tutorial.yaml

AWSTemplateFormatVersion: 2010-09-09

Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16

  PublicSubnetA:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.0.0/24
      AvailabilityZone: !Select [0, !GetAZs ]

  PublicSubnetB:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.1.0/24
      AvailabilityZone: !Select [1, !GetAZs ]

  PrivateSubnetA:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.2.0/24
      AvailabilityZone: !Select [0, !GetAZs ]

  PrivateSubnetB:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.3.0/24
      AvailabilityZone: !Select [1, !GetAZs ]

  AppLaunchConfig:
    Type: AWS::AutoScaling::LaunchConfiguration
    Properties:
      ImageId: ami-0389b2a3c4948b1a0
      InstanceType: t2.micro
      SecurityGroups:
        - !Ref InstanceSecurityGroup
      UserData:
        Fn::Base64:
          Fn::Sub: |
            #!/bin/bash -xe
            yum update -y
            yum install -y httpd
            systemctl start httpd
            systemctl enable httpd
            echo "Hello from $(hostname -f)" > /var/www/html/index.html

  InstanceSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Letting HTTP into our instance
      VpcId: !Ref VPC
      SecurityGroupIngress:
        - FromPort: 80
          IpProtocol: tcp
          ToPort: 80
          SourceSecurityGroupId: !Ref ApplicationLoadBalancerSecurityGroup

  InternetGateway:
    Type: AWS::EC2::InternetGateway
    DependsOn: VPC

  AttachGateway:
    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: AttachGateway
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway

  PublicSubnetARouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId: !Ref PublicSubnetA
      RouteTableId: !Ref PublicRouteTable

  PublicSubnetBRouteTableAssociation:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId: !Ref PublicSubnetB
      RouteTableId: !Ref PublicRouteTable

  ApplicationLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      SecurityGroups:
        - !Ref ApplicationLoadBalancerSecurityGroup
      Subnets:
        - !Ref PublicSubnetA
        - !Ref PublicSubnetB

  ApplicationLoadBalancerSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: SSH and HTTP
      VpcId: !Ref VPC
      SecurityGroupIngress:
        - CidrIp: 0.0.0.0/0
          FromPort: 80
          IpProtocol: tcp
          ToPort: 80

  Listener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
        - Type: forward
          TargetGroupArn: !Ref TargetGroup
      LoadBalancerArn: !Ref ApplicationLoadBalancer
      Port: 80
      Protocol: HTTP

  TargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      Port: 80
      Protocol: HTTP
      VpcId: !Ref VPC

  AutoScalingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      LaunchConfigurationName: !Ref AppLaunchConfig
      VPCZoneIdentifier:
        - !Ref PublicSubnetA
        - !Ref PublicSubnetB
      DesiredCapacity: 3
      MinSize: 3
      MaxSize: 3
      TargetGroupARNs:
        - !Ref TargetGroup

  Database:
    Type: AWS::RDS::DBInstance
    Properties:
      VPCSecurityGroups:
        - !Ref DbSecurityGroup
      AllocatedStorage: "10"
      DBSubnetGroupName: !Ref DbSubnetGroup
      DBInstanceClass: "db.t2.micro"
      Engine: "postgres"
      MasterUsername: Username
      MasterUserPassword: Password
      MultiAZ: true

  DbSubnetGroup:
    Type: "AWS::RDS::DBSubnetGroup"
    Properties:
      DBSubnetGroupDescription: DBSubnetGroup
      SubnetIds: # (6)
        - !Ref PrivateSubnetA
        - !Ref PrivateSubnetB

  DbSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Database
      VpcId: !Ref VPC
      SecurityGroupIngress:
        - FromPort: -1
          IpProtocol: -1
          ToPort: -1
          SourceSecurityGroupId: !Ref InstanceSecurityGroup

can you tell me why this script is not working for me