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From "sam liu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-6205) Update the value of the new version properties of the deprecated property "mapred.child.java.opts"
Date Fri, 26 Dec 2014 16:52:13 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-6205?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14259140#comment-14259140
] 

sam liu commented on MAPREDUCE-6205:
------------------------------------

Yes, the MapReduceChildJVM#getChildJavaOpts makes the old property as fallback. However, this
solution has two disadvantages:
1. During map/reduce task execution, the program might get incorrect value of new property
 MRJobConfig.MAP_JAVA_OPTS and MRJobConfig.REDUCE_JAVA_OPTS, if only the value of "mapred.child.java.opts"
is defined before.
2. Inconsistent handling style. For most of other deprecated properties, Hadoop will automatically
update the value of their new version with the value of old version. However, hadoop does
not use same style to handle the deprecation of property "mapred.child.java.opts"

> Update the value of the new version properties of the deprecated property "mapred.child.java.opts"
> --------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-6205
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6205
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>    Affects Versions: trunk
>            Reporter: sam liu
>            Assignee: sam liu
>            Priority: Minor
>         Attachments: MAPREDUCE-6205.patch, MAPREDUCE-6205.patch
>
>
> In current hadoop code, the old property "mapred.child.java.opts" is deprecated and its
new versions are MRJobConfig.MAP_JAVA_OPTS and MRJobConfig.REDUCE_JAVA_OPTS. However, when
user set a value to the deprecated property "mapred.child.java.opts", hadoop won't automatically
update its new versions properties MRJobConfig.MAP_JAVA_OPTS("mapreduce.map.java.opts") and
MRJobConfig.REDUCE_JAVA_OPTS("mapreduce.reduce.java.opts"). As hadoop will update the new
version properties for many other deprecated properties, we also should support such feature
on the old property "mapred.child.java.opts", otherwise it might bring some imcompatible issues.



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