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AWS Certified SysOps Administrator - Associate Exam Prep

CloudFormation Features: Part II

Build on your understanding of CloudFormation by understanding more of its core features.

We'll cover the following...

CreatePolicy

The CreatePolicy attribute can be used with a resource to prevent its status from reaching the create complete state until AWS CloudFormation receives a certain number of signals from the resource. The CreatePolicy attribute is only supported by the following resource types:

  • AWS::AppStream::Fleet
  • AWS::AutoScaling::AutoScalingGroup
  • AWS::EC2::Instance
  • AWS::CloudFormation::WaitCondition

In the following code, we have a resource, EducativeASG, with desired capacity 3. We’ve associated a creation policy with this ASG to ensure that CloudFormation receives three SUCCESS signals, one from each of the ASG instances.

YAML
EducativeASG:
  Type: AWS::AutoScaling::AutoScalingGroup
  Properties:
    AvailabilityZones:
      Fn::GetAZs: ''
    LaunchConfigurationName:
      Ref: LaunchConfig
    DesiredCapacity: '3' # Create 3 instances in the Auto Scaling group
    MinSize: '1'
    MaxSize: '10'
  CreationPolicy:
    ResourceSignal:
      Count: '3' # Ensure that all three instances created by the ASG sent the 'SUCCESS' signal
      Timeout: PT15M # Specifies the timeout for the CreationPolicy

UpdatePolicy

We can use UpdatePolicy to specify how CloudFormation should update a resource. The UpdatePolicy attribute is supported for the following resource types in CloudFormation:

  • AWS::AppStream::Fleet
  • AWS::AutoScaling::AutoScalingGroup
  • AWS::ElastiCache::ReplicationGroup
  • AWS::OpenSearchService::Domain
...