What combiners is and when you should use a combiner in a MapReduce Job?

670

What is shuffling in mapreduce?

651

What combiners are and when you should utilize a combiner in a map reduce job?

654

What is a "reducer" in Hadoop?

914

Where sorting is done on mapper node or reducer node in MapReduce?

723

What is the Job interface in MapReduce framework?

951

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.

892

What is the difference between map and reduce?

685

Explain what does the conf.setmapper class do?

662

Explain about the partitioning, shuffle and sort phase

723

How does fault tolerance work in mapreduce?

681

What is identity mapper and chain mapper?

713

Can we submit the mapreduce job from slave node?

1161

What MapReduce framework consists of?

1144

what are the basic parameters of a Mapper?

862