Add Container Linux Config snippets feature

* Introduce the ability to support Container Linux Config
"snippets" for controllers and workers on cloud platforms.
This allows end-users to customize hosts by providing Container
Linux configs that are additively merged into the base configs
defined by Typhoon. Config snippets are validated, merged, and
show any errors during `terraform plan`
* Example uses include adding systemd units, network configs,
mounts, files, raid arrays, or other disk provisioning features
provided by Container Linux Configs (using Ignition low-level)
* Requires terraform-provider-ct v0.2.1 plugin

aws/container-linux/kubernetes/controllers.tf

@@ -78,4 +78,5 @@ data "ct_config" "controller_ign" {
   count        = "${var.controller_count}"
   content      = "${element(data.template_file.controller_config.*.rendered, count.index)}"
   pretty_print = false
+  snippets     = ["${var.controller_clc_snippets}"]
 }

aws/container-linux/kubernetes/variables.tf

@@ -60,6 +60,18 @@ variable "worker_type" {
   description = "Worker EC2 instance type"
 }
 
+variable "controller_clc_snippets" {
+  type        = "list"
+  description = "Controller Container Linux Config snippets"
+  default     = []
+}
+
+variable "worker_clc_snippets" {
+  type        = "list"
+  description = "Worker Container Linux Config snippets"
+  default     = []
+}
+
 # bootkube assets
 
 variable "asset_dir" {

aws/container-linux/kubernetes/workers.tf

@@ -16,4 +16,5 @@ module "workers" {
   ssh_authorized_key    = "${var.ssh_authorized_key}"
   service_cidr          = "${var.service_cidr}"
   cluster_domain_suffix = "${var.cluster_domain_suffix}"
+  clc_snippets          = "${var.worker_clc_snippets}"
 }

aws/container-linux/kubernetes/workers/variables.tf

@@ -71,3 +71,9 @@ variable "cluster_domain_suffix" {
   type        = "string"
   default     = "cluster.local"
 }
+
+variable "clc_snippets" {
+  type        = "list"
+  description = "Container Linux Config snippets"
+  default     = []
+}

aws/container-linux/kubernetes/workers/workers.tf

@@ -71,4 +71,5 @@ data "template_file" "worker_config" {
 data "ct_config" "worker_ign" {
   content      = "${data.template_file.worker_config.rendered}"
   pretty_print = false
+  snippets     = ["${var.clc_snippets}"]
 }

digital-ocean/container-linux/kubernetes/controllers.tf

@@ -90,4 +90,6 @@ data "ct_config" "controller_ign" {
   count        = "${var.controller_count}"
   content      = "${element(data.template_file.controller_config.*.rendered, count.index)}"
   pretty_print = false
+
+  snippets = ["${var.controller_clc_snippets}"]
 }

digital-ocean/container-linux/kubernetes/variables.tf

@@ -48,6 +48,18 @@ variable "ssh_fingerprints" {
   description = "SSH public key fingerprints. (e.g. see `ssh-add -l -E md5`)"
 }
 
+variable "controller_clc_snippets" {
+  type        = "list"
+  description = "Controller Container Linux Config snippets"
+  default     = []
+}
+
+variable "worker_clc_snippets" {
+  type        = "list"
+  description = "Worker Container Linux Config snippets"
+  default     = []
+}
+
 # bootkube assets
 
 variable "asset_dir" {

digital-ocean/container-linux/kubernetes/workers.tf

@@ -51,4 +51,5 @@ data "template_file" "worker_config" {
 data "ct_config" "worker_ign" {
   content      = "${data.template_file.worker_config.rendered}"
   pretty_print = false
+  snippets     = ["${var.worker_clc_snippets}"]
 }

google-cloud/container-linux/kubernetes/cluster.tf

@@ -17,6 +17,7 @@ module "controllers" {
   ssh_authorized_key    = "${var.ssh_authorized_key}"
   service_cidr          = "${var.service_cidr}"
   cluster_domain_suffix = "${var.cluster_domain_suffix}"
+  clc_snippets          = "${var.controller_clc_snippets}"
 }
 
 module "workers" {
@@ -37,4 +38,5 @@ module "workers" {
   ssh_authorized_key    = "${var.ssh_authorized_key}"
   service_cidr          = "${var.service_cidr}"
   cluster_domain_suffix = "${var.cluster_domain_suffix}"
+  clc_snippets          = "${var.worker_clc_snippets}"
 }

google-cloud/container-linux/kubernetes/controllers/controllers.tf

@@ -87,4 +87,5 @@ data "ct_config" "controller_ign" {
   count        = "${var.count}"
   content      = "${element(data.template_file.controller_config.*.rendered, count.index)}"
   pretty_print = false
+  snippets     = ["${var.clc_snippets}"]
 }

google-cloud/container-linux/kubernetes/controllers/variables.tf

@@ -3,9 +3,9 @@ variable "cluster_name" {
   description = "Unique cluster name"
 }
 
-variable "ssh_authorized_key" {
+variable "region" {
   type        = "string"
-  description = "SSH public key for logging in as user 'core'"
+  description = "Google Cloud region (e.g. us-central1, see `gcloud compute regions list`)."
 }
 
 variable "network" {
@@ -30,11 +30,6 @@ variable "count" {
   description = "Number of controller compute instances the instance group should manage"
 }
 
-variable "region" {
-  type        = "string"
-  description = "Google Cloud region (e.g. us-central1, see `gcloud compute regions list`)."
-}
-
 variable "machine_type" {
   type        = "string"
   description = "Machine type for compute instances (e.g. gcloud compute machine-types list)"
@@ -51,12 +46,22 @@ variable "disk_size" {
   description = "The size of the disk in gigabytes."
 }
 
-// configuration
+# configuration
 
 variable "networking" {
   description = "Choice of networking provider (flannel or calico)"
   type        = "string"
-  default     = "flannel"
+  default     = "calico"
+}
+
+variable "kubeconfig" {
+  type        = "string"
+  description = "Generated Kubelet kubeconfig"
+}
+
+variable "ssh_authorized_key" {
+  type        = "string"
+  description = "SSH public key for logging in as user 'core'"
 }
 
 variable "service_cidr" {
@@ -75,7 +80,8 @@ variable "cluster_domain_suffix" {
   default     = "cluster.local"
 }
 
-variable "kubeconfig" {
+variable "clc_snippets" {
-  type        = "string"
+  type        = "list"
-  description = "Generated Kubelet kubeconfig"
+  description = "Container Linux Config snippets"
+  default     = []
 }

google-cloud/container-linux/kubernetes/variables.tf

@@ -52,6 +52,18 @@ variable "worker_preemptible" {
   description = "If enabled, Compute Engine will terminate workers randomly within 24 hours"
 }
 
+variable "controller_clc_snippets" {
+  type        = "list"
+  description = "Controller Container Linux Config snippets"
+  default     = []
+}
+
+variable "worker_clc_snippets" {
+  type        = "list"
+  description = "Worker Container Linux Config snippets"
+  default     = []
+}
+
 # bootkube assets
 
 variable "asset_dir" {

google-cloud/container-linux/kubernetes/workers/variables.tf

@@ -59,7 +59,7 @@ variable "kubeconfig" {
 
 variable "ssh_authorized_key" {
   type        = "string"
-  description = "SSH public key for logging in as user 'core'"
+  description = "SSH public key for user 'core'"
 }
 
 variable "service_cidr" {
@@ -78,6 +78,12 @@ variable "cluster_domain_suffix" {
   default     = "cluster.local"
 }
 
+variable "clc_snippets" {
+  type        = "list"
+  description = "Container Linux Config snippets"
+  default     = []
+}
+
 # unofficial, undocumented, unsupported, temporary
 
 variable "accelerator_type" {

google-cloud/container-linux/kubernetes/workers/workers.tf

@@ -32,6 +32,7 @@ data "template_file" "worker_config" {
 data "ct_config" "worker_ign" {
   content      = "${data.template_file.worker_config.rendered}"
   pretty_print = false
+  snippets     = ["${var.clc_snippets}"]
 }
 
 resource "google_compute_instance_template" "worker" {