ECS Autoscaling example

main.tf

resource "aws_appautoscaling_target" "ecs_target" {
  max_capacity       = "${var.max_size}"
  min_capacity       = "${var.min_size}"
  resource_id        = "${aws_ecs_service.webserver.id}"
  role_arn           = "${aws_iam_role.ecs_iam_role.arn}"
  scalable_dimension = "ecs:service:DesiredCount"
  service_namespace  = "ecs"
}

resource "aws_appautoscaling_policy" "ecs_policy" {
  name               = "website-autoscale"
  resource_id        = "${aws_appautoscaling_target.ecs_target.resource_id}"
  scalable_dimension = "${aws_appautoscaling_target.ecs_target.scalable_dimension}"
  service_namespace  = "${aws_appautoscaling_target.ecs_target.service_namespace}"
  policy_type        = "TargetTrackingScaling"

  target_tracking_scaling_policy_configuration {
    target_value = 10

    predefined_metric_specification {
      predefined_metric_type = "ALBRequestCountPerTarget"
    }
  }

  depends_on = ["aws_appautoscaling_target.ecs_target"]
}