terraform - autoscaling group that updates instances on changes

main.tf

   

## random LC name is assigned
resource "aws_launch_configuration" "main" {



      image_id       = "${var.ami}"

      instance_type  = "${var.instance_type}"

      key_name       = "${var.key_name}"

      security_group = ["${var.security_group}"]



    }

## name triggers ASG replacement.
    resource "aws_autoscaling_group" "main" {
      lifecycle { create_before_destroy = true }

      name                 = "someapp - ${aws_launch_configuration.main.name}"
      launch_configuration = "${aws_launch_configuration.main.name}"
      desired_capacity     = "${var.nodes}"
      min_size             = "${var.nodes}"
      max_size             = "${var.nodes}"
      min_elb_capacity     = "${var.nodes}"
      availability_zones   = ["${split(",", var.azs)}"]
      vpc_zone_identifier  = ["${split(",", var.subnet_ids)}"]
      load_balancers       = ["${aws_elb.someapp.id}"]
    }