Exam AWS Certified Solutions Architect - Professional topic 1 question 502 discussion

C Quoting "If you want to update existing instances when you update the LaunchConfiguration resource, you must specify an UpdatePolicy attribute for the Auto Scaling group. " https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-as-launchconfig.html

A. Ref: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-changesets.html

vote for C "To update existing instances when you update the AWS::AutoScaling::LaunchConfiguration resource, you can specify an UpdatePolicy attribute for the group. "

Vote C

I think the "best" answer is C

Answer A - Refer to Section "Update the AMI on an Amazon EC2 instance" in https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/updating.stacks.walkthrough.html.

When you update the launch configuration for an Auto Scaling group, CloudFormation deletes that resource and creates a new launch configuration with the updated properties and a new name. Existing instances are not affected. To update existing instances when you update the AWS::AutoScaling::LaunchConfiguration resource , Answer C is right

"UpdateStack to replace the EC2 instances with instances launched from the new AMI" A wrong - will only apply to EC2 instances managed separately B wrong C correct - have to use UpdatePolicy attribute on Auto Scaling group D wrong

I'll go with C

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-attribute-updatepolicy.html C.

B: - reason as below { "Resources": { "LaunchConfig": { "Type": "AWS::AutoScaling::LaunchConfiguration", "Properties": { "KeyName": { "Ref": "KeyName" }, "ImageId": { "Fn::FindInMap": [ "AWSRegionArch2AMI", { "Ref": "AWS::Region" }, { "Fn::FindInMap": [ "AWSInstanceType2Arch",

A - it us the changes

it's C

The best answer is A because: - creating a changeset is the accepted method for making changes to a stack. - it includes all the changes in the template that are required - changes that would be required would not just be updating the ASG UpdatePolicy attribute, it would also require updating the AMI ID, it would be worth parameterizing the AMI ID so that it's just a parameter change in the future. Launch Config would need replacing because a new AMI is being used and launch configs can't be updated, they are replaced and then deleted once you have successfully deployed an "in-service" instance so that roll-back can occur. There is more to this question than first considered. Don't rush to the first answer the makes sense, sometimes there is a better answer. B and C and not wrong but they are not the best answer. D could be done but really why would you do that?

C. === A. is not enough. Please, reference below https://aws.amazon.com/premiumsupport/knowledge-center/auto-scaling-group-rolling-updates/

Change set is to help you view changes before they are made in CF. To introduce new AMI then you have to look at the launch auto scaling group and update it and so I would go with C.

going with C