CODEWITHSUNDEEP
javahadoop
Deepak kumar Jha
Deepak kumar Jha

Reputation: 524

Does the parameter specified in mapred-site.xml overrides the parameter given in code in hadoop ?

If i have specified the value of parameter mapred.tasktracker.reduce.tasks.maximum in mapred-site.xml to be 2 and if the code of the program specified the reduce task to be as job.setNumReduceTasks(1), then will the parameter specified in mapred-site.xml be ignored or will it obeyed and the 2 reduce tasks will be executed simultaneously.

Upvotes: 0

Views: 228

Answers (1)

zsxwing
zsxwing

Reputation: 20836

You are mixed up by mapred.reduce.tasks and mapred.tasktracker.reduce.tasks.maximum. Actually, job.setNumReduceTasks(1) will set mapred.reduce.tasks to 1. And mapred.tasktracker.reduce.tasks.maximum is the maximum number of reduce tasks that will be run simultaneously by a task tracker. These are two totally different parameters.

What's more, the value of mapred.tasktracker.reduce.tasks.maximum in mapred-site.xml is the only effective value. You can not change it as the task tracker uses it when it is starting. mapred.reduce.tasks is a property for one Job. Different Jobs can have differerent mapred.reduce.tasks values.

Upvotes: 1

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