AWS EC2 Instance Not Launched in an Auto Scaling Group


Amazon Elastic Compute Cloud (EC2) provides resizable compute capacity in the cloud. An Auto Scaling Group (ASG) automatically adjusts the number of EC2 instances in response to changes in demand, ensuring high availability and managing the instance lifecycle. If an EC2 instance is not launched within an ASG, it might not benefit from the fault tolerance, automatic scaling, and scheduled scaling that ASGs provide. This could lead to potential service disruptions, increased manual intervention, and inconsistent infrastructure management.


1. Launch EC2 Instances within an Auto Scaling Group:

AWS Management Console:
  • Navigate to the EC2 service in the AWS Console.
  • In the EC2 Dashboard's left navigation pane, click on Auto Scaling Groups.
  • Click on Create Auto Scaling group.
  • Choose a launch template or launch configuration that corresponds to the desired EC2 instance configuration.
  • Follow the creation wizard, specifying the desired capacity, scaling policies, and other ASG settings.
  • After the ASG is created, it will automatically launch instances as per the desired capacity.

To create an Auto Scaling Group using a launch configuration:

aws autoscaling create-auto-scaling-group --auto-scaling-group-name ASG_NAME --launch-configuration-name LAUNCH_CONFIG_NAME --min-size MIN_INSTANCES --max-size MAX_INSTANCES --availability-zones AZ_LIST

Replace the placeholders (ASG_NAME, LAUNCH_CONFIG_NAME, etc.) with appropriate values.


Using Terraform, you can define an Auto Scaling Group as follows:

resource "aws_launch_configuration" "example" {
  # ... launch configuration properties ...

resource "aws_autoscaling_group" "example" {
  launch_configuration =
  min_size             = MIN_INSTANCES
  max_size             = MAX_INSTANCES

  availability_zones = ["us-west-2a", "us-west-2b"]
  # ... other ASG configurations ...

Ensure you replace placeholders (MIN_INSTANCES, MAX_INSTANCES, etc.) with appropriate values.


It's recommended to launch EC2 instances within an Auto Scaling Group when high availability, fault tolerance, or automatic scaling is a requirement. ASGs also provide lifecycle hooks, health checks, and integration with load balancers, further enhancing the management and reliability of your EC2 instances. Regularly review standalone EC2 instances to determine if they would benefit from being part of an ASG. Always consider cost implications, as ASGs might launch additional instances based on the specified policies.