FAQ
For example my application contains some class SomeClass. And this
application uses hadoop mapreduce. What will be if Mapper in it's map
function calls a method of SomeClass?
If I understand correct mapper is running on child nodes. For that
parent sends mapper and JobConf to childs. Will it send SomeClass too in
our case? And what if SomeClass needs for example property files, saved
in the local file system, not in distributed FS? Will child apply for
such file to parent?
Maybe I ask stupid questions. I still don't have clear idea of how
hadoop works and especially how it realize parallelization.

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  • Richard Yang at Mar 23, 2007 at 3:40 pm
    Hello Ilya,

    I only know one way to run one's program on Hadoop. That is to jar all your
    classes into a .jar and when using, specify the entry point of execution.
    http://lucene.apache.org/hadoop/hdfs_design.html
    should give you a clear concept upon Hadoop Map/Reduce.

    Best Regards

    Richard Yang
    richardyang@richardyang.net
    kusanagiyang@gmail.com



    -----Original Message-----
    From: Ilya Vishnevsky
    Sent: Friday, March 23, 2007 2:34 AM
    To: hadoop-user@lucene.apache.org
    Subject: Classes called from mapper and reducer.

    For example my application contains some class SomeClass. And this
    application uses hadoop mapreduce. What will be if Mapper in it's map
    function calls a method of SomeClass?
    If I understand correct mapper is running on child nodes. For that
    parent sends mapper and JobConf to childs. Will it send SomeClass too in
    our case? And what if SomeClass needs for example property files, saved
    in the local file system, not in distributed FS? Will child apply for
    such file to parent?
    Maybe I ask stupid questions. I still don't have clear idea of how
    hadoop works and especially how it realize parallelization.

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postedMar 23, '07 at 9:35a
activeMar 23, '07 at 3:40p
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websitehadoop.apache.org...
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Ilya Vishnevsky: 1 post Richard Yang: 1 post

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