FAQ

On Fri, Dec 31, 2010 at 9:28 AM, maha wrote:

Hi,

(1) I declared a global variable in my hadoop mainClass which gets
initialized in the 'run' function of this mainClass. When I try to access
this global static variable from the MapperClass, it appears to be
uninitialized.

Why is that? Is it because of the parallel execution of Hadoop
functions ? but , isn't the 'run' function supposed to be the one to run
first and prepare all the job configurations before the Maps even start?
The Mapper will run on a remote machine, in other JVM, so the variable you
set in Main class can not be shared with other VM.
(2) Fig 4.5 in http://developer.yahoo.com/hadoop/tutorial/module4.html shows the inputFormat to be the one running before the maps. My question is
in which node? The JobTracker node?
I think it should run on JobTracker, The inputFormat will split the file
and the map function will read the every splited file.
Thank you,
Maha



--
-----李平

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postedDec 31, '10 at 1:28a
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