List the main components of MapReduce Job?

The two main components of the MapReduce Job are the JobTracker and TaskTracker.

JobTracker - It is the master that creates and runs the job in the MapReduce. It runs on the name node and allocates the job to TaskTrackers. The JobTracker first receives the request from the client and talks to the name node to determine the location of the data. Then, it finds the best TaskTracker node to execute the tasks based on the data locality. JobTracker also monitors the individual TaskTrackers and submits the overall status of the job to the client.

TaskTracker - It is the slave that runs on the data node. TaskTracker runs the job sent by the JobTracker and reports the status of the task back to it. The TaskTracker will be assigned with the Mapper and Reducer tasks to execute the job.