When inline setup is enabled, each job's setup task runs as a thread directly inside the JobTracker instead of being forked out as a separate task by a TaskTracker. When inline setup is enabled, jobs that require a setup task can show increased performance because those jobs aren't waiting for TaskTrackers to get scheduled and then run the setup task.
Enabling the JobTracker to execute user-defined code as the privileged JT user is risky. If your cluster's original installation of MapR was version 1.2.7 or earlier, inline setup is enabled by default.
Disable inline setup on production clusters by setting the value of the
mapreduce.jobtracker.inline.setup.cleanup to false in mapred-site.xml.
Add the following section to the MapReduce v1 mapred-site.xml file: