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https://issues.apache.org/jira/browse/MAPREDUCE-762?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12731844#action_12731844
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Amar Kamat commented on MAPREDUCE-762:
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bq. I am not sure about this. So, this will be done like in the finally block
of the Child by sending a kill -pid to itself ?
Yeah. Just before the child commits suicide.
bq. What's the structure under TaskTracker.SUBDIR/pid ?
The structure would be jvm-id.pid and it would contain _user-name_, _pid_ and
_start-time_ of the child process. username is required for permissions while
start-time is required to be sure that the process has not changed.
bq. We should just follow the path of TaskController.killTaskJVM - that will
ensure it will work for all task controllers. Setting permissions to 600 for
the pid files owned by TT should be fine.
Yeah. TaskController.killTask() would be invoked which will do the forceful
exit of the process.
> Task's process trees may not be killed if a TT is restarted
> -----------------------------------------------------------
>
> Key: MAPREDUCE-762
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-762
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Reporter: Hemanth Yamijala
>
> Some work has been done to make sure the tasktrackers kill process trees of
> tasks when they finish (either successfully, or with failures or when they
> are killed). Related JIRAs are HADOOP-2721, HADOOP-5488 and HADOOP-5420. But
> when TTs are restarted, we do not handle killing of process trees - though
> tasks will themselves die on re-establishing contact with the TT.
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