Answer / Roushan Kumar Tiwary

In Hadoop MapReduce, the intermediate output is sorted automatically based on keys. To sort the output by values, you can implement a custom comparator for the value class and use it when defining the input format or output format.

In MapReduce, ideally how many mappers should be configured on a slave?

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Mention when to use Map reduce mode?

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Different ways of debugging a job in MapReduce?

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How hadoop mapreduce works?

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If reducers do not start before all mappers finish then why does the progress on mapreduce job shows something like map(50%) reduce(10%)? Why reducers progress percentage is displayed when mapper is not finished yet?

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What is an input reader in reference to mapreduce?

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What is identity mapper and identity reducer?

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How many Reducers run for a MapReduce job?

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what is a sequence file in Hadoop?

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What is a "reducer" in Hadoop?

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How to set which framework would be used to run mapreduce program?

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Explain what does the conf.setMapper Class do in MapReduce?

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