Question

A SysOps administrator manages an Auto Scaling group defined in a CloudFormation template. The team needs to deploy a new AMI by updating the launch template referenced in the stack. Business requirements state that during the update, at least 75% of instances must remain in service to handle live traffic, and CloudFormation should wait for each batch of replacement instances to signal successful application startup before proceeding. Which CloudFormation configuration meets these requirements?

Accepted Answer

Add an UpdatePolicy with AutoScalingRollingUpdate specifying MinInstancesInService, MaxBatchSize, and PauseTime with WaitOnResourceSignals set to true, and have the instances send cfn-signal on successful startup

Answer

Add a DeletionPolicy of Retain to the Auto Scaling group so old instances are preserved while new ones launch

Answer

Add an UpdatePolicy with AutoScalingReplacingUpdate so CloudFormation creates an entirely new Auto Scaling group before deleting the old one

Answer

Add a CreationPolicy with ResourceSignal Count and Timeout so CloudFormation waits for signals during the stack update