Summary
In this chapter, you learned how to create an ECS cluster, complete with an EC2 Auto Scaling group and ECS container instances based on a custom Amazon machine image, using an infrastructure-as-code approach to define all resources using CloudFormation.
You learned how an ECS cluster is simply a logical grouping of ECS container instances, and is composed of EC2 Auto Scaling groups that manage a collection of EC2 instances. EC2 Auto Scaling groups can dynamically scale up and down, and you attached an EC2 Auto Scaling launch configuration to your Auto Scaling group, which provides a common collection of settings applied to each new EC2 instance that is added to the group.
CloudFormation provides powerful features for ensuring instances in your Auto Scaling groups are initialized correctly, and you learned how you to configure user data to invoke the CloudFormation helper scripts you installed in your custom machine image, which then download configurable initialization logic defined...
