I'm thoroughly confused about which API is the recent one, which is the old
one and which method I should be using to write MapReduce applications.
I'm under the impression that MRv2 is primarily driven by the
org.apache.hadoop.mapreduce.* packages and MRv1 is primarily driven by the
I've been led to believe that MRv2 applications extend MapReduceBase and
implement Mapper, Reducer etc.
and conversely the MRv1 applications extend Mapper, Reducer directly.
However I can not find a canonical statement to back any of this up.
What's more I keep finding conflicting statements about these, such as
"'Hadoop - the definitive guide' gives example in MRv2 format" but then I
look at the examples and they use org.apache.hadoop.mapreduce.* packages,
but extend Mapper and extend Reducer, not MapReduceBase...
Can someone either point me at a canonical resource or just confirm / deny
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