terraform/gcp: Allow to use preemptible VM instances (#8480)

contrib/terraform/gcp/modules/kubernetes-cluster/main.tf

@@ -231,6 +231,11 @@ resource "google_compute_instance" "master" {
   lifecycle {
     ignore_changes = [attached_disk]
   }
+
+  scheduling {
+    preemptible = var.master_preemptible
+    automatic_restart = !var.master_preemptible
+  }
 }
 
 resource "google_compute_forwarding_rule" "master_lb" {
@@ -328,6 +333,11 @@ resource "google_compute_instance" "worker" {
   lifecycle {
     ignore_changes = [attached_disk]
   }
+
+  scheduling {
+    preemptible = var.worker_preemptible
+    automatic_restart = !var.worker_preemptible
+  }
 }
 
 resource "google_compute_address" "worker_lb" {

contrib/terraform/gcp/modules/kubernetes-cluster/variables.tf

@@ -27,6 +27,10 @@ variable "master_sa_scopes" {
   type = list(string)
 }
 
+variable "master_preemptible" {
+  type = bool
+}
+
 variable "worker_sa_email" {
   type = string
 }
@@ -35,6 +39,10 @@ variable "worker_sa_scopes" {
   type = list(string)
 }
 
+variable "worker_preemptible" {
+  type = bool
+}
+
 variable "ssh_pub_key" {}
 
 variable "ssh_whitelist" {