Start by checking the bootstrap action logs for errors or unexpected

Start by checking the bootstrap action logs for

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running simultaneously, but a log file can only display results linearly. Start by checking the bootstrap action logs for errors or unexpected configuration changes during the launch of the cluster. From there, look in the step logs to identify Hadoop jobs launched as part of a step 360
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Amazon EMR Management Guide Step 4: Check Cluster and Instance Health with errors. Examine the Hadoop job logs to identify the failed task attempts. The task attempt log will contain details about what caused a task attempt to fail. The following sections describe how to use the various log files to identify error in your cluster. Check the Bootstrap Action Logs Bootstrap actions run scripts on the cluster as it is launched. They are commonly used to install additional software on the cluster or to alter configuration settings from the default values. Checking these logs may provide insight into errors that occurred during set up of the cluster as well as configuration settings changes that could affect performance. Check the Step Logs There are four types of step logs. controller— Contains files generated by Amazon EMR (Amazon EMR) that arise from errors encountered while trying to run your step. If your step fails while loading, you can find the stack trace in this log. Errors loading or accessing your application are often described here, as are missing mapper file errors. stderr— Contains error messages that occurred while processing the step. Application loading errors are often described here. This log sometimes contains a stack trace. stdout— Contains status generated by your mapper and reducer executables. Application loading errors are often described here. This log sometimes contains application error messages. syslog— Contains logs from non-Amazon software, such as Apache and Hadoop. Streaming errors are often described here. Check stderr for obvious errors. If stderr displays a short list of errors, the step came to a quick stop with an error thrown. This is most often caused by an error in the mapper and reducer applications being run in the cluster. Examine the last lines of controller and syslog for notices of errors or failures. Follow any notices about failed tasks, particularly if it says "Job Failed". Check the Task Attempt Logs If the previous analysis of the step logs turned up one or more failed tasks, investigate the logs of the corresponding task attempts for more detailed error information. Check the Hadoop Daemon Logs In rare cases, Hadoop itself might fail. To see if that is the case, you must look at the Hadoop logs. They are located at /var/log/hadoop/ on each node. You can use the JobTracker logs to map a failed task attempt to the node it was run on. Once you know the node associated with the task attempt, you can check the health of the EC2 instance hosting that node to see if there were any issues such as running out of CPU or memory.
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  • Spring '12
  • LauraParker
  • Amazon Web Services, Amazon Elastic Compute Cloud

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