Note: The Terraform configurations included in the demo does NOT involve database provisioning. The app tier of this demo is currently using a dummy httpd server, and does not involve dynamic data.

terraform-aws-modules/vpc/aws, terraform-aws-modules/security-group/aws, terraform-aws-modules/ec2-instance/aws, terraform-aws-modules/alb/aws

1. Initiate Terraform working directory. Config Terraform version and provider version. versions.tf, terraform.tfvars

2. Create a VPC using Terraform VPC module. vpc.tf, vpc-variables.tf, vpc.auto.tfvars, vpc-outputs.tf

3. Create Private EC2 instances, Bastion Host and Security Groups for them respectively.

   Note: In later steps, the Private EC2 instances would be replaced with ASG launch template.

   • Create Security Groups using Terraform Security Group module.

     securitygroup-bastion.tf, securitygroup-private.tf, securitygroup-variables.tf, securitygroup-outputs.tf

   • Get AMI dynamically using Datasource and create EC2 instances as Bastion using Terraform EC2 Module. datasource-ami.tf,ec2-bastion.tf, ec2-variables.tf, ec2.auto.tfvars, ec2-outputs.tf

   • Create a private EC2 instance for each private subnet using Terraform EC2 Module.

     ec2-private.tf, ec2-variables.tf, ec2.auto.tfvars, ec2-outputs.tf

   • Create EIP and associate it with Bastion

     eip.tf, ec2-outputs.tf

4. Create ALB using Terraform Load Balancer Module.

   alb.tf, alb-variables.tf, alb-ouputs.tf, securitygroup-lb.tf

5. Create Launch Template for private instances and create ASG. asg.tf, asg-variables.tf,asg-outputs.tf Note: Remove the private instances created in previous steps.

• Handle certain instance types not available in some azs.
• Add Autoscaling notifications through SNS.
• Add Target Tracking Scaling Policies for ASG to scale base on CPU utilization and ALB target request count.
• CloudWatch Monitoring.