My Cloud Journey — Week 6 | Advanced AWS Part 2 | Application Load Balancer deployment using CloudFormation

In my previous post, I covered some important concepts that I found interesting during my exploration of advanced AWS topics. In this post, I will go into a specific exercise I completed using AWSCloudFormation, with subsequent posts focusing on additional exercises.

The task in this exercise is to set up a web infrastructure with an Application Load Balancer (ALB) distributing traffic across two EC2 instances in separate Availability Zones (AZs).

Here is the CloudFormation template that I used, written in YAML format.

The template sets up a Virtual Private Cloud (VPC) with public and private subnets across two Availability Zones (AZs), an Internet Gateway, routing tables, and an Application Load Balancer (ALB) with two target EC2 instances.

AWSTemplateFormatVersion: '2010-09-09'
Description: 'CloudFormation for ALB'

Resources:
  # My VPC
  MyVPC:
    Type: 'AWS::EC2::VPC'
    Properties:
      CidrBlock: '172.16.0.0/16'
      EnableDnsSupport: true
      EnableDnsHostnames: true
      Tags:
        - Key: Name
          Value: MyVPC

  # Public Subnet in AZ 1
  PublicSubnet1A:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref MyVPC
      CidrBlock: '172.16.1.0/24'
      AvailabilityZone: !Select [0, !GetAZs '']
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: PublicSubnet1A

  # App Private Subnet in AZ 1
  AppPrivateSubnet1A:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref MyVPC
      CidrBlock: '172.16.2.0/24'
      AvailabilityZone: !Select [0, !GetAZs '']
      Tags:
        - Key: Name
          Value: AppPrivateSubnet1A

  # Data Private Subnet in AZ 1
  DataPrivateSubnet1A:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref MyVPC
      CidrBlock: '172.16.3.0/24'
      AvailabilityZone: !Select [0, !GetAZs '']
      Tags:
        - Key: Name
          Value: DataPrivateSubnet1A

  # Public Subnet in AZ 2
  PublicSubnet2B:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref MyVPC
      CidrBlock: '172.16.4.0/24'
      AvailabilityZone: !Select [1, !GetAZs '']
      MapPublicIpOnLaunch: true
      Tags:
        - Key: Name
          Value: PublicSubnet2B

  # App Private Subnet in AZ 2
  AppPrivateSubnet2B:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref MyVPC
      CidrBlock: '172.16.5.0/24'
      AvailabilityZone: !Select [1, !GetAZs '']
      Tags:
        - Key: Name
          Value: AppPrivateSubnet2B

  # Data Private Subnet in AZ 2
  DataPrivateSubnet2B:
    Type: 'AWS::EC2::Subnet'
    Properties:
      VpcId: !Ref MyVPC
      CidrBlock: '172.16.6.0/24'
      AvailabilityZone: !Select [1, !GetAZs '']
      Tags:
        - Key: Name
          Value: DataPrivateSubnet2B

# Internet Gateway IGW
  InternetGateway:
    Type: 'AWS::EC2::InternetGateway'
    Properties:
      Tags:
        - Key: Name
          Value: MyVPC-IGW

# Attach Gateway  
  AttachGateway:
    Type: 'AWS::EC2::VPCGatewayAttachment'
    Properties:
      VpcId: !Ref MyVPC
      InternetGatewayId: !Ref InternetGateway

# Route Table
  PublicRouteTable:
    Type: 'AWS::EC2::RouteTable'
    Properties:
      VpcId: !Ref MyVPC
      Tags:
        - Key: Name
          Value: PublicRouteTable

# Public Route
  PublicRoute:
    Type: 'AWS::EC2::Route'
    DependsOn: AttachGateway
    Properties:
      RouteTableId: !Ref PublicRouteTable
      DestinationCidrBlock: '0.0.0.0/0'
      GatewayId: !Ref InternetGateway

# Public Subnet Association
  PublicSubnet1ARouteTableAssociation:
    Type: 'AWS::EC2::SubnetRouteTableAssociation'
    Properties:
      SubnetId: !Ref PublicSubnet1A
      RouteTableId: !Ref PublicRouteTable

# Application Load Balancer
  MyLoadBalancer:
    Type: 'AWS::ElasticLoadBalancingV2::LoadBalancer'
    Properties:
      Subnets:
        - !Ref PublicSubnet1A
        - !Ref PublicSubnet2B
      SecurityGroups:
        - !Ref WebServerSecurityGroup

# Target Group for ALB
  MyTargetGroup:
    Type: 'AWS::ElasticLoadBalancingV2::TargetGroup'
    Properties:
      Port: 80
      Protocol: HTTP
      VpcId: !Ref MyVPC
      Targets:
        - Id: !Ref WebServerInstance1A
          Port: 80
        - Id: !Ref WebServerInstance2B
          Port: 80

# Listener for ALB
  MyListener:
    Type: 'AWS::ElasticLoadBalancingV2::Listener'
    Properties:
      DefaultActions:
        - Type: forward
          TargetGroupArn: !Ref MyTargetGroup
      LoadBalancerArn: !Ref MyLoadBalancer
      Port: 80
      Protocol: HTTP

# Web Server Security Group
  WebServerSecurityGroup:
    Type: 'AWS::EC2::SecurityGroup'
    Properties:
      GroupDescription: Enable HTTP access via port 80
      VpcId: !Ref MyVPC
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: '80'
          ToPort: '80'
          CidrIp: 0.0.0.0/0

# WebServerInstance1A:
  WebServerInstance1A:
    Type: 'AWS::EC2::Instance'
    Properties:
      ImageId: 'ami-0bb84b8ffd87024d8'
      InstanceType: 't2.micro'
      SubnetId: !Ref PublicSubnet1A
      SecurityGroupIds:
        - !Ref WebServerSecurityGroup
      Tags:
        - Key: Name
          Value: WebServerInstance1A
      UserData:
        Fn::Base64:  !Sub  |
          #!/bin/bash
          yum update -y
          yum install -y httpd
          systemctl start httpd
          systemctl enable httpd
          echo "Hello World from WebServerInstance 1A" > /var/www/html/index.html

# WebServerInstance2B:
  WebServerInstance2B:
    Type: 'AWS::EC2::Instance'
    Properties:
      ImageId: 'ami-0bb84b8ffd87024d8'
      InstanceType: 't2.micro'
      SubnetId: !Ref PublicSubnet2B
      SecurityGroupIds:
        - !Ref WebServerSecurityGroup
      Tags:
        - Key: Name
          Value: WebServerInstance2B
      UserData:
        Fn::Base64:  !Sub  |
          #!/bin/bash
          yum update -y
          yum install -y httpd
          systemctl start httpd
          systemctl enable httpd
          echo "Hello World from WebServerInstance 2B" > /var/www/html/index.html

Here’s a breakdown of the key components:

1. VPC and Subnets: The template creates a VPC with a CIDR block of 172.16.0.0/16. It then defines six subnets: two public subnets (one in each AZ), two private app subnets, and two private data subnets.
2. Internet Gateway: An Internet Gateway is created and attached to the VPC, allowing resources in the public subnets to access the Internet.
3. Route Tables: A public route table is created, and a route is added to send all internet-bound traffic (0.0.0.0/0) through the Internet Gateway. The public subnets are associated with this route table.
4. Security Group: A security group is created to allow inbound HTTP traffic (port 80) from anywhere (0.0.0.0/0) to the web servers.
5. Application Load Balancer (ALB): An ALB is created and placed in the public subnets. It listens for incoming HTTP traffic on port 80.
6. Target Group: A target group is created for the ALB, which will route traffic to the registered targets (EC2 instances).
7. EC2 Instances: Two EC2 instances are launched, one in each public subnet. These instances will serve as the web servers behind the ALB. The instances are configured with a User Data script that installs Apache HTTP Server and creates a simple “Hello World” index.html file.

Here’s a screenshot of the deployed stack.

Join me next time as I share more CloudFormation deployments!

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