Terraform - Remove the need for region specific reference data (#1962)

* Dynamically retrieve aws_bastion_ami latest reference by querying AWS rather than hard coded

* Dynamically retrieve the list of availability_zones instead of needing to have them hard coded

* Limit availability zones to first 2, using slice extrapolation function

* Replace the need for hardcoded variable "aws_cluster_ami" by the data provided by Terraform

* Move ami choosing to vars, so people don't need to edit create infrastructure if they want another vendor image (as suggested by @atoms)

* Make name of the data block agnostic of distribution, given there are more than one distribution supported

* Add documentation about other distros being supported and what to change in which location to make these changes

contrib/terraform/aws/README.md

@@ -24,7 +24,7 @@ export AWS_DEFAULT_REGION="zzz"
 ```
 - Rename `contrib/terraform/aws/terraform.tfvars.example` to `terraform.tfvars`
 
-- Update `contrib/terraform/aws/terraform.tfvars` with your data
+- Update `contrib/terraform/aws/terraform.tfvars` with your data. By default, the Terraform scripts use CoreOS as base image. If you want to change this behaviour, see note "Using other distrib than CoreOs" below.
 - Allocate a new AWS Elastic IP. Use this for your `loadbalancer_apiserver_address` value (below)
 - Create an AWS EC2 SSH Key
 - Run with `terraform apply --var-file="credentials.tfvars"` or `terraform apply` depending if you exported your AWS credentials
@@ -48,6 +48,60 @@ Example (this one assumes you are using CoreOS)
 ```commandline
 ansible-playbook -i ./inventory/hosts ./cluster.yml -e ansible_ssh_user=core -e bootstrap_os=coreos -b --become-user=root --flush-cache
 ```
+***Using other distrib than CoreOs***
+If you want to use another distribution than CoreOS, you can modify the search filters of the 'data "aws_ami" "distro"' in variables.tf.
+
+For example, to use:
+- Debian Jessie, replace 'data "aws_ami" "distro"' in variables.tf with
+data "aws_ami" "distro" {
+  most_recent = true
+
+  filter {
+    name   = "name"
+    values = ["debian-jessie-amd64-hvm-*"]
+  }
+
+  filter {
+    name   = "virtualization-type"
+    values = ["hvm"]
+  }
+
+  owners = ["379101102735"]
+}
+
+- Ubuntu 16.04, replace 'data "aws_ami" "distro"' in variables.tf with
+data "aws_ami" "distro" {
+  most_recent = true
+
+  filter {
+    name   = "name"
+    values = ["ubuntu/images/hvm-ssd/ubuntu-xenial-16.04-amd64-*"]
+  }
+
+  filter {
+    name   = "virtualization-type"
+    values = ["hvm"]
+  }
+
+  owners = ["099720109477"]
+}
+
+- Centos 7, replace 'data "aws_ami" "distro"' in variables.tf with
+data "aws_ami" "distro" {
+  most_recent = true
+
+  filter {
+    name   = "name"
+    values = ["dcos-centos7-*"]
+  }
+
+  filter {
+    name   = "virtualization-type"
+    values = ["hvm"]
+  }
+
+  owners = ["688023202711"]
+}
 
 **Troubleshooting**
 

contrib/terraform/aws/create-infrastructure.tf

@@ -8,6 +8,8 @@ provider "aws" {
     region = "${var.AWS_DEFAULT_REGION}"
 }
 
+data "aws_availability_zones" "available" {}
+
 /*
 * Calling modules who create the initial AWS VPC / AWS ELB
 * and AWS IAM Roles for Kubernetes Deployment
@@ -18,7 +20,7 @@ module "aws-vpc" {
 
   aws_cluster_name = "${var.aws_cluster_name}"
   aws_vpc_cidr_block = "${var.aws_vpc_cidr_block}"
-  aws_avail_zones="${var.aws_avail_zones}"
+  aws_avail_zones="${slice(data.aws_availability_zones.available.names,0,2)}"
   aws_cidr_subnets_private="${var.aws_cidr_subnets_private}"
   aws_cidr_subnets_public="${var.aws_cidr_subnets_public}"
   default_tags="${var.default_tags}"
@@ -31,7 +33,7 @@ module "aws-elb" {
 
   aws_cluster_name="${var.aws_cluster_name}"
   aws_vpc_id="${module.aws-vpc.aws_vpc_id}"
-  aws_avail_zones="${var.aws_avail_zones}"
+  aws_avail_zones="${slice(data.aws_availability_zones.available.names,0,2)}"
   aws_subnet_ids_public="${module.aws-vpc.aws_subnet_ids_public}"
   aws_elb_api_port = "${var.aws_elb_api_port}"
   k8s_secure_api_port = "${var.k8s_secure_api_port}"
@@ -49,12 +51,13 @@ module "aws-iam" {
 * Create Bastion Instances in AWS
 *
 */
+
 resource "aws_instance" "bastion-server" {
-    ami = "${var.aws_bastion_ami}"
+    ami = "${data.aws_ami.distro.id}"
     instance_type = "${var.aws_bastion_size}"
     count = "${length(var.aws_cidr_subnets_public)}"
     associate_public_ip_address = true
-    availability_zone  = "${element(var.aws_avail_zones,count.index)}"
+    availability_zone  = "${element(slice(data.aws_availability_zones.available.names,0,2),count.index)}"
     subnet_id = "${element(module.aws-vpc.aws_subnet_ids_public,count.index)}"
 
 
@@ -76,13 +79,13 @@ resource "aws_instance" "bastion-server" {
 */
 
 resource "aws_instance" "k8s-master" {
-    ami = "${var.aws_cluster_ami}"
+    ami = "${data.aws_ami.distro.id}"
     instance_type = "${var.aws_kube_master_size}"
 
     count = "${var.aws_kube_master_num}"
 
 
-    availability_zone  = "${element(var.aws_avail_zones,count.index)}"
+    availability_zone  = "${element(slice(data.aws_availability_zones.available.names,0,2),count.index)}"
     subnet_id = "${element(module.aws-vpc.aws_subnet_ids_private,count.index)}"
 
 
@@ -108,13 +111,13 @@ resource "aws_elb_attachment" "attach_master_nodes" {
 
 
 resource "aws_instance" "k8s-etcd" {
-    ami = "${var.aws_cluster_ami}"
+    ami = "${data.aws_ami.distro.id}"
     instance_type = "${var.aws_etcd_size}"
 
     count = "${var.aws_etcd_num}"
 
 
-    availability_zone = "${element(var.aws_avail_zones,count.index)}"
+    availability_zone = "${element(slice(data.aws_availability_zones.available.names,0,2),count.index)}"
     subnet_id = "${element(module.aws-vpc.aws_subnet_ids_private,count.index)}"
 
 
@@ -132,12 +135,12 @@ resource "aws_instance" "k8s-etcd" {
 
 
 resource "aws_instance" "k8s-worker" {
-    ami = "${var.aws_cluster_ami}"
+    ami = "${data.aws_ami.distro.id}"
     instance_type = "${var.aws_kube_worker_size}"
 
     count = "${var.aws_kube_worker_num}"
 
-    availability_zone  = "${element(var.aws_avail_zones,count.index)}"
+    availability_zone  = "${element(slice(data.aws_availability_zones.available.names,0,2),count.index)}"
     subnet_id = "${element(module.aws-vpc.aws_subnet_ids_private,count.index)}"
 
     vpc_security_group_ids = [ "${module.aws-vpc.aws_security_group}" ]

contrib/terraform/aws/terraform.tfvars

@@ -5,10 +5,8 @@ aws_cluster_name = "devtest"
 aws_vpc_cidr_block = "10.250.192.0/18"
 aws_cidr_subnets_private = ["10.250.192.0/20","10.250.208.0/20"]
 aws_cidr_subnets_public = ["10.250.224.0/20","10.250.240.0/20"]
-aws_avail_zones = ["us-west-2a","us-west-2b"]
 
 #Bastion Host
-aws_bastion_ami = "ami-db56b9a3"
 aws_bastion_size = "t2.medium"
 
 
@@ -23,8 +21,6 @@ aws_etcd_size = "t2.medium"
 aws_kube_worker_num = 4
 aws_kube_worker_size = "t2.medium"
 
-aws_cluster_ami = "ami-db56b9a3"
-
 #Settings AWS ELB
 
 aws_elb_api_port = 6443

contrib/terraform/aws/variables.tf

@@ -20,6 +20,21 @@ variable "aws_cluster_name" {
   description = "Name of AWS Cluster"
 }
 
+data "aws_ami" "distro" {
+  most_recent = true
+
+  filter {
+    name   = "name"
+    values = ["CoreOS-stable-*"]
+  }
+
+  filter {
+    name   = "virtualization-type"
+    values = ["hvm"]
+  }
+
+  owners = ["595879546273"] #CoreOS
+}
 
 //AWS VPC Variables
 
@@ -27,11 +42,6 @@ variable "aws_vpc_cidr_block" {
   description = "CIDR Block for VPC"
 }
 
-variable "aws_avail_zones" {
-  description = "Availability Zones Used"
-  type = "list"
-}
-
 variable "aws_cidr_subnets_private" {
   description = "CIDR Blocks for private subnets in Availability Zones"
   type = "list"
@@ -44,10 +54,6 @@ variable "aws_cidr_subnets_public" {
 
 //AWS EC2 Settings
 
-variable "aws_bastion_ami" {
-    description = "AMI ID for Bastion Host in chosen AWS Region"
-}
-
 variable "aws_bastion_size" {
     description = "EC2 Instance Size of Bastion Host"
 }
@@ -81,9 +87,6 @@ variable "aws_kube_worker_size" {
     description = "Instance size of Kubernetes Worker Nodes"
 }
 
-variable "aws_cluster_ami" {
-    description = "AMI ID for Kubernetes Cluster"
-}
 /*
 * AWS ELB Settings
 *