add var 'worker_group_count' to replace 'length()' calls

data.tf

@@ -75,7 +75,7 @@ EOF
 
 data "template_file" "userdata" {
   template = "${file("${path.module}/templates/userdata.sh.tpl")}"
-  count    = "${length(var.worker_groups)}"
+  count    = "${var.worker_group_count}"
 
   vars {
     region              = "${data.aws_region.current.name}"

variables.tf

@@ -74,6 +74,12 @@ variable "worker_groups" {
   }]
 }
 
+variable "worker_group_count" {
+  description = "The number of maps contained within the worker_groups list."
+  type        = "string"
+  default     = "1"
+}
+
 variable "workers_group_defaults" {
   description = "Default values for target groups as defined by the list of maps."
   type        = "map"

workers.tf

@@ -5,7 +5,7 @@ resource "aws_autoscaling_group" "workers" {
   min_size             = "${lookup(var.worker_groups[count.index], "asg_min_size",lookup(var.workers_group_defaults, "asg_min_size"))}"
   launch_configuration = "${element(aws_launch_configuration.workers.*.id, count.index)}"
   vpc_zone_identifier  = ["${split(",", coalesce(lookup(var.worker_groups[count.index], "subnets", ""), join(",", var.subnets)))}"]
-  count                = "${length(var.worker_groups)}"
+  count                = "${var.worker_group_count}"
 
   tags = ["${concat(
     list(
@@ -30,7 +30,7 @@ resource "aws_launch_configuration" "workers" {
   key_name                    = "${lookup(var.worker_groups[count.index], "key_name", lookup(var.workers_group_defaults, "key_name"))}"
   user_data_base64            = "${base64encode(element(data.template_file.userdata.*.rendered, count.index))}"
   ebs_optimized               = "${lookup(var.worker_groups[count.index], "ebs_optimized", lookup(local.ebs_optimized, lookup(var.worker_groups[count.index], "instance_type", lookup(var.workers_group_defaults, "instance_type")), false))}"
-  count                       = "${length(var.worker_groups)}"
+  count                       = "${var.worker_group_count}"
 
   lifecycle {
     create_before_destroy = true