A DevOps engineer has implemented a CI/CD pipeline to deploy an AWS CloudFormation template that provisions a web application. The web application consists of an Application Load Balancer (ALB), a target group, a launch template that uses an Amazon Linux 2 AMI, an Auto Scaling group of Amazon EC2 instances, a security group, and an Amazon RDS for MySQL database. The launch template includes user data that specifies a script to install and start the application. The initial deployment of the application was successful. The DevOps engineer made changes to update the version of the application with the user data. The CI/CD pipeline has deployed a new version of the template. However, the health checks on the ALB are now failing. The health checks have marked all targets as unhealthy. During investigation, the DevOps engineer notices that the CloudFormation stack has a status of UPDATE_COMPLETE. However, when the DevOps engineer connects to one of the EC2 instances and checks /var/log/messages, the DevOps engineer notices that the Apache web server failed to start successfully because of a configuration error. How can the DevOps engineer ensure that the CloudFormation deployment will fail if the user data fails to successfully finish running?
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Marked answer: A
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To ensure that the CloudFormation deployment fails if the user data script does not successfully finish, you can use a combination of AWS CloudFormation's CreationPolicy, cfn-signal, and wait condition resources. These mechanisms can signal CloudFormation about the success or failure of the instance creation process, including the execution of user data scripts.
