feat!: add create_before_destroy=true to node pools (Azure#357)

Author: the-technat

README.md

@@ -34,7 +34,7 @@ resource "azurerm_subnet" "test" {
 locals {
   nodes = {
     for i in range(3) : "worker${i}" => {
-      name           = substr("worker${i}${random_id.prefix.hex}", 0, 12)
+      name           = substr("worker${i}${random_id.prefix.hex}", 0, 8)
       vm_size        = "Standard_D2s_v3"
       node_count     = 1
       vnet_subnet_id = azurerm_subnet.test.id

examples/multiple_node_pools/main.tf

@@ -11,4 +11,4 @@ variable "location" {
 variable "resource_group_name" {
   type    = string
   default = null
-}
+}

examples/multiple_node_pools/variables.tf

@@ -470,7 +470,7 @@ resource "azurerm_kubernetes_cluster_node_pool" "node_pool" {
   for_each = var.node_pools
 
   kubernetes_cluster_id         = azurerm_kubernetes_cluster.main.id
-  name                          = each.value.name
+  name                          = "${each.value.name}${substr(md5(jsonencode(each.value)), 0, 4)}"
   vm_size                       = each.value.vm_size
   capacity_reservation_group_id = each.value.capacity_reservation_group_id
   custom_ca_trust_enabled       = each.value.custom_ca_trust_enabled
@@ -592,10 +592,31 @@ resource "azurerm_kubernetes_cluster_node_pool" "node_pool" {
   depends_on = [azapi_update_resource.aks_cluster_post_create]
 
   lifecycle {
+    create_before_destroy = true
+    ignore_changes = [
+      name
+    ]
+    replace_triggered_by = [
+      null_resource.pool_name_keeper[each.key],
+    ]
+
     precondition {
       condition     = var.agents_type == "VirtualMachineScaleSets"
       error_message = "Multiple Node Pools are only supported when the Kubernetes Cluster is using Virtual Machine Scale Sets."
     }
+
+    precondition {
+      condition     = can(regex("[a-z0-9]{1,8}", each.value.name))
+      error_message = "A Node Pools name must consist of alphanumeric characters and have a maximum lenght of 8 characters (4 random chars added)"
+    }
+  }
+}
+
+resource "null_resource" "pool_name_keeper" {
+  for_each = var.node_pools
+
+  triggers = {
+    pool_name = each.value.name
   }
 }
 

main.tf

@@ -779,7 +779,7 @@ variable "node_pools" {
   description = <<-EOT
   A map of node pools that about to be created and attached on the Kubernetes cluster. The key of the map can be the name of the node pool, and the key must be static string. The value of the map is a `node_pool` block as defined below:
   map(object({
-    name                          = (Required) The name of the Node Pool which should be created within the Kubernetes Cluster. Changing this forces a new resource to be created. A Windows Node Pool cannot have a `name` longer than 6 characters.
+    name                          = (Required) The name of the Node Pool which should be created within the Kubernetes Cluster. Changing this forces a new resource to be created. A Windows Node Pool cannot have a `name` longer than 6 characters. A random suffix of 4 characters is always added to the name to avoid clashes during recreates.
     node_count                    = (Optional) The initial number of nodes which should exist within this Node Pool. Valid values are between `0` and `1000` (inclusive) for user pools and between `1` and `1000` (inclusive) for system pools and must be a value in the range `min_count` - `max_count`.
     tags                          = (Optional) A mapping of tags to assign to the resource. At this time there's a bug in the AKS API where Tags for a Node Pool are not stored in the correct case - you [may wish to use Terraform's `ignore_changes` functionality to ignore changes to the casing](https://www.terraform.io/language/meta-arguments/lifecycle#ignore_changess) until this is fixed in the AKS API.
     vm_size                       = (Required) The SKU which should be used for the Virtual Machines used in this Node Pool. Changing this forces a new resource to be created.