main.tf

resource "aws_vpc" "web" {
  cidr_block = "10.0.0.0/16"
}

resource "aws_subnet" "web-2a" {
  vpc_id = "${aws_vpc.web.id}"
  cidr_block = "10.0.1.0/24"
  availability_zone = "us-west-2a"
}
resource "aws_subnet" "web-2b" {
  vpc_id = "${aws_vpc.web.id}"
  cidr_block = "10.0.2.0/24"
  availability_zone = "us-west-2b"
}
resource "aws_subnet" "web-2c" {
  vpc_id = "${aws_vpc.web.id}"
  cidr_block = "10.0.3.0/24"
  availability_zone = "us-west-2c"
}

resource "aws_launch_configuration" "web" {
  /* old ami */
  /* image_id = "ami-21f78e11" */
  /* new ami */
  image_id = "ami-03d2fd33"
  instance_type = "t1.micro"
  user_data = "foobar-user-data-change"
  lifecycle {
    create_before_destroy = true
  }
}

resource "aws_autoscaling_group" "web" {
  name = "web"
  min_size = 3
  max_size = 3
  availability_zones = ["us-west-2a", "us-west-2b", "us-west-2c"]
  launch_configuration = "${aws_launch_configuration.web.id}"
  vpc_zone_identifier = [
    "${aws_subnet.web-2a.id}",
    "${aws_subnet.web-2b.id}",
    "${aws_subnet.web-2c.id}",
  ]

}