Explore the CloudFormation Template

In this section you will explore the CloudFormation template and learn how you were able to deploy the web application infrastructure using it

  • Go to the AWS CloudFormation console at https://console.aws.amazon.com/cloudformation

    1. Click on the CloudFormation stack that you deployed
    2. Click on the Template tab CFNViewTemplate
  • Alternate: You previously downloaded the CloudFormation Template staticwebapp.yaml. You can also view it in the text editor of your choice

The template is written in a format called YAML, which is commonly used for configuration files. CloudFormation templates can also be written in JSON.

Look through the template. You will notice several sections:

  • The Parameters section is used to prompt for inputs that can be used elsewhere in the template. The template is asking for several inputs, but also provides default values for each one.

    • Look through these and start to reason about what some are used for.
    • For example InstanceType is a parameter where the user can choose that Amazon EC2 instance type to deploy for the servers used in this Web App.
    • Search the file for !Ref InstanceType. !Ref! is a built-in function that refrences the value of a parameter. Here you can see it is used to provide a value to the Auto Scaling Launch Configuration, which is used to laucnh new EC2 instances.
  • The Conditions section is where you can setup if/then-like control of what happens during template deployment. It defines the circumstances under which entities are created or configured.

  • The Resources section is the “heart” of the template. It is where you define the infrastructure to be deployed. Look at the first resource defined.

    • It is the Amazon DynamoDB table used as the mock for the RecommendationService
    • It has a logical ID which in this case is DynamoDBServiceMockTable. This logical ID is how we refer to the DynamoDB table resource within the CloudFormation template.
    • It has a Type which tells CloudFormation which type of resource to create. In this case a AWS::DynamoDB::Table
    • And it has Properties that define the values used to create the VPC
  • The Outputs section is used to display selective information about resources in the stack.

    • In this case it uses the built-in function !GetAtt to get the DNS Name for the Application Load Balancer.
    • This URL is what you used to access the WebApp
  • The Metadata section here is used to group and order how the CloudFormation parameters are displayed when you deploy the template using the AWS Console