1. In a new file, define the template version and description:

      AWSTemplateFormatVersion: "2010-09-09"  
      Description: Create a weighted DNS setup for canary deployments.

2. Start the Parameters section and the required parameters:

      Parameters: 
        HostedZoneName: 
          Type: String 
          Description: The hosted zone to create records in 
 
        DomainName: 
          Type: String 
          Description: The domain name to create in the hosted zone 
 
        OldResource: 
          Type: String 
          Description: The older resource domain name 
 
        NewResource: 
          Type: String 
          Description: The newer resource domain name

3. Include the optional parameters (such as those with defaults) in the Parameters section:

      OldWeight: 
        Type: Number 
        Default: 1 
        Description: The ratio of requests to send to the older endpoint 
 
      NewWeight: 
        Type: Number 
        Default: 0 
        Description: The ratio of requests to send to the newer endpoint

4. Start the Resources section of the template, and define your record set group:

      Resources: 
        RecordSetGroup: 
          Type: AWS::Route53::RecordSetGroup 
          Properties: 
            HostedZoneName: !Ref HostedZoneName 
            Comment: Canary deployment record set group 
            RecordSets: 
              - Name: !Join [ ".", [ Ref: DomainName, Ref: 
                  HostedZoneName ] ] 
                Type: CNAME 
                TTL: "300" 
                SetIdentifier: Old 
                Weight: !Ref OldWeight 
                ResourceRecords: 
                  - !Ref OldResource 
              - Name: !Join [ ".", [ Ref: DomainName, Ref: 
                  HostedZoneName ] ] 
                Type: CNAME 
                TTL: "300" 
                SetIdentifier: New 
                Weight: !Ref NewWeight 
                ResourceRecords: 
                  - !Ref NewResource

5. Save the template with a known filename; for example, 07-canary-deployments.yaml.
6. Launch the template with the following CLI command:

      aws cloudformation create-stack 
        --stack-name canary 
        --template-body file://07-canary-deployments.yaml 
        --parameters 
        ParameterKey=DomainName,ParameterValue=<your-domain-name> 
        ParameterKey=OldResource,ParameterValue=<old-resource-dns> 
        ParameterKey=NewResource,ParameterValue=<new-resource-dns> 
        ParameterKey=HostedZoneName,ParameterValue=<your-hosted-zone> 

7. When ready, update the stack to change (just) the domain weighting with the following CLI command:

      aws cloudformation update-stack 
        --stack-name canary 
        --parameters 
        ParameterKey=HostedZoneName,UsePreviousValue=true 
        ParameterKey=DomainName,UsePreviousValue=true 
        ParameterKey=OldResource,UsePreviousValue=true 
        ParameterKey=NewResource,UsePreviousValue=true 
        ParameterKey=OldWeight,ParameterValue=0 
        ParameterKey=NewWeight,ParameterValue=1 
        --use-previous-template