A Python script that fefches from the metadata block uses it own logic to perform all of the tasks, simplifying the usedata complexity
https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/cfn-init.html
both cfn-init & cfn-signal script needs to be invoked explicitly from user data script
/opt/aws/bin/cfn-init -v --stack STACK_NAME --resource EC2_INSTANCE_LOGICAL_ID --region REGION