Service role for automatic scaling in Amazon EMR (Auto Scaling role) - Amazon EMR
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Service role for automatic scaling in Amazon EMR (Auto Scaling role)

The Auto Scaling role for Amazon EMR performs a similar function as the service role, but allows additional actions for dynamically scaling environments.

  • The default role name is EMR_AutoScaling_DefaultRole.

  • The default managed policy attached to EMR_AutoScaling_DefaultRole is AmazonElasticMapReduceforAutoScalingRole.

The contents of version 1 of AmazonElasticMapReduceforAutoScalingRole are shown below.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "cloudwatch:DescribeAlarms",
                "elasticmapreduce:ListInstanceGroups",
                "elasticmapreduce:ModifyInstanceGroups"
            ],
            "Effect": "Allow",
            "Resource": "*"
        }
    ]
}

Your service role should use the following trust policy.

Important

The following trust policy includes the aws:SourceArn and aws:SourceAccount global condition keys, which limit the permissions that you give Amazon EMR to particular resources in your account. Using them can protect you against the confused deputy problem.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service":  [
                    "elasticmapreduce.amazonaws.com",
                    "application-autoscaling.amazonaws.com"
                ]
            },
            "Action": "sts:AssumeRole",
            "Condition": {
                "StringEquals": {
                    "aws:SourceAccount": "<account-id>"
                },
                "ArnLike": {
                    "aws:SourceArn": "arn:aws:elasticmapreduce:<region>:<account-id>:*"
                }
            }
        }
    ]
}