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From "Allen Wittenauer (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-3813) RackResolver should maintain a cache to avoid repetitive lookups.
Date Mon, 06 Feb 2012 05:49:59 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-3813?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13201052#comment-13201052
] 

Allen Wittenauer commented on MAPREDUCE-3813:
---------------------------------------------

Woops, also meant to point out that properly configured hosts have an OS-level cache for hostnames.
 So unless there are some benchmarks to back up the claims, I'm not convinced that hostname
resolution should be an issue (with the caveat that the machines should be configured correctly).
                
> RackResolver should maintain a cache to avoid repetitive lookups.
> -----------------------------------------------------------------
>
>                 Key: MAPREDUCE-3813
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3813
>             Project: Hadoop Map/Reduce
>          Issue Type: Sub-task
>          Components: mrv2, performance
>    Affects Versions: 0.23.0
>            Reporter: Vinod Kumar Vavilapalli
>            Assignee: Vinod Kumar Vavilapalli
>             Fix For: 0.23.1
>
>         Attachments: MAPREDUCE-3813-20120205.txt
>
>
> With the current code, during task creation, we repeatedly resolve hosts and RackResolver
doesn't cache any of the results. Caching will improve performance.

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