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.
On Thu, Dec 6, 2012 at 8:27 PM, Ajay Srivastava
> 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.
> Ajay Srivastava