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Posted to mapreduce-issues@hadoop.apache.org by "Alejandro Abdelnur (JIRA)" <ji...@apache.org> on 2013/01/04 14:54:13 UTC
[jira] [Commented] (MAPREDUCE-4907) TrackerDistributedCacheManager
issues too many getFileStatus calls
[ https://issues.apache.org/jira/browse/MAPREDUCE-4907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13543888#comment-13543888 ]
Alejandro Abdelnur commented on MAPREDUCE-4907:
-----------------------------------------------
Sandy, patch looks good, I was looking at trunk/branch-2 and I think we should have the same optimization for trunk/branch-2 (in ClientDistributedCacheManager).
> 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
>
>
> 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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