chore: use zonal GKE cluster to reduce provisioning time

Switch cluster and all node pools from regional to zonal (`europe-west4-b`) to avoid the 40+ minute provisioning time of a regional (multi-zone) cluster. Adds a `zone` variable to the GKE module and cluster config, and updates the workflow's `gcloud get-credentials` call to use `--zone` instead of `--region`.

.github/release/clusters/logos-storage-rel-tests-gcp-europe-west4/main.tf

@@ -5,6 +5,7 @@ module "gke" {
   name                       = "logos-storage-rel-tests"
   project                    = var.project
   region                     = var.region
+  zone                       = var.zone
   kubernetes_release_channel = "STABLE"
   node_pool_name             = "infra-e2-standard-4"
   node_pool_machine_type     = "e2-standard-4"
@@ -21,7 +22,7 @@ module "gke" {
 resource "google_container_node_pool" "runners-ci" {
   name     = "runners-ci-e2-standard-2"
   cluster  = module.gke.kubernetes_cluster_id
-  location = var.region
+  location = var.zone
   project  = var.project
 
   autoscaling {
@@ -47,7 +48,7 @@ resource "google_container_node_pool" "runners-ci" {
 resource "google_container_node_pool" "tests-pods" {
   name     = "tests-e2-medium"
   cluster  = module.gke.kubernetes_cluster_id
-  location = var.region
+  location = var.zone
   project  = var.project
 
   autoscaling {

.github/release/clusters/logos-storage-rel-tests-gcp-europe-west4/variables.tf

@@ -7,3 +7,8 @@ variable "region" {
   description = "GCP region (e.g. europe-west4)"
   type        = string
 }
+
+variable "zone" {
+  description = "GCP zone for the cluster (e.g. europe-west4-b)"
+  type        = string
+}

.github/release/clusters/modules/gke/main.tf

@@ -1,7 +1,7 @@
 # Kubernetes cluster
 resource "google_container_cluster" "this" {
   name     = local.name
-  location = var.region
+  location = var.zone
   project  = var.project
 
   # Create an empty cluster — all node pools are managed as separate resources
@@ -28,7 +28,7 @@ resource "google_container_cluster" "this" {
 resource "google_container_node_pool" "default" {
   name     = var.node_pool_name
   cluster  = google_container_cluster.this.id
-  location = var.region
+  location = var.zone
   project  = var.project
 
   autoscaling {

.github/release/clusters/modules/gke/variables.tf

@@ -11,7 +11,12 @@ variable "project" {
 
 variable "region" {
   type        = string
-  description = "The GCP region for the cluster (regional cluster spans 3 zones)."
+  description = "The GCP region (used for the provider and node pool location)."
+}
+
+variable "zone" {
+  type        = string
+  description = "The GCP zone for the cluster. Using a single zone avoids the longer provisioning time of a regional (multi-zone) cluster."
 }
 
 # Kubernetes Control Plane

.github/workflows/release.yml

@@ -211,6 +211,7 @@ jobs:
     env:
       TF_VAR_project: ${{ secrets.RELEASE_TESTS_GCP_PROJECT }}
       TF_VAR_region: europe-west4
+      TF_VAR_zone: europe-west4-b
       STORAGEDOCKERIMAGE: ${{ needs.build-docker-dist-tests.outputs.logos_storage_image }}
       TEST_TYPE: release-tests
       BRANCH: ${{ inputs.branch || 'master' }}
@@ -249,7 +250,7 @@ jobs:
       - name: Get kubeconfig
         run: |
           gcloud container clusters get-credentials logos-storage-rel-tests-gcp-europe-west4 \
-            --region europe-west4 \
+            --zone europe-west4-b \
             --project ${{ secrets.RELEASE_TESTS_GCP_PROJECT }}
 
       - name: Create in-cluster app kubeconfig secret