AWSTemplateFormatVersion: 2010-09-09

Description: Reference Architecture to host Drupal on AWS - Creates an Application Load Balancer

Metadata:

  AWS::CloudFormation::Interface:
    ParameterGroups:
    - Label:
        default: ALB Parameters
      Parameters:
        - Vpc
        - PublicAlbAcmCertificate
        - PublicAlbSecurityGroup
        - PublicSubnet0
        - PublicSubnet1
        - PublicSubnet2
    ParameterLabels:
      Vpc:
        default: Vpc Id
      PublicAlbAcmCertificate:
        default: ALB Certificate ARN
      PublicAlbSecurityGroup:
        default: Public ALB Security Group
      PublicSubnet0:
        default: Public Subnet for AZ 0
      PublicSubnet1:
        default: Public Subnet for AZ 1
      PublicSubnet2:
        default: Public Subnet for AZ 2

Parameters:

  PublicAlbAcmCertificate:
    AllowedPattern: ^$|(arn:aws:acm:)([a-z0-9/:-])*([a-z0-9])$
    Description: '[ Optional ] The AWS Certification Manager certificate ARN for the ALB certificate - this certificate should be created in the region you wish to run the ALB and must reference the Drupal domain name you use below.'
    Type: String
  PublicAlbSecurityGroup:
    Description: Select the ALB security group.
    Type: AWS::EC2::SecurityGroup::Id
  PublicSubnet0:
    Description: Select an existing public subnet for AZ 0.
    Type: AWS::EC2::Subnet::Id
  PublicSubnet1:
    Description: Select an existing public subnet for AZ 1.
    Type: AWS::EC2::Subnet::Id
  PublicSubnet2:
    Description: Select an existing public subnet for AZ 2.
    Type: AWS::EC2::Subnet::Id
  Vpc:
    Description: Select an existing Vpc
    Type: AWS::EC2::VPC::Id

Conditions:

  SslCertificate:
    !Not [!Equals [ '', !Ref PublicAlbAcmCertificate ] ]
  NoSslCertificate:
    !Equals [ '', !Ref PublicAlbAcmCertificate ]
  MoreThan2AZ:
    !Or [
      !Equals [ !Ref 'AWS::Region', us-east-1 ],
      !Equals [ !Ref 'AWS::Region', us-east-2 ],
      !Equals [ !Ref 'AWS::Region', us-west-2 ],
      !Equals [ !Ref 'AWS::Region', eu-west-1 ],
      !Equals [ !Ref 'AWS::Region', sa-east-1 ],
      !Equals [ !Ref 'AWS::Region', ap-northeast-1 ],
      !Equals [ !Ref 'AWS::Region', ap-southeast-2 ]
    ]

Resources:
  
  PublicAlbListenerNoSslCertificate:
    Type : AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
      - Type: forward
        TargetGroupArn: !Ref PublicAlbTargetGroup
      LoadBalancerArn: !Ref PublicApplicationLoadBalancer
      Port: 80
      Protocol: HTTP
  PublicAlbListenerSslCertificate:
    Condition: SslCertificate
    Type : AWS::ElasticLoadBalancingV2::Listener
    Properties:
      Certificates:
      - CertificateArn: !Ref PublicAlbAcmCertificate
      DefaultActions:
      - Type: forward
        TargetGroupArn: !Ref PublicAlbTargetGroup
      LoadBalancerArn: !Ref PublicApplicationLoadBalancer
      Port: 443
      Protocol: HTTPS
  PublicApplicationLoadBalancer: 
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Scheme: internet-facing
      Subnets:
        !If [
          MoreThan2AZ,
          [ !Ref PublicSubnet0, !Ref PublicSubnet1, !Ref PublicSubnet2 ],
          [ !Ref PublicSubnet0, !Ref PublicSubnet1 ]
        ]
      LoadBalancerAttributes:
      - Key: idle_timeout.timeout_seconds
        Value: 60
      SecurityGroups:
      - !Ref PublicAlbSecurityGroup
      Tags:
      - Key: Name
        Value: !Join [ '', [ 'Public ALB / ', !Ref 'AWS::StackName' ] ]
  PublicAlbTargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      HealthCheckIntervalSeconds: 30
      HealthCheckPath: /
      HealthCheckTimeoutSeconds: 5
      Name: 'DrupalPublicAlb'
      Port: 80
      Protocol: HTTP
      Tags:
      - Key: Name
        Value: !Join [ '', [ 'Public ALB / ', !Ref 'AWS::StackName' ] ]
      UnhealthyThresholdCount: 5
      VpcId: !Ref Vpc

Outputs:

  PublicAlbTargetGroupArn:
    Value:
      !Ref PublicAlbTargetGroup
  PublicAlbCanonicalHostedZoneId:
    Value:
      !GetAtt PublicApplicationLoadBalancer.CanonicalHostedZoneID
  PublicAlbDnsName:
    Value:
      !GetAtt PublicApplicationLoadBalancer.DNSName
  PublicAlbHostname:
    Value:
      !If [ NoSslCertificate, !Join [ '', [ 'http://', !GetAtt PublicApplicationLoadBalancer.DNSName ] ], !Join [ '', [ 'https://', !GetAtt PublicApplicationLoadBalancer.DNSName ] ] ]
  SslCertificate:
    Value:
      !If [ SslCertificate, True, False ]