Terraform ECS EC2 ASG how to zero task instance stop

autoscaling code

module "autoscaling" {
  source  = "terraform-aws-modules/autoscaling/aws"
  version = "~> 6.5"

  name = "${local.name}-asg"

  security_groups = [module.autoscaling_sg.security_group_id]
  ignore_desired_capacity_changes = true

  image_id = jsondecode(data.aws_ssm_parameter.ecs_optimized_ami.value)["image_id"]
  instance_type = "t4g.small"
  key_name = "dpgg-match"

  user_data = base64encode(local.user_data)
  
  network_interfaces = [
    {
      associate_public_ip_address = true
      delete_on_termination       = true
    }
  ]

  block_device_mappings = [
    {
      device_name = "/dev/xvda"
      ebs = {
        volume_size = 40
        volume_type = "gp2"
      }
    }
  ]

  create_iam_instance_profile = true
  iam_role_name               = local.name
  iam_role_description        = "ECS role for ${local.name}"
  iam_role_policies = {
    AmazonEC2ContainerServiceforEC2Role = "arn:aws:iam::aws:policy/service-role/AmazonEC2ContainerServiceforEC2Role"
    AmazonSSMManagedInstanceCore        = "arn:aws:iam::aws:policy/AmazonSSMManagedInstanceCore"
  }

  vpc_zone_identifier = module.vpc.public_subnets
  health_check_type   = "EC2"
  min_size            = 0
  max_size            = 3
  desired_capacity    = 1

  termination_policies = ["OldestInstance"]

  autoscaling_group_tags = {
    ECS = "True"
    Terraform = "True"
  }

  tags = local.tags
}

How can I automatically stop instances with zero task running in the ECS EC2 Autoscaling Group?

When I searched on Google, I was told to change termination_policies to OldestInstance option, but it was not effective.

The OldestInstance option tells ASG in which order to terminate instances, but not when. What you are looking for is ECS Capacity Providers:

> When you use an Auto Scaling group capacity provider with managed scaling turned on, Amazon ECS creates two custom CloudWatch metrics and a target tracking scaling policy that attaches to your Auto Scaling group. Amazon ECS then manages the scale-in and scale-out actions of the Auto Scaling group based on the load your tasks put on your cluster.

More details: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/cluster-auto-scaling.html