refactor: Harmonize subnet variables (cattle-ops#420)

* Introduce new variable and deprecate the old ones

* Use new variable

* Fix validation error

* Move deprecated variables to the end

* Make it a boolean expression

* Update docs

* Fix examples

* Make deprecated variable optional to support new `subnet_id`

* Fix license

* Fix Terraform code format with version 1.0.8

Author: kayman-mk

README.md

@@ -33,10 +33,9 @@ module "runner" {
   aws_region  = var.aws_region
   environment = var.environment
 
-  vpc_id                   = module.vpc.vpc_id
-  subnet_ids_gitlab_runner = module.vpc.private_subnets
-  subnet_id_runners        = element(module.vpc.private_subnets, 0)
-  metrics_autoscaling      = ["GroupDesiredCapacity", "GroupInServiceCapacity"]
+  vpc_id              = module.vpc.vpc_id
+  subnet_id           = element(module.vpc.private_subnets, 0)
+  metrics_autoscaling = ["GroupDesiredCapacity", "GroupInServiceCapacity"]
 
   runners_name             = var.runner_name
   runners_gitlab_url       = var.gitlab_url

examples/runner-default/main.tf

@@ -31,9 +31,8 @@ module "runner" {
   docker_machine_security_group_description = "Custom description for docker-machine"
   gitlab_runner_security_group_description  = "Custom description for gitlab-runner"
 
-  vpc_id                   = module.vpc.vpc_id
-  subnet_ids_gitlab_runner = module.vpc.public_subnets
-  subnet_id_runners        = element(module.vpc.public_subnets, 0)
+  vpc_id    = module.vpc.vpc_id
+  subnet_id = element(module.vpc.public_subnets, 0)
 
   runners_executor   = "docker"
   runners_name       = var.runner_name

examples/runner-docker/main.tf

@@ -29,9 +29,8 @@ module "runner" {
   aws_region  = var.aws_region
   environment = var.environment
 
-  vpc_id                   = module.vpc.vpc_id
-  subnet_ids_gitlab_runner = module.vpc.private_subnets
-  subnet_id_runners        = element(module.vpc.private_subnets, 0)
+  vpc_id    = module.vpc.vpc_id
+  subnet_id = element(module.vpc.private_subnets, 0)
 
   runners_name       = var.runner_name
   runners_gitlab_url = var.gitlab_url

examples/runner-pre-registered/main.tf

@@ -32,9 +32,8 @@ module "runner" {
 
   runners_use_private_address = false
 
-  vpc_id                   = module.vpc.vpc_id
-  subnet_ids_gitlab_runner = module.vpc.public_subnets
-  subnet_id_runners        = element(module.vpc.public_subnets, 0)
+  vpc_id    = module.vpc.vpc_id
+  subnet_id = element(module.vpc.public_subnets, 0)
 
   docker_machine_spot_price_bid = "on-demand-price"
 

examples/runner-public/main.tf

@@ -1,7 +1,7 @@
 data "aws_caller_identity" "current" {}
 
 data "aws_subnet" "runners" {
-  id = var.subnet_id_runners
+  id = length(var.subnet_id) > 0 ? var.subnet_id : var.subnet_id_runners
 }
 
 data "aws_availability_zone" "runners" {
@@ -99,7 +99,7 @@ locals {
       aws_region                  = var.aws_region
       gitlab_url                  = var.runners_gitlab_url
       runners_vpc_id              = var.vpc_id
-      runners_subnet_id           = var.subnet_id_runners
+      runners_subnet_id           = length(var.subnet_id) > 0 ? var.subnet_id : var.subnet_id_runners
       runners_aws_zone            = data.aws_availability_zone.runners.name_suffix
       runners_instance_type       = var.docker_machine_instance_type
       runners_spot_price_bid      = var.docker_machine_spot_price_bid == "on-demand-price" ? "" : var.docker_machine_spot_price_bid
@@ -174,7 +174,7 @@ data "aws_ami" "docker-machine" {
 
 resource "aws_autoscaling_group" "gitlab_runner_instance" {
   name                      = var.enable_asg_recreation ? "${aws_launch_template.gitlab_runner_instance.name}-asg" : "${var.environment}-as-group"
-  vpc_zone_identifier       = var.subnet_ids_gitlab_runner
+  vpc_zone_identifier       = length(var.subnet_id) > 0 ? [var.subnet_id] : var.subnet_ids_gitlab_runner
   min_size                  = "1"
   max_size                  = "1"
   desired_capacity          = "1"

main.tf

@@ -19,14 +19,10 @@ variable "vpc_id" {
   type        = string
 }
 
-variable "subnet_id_runners" {
-  description = "List of subnets used for hosting the gitlab-runners."
+variable "subnet_id" {
+  description = "Subnet id used for the runner and executors. Must belong to the VPC specified above."
   type        = string
-}
-
-variable "subnet_ids_gitlab_runner" {
-  description = "Subnet used for hosting the GitLab runner."
-  type        = list(string)
+  default     = "" # TODO remove as soon as subnet_id_runners and subnet_ids_gitlab_runner are gone. Variable is mandatory now.
 }
 
 variable "extra_security_group_ids_runner_agent" {
@@ -726,3 +722,15 @@ variable "docker_machine_egress_rules" {
     description      = "Allow all egress traffic for docker machine build runners"
   }]
 }
+
+variable "subnet_id_runners" {
+  description = "Deprecated! Use subnet_id instead. List of subnets used for hosting the gitlab-runners."
+  type        = string
+  default     = ""
+}
+
+variable "subnet_ids_gitlab_runner" {
+  description = "Deprecated! Use subnet_id instead. Subnet used for hosting the GitLab runner."
+  type        = list(string)
+  default     = []
+}