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Amazon EMR
Management Guide

Streaming Cluster Errors

You can usually find the cause of a streaming error in a syslog file. Link to it on the Steps pane.

The following errors are common to streaming clusters.

Is data being sent to the mapper in the wrong format?

To check if this is the case, look for an error message in the syslog file of a failed task attempt in the task attempt logs. For more information, see View Log Files.

Is your script timing out?

The default timeout for a mapper or reducer script is 600 seconds. If your script takes longer than this, the task attempt will fail. You can verify this is the case by checking the syslog file of a failed task attempt in the task attempt logs. For more information, see View Log Files.

You can change the time limit by setting a new value for the mapred.task.timeout configuration setting. This setting specifies the number of milliseconds after which Amazon EMR will terminate a task that has not read input, written output, or updated its status string. You can update this value by passing an additional streaming argument -jobconf mapred.task.timeout=800000.

Are you passing in invalid streaming arguments?

Hadoop streaming supports only the following arguments. If you pass in arguments other than those listed below, the cluster will fail.

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-blockAutoGenerateCacheFiles -cacheArchive -cacheFile -cmdenv -combiner -debug -input -inputformat -inputreader -jobconf -mapper -numReduceTasks -output -outputformat -partitioner -reducer -verbose

In addition, Hadoop streaming only recognizes arguments passed in using Java syntax; that is, preceded by a single hyphen. If you pass in arguments preceded by a double hyphen, the cluster will fail.

Did your script exit with an error?

If your mapper or reducer script exits with an error, you can locate the error in the stderr file of task attempt logs of the failed task attempt. For more information, see View Log Files.