catch it.  You mention that this was a "fix" which was regressed
between 0.23 and branch-2... is there a JIRA number for this already?

* Optimizations: you mention "doing a simple immediate file status if the path contains no
globs, etc".  The existing code already does this.  It was added in HADOOP-9877.  Are we missing
a case?  I didn't understand the comment about "Additional optimizations to reduce rpcs actually
increases them if directories contain 1 item."  Which specific optimization(s) are increasing
RPCs for you and how can we avoid this?

* You added a comment that "FileContext returns a path to the home dir of the user that started
the jvm instead of the ugi user so we'll just workaround it."  I wasn't aware of this issue.
 Is there a JIRA number?  This seems like an inconsistency that we should note in the test,
along with a link to the JIRA that should fix it.

* There's a bunch of reorganization here, perhaps almost a rewrite of the main part of the
globber.

Let's split these into separate JIRAs so that it's easier to review.

> Globbing optimizations and regression fix
> -----------------------------------------
>
>                 Key: HADOOP-10942
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10942
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>    Affects Versions: 3.0.0, 2.1.0-beta
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>            Priority: Critical
>         Attachments: HADOOP-10942.patch
>
>
> When globbing was commonized to support both filesystem and filecontext, it regressed
a fix that prevents an intermediate glob that matches a file from throwing a confusing permissions
exception.  The hdfs traverse check requires the exec bit which a file does not have.
> Additional optimizations to reduce rpcs actually increases them if directories contain
1 item.



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