Configure controller and worker node architecture separately

* On platforms that support ARM64 instances, configure controller
and worker node host architectures separately
* For example, you can run arm64 controllers and amd64 workers
* Add `controller_arch` and `worker_arch` variables
* Remove `arch` variable

aws/flatcar-linux/kubernetes/ami.tf

@@ -1,7 +1,7 @@
 locals {
   # Pick a Flatcar Linux AMI
   # flatcar-stable -> Flatcar Linux AMI
-  ami_id  = var.arch == "arm64" ? data.aws_ami.flatcar-arm64[0].image_id : data.aws_ami.flatcar.image_id
+  ami_id  = var.controller_arch == "arm64" ? data.aws_ami.flatcar-arm64[0].image_id : data.aws_ami.flatcar.image_id
   channel = split("-", var.os_image)[1]
 }
 
@@ -26,7 +26,7 @@ data "aws_ami" "flatcar" {
 }
 
 data "aws_ami" "flatcar-arm64" {
-  count = var.arch == "arm64" ? 1 : 0
+  count = var.controller_arch == "arm64" ? 1 : 0
 
   most_recent = true
   owners      = ["075585003325"]

aws/flatcar-linux/kubernetes/variables.tf

@@ -190,17 +190,27 @@ variable "cluster_domain_suffix" {
   default     = "cluster.local"
 }
 
-variable "arch" {
+variable "controller_arch" {
   type        = string
-  description = "Container architecture (amd64 or arm64)"
+  description = "Controller node(s) architecture (amd64 or arm64)"
   default     = "amd64"
-
   validation {
-    condition     = var.arch == "amd64" || var.arch == "arm64"
-    error_message = "The arch must be amd64 or arm64."
+    condition     = contains(["amd64", "arm64"], var.controller_arch)
+    error_message = "The controller_arch must be amd64 or arm64."
   }
 }
 
+variable "worker_arch" {
+  type        = string
+  description = "Worker node(s) architecture (amd64 or arm64)"
+  default     = "amd64"
+  validation {
+    condition     = contains(["amd64", "arm64"], var.worker_arch)
+    error_message = "The worker_arch must be amd64 or arm64."
+  }
+}
+
+
 variable "daemonset_tolerations" {
   type        = list(string)
   description = "List of additional taint keys kube-system DaemonSets should tolerate (e.g. ['custom-role', 'gpu-role'])"

aws/flatcar-linux/kubernetes/workers.tf

@@ -9,7 +9,7 @@ module "workers" {
   worker_count    = var.worker_count
   instance_type   = var.worker_type
   os_image        = var.os_image
-  arch            = var.arch
+  arch            = var.worker_arch
   disk_type       = var.worker_disk_type
   disk_size       = var.worker_disk_size
   disk_iops       = var.worker_disk_iops