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From "Hemanth Yamijala (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-771) Setup and cleanup tasks remain in UNASSIGNED state for a long time on tasktrackers with long running high RAM tasks
Date Mon, 20 Jul 2009 06:57:15 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12733143#action_12733143
] 

Hemanth Yamijala commented on MAPREDUCE-771:
--------------------------------------------

Results of ant test and test-contrib:

All tests except TestKillSubProcesses passed. Checking the logs I found it is the same as
the one documented in MAPREDUCE-408.

I've also run functional tests on the Yahoo! distribution of Hadoop (essentially same source
patch), and verified that the fix is fine. Will run a couple of more functional tests and
commit.

> Setup and cleanup tasks remain in UNASSIGNED state for a long time on tasktrackers with
long running high RAM tasks
> -------------------------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-771
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-771
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: jobtracker
>    Affects Versions: 0.21.0
>            Reporter: Hemanth Yamijala
>            Assignee: Hemanth Yamijala
>            Priority: Blocker
>             Fix For: 0.21.0
>
>         Attachments: MAPREDUCE-771.patch, MAPREDUCE-771.patch
>
>
> When a high RAM job's task is scheduled on a tasktracker, the number of slots it occupies
will be more than one. If enough such tasks are scheduled, there can come a situation when
there are no more slots free on the node but the number of tasks running is less than the
number of slots. The jobtracker currently schedules a setup or cleanup task based on how many
tasks are running on the system, rather than slots. As a result of this, it can schedule a
setup or cleanup task on a tasktracker without any free slots. If the high RAM job's tasks
are long running, this will significantly delay the running of the setup or cleanup task,
and thus the entire job.

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