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https://issues.apache.org/jira/browse/MAPREDUCE-2261?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12981742#action_12981742
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Devaraj K commented on MAPREDUCE-2261:
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Hi Todd,
Existing fair scheduler assigns a single job per heart beat
even more slots are available in the task tracker. Next job will be assigned to
the same task tracker for the next heart beat only. This way we can assign
multiple tasks but we cannot assign multiple tasks for the same heart beat.
Fair Multi Task assignment scheduler assigns multiple jobs to the task
tracker as in the below way.
If number of jobs in the queue is less than the cluster capacity or
equal, then it calculates the no of jobs can be assigned to the each task
tracker (shared equally manner) and it will assign multiple jobs to the each
task tracker for a heart beat.
If number of jobs in the queue is more than the cluster capacity, then
it assigns multiple jobs to the task tracker based on the task tracker capacity
for a heart beat. This repeats for all the task trackers in the cluster.
> Fair Multiple Task Assignment Scheduler (Assigning multiple tasks per heart
> beat)
> ---------------------------------------------------------------------------------
>
> Key: MAPREDUCE-2261
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-2261
> Project: Hadoop Map/Reduce
> Issue Type: New Feature
> Affects Versions: 0.21.0
> Reporter: Devaraj K
>
> Functionality wise the Fair Multiple Task Assignment Scheduler behaves
> the same way except the assignment of Tasks. Instead of assigning a single
> Task per heartbeat, it checks for all the jobs if any local or non-local Task
> that can be launched.
> Fair Multiple Task Assignment Scheduler has the advantage of assigning
> multiple jobs per heart beat interval depending upon the slots available on
> the Task Tracker, by configuring the number of parallel tasks to be executed
> in a Task Tracker at any point of time. The advantages are as follows:
> a) Parallel Execution allows tasks be to submitted and processed in parallel
> independent of the status of other tasks.
> b) More number of tasks is assigned in a heartbeat interval and consequently
> multitasking capability increases.
> c) With multi task assignment, Task Tracker efficiency is increased.
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