AWS Auto Scaling Lifecycle Hooks allow you to perform custom actions as instances are launched or terminated in your Auto Scaling group. This can be useful if you need to perform tasks such as configuring software or setting up databases on newly launched instances, or cleaning up resources on terminated instances. In this tutorial, we will go over how to create and manage lifecycle hooks using the AWS CLI.

Before you begin, you’ll need to have the AWS CLI installed and configured on your local machine. You’ll also need to have an Auto Scaling group already set up.

Step 1: Create a Lifecycle Hook To create a lifecycle hook, you’ll need to use the create-lifecycle-hook command. Here’s an example command:

aws autoscaling create-lifecycle-hook --lifecycle-hook-name my-lifecycle-hook --auto-scaling-group-name my-auto-scaling-group --lifecycle-transition autoscaling:EC2_INSTANCE_TERMINATING --heartbeat-timeout 300 --default-result CONTINUE

In this command, we’re creating a lifecycle hook named my-lifecycle-hook for the Auto Scaling group my-auto-scaling-group. The lifecycle-transition parameter specifies that the hook will be triggered when instances are terminated. The heartbeat-timeout parameter specifies how long Auto Scaling waits for a signal from the instance before continuing with the termination process. The default-result parameter specifies what action to take if the hook times out or fails. In this case, we’re telling Auto Scaling to continue with the termination process (CONTINUE).

Step 2: Perform Custom Actions Once you’ve created a lifecycle hook, you can perform custom actions by specifying a script or command to run on the instance. You can do this using the put-lifecycle-hook command. Here’s an example command:

aws autoscaling put-lifecycle-hook --lifecycle-hook-name my-lifecycle-hook --auto-scaling-group-name my-auto-scaling-group --lifecycle-transition autoscaling:EC2_INSTANCE_TERMINATING --heartbeat-timeout 300 --default-result CONTINUE --notification-target-arn arn:aws:sns:us-west-2:123456789012:my-sns-topic --role-arn arn:aws:iam::123456789012:role/my-role --heartbeat-timeout 3600 --heartbeat-timeout-action ABANDON --lifecycle-transition-action CONTINUE

In this command, we’re updating the lifecycle hook my-lifecycle-hook for the Auto Scaling group my-auto-scaling-group to specify a script or command to run on the instance. We’re also specifying an SNS topic to receive notifications about the lifecycle hook, and an IAM role to assume when running the script or command.

Step 3: Complete the Lifecycle Hook Once your custom actions have been performed, you’ll need to complete the lifecycle hook to allow Auto Scaling to continue with the termination process. You can do this using the complete-lifecycle-action command. Here’s an example command:

aws autoscaling complete-lifecycle-action --lifecycle-hook-name my-lifecycle-hook --auto-scaling-group-name my-auto-scaling-group --lifecycle-action-result CONTINUE --instance-id i-0123456789abcdef0

In this command, we’re completing the lifecycle hook my-lifecycle-hook for the Auto Scaling group my-auto-scaling-group. We’re specifying that the result of the hook is CONTINUE, and we’re providing the ID of the instance that the hook was triggered for.

Step 4: Delete the Lifecycle Hook If you no longer need a lifecycle hook, you can delete it using the delete-lifecycle-hook command. Here’s an example command:

aws autoscaling delete-lifecycle-hook ---lifecycle-hook-name my-lifecycle-hook --auto-scaling-group-name my-auto-scaling-group

In this command, we’re deleting the lifecycle hook `my-lifecycle-hook` for the Auto Scaling group `my-auto-scaling-group`.

That's it! You now know how to create, manage, and delete lifecycle hooks using the AWS CLI. Lifecycle hooks can be a powerful tool for automating custom actions in your Auto Scaling group, so be sure to explore all of the available options and see how they can benefit your infrastructure.