Given that Speculative Execution *is* the answer to such scenarios,
I'd say the answer to your question without it, is *nothing*.

If a task does not report status for over 10 minutes (default), it is
killed and retried. If it does report status changes (such as
counters, task status, etc.) but is slow due to environmental or other
reasons, then the JobTracker, without speculative execution logic
turned on, will assume it is normal.

On Thu, Dec 6, 2012 at 8:27 PM, Ajay Srivastava
<[EMAIL PROTECTED]> wrote:
> Hi,
>
> What is the behavior of jobTracker if speculative execution is off and a task on data node is running extremely slow?
> Will the jobTracker simply wait till the slow running task finishes or it will try to heal the situation? Assuming that heartbeat from the node running slow task are regular.
>
>
>
> Regards,
> Ajay Srivastava

--
Harsh J

Thanks Mahesh & Harsh.

On 07-Dec-2012, at 7:42 AM, Mahesh Balija wrote:

To simply, if you turn-off the speculative execution then the system will never bother about slow running jobs unless they won't report beyond specified time (10 minutes).
If you have set speculative execution to true then the system may spawn another instance of mapper and consider the output of the fast running once or early completing task.

Best,
Mahesh Balija,
Calsoft Labs.

On Thu, Dec 6, 2012 at 8:27 PM, Ajay Srivastava <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote:
Hi,

What is the behavior of jobTracker if speculative execution is off and a task on data node is running extremely slow?
Will the jobTracker simply wait till the slow running task finishes or it will try to heal the situation? Assuming that heartbeat from the node running slow task are regular.

Regards,
Ajay Srivastava