Add ability to load balance TCP applications on AWS

* Add ability to load balance TCP applications (e.g. NodePort)
* Output the network load balancer ARN as `nlb_id`
* Accept a `worker_target_groups` (ARN) list to which worker
instances should be added
* AWS NLBs and target groups don't support UDP

aws/container-linux/kubernetes/outputs.tf

@@ -37,6 +37,11 @@ output "kubeconfig" {
 
 # Outputs for custom load balancing
 
+output "nlb_id" {
+  description = "ARN of the Network Load Balancer"
+  value       = "${aws_lb.nlb.id}"
+}
+
 output "worker_target_group_http" {
   description = "ARN of a target group of workers for HTTP traffic"
   value       = "${module.workers.target_group_http}"

aws/container-linux/kubernetes/variables.tf

@@ -71,6 +71,12 @@ variable "worker_price" {
   description = "Spot price in USD for autoscaling group spot instances. Leave as default empty string for autoscaling group to use on-demand instances. Note, switching in-place from spot to on-demand is not possible: https://github.com/terraform-providers/terraform-provider-aws/issues/4320"
 }
 
+variable "worker_target_groups" {
+  type        = "list"
+  description = "Additional target group ARNs to which worker instances should be added"
+  default     = []
+}
+
 variable "controller_clc_snippets" {
   type        = "list"
   description = "Controller Container Linux Config snippets"

aws/container-linux/kubernetes/workers.tf

@@ -11,6 +11,7 @@ module "workers" {
   os_image        = "${var.os_image}"
   disk_size       = "${var.disk_size}"
   spot_price      = "${var.worker_price}"
+  target_groups   = ["${var.worker_target_groups}"]
 
   # configuration
   kubeconfig            = "${module.bootkube.kubeconfig-kubelet}"

aws/container-linux/kubernetes/workers/variables.tf

@@ -64,6 +64,12 @@ variable "spot_price" {
   description = "Spot price in USD for autoscaling group spot instances. Leave as default empty string for autoscaling group to use on-demand instances. Note, switching in-place from spot to on-demand is not possible: https://github.com/terraform-providers/terraform-provider-aws/issues/4320"
 }
 
+variable "target_groups" {
+  type        = "list"
+  description = "Additional target group ARNs to which instances should be added"
+  default     = []
+}
+
 variable "clc_snippets" {
   type        = "list"
   description = "Container Linux Config snippets"

aws/container-linux/kubernetes/workers/workers.tf

@@ -19,6 +19,7 @@ resource "aws_autoscaling_group" "workers" {
   target_group_arns = [
     "${aws_lb_target_group.workers-http.id}",
     "${aws_lb_target_group.workers-https.id}",
+    "${var.target_groups}",
   ]
 
   lifecycle {