Fix failing GKE cluster creation in custom VPC (Terraform)

When creating a GKE cluster in terraform with a non-default (custom) VPC
the subnetwork must be specified otherwise the operation will fail with an expected error.

Expected error when subnetwork isn't set:
- "Error: googleapi: Error 400: Network "MY-VPC-NAME" requires specifying a subnetwork., badRequest"

User should follow the instructions in README.md and specify the required fields based on whether
the cluster will run in a default VPC or custom VPC.

Tests performed:
- Able to create cluster in default VPC in a backwards compatible way - passed
- Able to create cluster in a user defined non-default network and subnetwork - passed

Reference
- googleforgames#1641
- https://www.terraform.io/docs/providers/google/r/container_cluster.html

examples/terraform-submodules/gke/.gitignore

@@ -0,0 +1,2 @@
+development.tfvars
+production.tfvars

examples/terraform-submodules/gke/README.md

@@ -0,0 +1,43 @@
+This terraform module creates an Agones cluster on GKE. 
+
+# Prerequisites
+- Terraform 0.12.x
+- Helm 2.x
+- An existing GCP Project
+- Enabled service API(s)
+
+# Enabling Service APIs
+
+Enable each required API below by following [the enabling APIs guide](https://cloud.google.com/endpoints/docs/openapi/enable-api#gcloud).
+
+Required APIs:
+- container.googleapis.com (Kubernetes)
+
+# Examples
+
+## Create an Agones in a default VPC.
+
+
+Required fields:
+- project
+
+```terraform apply -var project="<YOUR_GCP_ProjectID>" [-var agones_version="1.6.0"]```
+
+## Create an Agones cluster in a custom VPC.
+Required fields:
+- project
+- network
+- subnetwork
+
+
+```terraform apply -var project="<YOUR_GCP_ProjectID>" -var network="<YOUR_NETWORK_NAME>" -var subnetwork="<YOUR_SUBNETWORK_NAME>" [-var agones_version="1.6.0"]```
+
+# Troubleshooting
+
+## Unknown command "init" for "helm"
+```Error: Error running command 'helm init --client-only': exit status 1. Output: Error: unknown command "init" for "helm```
+
+The above error occurs when helm3 is installed instead of helm2. You must use helm v2.x. Validate your version by running the command bellow:
+
+```helm version```
+

examples/terraform-submodules/gke/auth.tf

@@ -0,0 +1,22 @@
+
+// Copyright 2020 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+provider "google" {
+  version = "~> 2.10"
+}
+
+provider "google-beta" {
+  version = "~> 2.10"
+}

examples/terraform-submodules/gke/module.tf

@@ -12,64 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-
-// Run:
-//  terraform apply -var project="<YOUR_GCP_ProjectID>" [-var agones_version="1.4.0"]
-
-provider "google" {
-  version = "~> 2.10"
-}
-
-provider "google-beta" {
-  version = "~> 2.10"
-}
-
-variable "project" {
-  default = ""
-}
-
-variable "name" {
-  default = "agones-terraform-example"
-}
-
-// Install latest version of agones
-variable "agones_version" {
-  default = ""
-}
-
-variable "machine_type" {
-  default = "n1-standard-4"
-}
-
-// Note: This is the number of gameserver nodes. The Agones module will automatically create an additional
-// two node pools with 1 node each for "agones-system" and "agones-metrics".
-variable "node_count" {
-  default = "4"
-}
-variable "zone" {
-  default     = "us-west1-c"
-  description = "The GCP zone to create the cluster in"
-}
-
-variable "network" {
-  default     = "default"
-  description = "The name of the VPC network to attach the cluster and firewall rule to"
-}
-
-variable "log_level" {
-  default = "info"
-}
-
-variable "feature_gates" {
-  default = ""
-}
-
 module "gke_cluster" {
   // ***************************************************************************************************
-  // Update ?ref= to the agones release you are installing. For example, ?ref=release-1.3.0 corresponds
-  // to Agones version 1.3.0
+  // Update ?ref= to the agones release you are installing. For example, ?ref=release-1.6.0 corresponds
+  // to Agones version 1.6.0
   // ***************************************************************************************************
-  source = "git::https://github.com/googleforgames/agones.git//install/terraform/modules/gke/?ref=master"
+  #source = "git::https://github.com/googleforgames/agones.git//install/terraform/modules/gke/?ref=master"
+  source = "../../../install/terraform/modules/gke"
 
   cluster = {
     "name"             = var.name
@@ -78,13 +27,14 @@ module "gke_cluster" {
     "initialNodeCount" = var.node_count
     "project"          = var.project
     "network"          = var.network
+    "subnetwork"       = var.subnetwork
   }
 }
 
 module "helm_agones" {
   // ***************************************************************************************************
-  // Update ?ref= to the agones release you are installing. For example, ?ref=release-1.3.0 corresponds
-  // to Agones version 1.3.0
+  // Update ?ref= to the agones release you are installing. For example, ?ref=release-1.6.0 corresponds
+  // to Agones version 1.6.0
   // ***************************************************************************************************
   source = "git::https://github.com/googleforgames/agones.git//install/terraform/modules/helm/?ref=master"
 
@@ -97,13 +47,3 @@ module "helm_agones" {
   cluster_ca_certificate = module.gke_cluster.cluster_ca_certificate
   log_level              = var.log_level
 }
-
-output "host" {
-  value = module.gke_cluster.host
-}
-output "token" {
-  value = module.gke_cluster.token
-}
-output "cluster_ca_certificate" {
-  value = module.gke_cluster.cluster_ca_certificate
-}

examples/terraform-submodules/gke/output.tf

@@ -0,0 +1,9 @@
+output "host" {
+  value = module.gke_cluster.host
+}
+output "token" {
+  value = module.gke_cluster.token
+}
+output "cluster_ca_certificate" {
+  value = module.gke_cluster.cluster_ca_certificate
+}

examples/terraform-submodules/gke/variables.tf

@@ -0,0 +1,59 @@
+// Copyright 2020 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+variable "project" {
+  default = ""
+}
+
+variable "name" {
+  default = "agones-terraform-example"
+}
+
+// Install latest version of agones
+variable "agones_version" {
+  default = ""
+}
+
+variable "machine_type" {
+  default = "n1-standard-4"
+}
+
+// Note: This is the number of gameserver nodes. The Agones module will automatically create an additional
+// two node pools with 1 node each for "agones-system" and "agones-metrics".
+variable "node_count" {
+  default     = "4"
+  description = "The number of gameserver nodes."
+}
+
+variable "zone" {
+  default     = "us-west1-c"
+  description = "The GCP zone to create the cluster in"
+}
+
+variable "network" {
+  description = "The name of the VPC network to attach the cluster and firewall rule to"
+}
+
+variable "subnetwork" {
+  default     = ""
+  description = "The subnetwork to host the cluster in. Required field if network value isn't 'default'."
+}
+
+variable "log_level" {
+  default = "info"
+}
+
+variable "feature_gates" {
+  default = ""
+}

install/terraform/modules/gke/cluster.tf

@@ -28,6 +28,7 @@ locals {
   machineType       = lookup(var.cluster, "machineType", "n1-standard-4")
   initialNodeCount  = lookup(var.cluster, "initialNodeCount", "4")
   network           = lookup(var.cluster, "network", "default")
+  subnetwork        = lookup(var.cluster, "subnetwork")
   kubernetesVersion = lookup(var.cluster, "kubernetesVersion", "1.15")
 }
 
@@ -45,10 +46,11 @@ local.zone)}
 }
 
 resource "google_container_cluster" "primary" {
-  name     = local.name
-  location = local.zone
-  project  = local.project
-  network  = local.network
+  name       = local.name
+  location   = local.zone
+  project    = local.project
+  network    = local.network
+  subnetwork = local.subnetwork
 
   min_master_version = local.kubernetesVersion
 

install/terraform/modules/gke/variables.tf

@@ -31,6 +31,7 @@ variable "cluster" {
     "initialNodeCount"  = "4"
     "project"           = "agones"
     "network"           = "default"
+    "subnetwork"        = ""
     "kubernetesVersion" = "1.15"
   }
 }