05. Create an ASG

In this project, we will:

• Create an Application Load Balancer (ALB) and a Target Group.
• Create a Launch Template to define EC2 instance settings.
• Create an Auto Scaling Group (ASG) that automatically manages EC2 instances behind the ALB.
• Test automatic scaling and self-healing behavior.

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🌐 01. Create a Target Group

1. Navigate to EC2 Console → Target Groups → Create Target Group.
2. Target type: Instances
3. Name: demo-tg-alb
4. Protocol: HTTP
5. Port: 80
6. VPC: Select your default VPC.
7. Click Next.
8. Skip registering targets for now.
9. Click Create target group.

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🌍 02. Create an Application Load Balancer (ALB)

1. Navigate to EC2 Console → Load Balancers → Create Load Balancer.
2. Choose Application Load Balancer.
3. Name: demo-alb
4. Scheme: Internet-facing
5. IP address type: IPv4
6. Listeners: Protocol HTTP, Port 80
7. VPC: Select your default VPC.
8. Availability Zones: Select at least two subnets.
9. Under Security Groups, select or create one that allows HTTP (port 80).
10. Target Groups: Select existing target group demo-tg-alb.
11. Click Create Load Balancer.

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🚀 03. Create a Launch Template

1. Navigate to Launch Templates → Create launch template.
2. Enter:
   • Name: DemoLaunchTemplates
   • Version description: v1
3. Under Amazon Machine Image (AMI):
   • Choose Amazon Linux 2.
4. Under Instance type:
   • Select t3.micro.
5. Key pair: Select No key pair.
6. Network settings:
   • Skip subnets.
   • Choose existing Security Group: asg-sg (allows HTTP).
7. Scroll to Advanced details → User data:
   • Paste this sample user data script:

     #!/bin/bash
     yum update -y
     yum install -y httpd
     systemctl start httpd
     systemctl enable httpd
     echo "<h1>Hello World from $(hostname -f)</h1>" > /var/www/html/index.html

8. Click Create launch template.

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🧱 04. Create an Auto Scaling Group (ASG)

1. Navigate to Auto Scaling Groups → Create Auto Scaling Group.
2. Name: DemoASG
3. Launch Template: Select DemoLaunchTemplate.
4. Click Next.

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🌐 05. Configure Network

1. VPC: Select your existing VPC.
2. Subnets: Choose at least two Availability Zones.
3. Leave AZ Distribution: Balanced best effort.
4. Click Next.

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⚖️ 06. Attach Load Balancer

1. Under Load balancing options:
   • Choose Attach to an existing load balancer.
   • Select Target Group: demo-tg-alb.
2. Enable ELB Health Checks.
3. Click Next.

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📊 07. Configure Group Size

1. Desired capacity: 2
2. Minimum capacity: 1
3. Maximum capacity: 4
4. Leave Automatic scaling policies disabled.
5. Instance maintenance policy: No policy
6. Skip:
   • Additional capacity settings
   • Notifications
   • Tags
7. Click Next → Create Auto Scaling Group.

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🔄 08. Verify Instance Creation

1. Go to ASG → Activity tab.
   • Observe creation of two EC2 instances.
2. Go to Instance Management tab:
   • Instances transition from Pending → InService.

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🌍 09. Test Load Balancer

1. Go to Load Balancers → demo-alb.
2. Copy the DNS name.
3. Open it in a browser.
4. You’ll see: Hello World from ip-xx-xx-xx-xx

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🧠 10. Test Auto-Healing

1. Go to EC2 → Select one instance → Terminate.
2. Open ASG → Activity History:

• One instance terminated.
• New instance automatically launched.

3. Observe replacement in Pending → InService state.

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📈 11. Experiment with Scaling

1. Edit ASG Desired Capacity:

• Set to 1 → ASG terminates one instance.
• Set to 4 → ASG launches two more instances.

2. Refresh Target Group to confirm all instances are registered.

This manual apporach is kind of limited if we see.

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✅ Summary

Component	Description
Target Group	Registers EC2 instances for load balancing
Application Load Balancer	Distributes incoming traffic
Launch Template	Defines EC2 configuration and startup script
Auto Scaling Group	Automatically maintains desired instance count
Health Checks	Detect and replace unhealthy instances