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From "Robert Joseph Evans (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-2494) Make the distributed cache delete entires using LRU priority
Date Mon, 18 Jul 2011 18:09:58 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13067184#comment-13067184
] 

Robert Joseph Evans commented on MAPREDUCE-2494:
------------------------------------------------

I am requesting that someone please review the patch for the 0.20 security line.  The changes
are almost identical to what went into trunk.

Thanks

> Make the distributed cache delete entires using LRU priority
> ------------------------------------------------------------
>
>                 Key: MAPREDUCE-2494
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2494
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: distributed-cache
>    Affects Versions: 0.20.205.0, 0.21.0
>            Reporter: Robert Joseph Evans
>            Assignee: Robert Joseph Evans
>             Fix For: 0.23.0
>
>         Attachments: MAPREDUCE-2494-20.20X-V1.patch, MAPREDUCE-2494-V1.patch, MAPREDUCE-2494-V2.patch
>
>
> Currently the distributed cache will wait until a cache directory is above a preconfigured
threshold.  At which point it will delete all entries that are not currently being used. 
It seems like we would get far fewer cache misses if we kept some of them around, even when
they are not being used.  We should add in a configurable percentage for a goal of how much
of the cache should remain clear when not in use, and select objects to delete based off of
how recently they were used, and possibly also how large they are/how difficult is it to download
them again.

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