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From "Rick Cox (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1245) value for mapred.tasktracker.tasks.maximum taken from two different sources
Date Mon, 08 Oct 2007 00:33:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12533014
] 

Rick Cox commented on HADOOP-1245:
----------------------------------

I've also run into this, and came up with a patch that involved:

- adding a 'maxTasks' value to the TaskTrackerStatus (set by the local mapred.tasktracker.tasks.maximum)
- modifying JobTracker to track totalTaskCapacity instead of per-node maxTasks, and to use
the particular task tracker's maxTasks value when deciding whether to assign it another task

If this seems like a reasonable approach, I can do more testing and provide a patch.

> value for mapred.tasktracker.tasks.maximum taken from two different sources
> ---------------------------------------------------------------------------
>
>                 Key: HADOOP-1245
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1245
>             Project: Hadoop
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.12.3
>            Reporter: Michael Bieniosek
>
> I want to create a cluster with machines with different numbers of CPUs.  Consequently,
each machine should have a different value for mapred.tasktracker.tasks.maximum, since my
map tasks are CPU bound.
> However, hadoop uses BOTH the values for mapred.tasktracker.tasks.maximum on the jobtracker
and the tasktracker.  
> When a new job starts up, the jobtracker uses its (single) value for mapred.tasktracker.tasks.maximum
to assign tasks.  This means that each tasktracker gets the same number of tasks, regardless
of how I configured that particular machine.
> After the first task finishes on each tasktracker, the tasktracker will request new tasks
from the jobtracker according to the tasktracker's value for mapred.tasktracker.tasks.maximum.
 So after the first round of map tasks is done, the cluster reverts to a mode that works well
for heterogeneous clusters.
> The jobtracker should not consult its config for the value of mapred.tasktracker.tasks.maximum.
 It should assign tasks (or allow tasktrackers to request tasks) according to each tasktracker's
value of mapred.tasktracker.tasks.maximum.

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