1+ # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2+ # CREATE ALL THE RESOURCES TO DEPLOY AN APP IN AN AUTO SCALING GROUP WITH AN ELB
3+ # This template runs a simple "Hello, World" web server in Auto Scaling Group (ASG) with an Elastic Load Balancer
4+ # (ELB) in front of it to distribute traffic across the EC2 Instances in the ASG.
5+ # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
6+
7+ # ------------------------------------------------------------------------------
8+ # CONFIGURE OUR AWS CONNECTION
9+ # ------------------------------------------------------------------------------
10+
11+ provider "aws" {
12+ region = " us-east-1"
13+ }
14+
15+ # ---------------------------------------------------------------------------------------------------------------------
16+ # GET THE LIST OF AVAILABILITY ZONES IN THE CURRENT REGION
17+ # Every AWS accout has slightly different availability zones in each region. For example, one account might have
18+ # us-east-1a, us-east-1b, and us-east-1c, while another will have us-east-1a, us-east-1b, and us-east-1d. This resource
19+ # queries AWS to fetch the list for the current account and region.
20+ # ---------------------------------------------------------------------------------------------------------------------
21+
22+ data "aws_availability_zones" "all" {}
23+
24+ # ---------------------------------------------------------------------------------------------------------------------
25+ # CREATE THE AUTO SCALING GROUP
26+ # ---------------------------------------------------------------------------------------------------------------------
27+
28+ resource "aws_autoscaling_group" "example" {
29+ launch_configuration = " ${ aws_launch_configuration . example . id } "
30+ availability_zones = " ${ data . aws_availability_zones . all . names } "
31+
32+ min_size = 2
33+ max_size = 10
34+
35+ load_balancers = " ${ aws_elb . example . name } "
36+ health_check_type = " ELB"
37+
38+ tag {
39+ key = " Name"
40+ value = " terraform-asg-example"
41+ propagate_at_launch = true
42+ }
43+ }
44+
45+ # ---------------------------------------------------------------------------------------------------------------------
46+ # CREATE A LAUNCH CONFIGURATION THAT DEFINES EACH EC2 INSTANCE IN THE ASG
47+ # ---------------------------------------------------------------------------------------------------------------------
48+
49+ resource "aws_launch_configuration" "example" {
50+ # Ubuntu Server 14.04 LTS (HVM), SSD Volume Type in us-east-1
51+ image_id = " ami-2d39803a"
52+ instance_type = " t2.micro"
53+ security_groups = " ${ aws_security_group . instance . id } "
54+
55+ user_data = <<- EOF
56+ #!/bin/bash
57+ echo "Hello, World" > index.html
58+ nohup busybox httpd -f -p "${ var . server_port } " &
59+ EOF
60+
61+ # Important note: whenever using a launch configuration with an auto scaling group, you must set
62+ # create_before_destroy = true. However, as soon as you set create_before_destroy = true in one resource, you must
63+ # also set it in every resource that it depends on, or you'll get an error about cyclic dependencies (especially when
64+ # removing resources). For more info, see:
65+ #
66+ # https://www.terraform.io/docs/providers/aws/r/launch_configuration.html
67+ # https://terraform.io/docs/configuration/resources.html
68+ lifecycle {
69+ create_before_destroy = true
70+ }
71+ }
72+
73+ # ---------------------------------------------------------------------------------------------------------------------
74+ # CREATE THE SECURITY GROUP THAT'S APPLIED TO EACH EC2 INSTANCE IN THE ASG
75+ # ---------------------------------------------------------------------------------------------------------------------
76+
77+ resource "aws_security_group" "instance" {
78+ name = " terraform-example-instance"
79+
80+ # Inbound HTTP from anywhere
81+ ingress {
82+ from_port = " ${ var . server_port } "
83+ to_port = " ${ var . server_port } "
84+ protocol = " tcp"
85+ cidr_blocks = " 0.0.0.0/0"
86+ }
87+
88+ # aws_launch_configuration.launch_configuration in this module sets create_before_destroy to true, which means
89+ # everything it depends on, including this resource, must set it as well, or you'll get cyclic dependency errors
90+ # when you try to do a terraform destroy.
91+ lifecycle {
92+ create_before_destroy = true
93+ }
94+ }
95+
96+ # ---------------------------------------------------------------------------------------------------------------------
97+ # CREATE AN ELB TO ROUTE TRAFFIC ACROSS THE AUTO SCALING GROUP
98+ # ---------------------------------------------------------------------------------------------------------------------
99+
100+ resource "aws_elb" "example" {
101+ name = " terraform-asg-example"
102+ security_groups = " ${ aws_security_group . elb . id } "
103+ availability_zones = " ${ data . aws_availability_zones . all . names } "
104+
105+ health_check {
106+ healthy_threshold = 2
107+ unhealthy_threshold = 2
108+ timeout = 3
109+ interval = 30
110+ target = " HTTP:${ var . server_port } /"
111+ }
112+
113+ # This adds a listener for incoming HTTP requests.
114+ listener {
115+ lb_port = 80
116+ lb_protocol = " http"
117+ instance_port = " ${ var . server_port } "
118+ instance_protocol = " http"
119+ }
120+ }
121+
122+ # ---------------------------------------------------------------------------------------------------------------------
123+ # CREATE A SECURITY GROUP THAT CONTROLS WHAT TRAFFIC AN GO IN AND OUT OF THE ELB
124+ # ---------------------------------------------------------------------------------------------------------------------
125+
126+ resource "aws_security_group" "elb" {
127+ name = " terraform-example-elb"
128+
129+ # Inbound HTTP from anywhere
130+ ingress {
131+ from_port = 80
132+ to_port = 80
133+ protocol = " tcp"
134+ cidr_blocks = " 0.0.0.0/0"
135+ }
136+ }
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