Add a mechanism to lookup the AMI from current region

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/) and this
 project adheres to [Semantic Versioning](http://semver.org/).
 
+## [v0.1.2] - 2018-06-07
+
+### Added
+
+- A way to detect AMI according to region while still allow user to overwrite it
+
 ## [v0.1.0] - 2018-06-07
 
 ### Added

README.md

@@ -28,7 +28,6 @@ module "eks" {
   subnets               = ["subnet-abcde012", "subnet-bcde012a"]
   tags                  = "${map("Environment", "test")}"
   vpc_id                = "vpc-abcde012"
-  workers_ami_id        = "ami-123456"
   cluster_ingress_cidrs = ["24.18.23.91/32"]
 }
 ```
@@ -66,6 +65,14 @@ Report issues/questions/feature requests on in the [issues](https://github.com/t
 
 Full contributing [guidelines are covered here](https://github.com/terraform-aws-modules/terraform-aws-eks/blob/master/CONTRIBUTING.md).
 
+## AMI
+
+According to [AWS guide](https://docs.aws.amazon.com/eks/latest/userguide/getting-started.html), we should use the EKS-optimized AMI. Unfortunately, the AMI is being rolled out quite slowly. So, we have a variable that set up the mapping between the region in which you are rolling out EKS with the AMI that we will be using for the instance.
+
+If you wish to use your own AMI, you can do so by overwriting this `mapping` action with the variable `workers_ami_id`. Otherwise, we will simply map from the region to the AMI via the map (no pun intended) in variable `workers_ami_mapping`.
+
+Please note that the maintainer of this module will try to keep the list as always up-to-date, but if for some reason you think it's out of date, please feel free to provide the correct value via that variable, and the module will look up correctly.
+
 ## IAM Permissions
 
 Testing and using this repo requires a minimum set of IAM permissions. Test permissions
@@ -94,7 +101,8 @@ MIT Licensed. See [LICENSE](https://github.com/terraform-aws-modules/terraform-a
 | subnets | A list of subnets to associate with the cluster's underlying instances. | list | - | yes |
 | tags | A map of tags to add to all resources | string | `<map>` | no |
 | vpc_id | VPC id where the cluster and other resources will be deployed. | string | - | yes |
-| workers_ami_id | AMI ID for the eks workers. | string | - | yes |
+| workers_ami_id | AMI ID for the eks workers. | string | `` | no |
+| workers_ami_mapping | Mapping from the region to the [EKS optimized AMI](https://docs.aws.amazon.com/eks/latest/userguide/getting-started.html) | map | `<map>` | no |
 | workers_asg_desired_capacity | description | string | `1` | no |
 | workers_asg_max_size | description | string | `3` | no |
 | workers_asg_min_size | description | string | `1` | no |

local.tf

@@ -127,4 +127,7 @@ users:
         - "-i"
         - "${var.cluster_name}"
 KUBECONFIG
+
+  # A mechanism to detect the AMI that we wish to use
+  worker_instance_ami = "${length(var.workers_ami_mapping) > 0? var.workers_ami_id : lookup(var.workers_ami_mapping, data.aws_region.current.name)}"
 }

main.tf

@@ -29,7 +29,6 @@
 *   subnets               = ["subnet-abcde012", "subnet-bcde012a"]
 *   tags                  = "${map("Environment", "test")}"
 *   vpc_id                = "vpc-abcde012"
-*   workers_ami_id        = "ami-123456"
 *   cluster_ingress_cidrs = ["24.18.23.91/32"]
 * }
 * ```
@@ -67,6 +66,15 @@ To test your kubectl connection manually, see the [eks_test_fixture README](http
 
 * Full contributing [guidelines are covered here](https://github.com/terraform-aws-modules/terraform-aws-eks/blob/master/CONTRIBUTING.md).
 
+## AMI
+
+
+According to [AWS guide](https://docs.aws.amazon.com/eks/latest/userguide/getting-started.html), we should use the EKS-optimized AMI. Unfortunately, the AMI is being rolled out quite slowly. So, we have a variable that set up the mapping between the region in which you are rolling out EKS with the AMI that we will be using for the instance.
+
+If you wish to use your own AMI, you can do so by overwriting this `mapping` action with the variable `workers_ami_id`. Otherwise, we will simply map from the region to the AMI via the map (no pun intended) in variable `workers_ami_mapping`.
+
+Please note that the maintainer of this module will try to keep the list as always up-to-date, but if for some reason you think it's out of date, please feel free to provide the correct value via that variable, and the module will look up correctly.
+
 * ## IAM Permissions
 
 * Testing and using this repo requires a minimum set of IAM permissions. Test permissions

variables.tf

@@ -28,6 +28,7 @@ variable "vpc_id" {
 
 variable "workers_ami_id" {
   description = "AMI ID for the eks workers."
+  default     = ""
 }
 
 variable "workers_asg_desired_capacity" {
@@ -49,3 +50,13 @@ variable "workers_instance_type" {
   description = "Size of the workers instances."
   default     = "m4.large"
 }
+
+variable "workers_ami_mapping" {
+  description = "Mapping from the region to the [EKS optimized AMI](https://docs.aws.amazon.com/eks/latest/userguide/getting-started.html)"
+  type        = "map"
+
+  default = {
+    us-east-1 = "ami-dea4d5a1"
+    us-west-2 = "ami-73a6e20b"
+  }
+}

workers.tf

@@ -19,7 +19,7 @@ resource "aws_launch_configuration" "workers" {
   associate_public_ip_address = true
   name_prefix                 = "${var.cluster_name}"
   iam_instance_profile        = "${aws_iam_instance_profile.workers.name}"
-  image_id                    = "${var.workers_ami_id}"
+  image_id                    = "${local.worker_instance_ami}"
   instance_type               = "${var.workers_instance_type}"
   security_groups             = ["${aws_security_group.workers.id}"]
   user_data_base64            = "${base64encode(local.workers_userdata)}"