CloudFormation Mappings¶

• Mappings are fixed variables within your CloudFormation Template.
• They're very handy to differentiate between different environments (dev vs prod), regions (AWS regions), AMI types etc
• All the Values are hardcoded within the template:

RegionMap:
    us-east-1:
        "32": "ami-6411e20d"
        "64": "ami-7a11e213"
    us-west-1:
        "32": "ami-c9c7978c"
        "64": "ami-cfc7978a"
    eu-west-1:
        "32": "ami-37c2f643"
        "64": "ami-31c2f645"
Resources:
    myEc2Instance:
        Type: AWS::EC2::Instance
        Properties:
            ImageId: !FindInMap [RegionMap, !Ref AWS::Region, 32]
        InstanceType: m1.small        

You can reference the map using

!FindInMap [ MapName, TopLevelKey, SecondLevelKey ]

When would you use mappings vs parameters?¶

• Mappings are great when you know in advance all the values that can be taken and that they can be deducted from variables such as:
  • Region
  • Availability Zone
  • AWS Account
  • Environment (dev vs prod)
  • etc
• They allow safer control over the template
• Use parameters when the values are really user specific