Run a Script in a Cluster

Amazon EMR enables you to run a script at any time during step processing in your cluster. You specify a step that runs a script either when you create your cluster or you can add a step if your cluster is in the WAITING state. For more information about adding steps, see Submit Work to a Cluster.

To run a script before step processing begins, use a bootstrap action. For more information about bootstrap actions, see (Optional) Create Bootstrap Actions to Install Additional Software.

Submitting a Custom JAR Step Using the AWS CLI

Note

You can now use command-runner.jar in many cases instead of script-runner.jar. command-runner.jar does not need to have a full path for the JAR. For more information, see Command Runner.

This section describes how to add a step to run a script. The script-runner.jar takes arguments to the path to a script and any additional arguments for the script. The JAR file runs the script with the passed arguments.

Important

script-runner.jar is located at s3://region.elasticmapreduce/libs/script-runner/script-runner.jar where region is the region in which your EMR cluster resides.

The cluster containing a step that runs a script looks similar to the following examples.

To add a step to run a script using the AWS CLI

To run a script using the AWS CLI, type the following command, replace myKey with the name of your EC2 key pair and replace mybucket with your S3 bucket. This cluster runs the script my_script.sh on the master node when the step is processed.
```
Copy
aws emr create-cluster --name "Test cluster" –-release-label emr-5.6.0 --applications Name=Hive Name=Pig --use-default-roles --ec2-attributes KeyName=myKey --instance-type m3.xlarge --instance-count 3 --steps Type=CUSTOM_JAR,Name=CustomJAR,ActionOnFailure=CONTINUE,Jar=s3://region.elasticmapreduce/libs/script-runner/script-runner.jar,Args=["s3://mybucket/script-path/my_script.sh"]
```
When you specify the instance count without using the --instance-groups parameter, a single master node is launched, and the remaining instances are launched as core nodes. All nodes use the instance type specified in the command.

Note

If you have not previously created the default Amazon EMR service role and EC2 instance profile, type aws emr create-default-roles to create them before typing the create-cluster subcommand.

For more information on using Amazon EMR commands in the AWS CLI, see http://docs.aws.amazon.com/cli/latest/reference/emr.

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