fix: instance type and architecture incompatiblity

Author: oycyc

data.tf

@@ -13,7 +13,7 @@ data "aws_ami" "amazon_linux_2023" {
 
   filter {
     name   = "architecture"
-    values = ["x86_64"]
+    values = [var.architecture]
   }
 
   filter {

main.tf

@@ -1,3 +1,25 @@
+locals {
+  # Validate that only 'arm64' architecture is used with 'g' processor instances to ensure compatibility.
+  # https://docs.aws.amazon.com/ec2/latest/instancetypes/instance-type-names.html
+  is_instance_compatible = (
+    # True if does not contain 'g' when architecture is x86_64
+    (var.architecture == "x86_64" && !can(regex("g", var.instance_type))) ||
+    # True if contains 'g' when architecture is arm64
+    (var.architecture == "arm64" && can(regex("g", var.instance_type)))
+  )
+}
+
+resource "null_resource" "validate_instance_type" {
+  count = local.is_instance_compatible ? 0 : 1
+
+  lifecycle {
+    precondition {
+      condition     = local.is_instance_compatible
+      error_message = "The instance_type must be compatible with the specified architecture. For x86_64, you cannot use instance types with ARM processors (e.g., t3, m5, c5). For arm64, use instance types with 'g' indicating ARM processor (e.g., t4g, c6g, m6g)."
+    }
+  }
+}
+
 module "role_label" {
   source  = "cloudposse/label/null"
   version = "0.25.0"

variables.tf

@@ -30,6 +30,12 @@ variable "ami" {
   description = "The AMI to use for the SSM Agent EC2 Instance. If not provided, the latest Amazon Linux 2023 AMI will be used. Note: This will update periodically as AWS releases updates to their AL2023 AMI. Pin to a specific AMI if you would like to avoid these updates."
 }
 
+variable "architecture" {
+  description = "The architecture of the AMI (e.g., x86_64, arm64)"
+  type        = string
+  default     = "arm64"
+}
+
 variable "user_data" {
   default     = <<EOT
 #!/bin/bash

versions.tf

@@ -11,5 +11,9 @@ terraform {
       source  = "hashicorp/time"
       version = ">= 0.7"
     }
+    null = {
+      source  = "hashicorp/null"
+      version = ">= 3.2"
+    }
   }
 }