setup and cleanup methods of Mapper/Reducer in Hadoop MapReduce -


are setup , cleanup methods called in each mapper , reducer tasks respectively? or called once @ start of overall mapper , reducer jobs?

they called each task, if have 20 mappers running, setup / cleanup called each one.

one gotcha standard run method both mapper , reducer not catch exceptions around map / reduce methods - if exception thrown in these methods, clean method not called.


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