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From "Michael Bieniosek (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1245) value for mapred.tasktracker.tasks.maximum taken from jobtracker, not tasktracker
Date Wed, 10 Oct 2007 20:27:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12533868

Michael Bieniosek commented on HADOOP-1245:

It might be enough to use the value at the jobtracker as a default, and override with the
tasktracker value if it's present (along with the compatibility note).  

If a tasktracker is configured differently than the jobtracker, it's more likely the configurer
intended the tasktracker's value to be used, as opposed to the configurer expecting the tasktracker
value to be ignored.  So I doubt using the jobtracker as an overridable default will break

> value for mapred.tasktracker.tasks.maximum taken from jobtracker, not tasktracker
> ---------------------------------------------------------------------------------
>                 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
>            Assignee: Michael Bieniosek
>         Attachments: tasktracker-max-tasks-1245.patch
> 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.
> 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.
> 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.
> Originally, I thought the behavior was slightly different, so this issue contained this
> 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.

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