MapReduce Interview Questions, Answers for Freshers and Experienced asked in various Company Job Interviews

MapReduce Interview Questions

Questions Answers Views Company eMail

What are combiners? When should I use a combiner in my MapReduce Job?

865

In Map Reduce why map write output to Local Disk instead of HDFS?

867

What is a partitioner and how the user can control which key will go to which reducer?

888

How does Mappers run method works?

838

How does MapReduce framework view its input internally?

829

What are the steps involved in MapReduce framework?

931

What is the Job interface in MapReduce framework?

861

How to overwrite an existing output file during execution of mapreduce jobs?

MRO,

1047

Detail description of the Reducer phases?

809

Can there be no Reducer?

809

What is the utility of using Writable Comparable Custom Class in Map Reduce code?

944

What is the core of the job in MapReduce framework?

794

MapReduce Types and Formats and Setting up a Hadoop Cluster?

875

It can be possible that a Job has 0 reducers?

927

Why Mapreduce output written in local disk?

954

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Un-Answered Questions { MapReduce }

Clarify what is shuffling in map reduce?

595

In MapReduce how to change the name of the output file from part-r-00000?

601

Explain what is “map” and what is "reducer" in hadoop?

596

List the network requirements for using Hadoop ?

585

How to compress mapper output in Hadoop?

631

Where is Mapper output stored?

805

What is the process of changing the split size if there is limited storage space on Commodity Hardware?

651

What is the default value of map and reduce max attempts?

893

What is OutputCommitter?

750

Explain the Reducer's reduce phase?

1011

How many InputSplits is made by a Hadoop Framework?

580

Explain what you understand by speculative execution

559

What happens when a datanode fails ?

726

How would you tackle calculating the number of unique visitors for each hour by mining a huge apache log? You can use post processing on the output of the mapreduce job.

770

Which interface needs to be implemented to create Mapper and Reducer for the Hadoop?

1172

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