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Posted to mapreduce-issues@hadoop.apache.org by "Fengdong Yu (JIRA)" <ji...@apache.org> on 2012/12/07 06:33:21 UTC

[jira] [Created] (MAPREDUCE-4857) Fix 126 error during map/reduce phase

Fengdong Yu created MAPREDUCE-4857:
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             Summary: Fix 126 error during map/reduce phase
                 Key: MAPREDUCE-4857
                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4857
             Project: Hadoop Map/Reduce
          Issue Type: Bug
    Affects Versions: 1.0.4
            Reporter: Fengdong Yu
             Fix For: 1.0.4


There is rare happenings during map or reduce phase, but mostly in map phase, the Exception messages: 
java.lang.Throwable: Child Error
	at org.apache.hadoop.mapred.TaskRunner.run(TaskRunner.java:271)
Caused by: java.io.IOException: Task process exit with nonzero status of 126.
	at org.apache.hadoop.mapred.TaskRunner.run(TaskRunner.java:258)

and error logs are cleaned, so It's very hard to debug.

but I compared DefaultTaskController.java with 0.22, they use "bash command" to start the job scritp, but 1.0.4 use "bash, "-c", command".

I removed "-c", everything is ok, 126 error code never happen again.

I read man document of bash, it indicates when fork a new thread with write command, another thread with "bash -c" also has a writable fd. so it could return 126 status occasionally.


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