FEAT: Add placement constraints (#22)

* FEAT: Adds placement constraint as an optional parameter.

* CHORE: terraform fmt repo

* Add lifecycle precondition for service

README.adoc

@@ -105,6 +105,11 @@ Both use the same format, but `application_container` will automatically be set
 |Configure any other options for container definitions
 |no
 |None (Though log_configuration is automatically configured for CloudWatch)
+
+|`placement_constraints`
+|A list of placement constraints for the service. Not valid for FARGATE launch_type. SEE: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/cluster-query-language.html and https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/ecs_service#placement_constraints
+|no
+|[]
 |===
 
 

examples/autoscaling-with-custom-metrics/main.tf

@@ -71,7 +71,7 @@ module "service" {
     {
       listener_arn      = data.aws_lb_listener.http.arn
       security_group_id = one(data.aws_lb.main.security_groups)
-      conditions        = [
+      conditions = [
         {
           path_pattern = "/${local.application_name}/*"
         }
@@ -94,7 +94,7 @@ module "service" {
         metric = {
           metric_name = "ApproximateNumberOfMessagesVisible"
           namespace   = "AWS/SQS"
-          dimensions  = [
+          dimensions = [
             {
               name  = "QueueName"
               value = "my-queue"

examples/autoscaling/main.tf

@@ -21,7 +21,7 @@ data "aws_vpc" "main" {
 data "aws_subnets" "private" {
   #  Reference your existing subnets which usually is created centrally in -aws repo
   filter {
-    name = "vpc-id"
+    name   = "vpc-id"
     values = [data.aws_vpc.main.id]
   }
 
@@ -69,7 +69,7 @@ module "service" {
   lb_listeners = [{
     listener_arn      = data.aws_lb_listener.http.arn
     security_group_id = one(data.aws_lb.main.security_groups)
-    conditions        = [{
+    conditions = [{
       path_pattern = "/${local.application_name}/*"
     }]
   }]
@@ -82,7 +82,7 @@ module "service" {
   }
 
   autoscaling_schedule = {
-    timezone  = "Europe/Oslo"
+    timezone = "Europe/Oslo"
     # Increase capacity in weekdays
     schedules = [
       {

examples/on-prem/main.tf

@@ -3,7 +3,7 @@ provider "aws" {
 }
 
 locals {
-  name_prefix = "infrademo"
+  name_prefix      = "infrademo"
   application_name = "my-webapp"
 }
 
@@ -30,9 +30,16 @@ module "service" {
   launch_type = "EXTERNAL"
 
   application_container = {
-    name = "main"
-    image = "nginx:latest"
-    port = 80
+    name     = "main"
+    image    = "nginx:latest"
+    port     = 80
     protocol = "HTTP"
   }
+
+  placement_constraints = [
+    {
+      type       = "memberOf"
+      expression = "attribute:your_custom_attribute in [your_first_value, your_second_value]"
+    }
+  ]
 }

examples/simple/main.tf

@@ -3,7 +3,7 @@ provider "aws" {
 }
 
 locals {
-  name_prefix = "infrademo"
+  name_prefix      = "infrademo"
   application_name = "my-webapp"
 }
 
@@ -19,7 +19,7 @@ data "aws_vpc" "main" {
 
 data "aws_subnets" "private" {
   filter {
-    name = "vpc-id"
+    name   = "vpc-id"
     values = [data.aws_vpc.main.id]
   }
 
@@ -38,7 +38,7 @@ data "aws_lb" "main" {
 
 data "aws_lb_listener" "http" {
   load_balancer_arn = data.aws_lb.main.arn
-  port = 80
+  port              = 80
 }
 
 /*
@@ -50,9 +50,9 @@ module "service" {
 
   application_name = local.application_name
 
-  vpc_id                   = data.aws_vpc.main.id
-  private_subnet_ids       = data.aws_subnets.private.ids
-  cluster_id               = data.aws_ecs_cluster.main.id
+  vpc_id             = data.aws_vpc.main.id
+  private_subnet_ids = data.aws_subnets.private.ids
+  cluster_id         = data.aws_ecs_cluster.main.id
 
   application_container = {
     name     = "main"

main.tf

@@ -487,11 +487,28 @@ resource "aws_ecs_service" "service" {
     }
   }
 
+  # Placement constraints for EC2 and EXTERNAL launch types. Can be used to ensure that services are placed on specific instances.
+  dynamic "placement_constraints" {
+    for_each = var.placement_constraints
+
+    content {
+      type       = placement_constraints.value.type
+      expression = placement_constraints.value.expression
+    }
+  }
+
   timeouts {
     create = var.ecs_service_timeouts.create
     update = var.ecs_service_timeouts.update
     delete = var.ecs_service_timeouts.delete
   }
+
+  lifecycle {
+    precondition {
+      condition     = !(length(var.placement_constraints) > 0 && var.launch_type == "FARGATE")
+      error_message = "Placement constraints are not valid for FARGATE launch type"
+    }
+  }
 }
 
 resource "aws_ecs_service" "service_with_autoscaling" {
@@ -544,9 +561,24 @@ resource "aws_ecs_service" "service_with_autoscaling" {
     }
   }
 
+  # Placement constraints for EC2 and EXTERNAL launch types. Can be used to ensure that services are placed on specific instances.
+  dynamic "placement_constraints" {
+    for_each = var.placement_constraints
+
+    content {
+      type       = placement_constraints.value.type
+      expression = placement_constraints.value.expression
+    }
+  }
+
 
   lifecycle {
     ignore_changes = [desired_count]
+
+    precondition {
+      condition     = !(length(var.placement_constraints) > 0 && var.launch_type == "FARGATE")
+      error_message = "Placement constraints are not valid for FARGATE launch type"
+    }
   }
 
   timeouts {
@@ -611,7 +643,7 @@ resource "aws_appautoscaling_policy" "ecs_service" {
           content {
             label = metrics.value.label
             id    = metrics.value.id
-            dynamic metric_stat {
+            dynamic "metric_stat" {
               for_each = metrics.value.metric_stat[*]
               content {
                 metric {
@@ -628,7 +660,7 @@ resource "aws_appautoscaling_policy" "ecs_service" {
                 stat = metric_stat.value.stat
               }
             }
-            expression = metrics.value.expression
+            expression  = metrics.value.expression
             return_data = metrics.value.return_data
           }
         }

variables.tf

@@ -90,6 +90,15 @@ variable "lb_listeners" {
   default = []
 }
 
+variable "placement_constraints" {
+  description = "Placement constraints for the service. Note: A maximum of 10 placement constraints may be added to a service. Used to force deployment to specific instances. Not valid for FARGATE launch type."
+  type = list(object({
+    type       = string
+    expression = optional(string)
+  }))
+  default = []
+}
+
 variable "lb_deregistration_delay" {
   description = "The amount time for Elastic Load Balancing to wait before changing the state of a deregistering target from draining to unused."
   type        = number
@@ -237,9 +246,9 @@ variable "xray_daemon_config_path" {
 variable "custom_metrics" {
   description = "The custom metrics for autoscaling. Check https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/appautoscaling_policy#create-target-tracking-scaling-policy-using-metric-math for more information."
   type = list(object({
-    label = string
-    id    = string
-    expression  = optional(string)
+    label      = string
+    id         = string
+    expression = optional(string)
     metric_stat = optional(object({
       metric = object({
         metric_name = string