Create AWS Application Load Balancer Using CloudFormation

 

In this post we will create an AWS application load balancer using CloudFormation.

The EC2 servers

In the previous post, we have presented a creation of VPC and EC2 based web server. To create an application load balancer we need to use at least two different availability zones. I have modified the previous template to create two EC2 machines in two availability zones.

Parameters:
  LatestAmiId:
    Type: AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>
    Default: /aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      Tags:
        - Key: Name
          Value: po-vpc
  Subnet1:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.1.0/24
      AvailabilityZone: us-east-1a
      Tags:
        - Key: Name
          Value: po-subnet1
  Subnet2:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.2.0/24
      AvailabilityZone: us-east-1b
      Tags:
        - Key: Name
          Value: po-subnet2
  InternetGateway:
    Type: AWS::EC2::InternetGateway
    DependsOn: VPC
    Properties:
      Tags:
        - Key: Name
          Value: po-route-table
  AttachGateway:
    Type: AWS::EC2::VPCGatewayAttachment
    Properties:
      VpcId: !Ref VPC
      InternetGatewayId: !Ref InternetGateway
  RouteTable1:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: po-route-table1
  RouteTable2:
    Type: AWS::EC2::RouteTable
    Properties:
      VpcId: !Ref VPC
      Tags:
        - Key: Name
          Value: po-route-table2
  RouteTableAssociate1:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId:
        Ref: Subnet1
      RouteTableId:
        Ref: RouteTable1
  RouteTableAssociate2:
    Type: AWS::EC2::SubnetRouteTableAssociation
    Properties:
      SubnetId:
        Ref: Subnet2
      RouteTableId:
        Ref: RouteTable2
  PublicRoute1:
    Type: AWS::EC2::Route
    DependsOn: AttachGateway
    Properties:
      RouteTableId: !Ref RouteTable1
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway
  PublicRoute2:
    Type: AWS::EC2::Route
    DependsOn: AttachGateway
    Properties:
      RouteTableId: !Ref RouteTable2
      DestinationCidrBlock: 0.0.0.0/0
      GatewayId: !Ref InternetGateway
  SecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      VpcId: !Ref VPC
      GroupDescription: the security group
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          CidrIp: 0.0.0.0/0
        - IpProtocol: tcp
          FromPort: 22
          ToPort: 22
          CidrIp: 0.0.0.0/0
      Tags:
        - Key: Name
          Value: po-security-group
  Server1:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.micro
      ImageId: !Ref LatestAmiId
      SubnetId: !Ref Subnet1
      KeyName: PO
      SecurityGroupIds:
        - !Ref SecurityGroup
      Tags:
        - Key: Name
          Value: po-server1
  Server2:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.micro
      ImageId: !Ref LatestAmiId
      SubnetId: !Ref Subnet2
      KeyName: PO
      SecurityGroupIds:
        - !Ref SecurityGroup
      Tags:
        - Key: Name
          Value: po-server2
  ElasticIP1:
    Type: AWS::EC2::EIP
    Properties:
      Domain: vpc
      InstanceId: !Ref Server1
      Tags:
        - Key: Name
          Value: po-elastic-ip1
  ElasticIP2:
    Type: AWS::EC2::EIP
    Properties:
      Domain: vpc
      InstanceId: !Ref Server2
      Tags:
        - Key: Name
          Value: po-elastic-ip2

The Application Load Balancer

Now we have 2 EC2 servers running in two different availability zones, and we can configure the application load balancer.

ApplicationLoadBalancer:
  Type: AWS::ElasticLoadBalancingV2::LoadBalancer
  DependsOn: AttachGateway
  Properties:
    IpAddressType: ipv4
    Scheme: internet-facing
    SecurityGroups:
      - !Ref SecurityGroup
    Subnets:
      - !Ref Subnet1
      - !Ref Subnet2
    Type: application
    Tags:
      - Key: Name
        Value: po-alb

The application load balancer is connected to the two subnets, each one in a different availability zone. Next we configure the targets for the application load balancer to be the two EC2 servers.

TargetGroup:
  Type: AWS::ElasticLoadBalancingV2::TargetGroup
  Properties:
    Port: 80
    Protocol: HTTP
    TargetType: instance
    VpcId: !Ref VPC
    Targets:
      - Id: !Ref Server1
      - Id: !Ref Server2
    Tags:
      - Key: Name
        Value: po-alb-tg

The last step is to configure a listener that the application load balancer will serve request on its port.

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

Final Note

We have presented how to configure an application load balancer on AWS using the AWS CloudFormation. In the next post, we will configure a CloudFront CDN for it.