Infer latest Amazon Linux 2 instead of hardcode (#5)

Author: int128

README.md

@@ -102,7 +102,7 @@ This is an open source software. Feel free to open issues and pull requests.
 
 | Name | Description | Type | Default | Required |
 |------|-------------|:----:|:-----:|:-----:|
-| image\_id | AMI of the NAT instance | string | `"ami-04b762b4289fba92b"` | no |
+| image\_id | AMI of the NAT instance. Default to the latest Amazon Linux 2 | string | `""` | no |
 | instance\_types | Candidates of spot instance type for the NAT instance. This is used in the mixed instances policy | list | `[ "t3.nano", "t3a.nano" ]` | no |
 | key\_name | Name of the key pair for the NAT instance. You can set this to assign the key pair to the NAT instance | string | `""` | no |
 | name | Name for all the resources as identifier | string | n/a | yes |

main.tf

@@ -49,9 +49,35 @@ resource "aws_route" "this" {
   network_interface_id   = aws_network_interface.this.id
 }
 
+# AMI of the latest Amazon Linux 2 
+data "aws_ami" "this" {
+  most_recent = true
+  owners      = ["amazon"]
+  filter {
+    name   = "architecture"
+    values = ["x86_64"]
+  }
+  filter {
+    name   = "root-device-type"
+    values = ["ebs"]
+  }
+  filter {
+    name   = "name"
+    values = ["amzn2-ami-hvm-*"]
+  }
+  filter {
+    name   = "virtualization-type"
+    values = ["hvm"]
+  }
+  filter {
+    name   = "block-device-mapping.volume-type"
+    values = ["gp2"]
+  }
+}
+
 resource "aws_launch_template" "this" {
   name_prefix = var.name
-  image_id    = var.image_id
+  image_id    = var.image_id != "" ? var.image_id : data.aws_ami.this.id
   key_name    = var.key_name
 
   iam_instance_profile {

variables.tf

@@ -20,9 +20,8 @@ variable "private_route_table_ids" {
 }
 
 variable "image_id" {
-  description = "AMI of the NAT instance"
-  # Amazon Linux 2 AMI (HVM), SSD Volume Type
-  default = "ami-04b762b4289fba92b"
+  description = "AMI of the NAT instance. Default to the latest Amazon Linux 2"
+  default     = ""
 }
 
 variable "instance_types" {