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https://issues.apache.org/jira/browse/MAPREDUCE-4907?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sandy Ryza updated MAPREDUCE-4907:
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Attachment: MAPREDUCE-4907-trunk-1.patch
> TrackerDistributedCacheManager issues too many getFileStatus calls
> ------------------------------------------------------------------
>
> Key: MAPREDUCE-4907
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4907
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: mrv1, tasktracker
> Affects Versions: 1.1.1
> Reporter: Sandy Ryza
> Assignee: Sandy Ryza
> Attachments: MAPREDUCE-4907.patch, MAPREDUCE-4907-trunk-1.patch,
> MAPREDUCE-4907-trunk-1.patch, MAPREDUCE-4907-trunk-1.patch,
> MAPREDUCE-4907-trunk.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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