You are designing a Cloudformation template to create a set of EC2 Instance and install an application package. You need to ensure that the stack is only successful if the software package gets installed successfully. How can you check this?

Answer options:

A.Use the cfn-signal helper script.
B.Use the Change sets feature.
C.Use Cloudwatch logs to signal the completion.
D.Use Cloudtrail to signal the completion.

Answer – A
The AWS Documentation mentions the following.
The cfn-signal helper script signals AWS CloudFormation to indicate whether Amazon EC2 instances have been successfully created or updated. If you install and configure software applications on instances, you can signal AWS CloudFormation when those software applications are ready.
Options C and D are incorrect because they cannot signal the completion of the software packages.
Option B is incorrect because this is only used if you need to make changes to the running resources in a stack, you update the stack.
For more information on how cfn signal, please refer to the below URL-
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-signal.html