You use CloudFormation to launch an Auto Scaling group. In the CloudFormation stack, you create a lifecycle hook in the ASG that puts a new instance in the Wait state while the custom script of the user data is running. The script installs the web application, initializes customer data and performs a health check of the instance. After the health check has passed, how would you put the instance back to the InService state in the Auto Scaling group?

Answer options:

A.Use the record-lifecycle-action-heartbeat CLI command or the RecordLifecycleActionHeartbeat operation in the script.
B.In the script, use the AWS CLI command complete-lifecycle-action to finish the lifecycle hook customer actions.
C.Use the AWS CLI command put-lifecycle-hook to complete the lifecycle actions and put the instance back to the normal process of the Auto Scaling group.
D.In the script, use the AWS CLI command attach-instances to attach the instance to the ASG, which completes the lifecycle action and modifies the instance state from Wait to InService.

Correct Answer – B
Option A is incorrect because the record-lifecycle-action-heartbeat command is used to restart the timeout period and keep the instance in the Wait state. It cannot complete the lifecycle period for an instance in the Pending:Wait state.
Option B is CORRECT because in the script, the complete-lifecycle-action command should be used to finish the lifecycle action before the timeout period ends. The following is an example:
"aws autoscaling complete-lifecycle-action --lifecycle-hook-name my-lifecycle-hook --auto-scaling-group-name my-auto-scaling-group --lifecycle-action-result CONTINUE --lifecycle-action-token bcd2f1b8-9a78-44d3-8a7a-4dd07d7cf635"
Option C is incorrect because the put-lifecycle-hook CLI command creates or updates a lifecycle hook for a specified Auto Scaling group. It is unsuitable to be used in this scenario.
Option D is incorrect because the AWS CLI command attach-instances attaches EC2 instances to the ASG. It cannot finish the custom actions in a lifecycle hook.
Reference:
https://docs.aws.amazon.com/autoscaling/ec2/userguide/lifecycle-hooks.html,
https://docs.aws.amazon.com/cli/latest/reference/autoscaling/complete-lifecycle-action.html.