Add support for nodepool autoscaling (Azure#75)

* Add nodepool autoscaling support

Signed-off-by: Lays Rodrigues <lays.silva@sensedia.com>

* Add test/fixture for autoscaling support

Signed-off-by: Lays Rodrigues <lays.silva@sensedia.com>

* Update README example usage

Signed-off-by: Lays Rodrigues <lays.silva@sensedia.com>

* Update variables.tf

* Update variables.tf

add description

* Update README.md

format

* Update main.tf

format

* Update variables.tf

* Update main.tf

format

* Update README.md

format

* Update variables.tf

* Update README.md

* Update main.tf

* Update README.md

Co-authored-by: Yuping Wei <56525716+yupwei68@users.noreply.github.com>

Author: lays147

README.md

@@ -48,6 +48,10 @@ module "aks" {
   rbac_aad_admin_group_object_ids  = [data.azuread_group.aks_cluster_admins.id]
   rbac_aad_managed                 = true
   private_cluster_enabled          = true # default value
+  enable_auto_scaling              = true
+  agents_min_count                 = 1
+  agents_max_count                 = 2
+  agents_count                     = null # Please set `agents_count` `null` while `enable_auto_scaling` is `true` to avoid possible `agents_count` changes.
 
   depends_on = [module.network]
 }

main.tf

@@ -31,6 +31,9 @@ resource "azurerm_kubernetes_cluster" "main" {
     vm_size              = var.agents_size
     os_disk_size_gb      = var.os_disk_size_gb
     vnet_subnet_id       = var.vnet_subnet_id
+    enable_auto_scaling  = var.enable_auto_scaling
+    max_count            = var.enable_auto_scaling ? var.agents_max_count : null
+    min_count            = var.enable_auto_scaling ? var.agents_min_count : null
   }
 
   dynamic "service_principal" {

test/fixture/main.tf

@@ -40,7 +40,12 @@ module "aks" {
   sku_tier                        = "Paid"
   enable_kube_dashboard           = true
   private_cluster_enabled         = true
-  depends_on                      = [azurerm_resource_group.main]
+  enable_auto_scaling             = true
+  agents_min_count                = 1
+  agents_max_count                = 2
+  agents_count                    = null
+
+  depends_on = [azurerm_resource_group.main]
 }
 
 module "aks_without_monitor" {

variables.tf

@@ -45,7 +45,7 @@ variable "log_retention_in_days" {
 }
 
 variable "agents_count" {
-  description = "The number of Agents that should exist in the Agent Pool"
+  description = "The number of Agents that should exist in the Agent Pool. Please set `agents_count` `null` while `enable_auto_scaling` is `true` to avoid possible `agents_count` changes."
   type        = number
   default     = 2
 }
@@ -163,3 +163,21 @@ variable "orchestrator_version" {
   type        = string
   default     = null
 }
+
+variable "enable_auto_scaling" {
+  description = "Enable node pool autoscaling"
+  type        = bool
+  default     = false
+}
+
+variable "agents_max_count" {
+  type        = number
+  description = "Maximum number of nodes in a pool"
+  default     = null
+}
+
+variable "agents_min_count" {
+  type        = number
+  description = "Minimum number of nodes in a pool"
+  default     = null
+}