Allow Flatcar Linux os_image on AWS, rename os_channel

* Replace os_channel variable with os_image to align naming
across clouds. Users who set this option to stable, beta, or
alpha should now set os_image to coreos-stable, coreos-beta,
or coreos-alpha.
* Default os_image to coreos-stable. This continues to use
the most recent image from the stable channel as always.
* Allow Container Linux derivative Flatcar Linux by setting
os_image to `flatcar-stable`, `flatcar-beta`, `flatcar-alpha`

CHANGES.md

@@ -9,10 +9,12 @@ Notable changes between versions.
 
 #### AWS
 
-* Allow "preemptible" workers via spot instances ([#202](https://github.com/poseidon/typhoon/pull/202))
+* Allow preemptible workers via spot instances ([#202](https://github.com/poseidon/typhoon/pull/202))
-  * Add `worker_price` to allow worker spot instances. Defaults to empty string for the worker autoscaling group to use regular on-demand instances.
+  * Add `worker_price` to allow worker spot instances. Default to empty string for the worker autoscaling group to use regular on-demand instances.
   * Add `spot_price` to internal `workers` module for spot [worker pools](https://typhoon.psdn.io/advanced/worker-pools/)
-  * Note: Unlike GCP `preemptible` workers, spot instances require you to pick a bid price.
+* Allow Container Linux derivative [Flatcar Linux](https://docs.flatcar-linux.org/) by setting `os_image` to `flatcar-stable`, `flatcar-beta`, `flatcar-alpha`.
+* Replace `os_channel` variable with `os_image` to align naming across clouds
+  * Please change values `stable`, `beta`, or `alpha` to `coreos-stable` (default), `coreos-beta`, `coreos-alpha` (action required!)
 
 #### Addons
 

aws/container-linux/kubernetes/ami.tf

@@ -1,3 +1,12 @@
+locals {
+  # Pick a CoreOS Container Linux derivative
+  # coreos-stable -> Container Linux AMI
+  # flatcar-stable -> Flatcar Linux AMI
+  ami_id = "${local.flavor == "flatcar" ? data.aws_ami.flatcar.image_id : data.aws_ami.coreos.image_id}"
+  flavor = "${element(split("-", var.os_image), 0)}"
+  channel = "${element(split("-", var.os_image), 1)}"
+}
+
 data "aws_ami" "coreos" {
   most_recent = true
   owners      = ["595879546273"]
@@ -14,6 +23,27 @@ data "aws_ami" "coreos" {
 
   filter {
     name   = "name"
-    values = ["CoreOS-${var.os_channel}-*"]
+    values = ["CoreOS-${local.channel}-*"]
   }
 }
+
+data "aws_ami" "flatcar" {
+  most_recent = true
+  owners      = ["075585003325"]
+
+  filter {
+    name   = "architecture"
+    values = ["x86_64"]
+  }
+
+  filter {
+    name   = "virtualization-type"
+    values = ["hvm"]
+  }
+
+  filter {
+    name   = "name"
+    values = ["Flatcar-${local.channel}-*"]
+  }
+}
+

aws/container-linux/kubernetes/controllers.tf

@@ -23,7 +23,7 @@ resource "aws_instance" "controllers" {
 
   instance_type = "${var.controller_type}"
 
-  ami       = "${data.aws_ami.coreos.image_id}"
+  ami       = "${local.ami_id}"
   user_data = "${element(data.ct_config.controller_ign.*.rendered, count.index)}"
 
   # storage

aws/container-linux/kubernetes/variables.tf

@@ -41,10 +41,10 @@ variable "worker_type" {
   description = "EC2 instance type for workers"
 }
 
-variable "os_channel" {
+variable "os_image" {
   type        = "string"
-  default     = "stable"
+  default     = "coreos-stable"
-  description = "Container Linux AMI channel (stable, beta, alpha)"
+  description = "AMI channel for a Container Linux derivative (coreos-stable, coreos-beta, coreos-alpha, flatcar-stable, flatcar-beta, flatcar-alpha)"
 }
 
 variable "disk_size" {

aws/container-linux/kubernetes/workers.tf

@@ -8,7 +8,7 @@ module "workers" {
   security_groups = ["${aws_security_group.worker.id}"]
   count           = "${var.worker_count}"
   instance_type   = "${var.worker_type}"
-  os_channel      = "${var.os_channel}"
+  os_image      = "${var.os_image}"
   disk_size       = "${var.disk_size}"
   spot_price      = "${var.worker_price}"
 

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

@@ -1,3 +1,12 @@
+locals {
+  # Pick a CoreOS Container Linux derivative
+  # coreos-stable -> Container Linux AMI
+  # flatcar-stable -> Flatcar Linux AMI
+  ami_id = "${local.flavor == "flatcar" ? data.aws_ami.flatcar.image_id : data.aws_ami.coreos.image_id}"
+  flavor = "${element(split("-", var.os_image), 0)}"
+  channel = "${element(split("-", var.os_image), 1)}"
+}
+
 data "aws_ami" "coreos" {
   most_recent = true
   owners      = ["595879546273"]
@@ -14,6 +23,27 @@ data "aws_ami" "coreos" {
 
   filter {
     name   = "name"
-    values = ["CoreOS-${var.os_channel}-*"]
+    values = ["CoreOS-${local.channel}-*"]
   }
 }
+
+data "aws_ami" "flatcar" {
+  most_recent = true
+  owners      = ["075585003325"]
+
+  filter {
+    name   = "architecture"
+    values = ["x86_64"]
+  }
+
+  filter {
+    name   = "virtualization-type"
+    values = ["hvm"]
+  }
+
+  filter {
+    name   = "name"
+    values = ["Flatcar-${local.channel}-*"]
+  }
+}
+

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

@@ -34,10 +34,10 @@ variable "instance_type" {
   description = "EC2 instance type"
 }
 
-variable "os_channel" {
+variable "os_image" {
   type        = "string"
-  default     = "stable"
+  default     = "coreos-stable"
-  description = "Container Linux AMI channel (stable, beta, alpha)"
+  description = "AMI channel for a Container Linux derivative (coreos-stable, coreos-beta, coreos-alpha, flatcar-stable, flatcar-beta, flatcar-alpha)"
 }
 
 variable "disk_size" {

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

@@ -41,7 +41,7 @@ resource "aws_autoscaling_group" "workers" {
 
 # Worker template
 resource "aws_launch_configuration" "worker" {
-  image_id      = "${data.aws_ami.coreos.image_id}"
+  image_id      = "${local.ami_id}"
   instance_type = "${var.instance_type}"
   spot_price    = "${var.spot_price}"
 

docs/advanced/worker-pools.md

@@ -33,7 +33,7 @@ module "tempest-worker-pool" {
 
   count         = 2
   instance_type = "m5.large"
-  os_channel    = "beta"    
+  os_image      = "coreos-beta"
 }
 ```
 
@@ -66,7 +66,7 @@ The AWS internal `workers` module supports a number of [variables](https://githu
 |:-----|:------------|:--------|:--------|
 | count | Number of instances | 1 | 3 |
 | instance_type | EC2 instance type | "t2.small" | "t2.medium" |
-| os_channel | Container Linux AMI channel | stable| "beta", "alpha" |
+| os_image | AMI channel for a Container Linux derivative | coreos-stable | coreos-stable, coreos-beta, coreos-alpha, flatcar-stable, flatcar-beta, flatcar-alpha |
 | disk_size | Size of the disk in GB | 40 | 100 |
 | spot_price | Spot price in USD for workers. Leave as default empty string for regular on-demand instances | "" | "0.10" |
 | service_cidr | Must match `service_cidr` of cluster | "10.3.0.0/16" | "10.3.0.0/24" |

docs/cl/aws.md

@@ -241,7 +241,7 @@ Reference the DNS zone id with `"${aws_route53_zone.zone-for-clusters.zone_id}"`
 | worker_count | Number of workers | 1 | 3 |
 | controller_type | EC2 instance type for controllers | "t2.small" | See below |
 | worker_type | EC2 instance type for workers | "t2.small" | See below |
-| os_channel | Container Linux AMI channel | stable | stable, beta, alpha |
+| os_image | AMI channel for a Container Linux derivative | coreos-stable | coreos-stable, coreos-beta, coreos-alpha, flatcar-stable, flatcar-beta, flatcar-alpha |
 | disk_size | Size of the EBS volume in GB | "40" | "100" |
 | disk_type | Type of the EBS volume | "gp2" | standard, gp2, io1 |
 | worker_price | Spot price in USD for workers. Leave as default empty string for regular on-demand instances | "" | "0.10" |