This gist has the configuration of the terraform which is responsible to create auto-scaling-group and launch configuration.

terrafrom-script-auto-scaling

resource "aws_launch_configuration" "launch_configuration" {
  name = "zox"
  image_id = "${var.ami_ubuntu}"
  instance_type = "${var.instance_type}"
  security_groups = ["${aws_security_group.sg.id}"]
  key_name = "${var.key_name}"
  lifecycle {
    create_before_destroy = true
  }
}

resource "aws_autoscaling_group" "autoscaling_group" {
  name = "asg-${var.environment}"
  launch_configuration = "${aws_launch_configuration.launch_configuration.id}"
  availability_zones = ["${var.az1}","${var.az2}","${var.az3}"]
  min_size = 1
  max_size = 5
  vpc_zone_identifier = ["${aws_subnet.public-subnet.id}"]
  load_balancers = ["${aws_elb.testing-elb.name}"]

  health_check_type = "ELB"

  tag {
    key = "Env"
    value = "${var.environment}"
    propagate_at_launch = true
  }
}