Reuse existing task definition family and revision (#108)

* Reuse existing task definition arn * Reuse task definition if provided * Update variables.tf * Update main.tf * Update variables.tf * Auto Format * Auto Format * Update main.tf Co-authored-by: cloudpossebot <[email protected]>
cloudposse · Feb 25, 2021 · afb8060 · afb8060
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Showing 4 changed files with 11 additions and 3 deletions.
diff --git a/README.md b/README.md
@@ -335,6 +335,7 @@ Available targets:
 | subnet\_ids | Subnet IDs used in Service `network_configuration` if `var.network_mode = "awsvpc"` | `list(string)` | `null` | no |
 | tags | Additional tags (e.g. `map('BusinessUnit','XYZ')` | `map(string)` | `{}` | no |
 | task\_cpu | The number of CPU units used by the task. If using `FARGATE` launch type `task_cpu` must match [supported memory values](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#task_size) | `number` | `256` | no |
+| task\_definition | Reuse an existing task definition family and revision for the ecs service instead of creating one | `string` | `null` | no |
 | task\_exec\_policy\_arns | A list of IAM Policy ARNs to attach to the generated task execution role. | `list(string)` | `[]` | no |
 | task\_exec\_role\_arn | The ARN of IAM role that allows the ECS/Fargate agent to make calls to the ECS API on your behalf | `string` | `""` | no |
 | task\_memory | The amount of memory (in MiB) used by the task. If using Fargate launch type `task_memory` must match [supported cpu value](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#task_size) | `number` | `512` | no |

diff --git a/docs/terraform.md b/docs/terraform.md
@@ -87,6 +87,7 @@
 | subnet\_ids | Subnet IDs used in Service `network_configuration` if `var.network_mode = "awsvpc"` | `list(string)` | `null` | no |
 | tags | Additional tags (e.g. `map('BusinessUnit','XYZ')` | `map(string)` | `{}` | no |
 | task\_cpu | The number of CPU units used by the task. If using `FARGATE` launch type `task_cpu` must match [supported memory values](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#task_size) | `number` | `256` | no |
+| task\_definition | Reuse an existing task definition family and revision for the ecs service instead of creating one | `string` | `null` | no |
 | task\_exec\_policy\_arns | A list of IAM Policy ARNs to attach to the generated task execution role. | `list(string)` | `[]` | no |
 | task\_exec\_role\_arn | The ARN of IAM role that allows the ECS/Fargate agent to make calls to the ECS API on your behalf | `string` | `""` | no |
 | task\_memory | The amount of memory (in MiB) used by the task. If using Fargate launch type `task_memory` must match [supported cpu value](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#task_size) | `number` | `512` | no |

diff --git a/main.tf b/main.tf
@@ -33,7 +33,7 @@ module "exec_label" {
 }
 
 resource "aws_ecs_task_definition" "default" {
-  count                    = local.enabled ? 1 : 0
+  count                    = local.enabled && var.task_definition == null ? 1 : 0
   family                   = module.this.id
   container_definitions    = var.container_definition_json
   requires_compatibilities = [var.launch_type]
@@ -287,7 +287,7 @@ resource "aws_security_group_rule" "nlb" {
 resource "aws_ecs_service" "ignore_changes_task_definition" {
   count                              = local.enabled && var.ignore_changes_task_definition ? 1 : 0
   name                               = module.this.id
-  task_definition                    = "${join("", aws_ecs_task_definition.default.*.family)}:${join("", aws_ecs_task_definition.default.*.revision)}"
+  task_definition                    = coalesce(var.task_definition, "${join("", aws_ecs_task_definition.default.*.family)}:${join("", aws_ecs_task_definition.default.*.revision)}")
   desired_count                      = var.desired_count
   deployment_maximum_percent         = var.deployment_maximum_percent
   deployment_minimum_healthy_percent = var.deployment_minimum_healthy_percent
@@ -369,7 +369,7 @@ resource "aws_ecs_service" "ignore_changes_task_definition" {
 resource "aws_ecs_service" "default" {
   count                              = local.enabled && var.ignore_changes_task_definition == false ? 1 : 0
   name                               = module.this.id
-  task_definition                    = "${join("", aws_ecs_task_definition.default.*.family)}:${join("", aws_ecs_task_definition.default.*.revision)}"
+  task_definition                    = coalesce(var.task_definition, "${join("", aws_ecs_task_definition.default.*.family)}:${join("", aws_ecs_task_definition.default.*.revision)}")
   desired_count                      = var.desired_count
   deployment_maximum_percent         = var.deployment_maximum_percent
   deployment_minimum_healthy_percent = var.deployment_minimum_healthy_percent

diff --git a/variables.tf b/variables.tf
@@ -312,3 +312,9 @@ variable "use_old_arn" {
   description = "A flag to enable/disable tagging the ecs resources that require the new arn format"
   default     = false
 }
+
+variable "task_definition" {
+  type        = string
+  description = "Reuse an existing task definition family and revision for the ecs service instead of creating one"
+  default     = null
+}