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https://issues.apache.org/jira/browse/MAPREDUCE-2637?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13063968#comment-13063968
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Luke Lu commented on MAPREDUCE-2637:
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I can see this being useful for interactive debugging of certain type of tasks
without access to local machines via ssh.
The basePort + taskId approach won't even work as the taskId can cover the
entire port range. The only approach that can possibly work is to use the
ephemeral port for the jpda ports and make them available in web UI and/or API.
> 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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