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