Merge ASG and LC submodules into one, added conditional creation (terraform-aws-modules#10)

* Merge ASG and LC submodules into one, added conditional creation

* Merged ASG and LC into single module

Author: antonbabenko

README.md

@@ -8,18 +8,15 @@ These types of resources are supported:
 * [Launch Configuration](https://www.terraform.io/docs/providers/aws/r/launch_configuration.html)
 * [Auto Scaling Group](https://www.terraform.io/docs/providers/aws/r/autoscaling_group.html)
 
-Root module calls these modules which can also be used separately to create independent resources:
-
-* [launch_configuration](https://github.com/terraform-aws-modules/terraform-aws-autoscaling/tree/master/modules/launch_configuration) - creates Launch Configuration
-* [autoscaling_group](https://github.com/terraform-aws-modules/terraform-aws-autoscaling/tree/master/modules/autoscaling_group) - creates Auto Scaling Group
-
 Usage
 -----
 
 ```hcl
 module "asg" {
   source = "terraform-aws-modules/autoscaling/aws"
 
+  name = "service"
+
   # Launch configuration
   lc_name = "example-lc"
 
@@ -67,6 +64,25 @@ module "asg" {
 }
 ```
 
+Conditional creation
+--------------------
+
+Normally this module creates both Auto Scaling Group (ASG) and Launch Configuration (LC), and connect them together.
+It is possible to customize this behaviour passing different parameters to this module:
+1. To create ASG, but not LC. Associate ASG with an existing LC:
+```hcl
+create_lc = false
+launch_configuration = "existing-launch-configuration"
+```
+
+1. To create LC, but not ASG. Outputs may produce errors.
+```hcl
+create_asg = false
+```
+
+1. To disable creation of both resources (LC and ASG) you can specify both arguments `create_lc = false` and `create_asg = false`. Sometimes you need to use this way to create resources in modules conditionally but Terraform does not allow to use `count` inside `module` block.
+
+
 Examples
 --------
 

examples/asg_ec2/main.tf

@@ -1,5 +1,12 @@
 provider "aws" {
   region = "eu-west-1"
+
+  # Make it faster by skipping something
+  skip_get_ec2_platforms      = true
+  skip_metadata_api_check     = true
+  skip_region_validation      = true
+  skip_credentials_validation = true
+  skip_requesting_account_id  = true
 }
 
 ##############################################################
@@ -44,15 +51,18 @@ data "aws_ami" "amazon_linux" {
 module "example" {
   source = "../../"
 
+  name = "example-with-ec2"
+
   # Launch configuration
   #
-  # Uncomment the value below and provide value of existing launch configuration to use it instead of making new one
-  # existing_launch_configuration = "aa"
+  # launch_configuration = "my-existing-launch-configuration" # Use the existing launch configuration
+  # create_lc = false # disables creation of launch configuration
   lc_name = "example-lc"
 
-  image_id        = "${data.aws_ami.amazon_linux.id}"
-  instance_type   = "t2.micro"
-  security_groups = ["${data.aws_security_group.default.id}"]
+  image_id                    = "${data.aws_ami.amazon_linux.id}"
+  instance_type               = "t2.micro"
+  security_groups             = ["${data.aws_security_group.default.id}"]
+  associate_public_ip_address = true
 
   ebs_block_device = [
     {
@@ -67,6 +77,7 @@ module "example" {
     {
       volume_size = "50"
       volume_type = "gp2"
+      delete_on_termination = true
     },
   ]
 

examples/asg_elb/main.tf

@@ -44,10 +44,12 @@ data "aws_ami" "amazon_linux" {
 module "example_asg" {
   source = "../../"
 
+  name = "example-with-elb"
+
   # Launch configuration
   #
-  # Uncomment the value below and provide value of existing launch configuration to use it instead of making new one
-  # existing_launch_configuration = "aa"
+  # launch_configuration = "my-existing-launch-configuration" # Use the existing launch configuration
+  # create_lc = false # disables creation of launch configuration
   lc_name = "example-lc"
 
   image_id        = "${data.aws_ami.amazon_linux.id}"

main.tf

@@ -1,12 +1,10 @@
 #######################
 # Launch configuration
 #######################
-module "launch_configuration" {
-  source = "./modules/launch_configuration"
+resource "aws_launch_configuration" "this" {
+  count = "${var.create_lc}"
 
-  count = "${var.existing_launch_configuration != "" ? 0 : 1}"
-
-  name                        = "${var.lc_name}"
+  name_prefix                 = "${coalesce(var.lc_name, var.name)}-"
   image_id                    = "${var.image_id}"
   instance_type               = "${var.instance_type}"
   iam_instance_profile        = "${var.iam_instance_profile}"
@@ -15,28 +13,31 @@ module "launch_configuration" {
   associate_public_ip_address = "${var.associate_public_ip_address}"
   user_data                   = "${var.user_data}"
   enable_monitoring           = "${var.enable_monitoring}"
-  spot_price                  = "${var.spot_price}"
   placement_tenancy           = "${var.placement_tenancy}"
+  ebs_optimized               = "${var.ebs_optimized}"
+  ebs_block_device            = "${var.ebs_block_device}"
+  ephemeral_block_device      = "${var.ephemeral_block_device}"
+  root_block_device           = "${var.root_block_device}"
+
+  lifecycle {
+    create_before_destroy = true
+  }
 
-  ebs_optimized          = "${var.ebs_optimized}"
-  ebs_block_device       = "${var.ebs_block_device}"
-  ephemeral_block_device = "${var.ephemeral_block_device}"
-  root_block_device      = "${var.root_block_device}"
+  # spot_price                  = "${var.spot_price}"  // placement_tenancy does not work with spot_price
 }
 
 ####################
-# Autoscaling Group
+# Autoscaling group
 ####################
-module "autoscaling_group" {
-  source = "./modules/autoscaling_group"
+resource "aws_autoscaling_group" "this" {
+  count = "${var.create_asg}"
 
-  name                 = "${var.asg_name}"
-  launch_configuration = "${var.existing_launch_configuration != "" ? var.existing_launch_configuration : module.launch_configuration.this_launch_configuration_id}"
+  name_prefix          = "${coalesce(var.asg_name, var.name)}-"
+  launch_configuration = "${var.create_lc ? element(concat(aws_launch_configuration.this.*.id, list(var.launch_configuration)), 0) : var.launch_configuration}"
   vpc_zone_identifier  = ["${var.vpc_zone_identifier}"]
-
-  max_size         = "${var.max_size}"
-  min_size         = "${var.min_size}"
-  desired_capacity = "${var.desired_capacity}"
+  max_size             = "${var.max_size}"
+  min_size             = "${var.min_size}"
+  desired_capacity     = "${var.desired_capacity}"
 
   load_balancers            = ["${var.load_balancers}"]
   health_check_grace_period = "${var.health_check_grace_period}"
@@ -55,5 +56,8 @@ module "autoscaling_group" {
   wait_for_capacity_timeout = "${var.wait_for_capacity_timeout}"
   protect_from_scale_in     = "${var.protect_from_scale_in}"
 
-  tags = "${var.tags}"
+  tags = ["${concat(
+      var.tags,
+      list(map("key", "Name", "value", var.name, "propagate_at_launch", true))
+   )}"]
 }