问题
We are using 3 cluster machine and mapreduce.tasktracker.reduce.tasks.maximum property is set to 9. When I set no of reducer is equal to or less than 9 job is getting succeeded but if I set greater than 9 then it is failing with the exception "Task attempt_201701270751_0001_r_000000_0 failed to ping TT for 60 seconds. Killing!". Can any one guide me what will be the problem
回答1:
There seem to be some bug in hadoop -0.20.
https://issues.apache.org/jira/browse/MAPREDUCE-1905 (for reference ).
Can you please try to increase the task timeout ?
(mapreduce.task.timeout to a higher value ) ( 0 will disable the timeout )
来源：https://stackoverflow.com/questions/42484684/reducers-failing