07. CF Mappings

Mappings are fixed variables within your template. They are very handy to differentiate between different environments like dev and prod. These are hardcoded within the template.

It looks like:

Mappings:
  RegionMap:
    us-east-1:
      HVM64: 1234
      HVMG2: 1235
    us-west-1:
      HVM64: 1236
      HVMG2: 1237
    eu-east-1:
      HVM64: 1238
      HVMG2: 1239

These are great when you know in in advance all the values that can be taken and that they can be deduced from variables such as:

• Region.
• Availability Zone.
• AWS Account.
• Environment (prod vs dev)

They also allows for safer control over the template.

For this we can use the Fn::FindInMap to return a named value from a specific key. Fo the last example, we could:

Resources:
  myEC2:
    Type: AWS::EC2::Instance
    Properties:
      ImageId: !FindInMap [RegionMap, !Ref "AWS::Region", HVM64]
      InstanceType: m1.small