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

azure/flatcar-linux/kubernetes/controllers.tf

@@ -2,8 +2,8 @@ locals {
   # Container Linux derivative
   # flatcar-stable -> Flatcar Linux Stable
   channel      = split("-", var.os_image)[1]
-  offer_suffix = var.arch == "arm64" ? "corevm" : "free"
-  urn          = var.arch == "arm64" ? local.channel : "${local.channel}-gen2"
+  offer_suffix = var.controller_arch == "arm64" ? "corevm" : "free"
+  urn          = var.controller_arch == "arm64" ? local.channel : "${local.channel}-gen2"
 
   # Typhoon ssh_authorized_key supports RSA or a newer formats (e.g. ed25519).
   # However, Azure requires an older RSA key to pass validations. To use a
@@ -63,7 +63,7 @@ resource "azurerm_linux_virtual_machine" "controllers" {
   }
 
   dynamic "plan" {
-    for_each = var.arch == "arm64" ? [] : [1]
+    for_each = var.controller_arch == "arm64" ? [] : [1]
     content {
       publisher = "kinvolk"
       product   = "flatcar-container-linux-${local.offer_suffix}"

azure/flatcar-linux/kubernetes/variables.tf

@@ -168,14 +168,25 @@ variable "worker_node_labels" {
   default     = []
 }
 
-variable "arch" {
-  type        = string
-  description = "Container architecture (amd64 or arm64)"
-  default     = "amd64"
+# advanced
 
+variable "controller_arch" {
+  type        = string
+  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."
   }
 }
 

azure/flatcar-linux/kubernetes/workers.tf

@@ -25,5 +25,5 @@ module "workers" {
   cluster_domain_suffix = var.cluster_domain_suffix
   snippets              = var.worker_snippets
   node_labels           = var.worker_node_labels
-  arch                  = var.arch
+  arch                  = var.worker_arch
 }