Jerry Chen created MAPREDUCE-4919:
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Summary: All maps hangs when set mapreduce.task.io.sort.factor to 1
Key: MAPREDUCE-4919
URL: https://issues.apache.org/jira/browse/MAPREDUCE-4919
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: client
Affects Versions: trunk
Reporter: Jerry Chen
Assignee: Jerry Chen
Fix For: trunk
In one of my testing that when I set mapreduce.task.io.sort.factor to 1, all
the maps hang and will never end. But the CPU usage for each node are very high
and until killed by the app master when time out comes, and the job failed.
I traced the problem and found out that all the maps hangs on the final merge
phase.
The while loop in computeBytesInMerges will never end with a factor of 1:
int f = 1; //in my case
int n = 16; //in my case
while (n > f || considerFinalMerge) {
...
n -= (f-1);
f = factor;
}
As the f-1 will equals 0 and n will always be 16 and the while runs for ever.
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