[jira] Updated: (MAPREDUCE-1973) Optimize input split creation

["Paul Burkhardt (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAPREDUCE-1973?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Paul Burkhardt updated MAPREDUCE-1973:
--------------------------------------

    Attachment: HADOOP-1973.patch

Please review.

> Optimize input split creation
> -----------------------------
>
>                 Key: MAPREDUCE-1973
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1973
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>    Affects Versions: 0.20.1, 0.20.2
>         Environment: Intel Nehalem cluster running Red Hat.
>            Reporter: Paul Burkhardt
>            Priority: Minor
>         Attachments: HADOOP-1973.patch
>
>
> The input split returns the locations that host the file blocks in the split. The locations are determined by the getBlockLocations method of the filesystem client which requires a remote connection to the filesystem (i.e. HDFS). The remote connection is made for each file in the entire input split. For jobs with many input files the network connections dominate the cost of writing the input split file.
> A job requests a listing of the input files from the remote filesystem and creates a FileStatus object as a handle for each file in the listing. The FileStatus object can be imbued with the necessary host information on the remote end and passed to the client-side in the bulk return of the listing request. A getHosts method of the FileStatus would then return the locations for the blocks comprising that file and eliminate the need for another trip to the remote filesystem.
> The INodeFile maintains the blocks for a file and is an obvious choice to be the originator for the locations of that file. It is also available to the FSDirectory which first creates the listing of FileStatus objects. We propose that the block locations be generated by the INodeFile to instantiate the FileStatus object during the getListing request.
> Our tests demonstrated a factor of 2000 speedup for approximately 60,000 input files.

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