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From GUOJUN Zhu <guojun_...@freddiemac.com>
Subject Re: JVM reuse in Map Tasks
Date Mon, 04 Jun 2012 13:06:59 GMT
For setup(), do you mean configure(JobConf)?     We need to deserialize a 
big object and do some other preparing work on it within the configure() 
for setting up. It takes a few seconds and it is the same for all task. We 
just declare the object as static and do not recreate it if it is not 
null.  By that way, we make sure only create it once and save the setup 
time for the rest of the tasks. 

Zhu, Guojun
Modeling Sr Graduate
Financial Engineering
Freddie Mac

   Arpit Wanchoo <Arpit.Wanchoo@guavus.com> 
   06/04/2012 08:12 AM
   Please respond to

"mapreduce-user@hadoop.apache.org" <mapreduce-user@hadoop.apache.org>

JVM reuse in Map Tasks


I wanted to check what exactly we gain  when JVM reusability is enabled in 
mapped job.

My doubt was regarding the setup() method of mapper. Is it called for a 
mapper even if it is using the JVM for previously run mapper ?
If yes then is there any way I can control it or stop from being called 
more than once.

Arpit Wanchoo | Sr. Software Engineer
Guavus Network Systems.
6th Floor, Enkay Towers, Tower B & B1,Vanijya Nikunj, Udyog Vihar Phase - 
V, Gurgaon,Haryana.
Mobile Number +91-9899949788 

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