Installing a cluster on user-provisioned infrastructure in AWS by using CloudFormation templates

AWSTemplateFormatVersion: 2010-09-09
Description: Template for Best Practice VPC with 1-3 AZs

Parameters:
  VpcCidr:
    AllowedPattern: ^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])(\/(1[6-9]|2[0-4]))$
    ConstraintDescription: CIDR block parameter must be in the form x.x.x.x/16-24.
    Default: 10.0.0.0/16
    Description: CIDR block for VPC.
    Type: String
  AvailabilityZoneCount:
    ConstraintDescription: "The number of availability zones. (Min: 1, Max: 3)"
    MinValue: 1
    MaxValue: 3
    Default: 1
    Description: "How many AZs to create VPC subnets for. (Min: 1, Max: 3)"
    Type: Number
  SubnetBits:
    ConstraintDescription: CIDR block parameter must be in the form x.x.x.x/19-27.
    MinValue: 5
    MaxValue: 13
    Default: 12
    Description: "Size of each subnet to create within the availability zones. (Min: 5 = /27, Max: 13 = /19)"
    Type: Number

Metadata:
  AWS::CloudFormation::Interface:
    ParameterGroups:
    - Label:
        default: "Network Configuration"
      Parameters:
      - VpcCidr
      - SubnetBits
    - Label:
        default: "Availability Zones"
      Parameters:
      - AvailabilityZoneCount
    ParameterLabels:
      AvailabilityZoneCount:
        default: "Availability Zone Count"
      VpcCidr:
        default: "VPC CIDR"
      SubnetBits:
        default: "Bits Per Subnet"

Conditions:
  DoAz3: !Equals [3, !Ref AvailabilityZoneCount]
  DoAz2: !Or [!Equals [2, !Ref AvailabilityZoneCount], Condition: DoAz3]

Resources:
  VPC:
    Type: "AWS::EC2::VPC"
    Properties:
      EnableDnsSupport: "true"
      EnableDnsHostnames: "true"
      CidrBlock: !Ref VpcCidr
  PublicSubnet:
    Type: "AWS::EC2::Subnet"
    Properties:
      VpcId: !Ref VPC
      CidrBlock: !Select [0, !Cidr [!Ref VpcCidr, 6, !Ref SubnetBits]]
      AvailabilityZone: !Select
      - 0
      - Fn::GetAZs: !Ref "AWS::Region"
  PublicSubnet2:
    Type: "AWS::EC2::Subnet"
    Condition: DoAz2
    Properties:
      VpcId: !Ref VPC
      CidrBlock: !Select [1, !Cidr [!Ref VpcCidr, 6, !Ref SubnetBits]]
      AvailabilityZone: !Select
      - 1
      - Fn::GetAZs: !Ref "AWS::Region"
  PublicSubnet3:
    Type: "AWS::EC2::Subnet"
    Condition: DoAz3
    Properties:
      VpcId: !Ref VPC
      CidrBlock: !Select [2, !Cidr [!Ref VpcCidr, 6, !Ref SubnetBits]]
      AvailabilityZone: !Select
      - 2
      - Fn::GetAZs: !Ref "AWS::Region"
  InternetGateway:
    Type: "AWS::EC2::InternetGateway"
  GatewayToInternet:
    Type: "AWS::EC2::VPCGatewayAttachment"
    Properties:
      VpcId: !Ref VPC
      InternetGatewayId: !Ref InternetGateway
  PublicRouteTable:
    Type: "AWS::EC2::RouteTable"
    Properties:
      VpcId: !Ref VPC
  PublicRoute:
    Type: "AWS::EC2::Route"
    DependsOn: GatewayToInternet
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway
  PublicSubnetRouteTableAssociation:
    Type: "AWS::EC2::SubnetRouteTableAssociation"
    Properties:
      SubnetId: !Ref PublicSubnet
      RouteTableId: !Ref PublicRouteTable
  PublicSubnetRouteTableAssociation2:
    Type: "AWS::EC2::SubnetRouteTableAssociation"
    Condition: DoAz2
    Properties:
      SubnetId: !Ref PublicSubnet2
      RouteTableId: !Ref PublicRouteTable
  PublicSubnetRouteTableAssociation3:
    Condition: DoAz3
    Type: "AWS::EC2::SubnetRouteTableAssociation"
    Properties:
      SubnetId: !Ref PublicSubnet3
      RouteTableId: !Ref PublicRouteTable
  PrivateSubnet:
    Type: "AWS::EC2::Subnet"
    Properties:
      VpcId: !Ref VPC
      CidrBlock: !Select [3, !Cidr [!Ref VpcCidr, 6, !Ref SubnetBits]]
      AvailabilityZone: !Select
      - 0
      - Fn::GetAZs: !Ref "AWS::Region"
  PrivateRouteTable:
    Type: "AWS::EC2::RouteTable"
    Properties:
      VpcId: !Ref VPC
  PrivateSubnetRouteTableAssociation:
    Type: "AWS::EC2::SubnetRouteTableAssociation"
    Properties:
      SubnetId: !Ref PrivateSubnet
      RouteTableId: !Ref PrivateRouteTable
  NAT:
    DependsOn:
    - GatewayToInternet
    Type: "AWS::EC2::NatGateway"
    Properties:
      AllocationId:
        "Fn::GetAtt":
        - EIP
        - AllocationId
      SubnetId: !Ref PublicSubnet
  EIP:
    Type: "AWS::EC2::EIP"
    Properties:
      Domain: vpc
  Route:
    Type: "AWS::EC2::Route"
    Properties:
      RouteTableId:
        Ref: PrivateRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId:
        Ref: NAT
  PrivateSubnet2:
    Type: "AWS::EC2::Subnet"
    Condition: DoAz2
    Properties:
      VpcId: !Ref VPC
      CidrBlock: !Select [4, !Cidr [!Ref VpcCidr, 6, !Ref SubnetBits]]
      AvailabilityZone: !Select
      - 1
      - Fn::GetAZs: !Ref "AWS::Region"
  PrivateRouteTable2:
    Type: "AWS::EC2::RouteTable"
    Condition: DoAz2
    Properties:
      VpcId: !Ref VPC
  PrivateSubnetRouteTableAssociation2:
    Type: "AWS::EC2::SubnetRouteTableAssociation"
    Condition: DoAz2
    Properties:
      SubnetId: !Ref PrivateSubnet2
      RouteTableId: !Ref PrivateRouteTable2
  NAT2:
    DependsOn:
    - GatewayToInternet
    Type: "AWS::EC2::NatGateway"
    Condition: DoAz2
    Properties:
      AllocationId:
        "Fn::GetAtt":
        - EIP2
        - AllocationId
      SubnetId: !Ref PublicSubnet2
  EIP2:
    Type: "AWS::EC2::EIP"
    Condition: DoAz2
    Properties:
      Domain: vpc
  Route2:
    Type: "AWS::EC2::Route"
    Condition: DoAz2
    Properties:
      RouteTableId:
        Ref: PrivateRouteTable2
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId:
        Ref: NAT2
  PrivateSubnet3:
    Type: "AWS::EC2::Subnet"
    Condition: DoAz3
    Properties:
      VpcId: !Ref VPC
      CidrBlock: !Select [5, !Cidr [!Ref VpcCidr, 6, !Ref SubnetBits]]
      AvailabilityZone: !Select
      - 2
      - Fn::GetAZs: !Ref "AWS::Region"
  PrivateRouteTable3:
    Type: "AWS::EC2::RouteTable"
    Condition: DoAz3
    Properties:
      VpcId: !Ref VPC
  PrivateSubnetRouteTableAssociation3:
    Type: "AWS::EC2::SubnetRouteTableAssociation"
    Condition: DoAz3
    Properties:
      SubnetId: !Ref PrivateSubnet3
      RouteTableId: !Ref PrivateRouteTable3
  NAT3:
    DependsOn:
    - GatewayToInternet
    Type: "AWS::EC2::NatGateway"
    Condition: DoAz3
    Properties:
      AllocationId:
        "Fn::GetAtt":
        - EIP3
        - AllocationId
      SubnetId: !Ref PublicSubnet3
  EIP3:
    Type: "AWS::EC2::EIP"
    Condition: DoAz3
    Properties:
      Domain: vpc
  Route3:
    Type: "AWS::EC2::Route"
    Condition: DoAz3
    Properties:
      RouteTableId:
        Ref: PrivateRouteTable3
      DestinationCidrBlock: 0.0.0.0/0
      NatGatewayId:
        Ref: NAT3
  S3Endpoint:
    Type: AWS::EC2::VPCEndpoint
    Properties:
      PolicyDocument:
        Version: 2012-10-17
        Statement:
        - Effect: Allow
          Principal: '*'
          Action:
          - '*'
          Resource:
          - '*'
      RouteTableIds:
      - !Ref PublicRouteTable
      - !Ref PrivateRouteTable
      - !If [DoAz2, !Ref PrivateRouteTable2, !Ref "AWS::NoValue"]
      - !If [DoAz3, !Ref PrivateRouteTable3, !Ref "AWS::NoValue"]
      ServiceName: !Join
      - ''
      - - com.amazonaws.
        - !Ref 'AWS::Region'
        - .s3
      VpcId: !Ref VPC

Outputs:
  VpcId:
    Description: ID of the new VPC.
    Value: !Ref VPC
  PublicSubnetIds:
    Description: Subnet IDs of the public subnets.
    Value:
      !Join [
        ",",
        [!Ref PublicSubnet, !If [DoAz2, !Ref PublicSubnet2, !Ref "AWS::NoValue"], !If [DoAz3, !Ref PublicSubnet3, !Ref "AWS::NoValue"]]
      ]
  PrivateSubnetIds:
    Description: Subnet IDs of the private subnets.
    Value:
      !Join [
        ",",
        [!Ref PrivateSubnet, !If [DoAz2, !Ref PrivateSubnet2, !Ref "AWS::NoValue"], !If [DoAz3, !Ref PrivateSubnet3, !Ref "AWS::NoValue"]]
      ]
  PublicRouteTableId:
    Description: Public Route table ID
    Value: !Ref PublicRouteTable
  PrivateRouteTableIds:
    Description: Private Route table IDs
    Value:
      !Join [
        ",",
        [
          !Join ["=", [
            !Select [0, "Fn::GetAZs": !Ref "AWS::Region"],
            !Ref PrivateRouteTable
          ]],
          !If [DoAz2,
               !Join ["=", [!Select [1, "Fn::GetAZs": !Ref "AWS::Region"], !Ref PrivateRouteTable2]],
               !Ref "AWS::NoValue"
          ],
          !If [DoAz3,
               !Join ["=", [!Select [2, "Fn::GetAZs": !Ref "AWS::Region"], !Ref PrivateRouteTable3]],
               !Ref "AWS::NoValue"
          ]
        ]
      ]

AWSTemplateFormatVersion: 2010-09-09
Description: Template for OpenShift Cluster Network Elements (Route53 & LBs)

Parameters:
  ClusterName:
    AllowedPattern: ^([a-zA-Z][a-zA-Z0-9\-]{0,26})$
    MaxLength: 27
    MinLength: 1
    ConstraintDescription: Cluster name must be alphanumeric, start with a letter, and have a maximum of 27 characters.
    Description: A short, representative cluster name to use for host names and other identifying names.
    Type: String
  InfrastructureName:
    AllowedPattern: ^([a-zA-Z][a-zA-Z0-9\-]{0,26})$
    MaxLength: 27
    MinLength: 1
    ConstraintDescription: Infrastructure name must be alphanumeric, start with a letter, and have a maximum of 27 characters.
    Description: A short, unique cluster ID used to tag cloud resources and identify items owned or used by the cluster.
    Type: String
  HostedZoneId:
    Description: The Route53 public zone ID to register the targets with, such as Z21IXYZABCZ2A4.
    Type: String
  HostedZoneName:
    Description: The Route53 zone to register the targets with, such as example.com. Omit the trailing period.
    Type: String
    Default: "example.com"
  PublicSubnets:
    Description: The internet-facing subnets.
    Type: List<AWS::EC2::Subnet::Id>
  PrivateSubnets:
    Description: The internal subnets.
    Type: List<AWS::EC2::Subnet::Id>
  VpcId:
    Description: The VPC-scoped resources will belong to this VPC.
    Type: AWS::EC2::VPC::Id

Metadata:
  AWS::CloudFormation::Interface:
    ParameterGroups:
    - Label:
        default: "Cluster Information"
      Parameters:
      - ClusterName
      - InfrastructureName
    - Label:
        default: "Network Configuration"
      Parameters:
      - VpcId
      - PublicSubnets
      - PrivateSubnets
    - Label:
        default: "DNS"
      Parameters:
      - HostedZoneName
      - HostedZoneId
    ParameterLabels:
      ClusterName:
        default: "Cluster Name"
      InfrastructureName:
        default: "Infrastructure Name"
      VpcId:
        default: "VPC ID"
      PublicSubnets:
        default: "Public Subnets"
      PrivateSubnets:
        default: "Private Subnets"
      HostedZoneName:
        default: "Public Hosted Zone Name"
      HostedZoneId:
        default: "Public Hosted Zone ID"

Resources:
  ExtApiElb:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Name: !Join ["-", [!Ref InfrastructureName, "ext"]]
      IpAddressType: ipv4
      Subnets: !Ref PublicSubnets
      Type: network

  IntApiElb:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Name: !Join ["-", [!Ref InfrastructureName, "int"]]
      Scheme: internal
      IpAddressType: ipv4
      Subnets: !Ref PrivateSubnets
      Type: network

  IntDns:
    Type: "AWS::Route53::HostedZone"
    Properties:
      HostedZoneConfig:
        Comment: "Managed by CloudFormation"
      Name: !Join [".", [!Ref ClusterName, !Ref HostedZoneName]]
      HostedZoneTags:
      - Key: Name
        Value: !Join ["-", [!Ref InfrastructureName, "int"]]
      - Key: !Join ["", ["kubernetes.io/cluster/", !Ref InfrastructureName]]
        Value: "owned"
      VPCs:
      - VPCId: !Ref VpcId
        VPCRegion: !Ref "AWS::Region"

  ExternalApiServerRecord:
    Type: AWS::Route53::RecordSetGroup
    Properties:
      Comment: Alias record for the API server
      HostedZoneId: !Ref HostedZoneId
      RecordSets:
      - Name:
          !Join [
            ".",
            ["api", !Ref ClusterName, !Join ["", [!Ref HostedZoneName, "."]]],
          ]
        Type: A
        AliasTarget:
          HostedZoneId: !GetAtt ExtApiElb.CanonicalHostedZoneID
          DNSName: !GetAtt ExtApiElb.DNSName

  InternalApiServerRecord:
    Type: AWS::Route53::RecordSetGroup
    Properties:
      Comment: Alias record for the API server
      HostedZoneId: !Ref IntDns
      RecordSets:
      - Name:
          !Join [
            ".",
            ["api", !Ref ClusterName, !Join ["", [!Ref HostedZoneName, "."]]],
          ]
        Type: A
        AliasTarget:
          HostedZoneId: !GetAtt IntApiElb.CanonicalHostedZoneID
          DNSName: !GetAtt IntApiElb.DNSName
      - Name:
          !Join [
            ".",
            ["api-int", !Ref ClusterName, !Join ["", [!Ref HostedZoneName, "."]]],
          ]
        Type: A
        AliasTarget:
          HostedZoneId: !GetAtt IntApiElb.CanonicalHostedZoneID
          DNSName: !GetAtt IntApiElb.DNSName

  ExternalApiListener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
      - Type: forward
        TargetGroupArn:
          Ref: ExternalApiTargetGroup
      LoadBalancerArn:
        Ref: ExtApiElb
      Port: 6443
      Protocol: TCP

  ExternalApiTargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      HealthCheckIntervalSeconds: 10
      HealthCheckPath: "/readyz"
      HealthCheckPort: 6443
      HealthCheckProtocol: HTTPS
      HealthyThresholdCount: 2
      UnhealthyThresholdCount: 2
      Port: 6443
      Protocol: TCP
      TargetType: ip
      VpcId:
        Ref: VpcId
      TargetGroupAttributes:
      - Key: deregistration_delay.timeout_seconds
        Value: 60

  InternalApiListener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
      - Type: forward
        TargetGroupArn:
          Ref: InternalApiTargetGroup
      LoadBalancerArn:
        Ref: IntApiElb
      Port: 6443
      Protocol: TCP

  InternalApiTargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      HealthCheckIntervalSeconds: 10
      HealthCheckPath: "/readyz"
      HealthCheckPort: 6443
      HealthCheckProtocol: HTTPS
      HealthyThresholdCount: 2
      UnhealthyThresholdCount: 2
      Port: 6443
      Protocol: TCP
      TargetType: ip
      VpcId:
        Ref: VpcId
      TargetGroupAttributes:
      - Key: deregistration_delay.timeout_seconds
        Value: 60

  InternalServiceInternalListener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
      - Type: forward
        TargetGroupArn:
          Ref: InternalServiceTargetGroup
      LoadBalancerArn:
        Ref: IntApiElb
      Port: 22623
      Protocol: TCP

  InternalServiceTargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      HealthCheckIntervalSeconds: 10
      HealthCheckPath: "/healthz"
      HealthCheckPort: 22623
      HealthCheckProtocol: HTTPS
      HealthyThresholdCount: 2
      UnhealthyThresholdCount: 2
      Port: 22623
      Protocol: TCP
      TargetType: ip
      VpcId:
        Ref: VpcId
      TargetGroupAttributes:
      - Key: deregistration_delay.timeout_seconds
        Value: 60

  RegisterTargetLambdaIamRole:
    Type: AWS::IAM::Role
    Properties:
      RoleName: !Join ["-", [!Ref InfrastructureName, "nlb", "lambda", "role"]]
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
        - Effect: "Allow"
          Principal:
            Service:
            - "lambda.amazonaws.com"
          Action:
          - "sts:AssumeRole"
      Path: "/"
      Policies:
      - PolicyName: !Join ["-", [!Ref InfrastructureName, "master", "policy"]]
        PolicyDocument:
          Version: "2012-10-17"
          Statement:
          - Effect: "Allow"
            Action:
              [
                "elasticloadbalancing:RegisterTargets",
                "elasticloadbalancing:DeregisterTargets",
              ]
            Resource: !Ref InternalApiTargetGroup
          - Effect: "Allow"
            Action:
              [
                "elasticloadbalancing:RegisterTargets",
                "elasticloadbalancing:DeregisterTargets",
              ]
            Resource: !Ref InternalServiceTargetGroup
          - Effect: "Allow"
            Action:
              [
                "elasticloadbalancing:RegisterTargets",
                "elasticloadbalancing:DeregisterTargets",
              ]
            Resource: !Ref ExternalApiTargetGroup

  RegisterNlbIpTargets:
    Type: "AWS::Lambda::Function"
    Properties:
      Handler: "index.handler"
      Role:
        Fn::GetAtt:
        - "RegisterTargetLambdaIamRole"
        - "Arn"
      Code:
        ZipFile: |
          import json
          import boto3
          import cfnresponse
          def handler(event, context):
            elb = boto3.client('elbv2')
            if event['RequestType'] == 'Delete':
              elb.deregister_targets(TargetGroupArn=event['ResourceProperties']['TargetArn'],Targets=[{'Id': event['ResourceProperties']['TargetIp']}])
            elif event['RequestType'] == 'Create':
              elb.register_targets(TargetGroupArn=event['ResourceProperties']['TargetArn'],Targets=[{'Id': event['ResourceProperties']['TargetIp']}])
            responseData = {}
            cfnresponse.send(event, context, cfnresponse.SUCCESS, responseData, event['ResourceProperties']['TargetArn']+event['ResourceProperties']['TargetIp'])
      Runtime: "python3.11"
      Timeout: 120

  RegisterSubnetTagsLambdaIamRole:
    Type: AWS::IAM::Role
    Properties:
      RoleName: !Join ["-", [!Ref InfrastructureName, "subnet-tags-lambda-role"]]
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
        - Effect: "Allow"
          Principal:
            Service:
            - "lambda.amazonaws.com"
          Action:
          - "sts:AssumeRole"
      Path: "/"
      Policies:
      - PolicyName: !Join ["-", [!Ref InfrastructureName, "subnet-tagging-policy"]]
        PolicyDocument:
          Version: "2012-10-17"
          Statement:
          - Effect: "Allow"
            Action:
              [
                "ec2:DeleteTags",
                "ec2:CreateTags"
              ]
            Resource: "arn:aws:ec2:*:*:subnet/*"
          - Effect: "Allow"
            Action:
              [
                "ec2:DescribeSubnets",
                "ec2:DescribeTags"
              ]
            Resource: "*"

  RegisterSubnetTags:
    Type: "AWS::Lambda::Function"
    Properties:
      Handler: "index.handler"
      Role:
        Fn::GetAtt:
        - "RegisterSubnetTagsLambdaIamRole"
        - "Arn"
      Code:
        ZipFile: |
          import json
          import boto3
          import cfnresponse
          def handler(event, context):
            ec2_client = boto3.client('ec2')
            if event['RequestType'] == 'Delete':
              for subnet_id in event['ResourceProperties']['Subnets']:
                ec2_client.delete_tags(Resources=[subnet_id], Tags=[{'Key': 'kubernetes.io/cluster/' + event['ResourceProperties']['InfrastructureName']}]);
            elif event['RequestType'] == 'Create':
              for subnet_id in event['ResourceProperties']['Subnets']:
                ec2_client.create_tags(Resources=[subnet_id], Tags=[{'Key': 'kubernetes.io/cluster/' + event['ResourceProperties']['InfrastructureName'], 'Value': 'shared'}]);
            responseData = {}
            cfnresponse.send(event, context, cfnresponse.SUCCESS, responseData, event['ResourceProperties']['InfrastructureName']+event['ResourceProperties']['Subnets'][0])
      Runtime: "python3.11"
      Timeout: 120

  RegisterPublicSubnetTags:
    Type: Custom::SubnetRegister
    Properties:
      ServiceToken: !GetAtt RegisterSubnetTags.Arn
      InfrastructureName: !Ref InfrastructureName
      Subnets: !Ref PublicSubnets

  RegisterPrivateSubnetTags:
    Type: Custom::SubnetRegister
    Properties:
      ServiceToken: !GetAtt RegisterSubnetTags.Arn
      InfrastructureName: !Ref InfrastructureName
      Subnets: !Ref PrivateSubnets

Outputs:
  PrivateHostedZoneId:
    Description: Hosted zone ID for the private DNS, which is required for private records.
    Value: !Ref IntDns
  ExternalApiLoadBalancerName:
    Description: Full name of the external API load balancer.
    Value: !GetAtt ExtApiElb.LoadBalancerFullName
  InternalApiLoadBalancerName:
    Description: Full name of the internal API load balancer.
    Value: !GetAtt IntApiElb.LoadBalancerFullName
  ApiServerDnsName:
    Description: Full hostname of the API server, which is required for the Ignition config files.
    Value: !Join [".", ["api-int", !Ref ClusterName, !Ref HostedZoneName]]
  RegisterNlbIpTargetsLambda:
    Description: Lambda ARN useful to help register or deregister IP targets for these load balancers.
    Value: !GetAtt RegisterNlbIpTargets.Arn
  ExternalApiTargetGroupArn:
    Description: ARN of the external API target group.
    Value: !Ref ExternalApiTargetGroup
  InternalApiTargetGroupArn:
    Description: ARN of the internal API target group.
    Value: !Ref InternalApiTargetGroup
  InternalServiceTargetGroupArn:
    Description: ARN of the internal service target group.
    Value: !Ref InternalServiceTargetGroup