AWS Certified SysOps Administrator Practice Exam

What may cause CloudFormation to complete successfully while the instance is still executing cfn-init?

1. The instance is not configured to wait for the signal

2. The cfn-signal script is incorrectly defined

3. You forgot the wait condition

4. The EC2 instance is incorrectly sized

The correct answer is: You forgot the wait condition

The correct answer emphasizes the significance of implementing a wait condition within a CloudFormation template to ensure that the CloudFormation stack does not complete until certain conditions, such as the execution of `cfn-init`, are met. In CloudFormation, when an instance is launched, it may take some time for necessary configurations and software installations to complete. The use of a wait condition allows the stack to pause progress until a signal is received that indicates the configuration is done. If the wait condition is omitted, the stack can finish creating resources without waiting for the instance to fully initialize. As a result, CloudFormation can report success even when the instance is still in the process of running configuration scripts like `cfn-init`. The inclusion of a wait condition is crucial in scenarios where you need to wait for the completion of initialization tasks before considering the stack creation to be fully successful. This not only affects the completion status but also ensures that the application is ready for use as intended.