CloudFormation template for Global Accelerator with Listeners

GlobalAccelerator.yaml

AWSTemplateFormatVersion: '2010-09-09'
Description:  >- 
  CloudFormation template for Global Accelerator with Listeners port 443 and Endpoints to exist ALB.
  Exist ALB Arn is fettched by Lambda.
  Finaly, we updating Dns recoord for domain to point to the Global Accelerator.

# ------------------------------------------------------------#
# Input Parameters
# ------------------------------------------------------------#
Parameters:
  DomainName:
    Type: String
    Default: "example.com"
    Description: Domain name used in ALB

  AlbName:
    Type: String
    Default: "myalb-*"
    Description: ALB Name  

  HostedZoneId:
    Type: String
    Description: Route53 domain hosted zone id
    
  usecase:
    Description: What is the use case?
    Type: String
    AllowedValues:
      - "prod"
      - "stage"
      - "dev"
      - "loadtest"
      - "dr"
      - "qa"
    Default: prod

Resources:
  LambdaExecutionRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - lambda.amazonaws.com
            Action:
              - 'sts:AssumeRole'
      Policies:
        - PolicyName: LambdaExecutionPolicy
          PolicyDocument:
            Version: '2012-10-17'
            Statement:
              - Effect: Allow
                Action:
                  - 'logs:CreateLogGroup'
                  - 'logs:CreateLogStream'
                  - 'logs:PutLogEvents'
                Resource: 'arn:aws:logs:*:*:*'
              - Effect: Allow
                Action:
                  - 'elasticloadbalancing:DescribeLoadBalancers'
                Resource: '*'

  AlbArnFetcher:
    Type: 'AWS::Lambda::Function'
    Properties:
      Handler: index.handler
      Role: !GetAtt 'LambdaExecutionRole.Arn'
      Code:
        ZipFile: |
          const AWS = require('aws-sdk');
          const response = require('cfn-response');
          exports.handler = (event, context) => {
            const albNamePattern = process.env.ALB_NAME;
            if (event.RequestType === 'Delete') {
              response.send(event, context, response.SUCCESS);
              return;
            }
            const elbv2 = new AWS.ELBv2();
            elbv2.describeLoadBalancers({}, (err, data) => {
              if (err) {
                response.send(event, context, response.FAILED, err);
              } else {
                const alb = data.LoadBalancers.find(lb => lb.LoadBalancerName.startsWith(albNamePattern));
                if (alb) {
                  response.send(event, context, response.SUCCESS, { AlbArn: alb.LoadBalancerArn });
                } else {
                  response.send(event, context, response.FAILED, { error: 'No matching ALB found' });
                }
              }
            });
          };
      Runtime: nodejs16.x
      Timeout: 15
      Environment:
        Variables:
          ALB_NAME: !Ref AlbName

  AlbArnCustomResource:
    Type: 'Custom::AlbArnFetcher'
    Properties:
      ServiceToken: !GetAtt 'AlbArnFetcher.Arn'

  AlbAccelerator:
    Type: 'AWS::GlobalAccelerator::Accelerator'
    Properties:
      Name: !Sub ${AWS::StackName}-alb
      IpAddressType: IPV4
      Enabled: true
      Tags:
        - Key: Name
          Value: !Sub ${AWS::StackName}-alb
        - Key: usecase
          Value: !Ref usecase
        - Key: Env
          Value: !Ref usecase
        - Key: Region
          Value: !Ref "AWS::Region"          
          
  AlbListener:
    Type: 'AWS::GlobalAccelerator::Listener'
    Properties:
      AcceleratorArn: !Ref AlbAccelerator
      PortRanges:
        - FromPort: 443
          ToPort: 443
      Protocol: TCP

  AlbEndpointGroup:
    Type: 'AWS::GlobalAccelerator::EndpointGroup'
    Properties:
      ListenerArn: !Ref AlbListener
      EndpointGroupRegion: !Ref 'AWS::Region'
      EndpointConfigurations:
        - EndpointId: !GetAtt 'AlbArnCustomResource.AlbArn'
          Weight: 100
          ClientIPPreservationEnabled: 'true'
      TrafficDialPercentage: 100
 # ------------------------------------------------------------#
 # Update DNS Recoord
 # The Hosted Zone ID for AWS Global Accelerator is a fixed value provided by AWS. 
 # It does not change and is the same for all AWS Global Accelerators. 
 # The Hosted Zone ID for AWS Global Accelerator is Z2BJ6XQ5FK7U4H.
 # ------------------------------------------------------------#


  RecordSetGroup:
    Type: 'AWS::Route53::RecordSetGroup'
    UpdateReplacePolicy: Delete  
    DeletionPolicy: Delete    
    Properties:
      HostedZoneId: !Ref HostedZoneId
      RecordSets:
        - Name: !Ref DomainName
          Type: A
          AliasTarget:
            DNSName: !GetAtt 'AlbAccelerator.DnsName'
            HostedZoneId: 'Z2BJ6XQ5FK7U4H' # this is the hosted zone ID for Global Accelerator
            EvaluateTargetHealth: 'false'



Outputs:
  LambdaExecutionRole:
    Value: !GetAtt LambdaExecutionRole.Arn
    Export:
      Name: !Sub ${AWS::StackName}-LambdaExecutionRole
  AlbArn:
    Description: 'Lambda fethed ALB ARN'
    Value: !GetAtt 'AlbArnCustomResource.AlbArn'
  AlbAcceleratorDomain:
    Description: 'Global ALB Dns Name'
    Value: !GetAtt AlbAccelerator.DnsName