Interview Questions on Hadoop

A Combiner is a mini-reduce process which operates only on data generated by a Mapper. When Mapper emits the data, combiner receives it as input and sends the output to a reducer. In Hadoop, a combiner is a feature that allows the intermediate output of the map tasks to be combined or reduced before being … Read more

Hadoop streaming is a utility which allows you to create and run map/reduce job. It is a generic API that allows programs written in any languages to be used as Hadoop mapper. Hadoop Streaming is a utility that comes with Apache Hadoop, a distributed storage and processing framework. It is a tool that allows users … Read more

If a data node fails the job tracker and name node will detect the failure. After that, all tasks are re-scheduled on the failed node and then name node will replicate the user data to another node. In Hadoop’s distributed file system, HDFS (Hadoop Distributed File System), when a data node fails, the following actions … Read more

There is a very unique way of indexing in Hadoop. Once the data is stored as per the block size, the HDFS will keep on storing the last part of the data which specifies the location of the next part of the data. As of my last knowledge update in January 2022, Hadoop Distributed File … Read more

Heartbeat is a signal which is used between a data node and name node, and between task tracker and job tracker. If the name node or job tracker doesn’t respond to the signal then it is considered that there is some issue with data node or task tracker. In Hadoop, the term “heartbeat” typically refers … Read more