[jira] Updated: (MAPREDUCE-1938) Ability for having user's classes take precedence over the system classes for tasks' classpath

["Devaraj Das (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAPREDUCE-1938?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Devaraj Das updated MAPREDUCE-1938:
-----------------------------------

    Attachment: mr-1938-bp20.patch

Patch for Y20. Not for commit here.

The patch defines a configuration option using which users can specify that the system classpath be added last in the list of classpaths created before launching a task. It also introduces a HADOOP_CLIENT_CLASSPATH env variable in the hadoop shell script that should be set to point to the user's jar/classpath (containing his implementation of the system classes) before submitting a job over command line.

> Ability for having user's classes take precedence over the system classes for tasks' classpath
> ----------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-1938
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-1938
>             Project: Hadoop Map/Reduce
>          Issue Type: New Feature
>          Components: job submission, task, tasktracker
>            Reporter: Devaraj Das
>             Fix For: 0.22.0
>
>         Attachments: mr-1938-bp20.patch
>
>
> It would be nice to have the ability in MapReduce to allow users to specify for their jobs alternate implementations of classes that are already defined in the MapReduce libraries. For example, an alternate implementation for CombineFileInputFormat. 

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