How to do it...

1. Go ahead and create a new CloudFormation template. We'll add some Parameters for the items we've mentioned previously:

      Parameters: 
        DomainName: 
          Description: Your domain name (example.org) 
          Type: String 
        LoadBalancerDNSNameRegionA: 
          Description: The DNS name of your ELB in region A 
          Type: String 
        LoadBalancerHostedZoneRegionA: 
          Description: The Hosted Zone ID of your ELB in region A 
          Type: String 
        LoadBalancerDNSNameRegionB: 
          Description: The DNS name of your ELB in region B 
          Type: String 
        LoadBalancerHostedZoneRegionB: 
          Description: The Hosted Zone ID of your ELB in region B 
          Type: String

2. The first Resource we want is the HostedZone resource for our domain name. Add it to your template as follows:

      Resources: 
        DNSHostedZone: 
          Type: AWS::Route53::HostedZone 
          Properties: 
            Name: !Ref DomainName

3. In order to have failover happen automatically, we're going to need to set up some health checks. We want health checks on the ELBs in both regions:

        RegionAHealthCheck: 
          Type: AWS::Route53::HealthCheck 
          Properties: 
            HealthCheckConfig: 
              FailureThreshold: 3 
              FullyQualifiedDomainName: !Ref LoadBalancerDNSNameRegionA 
              Port: 80 
              RequestInterval: 30 
              ResourcePath: "/" 
              Type: HTTP 
            HealthCheckTags: 
              - { Key: Name, Value: Region A Health Check } 
        RegionBHealthCheck: 
          Type: AWS::Route53::HealthCheck 
          Properties: 
            HealthCheckConfig: 
              FailureThreshold: 3 
              FullyQualifiedDomainName: !Ref LoadBalancerDNSNameRegionB 
              Port: 80 
              RequestInterval: 30 
              ResourcePath: "/" 
              Type: HTTP 
            HealthCheckTags: 
              - { Key: Name, Value: Region B Health Check }

4. We're now going to create four record sets for your domain:
   • a.<your-domain>-PRIMARY
   • b.<your-domain>-PRIMARY
   • a.<your-domain>-SECONDARY (failover to b)
   • b.<your-domain>-SECONDARY (failover to a)

5. These records correspond to ELB A and ELB B (or site A and B, if that term makes more sense to you), and they will allow each region to fail over to the other if the health check fails.
6. Let's start with the primary records for both ELBs:

        RegionAPrimary: 
          Type: AWS::Route53::RecordSet 
          Properties: 
            Name: !Join [ ., [ a, Ref: DomainName ] ] 
            Type: A 
            HostedZoneId: !Ref DNSHostedZone 
            AliasTarget: 
              HostedZoneId: !Ref LoadBalancerHostedZoneRegionA 
              DNSName: !Ref LoadBalancerDNSNameRegionA 
              Failover: PRIMARY 
              SetIdentifier: primary-region-a 
              HealthCheckId: !Ref RegionAHealthCheck 
        RegionBPrimary: 
          Type: AWS::Route53::RecordSet 
          Properties: 
            Name: !Join [ ., [ b, Ref: DomainName ] ] 
            Type: A 
            HostedZoneId: !Ref DNSHostedZone 
            AliasTarget: 
              HostedZoneId: !Ref LoadBalancerHostedZoneRegionB 
              DNSName: !Ref LoadBalancerDNSNameRegionB 
              Failover: PRIMARY 
              SetIdentifier: primary-region-b 
              HealthCheckId: !Ref RegionBHealthCheck

7. Now add the secondary (failover) records:

        RegionAFailover: 
          Type: AWS::Route53::RecordSet 
          Properties: 
            Name: !Join [ ., [ a, Ref: DomainName ] ] 
            Type: A 
            HostedZoneId: !Ref DNSHostedZone 
            AliasTarget: 
              HostedZoneId: !Ref LoadBalancerHostedZoneRegionB 
              DNSName: !Ref LoadBalancerDNSNameRegionB 
              Failover: SECONDARY 
              SetIdentifier: secondary-region-a 
        RegionBFailover: 
          Type: AWS::Route53::RecordSet 
          Properties: 
            Name: !Join [ ., [ b, Ref: DomainName ] ] 
            Type: A 
            HostedZoneId: !Ref DNSHostedZone 
            AliasTarget: 
              HostedZoneId: !Ref LoadBalancerHostedZoneRegionA 
              DNSName: !Ref LoadBalancerDNSNameRegionA 
              Failover: SECONDARY 
              SetIdentifier: secondary-region-b

8. Now we're going to add the root/apex record for our domain. For the purposes of this recipe, we're going to send requests originating from North America to region/ELB A, and requests from the rest of the world to region/ELB B:

        NorthAmericaGeolocation: 
          Type: AWS::Route53::RecordSet 
          Properties: 
            Name: !Ref DomainName 
            Type: A 
            HostedZoneId: !Ref DNSHostedZone 
            AliasTarget: 
              HostedZoneId: !Ref DNSHostedZone 
              DNSName: !Join [ ., [ a, Ref: DomainName ] ] 
            GeoLocation: 
              ContinentCode: NA # North America 
            SetIdentifier: geolocation-region-a 
        RestOfWorldGeolocation: 
          Type: AWS::Route53::RecordSet 
          Properties: 
            Name: !Ref DomainName 
            Type: A 
            HostedZoneId: !Ref DNSHostedZone 
            AliasTarget: 
              HostedZoneId: !Ref DNSHostedZone 
              DNSName: !Join [ ., [ b, Ref: DomainName ] ] 
            GeoLocation: 
              CountryCode: "*" # Rest of world 
            SetIdentifier: geolocation-region-b

9. That's it! You can now run this CloudFormation template in the AWS web console or via the CLI, as follows:

      aws cloudformation create-stack \
        --stack-name geolocation-failover \
        --template-body file://07-routing-based-on-location.yaml \
        --parameters \
        ParameterKey=DomainName,ParameterValue=gitrepository.com \
        ParameterKey=LoadBalancerDNSNameRegionA,ParameterValue=<elb-a> \
        ParameterKey=LoadBalancerHostedZoneRegionA, \
        ParameterValue=<elb-zoneid-a> \
        ParameterKey=LoadBalancerDNSNameRegionB,ParameterValue=<elb-b> \
        ParameterKey=LoadBalancerHostedZoneRegionB, \
        ParameterValue=<elb-zoneid-b>