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From "Sandy Ryza (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-4907) TrackerDistributedCacheManager issues too many getFileStatus calls
Date Sat, 29 Dec 2012 00:28:14 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-4907?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sandy Ryza updated MAPREDUCE-4907:
----------------------------------

    Target Version/s: 1.2.0
              Status: Patch Available  (was: Open)
    
> TrackerDistributedCacheManager issues too many getFileStatus calls
> ------------------------------------------------------------------
>
>                 Key: MAPREDUCE-4907
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4907
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv1, tasktracker
>    Affects Versions: 1.1.1
>            Reporter: Sandy Ryza
>            Assignee: Sandy Ryza
>         Attachments: MAPREDUCE-4907.patch
>
>
> TrackerDistributedCacheManager issues a number of redundant getFileStatus calls when
determining the timestamps and visibilities of files in the distributed cache.  300 distributed
cache files deep in the directory structure can hammer HDFS with a couple thousand requests.
> A couple optimizations can reduce this load:
> 1. determineTimestamps and determineCacheVisibilities both call getFileStatus on every
file.  We could cache the results of the former and use them for the latter.
> 2. determineCacheVisibilities needs to check that all ancestor directories of each file
have execute permissions for everyone.  This currently entails a getFileStatus on each ancestor
directory for each file.  The results of these getFileStatus calls could be cached as well.

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