normally job tracker and task tracker is on different nodes.
when I submit a pig script using UDF. I think the UDF constructor is first
run (several times, don't know why)
on the job tracker, and then it's run on each of the task trackers.
now I want to do some custom work inside the constructor, such as checking
the existence of certain files
which are specific to only task trackers. such work only needs to be done
on task trackers.
So , is there a way to figure out whether the UDF is being run on task
tracker or job tracker?