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From "Allen Wittenauer (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (MAPREDUCE-1374) Reduce memory footprint of FileSplit
Date Tue, 29 Jul 2014 22:35:39 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-1374?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Allen Wittenauer resolved MAPREDUCE-1374.
-----------------------------------------

    Resolution: Fixed

File splits moved to client.

> Reduce memory footprint of FileSplit
> ------------------------------------
>
>                 Key: MAPREDUCE-1374
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1374
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>    Affects Versions: 0.20.1, 0.21.0, 0.22.0
>            Reporter: Zheng Shao
>            Assignee: Zheng Shao
>         Attachments: MAPREDUCE-1374.1.patch, MAPREDUCE-1374.2.patch, MAPREDUCE-1374.3.patch
>
>
> We can have many FileInput objects in the memory, depending on the number of mappers.
> It will save tons of memory on JobTracker and JobClient if we intern those Strings for
host names.
> {code}
> FileInputFormat.java:
>       for (NodeInfo host: hostList) {
>         // Strip out the port number from the host name
> -        retVal[index++] = host.node.getName().split(":")[0];
> +        retVal[index++] = host.node.getName().split(":")[0].intern();
>         if (index == replicationFactor) {
>           done = true;
>           break;
>         }
>       }
> {code}
> More on String.intern(): http://www.javaworld.com/javaworld/javaqa/2003-12/01-qa-1212-intern.html
> It will also save a lot of memory by changing the class of {{file}} from {{Path}} to
{{String}}. {{Path}} contains a {{java.net.URI}} which internally contains ~10 String fields.
This will also be a huge saving.
> {code}
>   private Path file;
> {code}



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