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https://issues.apache.org/jira/browse/MAPREDUCE-6205?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14268495#comment-14268495
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Jason Lowe commented on MAPREDUCE-6205:
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I think we need to be _very_ careful with a patch like this, or it could easily
create more problems than it solves. Something like this can readily break
backwards compatibility. For example, if a user does
"-Dmapreduce.map.java.opts=X -Dmapred.child.java.opts=Y", then maps should get
X and reduces should get Y. We need to make sure that this code doesn't end up
setting maps and reduces to Y because of the order we processed those settings
and how they're aliased. mapred.child.java.opts is indeed deprecated, but it
is not strictly an alias for the map/reduce-specific settings.
> 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-6205.003.patch, 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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