Support for placement constraints

Author: diego

README.md

@@ -36,3 +36,12 @@ Sample to use an existing Target Group
 ```
   target_group = "arn:aws:elasticloadbalancing:us-east-1:11111111:targetgroup/mycustomtg/1111111"
 ```
+
+Sample to use Placement Constraints
+--------------------------------------
+```
+   placement_constraints {
+    type       = "memberOf"
+    expression = "attribute:ecs.availability-zone in [us-east-1a]"
+  }
+```

main.tf

@@ -19,6 +19,7 @@ resource "aws_ecs_task_definition" "this" {
   task_role_arn = "${aws_iam_role.this.arn}"
   execution_role_arn = "${var.enable_ssm ? aws_iam_role.this.arn : ""}"
   requires_compatibilities = ["${var.compatibilities}"]
+  placement_constraints = "${var.placement_constraints}"
 }
 
 resource "aws_ecs_task_definition" "private" {

variables.tf

@@ -109,4 +109,10 @@ variable "proto_http" {
 variable "target_group" {
   description = "Set existing Target Group for new service"
   default = ""
-}
+}
+
+variable "placement_constraints" {
+  description = "(Optional) A set of rules that are taken during task placement"
+  type        = "list"
+  default     = []
+}