How JobTracker works ?

When client application submits jobs to the JobTracker :

• JobTracker talks to the NameNode to find the location of the data

• It locates TaskTracker nodes with available slots for data and assigns the work to the chosen TaskTracker nodes

• The TaskTracker nodes are responsible to notify the JobTracker when a task fails and then JobTracker decides what to do then.

• JobTracker may resubmit the task on another node or it may mark that task to avoid.