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From: Ajay Srivastava <Ajay.Srivastava@guavus.com>
To: "<user@hadoop.apache.org>" <user@hadoop.apache.org>
Subject: Re: Query about Speculative Execution
Thread-Topic: Query about Speculative Execution
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Date: Fri, 7 Dec 2012 04:40:28 +0000
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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 n=
ever bother about slow running jobs unless they won't report beyond specifi=
ed time (10 minutes).
If you have set speculative execution to true then the system may spawn ano=
ther 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 <Ajay.Srivastava@guavus.com=
<mailto:Ajay.Srivastava@guavus.com>> wrote:
Hi,

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


Regards,
Ajay Srivastava


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<div>Thanks Mahesh &amp; Harsh.</div>
<div><br>
</div>
<div><br>
</div>
<br>
<div>
<div>On 07-Dec-2012, at 7:42 AM, Mahesh Balija wrote:</div>
<br class=3D"Apple-interchange-newline">
<blockquote type=3D"cite">To simply, if you turn-off the speculative execut=
ion then the system will never bother about slow running jobs unless they w=
on't report beyond specified time (10 minutes).<br>
If you have set speculative execution to true then the system may spawn ano=
ther instance of mapper and consider the output of the fast running once or=
 early completing task.<br>
<br>
Best,<br>
Mahesh Balija,<br>
Calsoft Labs.<br>
<br>
<div class=3D"gmail_quote">On Thu, Dec 6, 2012 at 8:27 PM, Ajay Srivastava =
<span dir=3D"ltr">
&lt;<a href=3D"mailto:Ajay.Srivastava@guavus.com" target=3D"_blank">Ajay.Sr=
ivastava@guavus.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">
Hi,<br>
<br>
What is the behavior of jobTracker if speculative execution is off and a ta=
sk on data node is running extremely slow?<br>
Will the jobTracker simply wait till the slow running task finishes or it w=
ill try to heal the situation? Assuming that heartbeat from the node runnin=
g slow task are regular.<br>
<br>
<br>
<br>
Regards,<br>
Ajay Srivastava </blockquote>
</div>
<br>
</blockquote>
</div>
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