Speculative execution is a per-job concept, so in 2.* release line, it is MR 
AM's responsibility.

Because there is a two level scheduling - one at RM and one at AM, AMs have not 
way of figuring out if there are other jobs are not. In general, AMs send 
container requests in a greedy manner and leave the responsibility of cross-job 
fairness to the RM and the scheduler.

In sum, to answer your question, speculative execution will be triggered only 
based on task run times, and irrespective of other jobs.

Thanks,
+Vinod Kumar Vavilapalli
Hortonworks Inc.
http://hortonworks.com/

On Oct 17, 2012, at 5:19 AM, Radim Kolar wrote:

> Is yarn smart enough to do speculative execution only if there are no other 
> jobs running or queued?

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