Add variable to specify desired AMI architecture

* Add `var.ami_architecture` to allow users to specify their desired AMI architecture.
* Make `data.aws_ami.this` conditional on whether `var.ami_id` is specified. If it is specified, it's not necessary to lookup the AMI ID.
* Updated the example / test case to test with the `var.ami_architecture` variable.

Resolves <#139>

Author: jeohist

.spacelift/config.yml

@@ -1,5 +1,5 @@
 version: 2
-module_version: 3.0.2
+module_version: 3.1.0
 
 tests:
   - name: AMD64-based workerpool

README.md

@@ -127,7 +127,7 @@ page.
 
 ## ARM-based AMI
 
-You can use an ARM-based AMI by setting the `ami_id` variable to an arm64 AMI, and `ec2_instance_type` to an ARM-based instance type (e.g. `t4g.micro`).
+You can use an ARM-based AMI by setting the `ami_architecture` to `arm64`, or the `ami_id` variable to an arm64 AMI, and `ec2_instance_type` to an ARM-based instance type (e.g. `t4g.micro`).
 
 We recommend using [Spacelift AMIs](https://github.com/spacelift-io/spacelift-worker-image/releases) because they come with every required tool preinstalled.
 

ami.tf

@@ -6,8 +6,10 @@ locals {
 }
 
 data "aws_ami" "this" {
+  count = var.ami_id == "" ? 0 : 1
+
   most_recent = true
-  name_regex  = "^spacelift-\\d{10}-x86_64$"
+  name_regex  = "^spacelift-\\d{10}-${var.ami_architecture}$"
   owners      = [local.ami_owner_ids[data.aws_partition.current.partition]]
 
   filter {
@@ -22,6 +24,6 @@ data "aws_ami" "this" {
 
   filter {
     name   = "architecture"
-    values = ["x86_64"]
+    values = [var.ami_architecture]
   }
 }

asg.tf

@@ -28,7 +28,7 @@ module "asg" {
   name = local.base_name
 
   iam_instance_profile_arn = aws_iam_instance_profile.this.arn
-  image_id                 = var.ami_id != "" ? var.ami_id : data.aws_ami.this.id
+  image_id                 = var.ami_id != "" ? var.ami_id : data.aws_ami.this[0].id
   instance_type            = var.ec2_instance_type
   security_groups          = var.security_groups
   enable_monitoring        = var.enable_monitoring

examples/arm64/main.tf

@@ -36,27 +36,6 @@ data "aws_subnets" "this" {
   }
 }
 
-data "aws_ami" "this" {
-  most_recent = true
-  name_regex  = "^spacelift-\\d{10}-arm64$"
-  owners      = ["643313122712"]
-
-  filter {
-    name   = "root-device-type"
-    values = ["ebs"]
-  }
-
-  filter {
-    name   = "virtualization-type"
-    values = ["hvm"]
-  }
-
-  filter {
-    name   = "architecture"
-    values = ["arm64"]
-  }
-}
-
 #### Spacelift worker pool ####
 
 module "this" {
@@ -69,7 +48,7 @@ module "this" {
     SPACELIFT_TOKEN            = "<token-here>"
     SPACELIFT_POOL_PRIVATE_KEY = "<private-key-here>"
   }
-  ami_id = data.aws_ami.this.id
+  ami_architecture = "arm64"
   # t4g.micro is just for using the random provider and a few resources.
   # If you are using more than a few resources as well as memory intensive providers it's recommended to use a t4g.medium or at least a t4g.small
   # https://docs.spacelift.io/concepts/worker-pools#hardware-recommendations

moved.tf

@@ -0,0 +1,4 @@
+moved {
+  from = data.aws_ami.this
+  to   = data.aws_ami.this[0]
+}

variables.tf

@@ -4,6 +4,16 @@ variable "ami_id" {
   default     = ""
 }
 
+variable "ami_architecture" {
+  type        = string
+  description = "Architecture of the Spacelift AMI. Currently, only x86_64 or arm64 are supported."
+  default     = "x86_64"
+  validation {
+    condition     = contains(["x86_64", "arm64"], var.ami_architecture)
+    error_message = "Currently, only x86_64 or arm64 are supported."
+  }
+}
+
 variable "secure_env_vars" {
   type        = map(string)
   sensitive   = true