Sometimes, Reduce tasks hang， State is unassigned
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Key: HADOOP-5407
URL: https://issues.apache.org/jira/browse/HADOOP-5407
Project: Hadoop Core
Issue Type: Bug
Components: mapred
Affects Versions: 0.19.0
Reporter: ZhuGuanyin
Hi, all
When our cluster runs for a long time, some reduce tasks running on some
tasktrackers hang. Their states are UNASSIGNED. Then, all reduce tasks on
these tasktracker will hang.
We kill the hang reduce task, then the reduce task attempt is re-scheduled to
this tasktracker, the attempt task continues to hang. We fail it, it goes to
another tasktracker, it is executed successfully.
Tasktracker which has hang reduce task will receive new reduce task, but the
reduce task continue to hang for ever.
When we reboot the tasktracker machine, reduce task no longer hangs.
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