Use Amazon EC2 launch templates with AWS Batch

AWS Batch supports using Amazon EC2 launch templates with your EC2 compute environments. With launch templates, you can modify the default configuration of your AWS Batch compute resources without needing to create customized AMIs.

You must create a launch template before you can associate it with a compute environment. You can create a launch template in the Amazon EC2 console. Or, you can use the AWS CLI or an AWS SDK. For example, the following JSON file represents a launch template that resizes the Docker data volume for the default AWS Batch compute resource AMI and also sets it to be encrypted.

{
    "LaunchTemplateName": "increase-container-volume-encrypt",
    "LaunchTemplateData": {
        "BlockDeviceMappings": [
            {
                "DeviceName": "/dev/xvda",
                "Ebs": {
                    "Encrypted": true,
                    "VolumeSize": 100,
                    "VolumeType": "gp2"
                }
            }
        ]
    }
}

You can create the previous launch template by saving the JSON to a file that's called lt-data.json and running the following AWS CLI command.

aws ec2 --region <region> create-launch-template --cli-input-json file://lt-data.json

For more information about launch templates, see Launching an Instance from a Launch Template in the Amazon EC2 User Guide.

If you use a launch template to create your compute environment, you can move the following existing compute environment parameters to your launch template:

The following launch template parameters are ignored by AWS Batch:

AWS Batch only updates the launch template with a new launch template version during infrastructure updates. For more information, see Updating compute environments.

Default and override launch templates

You can define a default launch template for the compute environment and an override launch template for specific instance types and families. This can be useful to you so that the default template is used for the majority of instance types in the compute environments.

The substitution variables $Default and $Latest can be used instead of naming a specific version. If you do not provide an override launch template, the default launch template is automatically applied.

If you use either the $Default or $Latest variable, AWS Batch will apply the current information at the time that the compute environment is created. If the default or latest version changes in the future, you must update the information through UpdateComputeEnvironment or through the AWS Management Console - AWS Batch.

To provide additional flexibility, you can define override launch templates are applied to specific compute instance types or families.

Use the targetInstanceTypes parameter to select the instance type or family that should use this override launch template. The instance type or family must be first identified by the instanceTypes parameter.

If you define launch template overrides and decide to remove them later, you can pass an empty array to unset the overrides parameter in the UpdateComputeEnvironment API operation. You can also choose to not include the overrides parameter when submitting the UpdateComputeEnvironment API operation. For more information see, LaunchTemplateSpecification.overrides

For more information, see LaunchTemplateSpecificationOverride.targetInstanceTypes in the AWS Batch API Reference guide.

Amazon EC2 user data in launch templates

You can supply Amazon EC2 user data in your launch template that's run by cloud-init when your instances launch. Your user data can perform common configuration scenarios, including but not limited to the following:

Amazon EC2 user data in launch templates must be in the MIME multi-part archive format. This is because your user data is merged with other AWS Batch user data that's required to configure your compute resources. You can combine multiple user data blocks together into a single MIME multi-part file. For example, you might want to combine a cloud boothook that configures the Docker daemon with a user data shell script that writes configuration information for the Amazon ECS container agent.

If you're using AWS CloudFormation, the AWS::CloudFormation::Init type can be used with the cfn-init helper script to perform common configuration scenarios.

A MIME multi-part file consists of the following components:

{
    "LaunchTemplateName": "base64-user-data",
    "LaunchTemplateData": {
        "UserData": "ewogICAgIkxhdW5jaFRlbXBsYXRlTmFtZSI6ICJpbmNyZWFzZS1jb250YWluZXItdm9sdW..."
    }
}