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From "Ramkumar Vadali (JIRA)" <j...@apache.org>
Subject [jira] Created: (MAPREDUCE-2167) Faster directory traversal for raid node
Date Fri, 29 Oct 2010 19:01:28 GMT
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

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.


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