Which action will accomplish this?
Add a health check to the Auto Scaling group to invoke an AWS Lambda function whenever an instance status is impaired.
Configure the Auto Scaling group to send a notification to an Amazon SNS topic whenever a failed instance launch occurs.
Create an Amazon CloudWatch alarm that invokes an AWS Lambda function when a failed AttachInstances Auto Scaling API call is made.
Create a status check alarm on Amazon EC2 to send a notification to an Amazon SNS topic whenever a status check fail occurs.
Explanations:
Adding a health check to the Auto Scaling group to invoke a Lambda function for impaired status checks will not notify you about failed instance launches. It is more about checking the instance health post-launch.
Configuring the Auto Scaling group to send a notification to an SNS topic whenever a failed instance launch occurs is the best approach. This ensures that an email notification is sent whenever an instance fails to launch, which directly addresses the requirement.
A CloudWatch alarm for a failed AttachInstances API call would not necessarily capture failed instance launches. The issue could be related to other factors, so this approach is too specific.
Creating a status check alarm on EC2 instances will notify you if the instance fails after launching (e.g., failed system or instance status check), but it does not help with failed instance launches.
I sort that the answer is:
Configure the Auto Scaling group to send a notification to an Amazon SNS topic whenever a failed instance launch occurs.