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Exercise: Implementing Load Balancing and Auto Scaling in AWS

This exercise demonstrates how to configure Elastic Load Balancing (ELB) and Auto Scaling in AWS to distribute traffic across multiple instances and automatically adjust capacity based on traffic demand.

Prerequisites

  1. AWS Account.
  2. Basic familiarity with EC2, ELB, and Auto Scaling.
  3. A web server setup script (optional, provided in Step 4).

Objective

  1. Launch multiple EC2 instances behind a Load Balancer (ALB).
  2. Configure Auto Scaling to adjust the number of instances based on demand.
  3. Test the setup by simulating traffic.

Step-by-Step Instructions

Step 1: Launch an EC2 Instance

  1. Go to the EC2 Dashboard and click Launch Instances.
  2. Choose Amazon Linux 2 AMI or Ubuntu.
  3. Select the instance type (t2.micro for free tier).
  4. Configure the instance:
    • Add storage (default is fine).
    • Create or use an existing security group allowing:
      • HTTP (Port 80) from anywhere.
      • SSH (Port 22) from your IP.
  5. Add a tag: Key: Name, Value: WebServer.
  6. Review and launch.

Step 2: Install a Web Server on the Instance

  1. SSH into the instance:

    ssh -i your-key.pem ec2-user@<Public-IP>

  2. Install and start a web server:

    • Amazon Linux: 
      sudo yum update -y
sudo yum install -y httpd
echo "Welcome to $(hostname)!" | sudo tee /var/www/html/index.html
sudo systemctl start httpd
sudo systemctl enable httpd
    • Ubuntu: 
      sudo apt update
sudo apt install -y apache2
echo "Welcome to $(hostname)!" | sudo tee /var/www/html/index.html
sudo systemctl start apache2
sudo systemctl enable apache2

  3. Confirm the web server is running by accessing the public IP in your browser.

Step 3: Create a Target Group for Load Balancing

  1. Navigate to EC2 Dashboard > Target Groups.
  2. Create a new Target Group:
    • Type: Instances.
    • Protocol: HTTP.
    • Port: 80.
    • Health Check Path: /.
  3. Register your running EC2 instance to the target group.

Step 4: Create an Application Load Balancer (ALB)

  1. Go to EC2 Dashboard > Load Balancers.
  2. Click Create Load Balancer > Application Load Balancer.
  3. Configure the ALB:
    • Name: WebApp-ALB.
    • Scheme: Internet-facing.
    • Listeners: HTTP (Port 80).
    • Availability Zones: Select at least two.
  4. Assign a security group allowing HTTP traffic (Port 80).
  5. Register the target group created in Step 3.
  6. Complete the setup and note the ALB DNS name.

Step 5: Configure Auto Scaling

  1. Navigate to Auto Scaling Groups.
  2. Click Create Auto Scaling Group.
  3. Configure the Auto Scaling group:
    • Launch Template or Configuration:
      • Create a new one with the same AMI and instance type as the initial EC2 instance.
    • VPC and Subnets: Use the same as the Load Balancer.
    • Attach the Auto Scaling group to the target group.
  4. Set Scaling Policies:
    • Minimum Instances: 1
    • Desired Instances: 1
    • Maximum Instances: 3
    • Add a scaling policy based on CPU utilization:
      • Target Tracking Scaling Policy: Target value of 50% CPU utilization.

Step 6: Test the Setup

  1. Open the ALB DNS name in your browser. It should load the web page served by one of the instances.
  2. Simulate high traffic by using a load testing tool (e.g., ab or locust): 
    ab -n 10000 -c 100 http://<ALB-DNS-Name>/
  3. Monitor Auto Scaling:
    • Go to the Auto Scaling group and observe the number of instances increasing.
    • Check the target group to see healthy instances being added.

Step 7: Clean Up

  1. Terminate the EC2 instances.
  2. Delete the Load Balancer.
  3. Delete the Target Group.
  4. Delete the Auto Scaling group.