feat: Allow for an existing ECS cluster to be used (terraform-aws-modules#233)

Author: henworth

README.md

@@ -336,13 +336,15 @@ allow_github_webhooks        = true
 | <a name="input_container_depends_on"></a> [container\_depends\_on](#input\_container\_depends\_on) | The dependencies defined for container startup and shutdown. A container can contain multiple dependencies. When a dependency is defined for container startup, for container shutdown it is reversed. The condition can be one of START, COMPLETE, SUCCESS or HEALTHY | <pre>list(object({<br>    containerName = string<br>    condition     = string<br>  }))</pre> | `null` | no |
 | <a name="input_container_memory"></a> [container\_memory](#input\_container\_memory) | The amount (in MiB) of memory used by the atlantis container. If not specified ecs\_task\_memory will be used | `number` | `null` | no |
 | <a name="input_container_memory_reservation"></a> [container\_memory\_reservation](#input\_container\_memory\_reservation) | The amount of memory (in MiB) to reserve for the container | `number` | `128` | no |
+| <a name="input_create_ecs_cluster"></a> [create\_ecs\_cluster](#input\_create\_ecs\_cluster) | Whether to create an ECS cluster or not | `bool` | `true` | no |
 | <a name="input_create_route53_record"></a> [create\_route53\_record](#input\_create\_route53\_record) | Whether to create Route53 record for Atlantis | `bool` | `true` | no |
 | <a name="input_custom_container_definitions"></a> [custom\_container\_definitions](#input\_custom\_container\_definitions) | A list of valid container definitions provided as a single valid JSON document. By default, the standard container definition is used. | `string` | `""` | no |
 | <a name="input_custom_environment_secrets"></a> [custom\_environment\_secrets](#input\_custom\_environment\_secrets) | List of additional secrets the container will use (list should contain maps with `name` and `valueFrom`) | <pre>list(object(<br>    {<br>      name      = string<br>      valueFrom = string<br>    }<br>  ))</pre> | `[]` | no |
 | <a name="input_custom_environment_variables"></a> [custom\_environment\_variables](#input\_custom\_environment\_variables) | List of additional environment variables the container will use (list should contain maps with `name` and `value`) | <pre>list(object(<br>    {<br>      name  = string<br>      value = string<br>    }<br>  ))</pre> | `[]` | no |
 | <a name="input_default_security_group_egress"></a> [default\_security\_group\_egress](#input\_default\_security\_group\_egress) | List of maps of egress rules to set on the default security group | `list(map(string))` | `[]` | no |
 | <a name="input_default_security_group_ingress"></a> [default\_security\_group\_ingress](#input\_default\_security\_group\_ingress) | List of maps of ingress rules to set on the default security group | `list(map(string))` | `[]` | no |
 | <a name="input_docker_labels"></a> [docker\_labels](#input\_docker\_labels) | The configuration options to send to the `docker_labels` | `map(string)` | `null` | no |
+| <a name="input_ecs_cluster_id"></a> [ecs\_cluster\_id](#input\_ecs\_cluster\_id) | ID of an existing ECS cluster where resources will be created | `string` | `""` | no |
 | <a name="input_ecs_container_insights"></a> [ecs\_container\_insights](#input\_ecs\_container\_insights) | Controls if ECS Cluster has container insights enabled | `bool` | `false` | no |
 | <a name="input_ecs_fargate_spot"></a> [ecs\_fargate\_spot](#input\_ecs\_fargate\_spot) | Whether to run ECS Fargate Spot or not | `bool` | `false` | no |
 | <a name="input_ecs_service_assign_public_ip"></a> [ecs\_service\_assign\_public\_ip](#input\_ecs\_service\_assign\_public\_ip) | Should be true, if ECS service is using public subnets (more info: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_cannot_pull_image.html) | `bool` | `false` | no |

main.tf

@@ -27,6 +27,9 @@ locals {
   # determine if the alb has authentication enabled, otherwise forward the traffic unauthenticated
   alb_authentication_method = length(keys(var.alb_authenticate_oidc)) > 0 ? "authenticate-oidc" : length(keys(var.alb_authenticate_cognito)) > 0 ? "authenticate-cognito" : "forward"
 
+  # ECS - existing or new?
+  ecs_cluster_id = var.create_ecs_cluster ? module.ecs.ecs_cluster_id : var.ecs_cluster_id
+
   # Container definitions
   container_definitions = var.custom_container_definitions == "" ? var.atlantis_bitbucket_user_token != "" ? jsonencode(concat([module.container_definition_bitbucket.json_map_object], var.extra_container_definitions)) : jsonencode(concat([module.container_definition_github_gitlab.json_map_object], var.extra_container_definitions)) : var.custom_container_definitions
 
@@ -494,6 +497,8 @@ module "ecs" {
   source  = "terraform-aws-modules/ecs/aws"
   version = "v3.3.0"
 
+  create_ecs = var.create_ecs_cluster
+
   name               = var.name
   container_insights = var.ecs_container_insights
 
@@ -780,7 +785,7 @@ data "aws_ecs_task_definition" "atlantis" {
 
 resource "aws_ecs_service" "atlantis" {
   name    = var.name
-  cluster = module.ecs.ecs_cluster_id
+  cluster = local.ecs_cluster_id
 
   task_definition                    = "${var.name}:${local.latest_task_definition_rev}"
   desired_count                      = var.ecs_service_desired_count

outputs.tf

@@ -53,7 +53,7 @@ output "ecs_security_group" {
 
 output "ecs_cluster_id" {
   description = "ECS cluster id"
-  value       = module.ecs.ecs_cluster_id
+  value       = local.ecs_cluster_id
 }
 
 output "ecs_cluster_arn" {

variables.tf

@@ -324,6 +324,18 @@ variable "trusted_entities" {
   default     = []
 }
 
+variable "create_ecs_cluster" {
+  description = "Whether to create an ECS cluster or not"
+  type        = bool
+  default     = true
+}
+
+variable "ecs_cluster_id" {
+  description = "ID of an existing ECS cluster where resources will be created"
+  type        = string
+  default     = ""
+}
+
 variable "ecs_fargate_spot" {
   description = "Whether to run ECS Fargate Spot or not"
   type        = bool