Answer / Purnendu Kumar Shukla

JobTracker is the central management service in Hadoop that coordinates all the tasks in a MapReduce job. It assigns tasks to nodes in the cluster, monitors their progress, and handles failures if they occur. The actions followed by Hadoop are:
1. Map: Each input record is processed by a mapper, which produces key-value pairs.
2. Shuffle: The output of each mapper is sorted and shuffled to the reducers based on their keys.
3. Reduce: Each reducer processes the data associated with a specific key and produces the final output.

What is an identity mapper and identity reducer?

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

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Why Mapper runs in heavy weight process and not in a thread in MapReduce?

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

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Explain the differences between a combiner and reducer

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What is the relation between MapReduce and Hive?

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

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What is the difference between a MapReduce InputSplit and HDFS block?

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how is data partitioned before it is sent to the reducer if no custom partitioner is defined in Hadoop?

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what is WebDAV in Hadoop?

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What is the difference between Job and Task in MapReduce?

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Where is the output of Mapper written in Hadoop?

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