Use Fedora CoreOS image streams on Google Cloud

* Add `os_stream` variable to set a Fedora CoreOS stream
to `stable` (default), `testing`, or `next`
* Deprecate `os_image` variable. Remove docs about uploading
Fedora CoreOS images manually, this is no longer needed
* https://docs.fedoraproject.org/en-US/fedora-coreos/update-streams/

Rel: https://github.com/coreos/fedora-coreos-docs/pull/70

google-cloud/fedora-coreos/kubernetes/controllers.tf

@@ -42,7 +42,7 @@ resource "google_compute_instance" "controllers" {
     auto_delete = true
 
     initialize_params {
-      image = var.os_image
+      image = var.os_image == "" ? data.google_compute_image.fedora-coreos.self_link : var.os_image
       size  = var.disk_size
     }
   }

google-cloud/fedora-coreos/kubernetes/image.tf

@@ -0,0 +1,6 @@
+
+# Fedora CoreOS most recent image from stream
+data "google_compute_image" "fedora-coreos" {
+  project = "fedora-coreos-cloud"
+  family  = "fedora-coreos-${var.os_stream}"
+}

google-cloud/fedora-coreos/kubernetes/variables.tf

@@ -46,9 +46,17 @@ variable "worker_type" {
   default     = "n1-standard-1"
 }
 
+variable "os_stream" {
+  type        = string
+  description = "Fedora CoreOS stream for compute instances (e.g. stable, testing, next)"
+  default = "stable"
+}
+
+# Deprecated
 variable "os_image" {
   type        = string
   description = "Fedora CoreOS image for compute instances (e.g. fedora-coreos)"
+  default = ""
 }
 
 variable "disk_size" {

google-cloud/fedora-coreos/kubernetes/workers.tf

@@ -8,6 +8,7 @@ module "workers" {
   network      = google_compute_network.network.name
   worker_count = var.worker_count
   machine_type = var.worker_type
+  os_stream    = var.os_stream
   os_image     = var.os_image
   disk_size    = var.disk_size
   preemptible  = var.worker_preemptible

google-cloud/fedora-coreos/kubernetes/workers/image.tf

@@ -0,0 +1,6 @@
+
+# Fedora CoreOS most recent image from stream
+data "google_compute_image" "fedora-coreos" {
+  project = "fedora-coreos-cloud"
+  family  = "fedora-coreos-${var.os_stream}"
+}

google-cloud/fedora-coreos/kubernetes/workers/variables.tf

@@ -34,9 +34,17 @@ variable "machine_type" {
   default     = "n1-standard-1"
 }
 
+variable "os_stream" {
+  type        = string
+  description = "Fedora CoreOS stream for compute instances (e.g. stable, testing, next)"
+  default = "stable"
+}
+
+# Deprecated
 variable "os_image" {
   type        = string
-  description = "Fedora CoreOS image for compute instanges (e.g. gcloud compute images list)"
+  description = "Fedora CoreOS image for compute instances (e.g. fedora-coreos)"
+  default = ""
 }
 
 variable "disk_size" {

google-cloud/fedora-coreos/kubernetes/workers/workers.tf

@@ -43,7 +43,7 @@ resource "google_compute_instance_template" "worker" {
   disk {
     auto_delete  = true
     boot         = true
-    source_image = var.os_image
+    source_image = var.os_image == "" ? data.google_compute_image.fedora-coreos.self_link : var.os_image
     disk_size_gb = var.disk_size
   }