Hadoop Interview Questions

1. What is Hadoop framework? 
Hadoop is a open source framework which is written in java by apche software foundation. This framework is used to wirite software application which requires to process vast amount of data (It could handle multi tera bytes of data). It works in-paralle on large clusters which could have 1000 of computers (Nodes) on the clusters. It also process data very reliably and fault-tolerant manner.

2. On What concept the Hadoop framework works? 
It works on MapReduce, and it is devised by the Google.


3. What is MapReduce ?

Map reduce is an algorithm or concept to process Huge amount of data in a faster way. As per its name you can divide it Map and Reduce.

• The main MapReduce job usually splits the input data-set into independent chunks. (Big data sets in the multiple small datasets)
  
  
• MapTask: will process these chunks in a completely parallel manner (One node can process one or more chunks).
  
  
• The framework sorts the outputs of the maps.
  
  
• Reduce Task : And the above output will be the input for the reducetasks, produces the final result.
  
  Your business logic would be written in the MappedTask and ReducedTask. Typically both the input and the output of the job are stored in a file-system (Not database). The framework takes care of scheduling tasks, monitoring them and re-executes the failed tasks.