[jira] Commented: (HADOOP-1245) value for mapred.tasktracker.tasks.maximum taken from two different sources

["Yuri Pradkin (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-1245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12532921 ] 

Yuri Pradkin commented on HADOOP-1245:
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I too came across this problem the hard way (our weaker nodes started thrashing, because they were running too many jobs.  In my case I don't even see it reverting to the desired behavior after the first round of jobs is
finished, - it's always the jobtracker's config value.  Maybe I'm using a different version of Hadoop? (it's 0.15 devel from svn). 

If anyone knows a way to run different number of tasks on different boxes, please let me know, because from what I see, there is no way to do it, which makes our hadoop cluster as lame as the lamest node in it.

> 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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