feat: added support for deploying instances into multiple instance types

Author: acourtiol

asg.tf

@@ -7,10 +7,31 @@ resource "aws_autoscaling_group" "main" {
   desired_capacity    = 1
   health_check_type   = "EC2"
   vpc_zone_identifier = [var.subnet_id]
+  capacity_rebalance  = var.use_spot_instances && length(var.instance_types) > 1 ? true : false
 
-  launch_template {
-    id      = aws_launch_template.main.id
-    version = "$Latest"
+  dynamic "mixed_instances_policy" {
+    for_each = length(var.instance_types) > 0 ? [1] : []
+    content {
+      instances_distribution {
+        on_demand_base_capacity                  = var.use_spot_instances ? 0 : 1
+        on_demand_percentage_above_base_capacity = var.use_spot_instances ? 0 : 100
+        spot_allocation_strategy                 = "price-capacity-optimized"
+      }
+
+      launch_template {
+        launch_template_specification {
+          launch_template_id = aws_launch_template.main.id
+          version            = "$Latest"
+        }
+
+        dynamic "override" {
+          for_each = var.instance_types
+          content {
+            instance_type = override.value
+          }
+        }
+      }
+    }
   }
 
   dynamic "tag" {

ec2.tf

@@ -35,7 +35,7 @@ resource "aws_launch_template" "main" {
   #checkov:skip=CKV_AWS_88:NAT instances must have a public IP.
   name          = var.name
   image_id      = local.ami_id
-  instance_type = var.instance_type
+  instance_type = length(var.instance_types) > 0 ? var.instance_types[0] : null
   key_name      = var.ssh_key_name
 
   block_device_mappings {
@@ -60,14 +60,6 @@ resource "aws_launch_template" "main" {
     security_groups             = local.security_groups
   }
 
-  dynamic "instance_market_options" {
-    for_each = var.use_spot_instances ? ["x"] : []
-
-    content {
-      market_type = "spot"
-    }
-  }
-
   dynamic "tag_specifications" {
     for_each = ["instance", "network-interface", "volume"]
 

main.tf

@@ -1,5 +1,5 @@
 locals {
-  is_arm             = can(regex("[a-zA-Z]+\\d+g[a-z]*\\..+", var.instance_type))
+  is_arm             = can(regex("[a-zA-Z]+\\d+g[a-z]*\\..+", var.instance_types[0]))
   ami_id             = var.ami_id != null ? var.ami_id : data.aws_ami.main[0].id
   cwagent_param_arn  = var.use_cloudwatch_agent ? var.cloudwatch_agent_configuration_param_arn != null ? var.cloudwatch_agent_configuration_param_arn : aws_ssm_parameter.cloudwatch_agent_config[0].arn : null
   cwagent_param_name = var.use_cloudwatch_agent ? var.cloudwatch_agent_configuration_param_arn != null ? split("/", data.aws_arn.ssm_param[0].resource)[1] : aws_ssm_parameter.cloudwatch_agent_config[0].name : null
@@ -80,4 +80,4 @@ resource "aws_ssm_parameter" "cloudwatch_agent_config" {
     METRICS_NAMESPACE           = var.cloudwatch_agent_configuration.namespace
     METRICS_ENDPOINT_OVERRIDE   = var.cloudwatch_agent_configuration.endpoint_override
   })
-}
+}

output.tf

@@ -28,9 +28,9 @@ output "ha_mode" {
   value       = var.ha_mode
 }
 
-output "instance_type" {
-  description = "Instance type used for the fck-nat instance"
-  value       = aws_launch_template.main.instance_type
+output "instance_types" {
+  description = "Instance types used for the fck-nat instance (from the ASG mixed instances policy or launch template default)"
+  value       = length(var.instance_types) > 0 ? var.instance_types : [aws_launch_template.main.instance_type]
 }
 
 output "ami_id" {

variables.tf

@@ -55,10 +55,10 @@ variable "ha_mode" {
   default     = true
 }
 
-variable "instance_type" {
-  description = "Instance type to use for the NAT instance"
-  type        = string
-  default     = "t4g.micro"
+variable "instance_types" {
+  description = "List of instance types to use for the NAT instance (ASG mixed instances policy)"
+  type        = list(string)
+  default     = ["t4g.nano"]
 }
 
 variable "ami_id" {