Hi ..

I'm currently trying to get information for a decision on which version of the 
Map/Reduce API to use for our Map/Reduce Jobs.  We have existing (production) 
code that uses the old API and some new code (non-production) that uses the new 
API, and we have some developers who will definitely not have much time to dig 
into Hadoop Sources to figure out how to do things right in the new API 
(instead of being able to look it up in a book), so the state of documentation 
does matter.

So far I got the following information:


-          The old API is deprecated and will be removed, but that will 
probably take at least a year

-          The new API does not provide really new functionality

-          There's library and contrib. code that has not been ported to the 
new API yet

-          Most of the existing thorough documentation (like Hadoop: the 
definitive Guide) covers the old API

-          Porting to the new API will probably become easier in future 
versions of Hadoop when more of the lib code and docs have been ported

So, what are your experiences with new vs. old API ?  Would you recommend to 
switch to the new API right now, or wait for a later release ?  Is it 
problematic to have applications using old and new API side by side ? How hard 
is it currently  to port old code to the new API ?

If these questions have been covered by some other thread already, please point 
me to it. I could not find much of a discussion browsing the mailing list 
archives, though.

Thanks in advance for any advice you can give,


Kai Londenberg

. . . . . . . . . . . . . . . . . . . . . . . .
Software Developer

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applied research technologies
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