What is the role of recordreader in hadoop mapreduce?

734

What MapReduce framework consists of?

1094

what is JobTracker in Hadoop? What are the actions followed by Hadoop?

769

How to compress mapper output in Hadoop?

676

What are the four basic parameters of a reducer?

653

What do you understand by mapreduce?

647

when do reducers play their role in a mapreduce task?

616

Map reduce jobs are failing on a cluster that was just restarted. They worked before restart. What could be wrong?

602

What do you mean by data locality?

673

what does the text input format do?

815

Is it possible to search for files using wildcards?

642

What happen if the number of the reducer is 0 in MapReduce?

652

For a Hadoop job, how will you write a custom partitioner?

652

What is shuffling in mapreduce?

607

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?

712