FUNDAMENTALS OF COMPUTER

Detailed explanation-1: -Input to the Reducer is the sorted output of the mappers. In this phase the framework fetches the relevant partition of the output of all the mappers, via HTTP.

Detailed explanation-2: -Inputs and Outputs (Java Perspective) The MapReduce framework operates on <key, value> pairs, that is, the framework views the input to the job as a set of <key, value> pairs and produces a set of <key, value> pairs as the output of the job, conceivably of different types.

Detailed explanation-3: -The Map function takes input from the disk as <key, value> pairs, processes them, and produces another set of intermediate <key, value> pairs as output. The Reduce function also takes inputs as <key, value> pairs, and produces <key, value> pairs as output.

Detailed explanation-4: -The output generated by the Reducer will be the final output which is then stored on HDFS(Hadoop Distributed File System). Reducer mainly performs some computation operation like addition, filtration, and aggregation.

Detailed explanation-5: -Reducer is a phase in hadoop which comes after Mapper phase. The output of the mapper is given as the input for Reducer which processes and produces a new set of output, which will be stored in the HDFS.