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From "Ramkumar Vadali (JIRA)" <j...@apache.org>
Subject [jira] Updated: (MAPREDUCE-2167) Faster directory traversal for raid node
Date Mon, 08 Nov 2010 22:10:25 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-2167?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ramkumar Vadali updated MAPREDUCE-2167:
---------------------------------------

    Attachment: MAPREDUCE-2167.3.patch

Added a comment explaining the use of the slots semaphore.

> Faster directory traversal for raid node
> ----------------------------------------
>
>                 Key: MAPREDUCE-2167
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2167
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: contrib/raid
>            Reporter: Ramkumar Vadali
>            Assignee: Ramkumar Vadali
>         Attachments: MAPREDUCE-2167.2.patch, MAPREDUCE-2167.3.patch, MAPREDUCE-2167.patch
>
>
> The RaidNode currently iterates over the directory structure to figure out which files
to RAID. With millions of files, this can take a long time - especially if some files are
already RAIDed and the RaidNode needs to look at parity files / parity file HARs to determine
if the file needs to be RAIDed.
> The directory traversal is encapsulated inside the class DirectoryTraversal, which examines
one file at a time, using the caller's thread.
> My proposal is to make this multi-threaded as follows:
>  * use a pool of threads inside DirectoryTraversal
>  * The caller's thread is used to retrieve directories, and each new directory is assigned
to a thread in the pool. The worker thread examines all the files the directory.
>  * If there sub-directories, those are added back as workitems to the pool.
> Comments?

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