setup and cleanup methods of Mapper/Reducer in Hadoop MapReduce

Question

Are setup and cleanup methods called in each mapper and reducer tasks respectively? Or are they called only once at the start of overall mapper and reducer jobs?

Answer 1

One clarification is helpful. The setup/cleanup methods are used for initialization and clean up at task level. Within a task, first initialization happens with a single call to setup() method and then all calls to map() [or reduce()] function will be done. After that another single call will be made to cleanup() method before exiting the task.