[Feature] Add option to use an existing private network.

autoscaler-agents.tf

@@ -14,7 +14,7 @@ locals {
       cluster_autoscaler_log_to_stderr    = var.cluster_autoscaler_log_to_stderr
       cluster_autoscaler_stderr_threshold = var.cluster_autoscaler_stderr_threshold
       ssh_key                             = local.hcloud_ssh_key_id
-      ipv4_subnet_id                      = hcloud_network.k3s.id
+      ipv4_subnet_id                      = data.hcloud_network.k3s.id
       snapshot_id                         = local.first_nodepool_snapshot_id
       firewall_id                         = hcloud_firewall.k3s.id
       cluster_name                        = local.cluster_prefix

init.tf

@@ -250,7 +250,7 @@ resource "null_resource" "kustomization" {
   provisioner "remote-exec" {
     inline = [
       "set -ex",
-      "kubectl -n kube-system create secret generic hcloud --from-literal=token=${var.hcloud_token} --from-literal=network=${hcloud_network.k3s.name} --dry-run=client -o yaml | kubectl apply -f -",
+      "kubectl -n kube-system create secret generic hcloud --from-literal=token=${var.hcloud_token} --from-literal=network=${data.hcloud_network.k3s.name} --dry-run=client -o yaml | kubectl apply -f -",
       "kubectl -n kube-system create secret generic hcloud-csi --from-literal=token=${var.hcloud_token} --dry-run=client -o yaml | kubectl apply -f -",
       local.csi_version != null ? "curl https://raw.githubusercontent.com/hetznercloud/csi-driver/${coalesce(local.csi_version, "v2.4.0")}/deploy/kubernetes/hcloud-csi.yml -o /var/post_install/hcloud-csi.yml" : "echo 'Skipping hetzner csi.'"
     ]

kube.tf.example

@@ -57,6 +57,11 @@ module "kube-hetzner" {
   # * For Hetzner locations see https://docs.hetzner.com/general/others/data-centers-and-connection/
   network_region = "eu-central" # change to `us-east` if location is ash
 
+  # If you want to create the private network before calling this module,
+  # you can do so and pass its id here. NOTE: make sure to adapt network_ipv4_cidr accordingly
+  # use_existing_network = true
+  # existing_network_id = hcloud_network.your_network.id
+
   # If you must change the network CIDR you can do so below, but it is highly advised against.
   # network_ipv4_cidr = "10.0.0.0/8"
 

main.tf

@@ -23,16 +23,21 @@ resource "hcloud_ssh_key" "k3s" {
 }
 
 resource "hcloud_network" "k3s" {
+  count    = var.use_existing_network ? 0 : 1
   name     = var.cluster_name
   ip_range = var.network_ipv4_cidr
   labels   = local.labels
 }
 
+data "hcloud_network" "k3s" {
+  id = var.use_existing_network ? var.existing_network_id : hcloud_network.k3s[0].id
+}
+
 # We start from the end of the subnets cidr array,
 # as we would have fewer control plane nodepools, than agent ones.
 resource "hcloud_network_subnet" "control_plane" {
   count        = length(var.control_plane_nodepools)
-  network_id   = hcloud_network.k3s.id
+  network_id   = data.hcloud_network.k3s.id
   type         = "cloud"
   network_zone = var.network_region
   ip_range     = local.network_ipv4_subnets[255 - count.index]
@@ -41,7 +46,7 @@ resource "hcloud_network_subnet" "control_plane" {
 # Here we start at the beginning of the subnets cidr array
 resource "hcloud_network_subnet" "agent" {
   count        = length(var.agent_nodepools)
-  network_id   = hcloud_network.k3s.id
+  network_id   = data.hcloud_network.k3s.id
   type         = "cloud"
   network_zone = var.network_region
   ip_range     = local.network_ipv4_subnets[count.index]

output.tf

@@ -4,7 +4,7 @@ output "cluster_name" {
 }
 
 output "network_id" {
-  value       = hcloud_network.k3s.id
+  value       = data.hcloud_network.k3s.id
   description = "The ID of the HCloud network."
 }
 

variables.tf

@@ -74,7 +74,20 @@ variable "network_region" {
   type        = string
   default     = "eu-central"
 }
-
+variable "use_existing_network" {
+  # Unfortunately, we need this extra boolean variable. If we only check that existing_network_id is null,
+  # terraform will complain that it cannot set `count` variables based on existing_network_id != null, because
+  # that id is an output value from hcloud_network.your_network.id, which terraform will only know 
+  # after its construction.
+  description = "If you want to create the private network before calling this module, you can do so and set this value to true. Then you must set existing_network_id, and set network_ipv4_cidr to a range which does not collide with your other nodes."
+  type        = bool
+  default     = false
+}
+variable "existing_network_id" {
+  description = "If you want to create the private network before calling this module, you can do so and pass its id here. NOTE: make sure to adapt network_ipv4_cidr accordingly to a range which does not collide with your other nodes. Only used if use_existing_network == true."
+  type        = string
+  default     = null
+}
 variable "network_ipv4_cidr" {
   description = "The main network cidr that all subnets will be created upon."
   type        = string