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

It's called per Mapper task or Reducer task. Here is the hadoop code.

public void run(Context context) throws IOException, InterruptedException {
    setup(context);
    try {
      while (context.nextKey()) {
        reduce(context.getCurrentKey(), context.getValues(), context);
      }
    } finally {
      cleanup(context);
    }
  }