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https://issues.apache.org/jira/browse/MAPREDUCE-2637?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13063779#comment-13063779
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Devaraj K commented on MAPREDUCE-2637:
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When the user faces any problem with the job code if they want to see the code
execution then it will be useful. If any problem is coming with large jobs they
can use this feature to find out the problem in the user code.
We can provide a configuration which will enable this feature explicitly if the
user wants it. This may not be much useful for the production environment. Here
scalability doesn’t come into picture because this will be used to debug issues
which are difficult to find out or hard to analyze with logs.
> Providing options to debug the mapreduce user code (Mapper, Reducer,
> Combiner, Sort implementations)
> ----------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-2637
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2637
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: tasktracker
> Reporter: Devaraj K
> Assignee: Devaraj K
>
> Presently Hadoop provides "mapred.child.java.opts" configuration which can be
> used to set JVM options for Child JVM running Map or Reduce Task.
> If we need to remote debug the Child JVM, we can add remote debugging options
> to this configuration value.
> But this will work only for single Child JVM. Other children will fail as the
> remote debugging port is already used.
> We cannot specify the remote debugging port dynamically.
> As a result, it's not possible to remote debug multiple Child JVMs.
> As a solution to this problem, we can provide a configuration to debug Task
> JVMs in this scenario.
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