feat: add instance requirements option for docker autoscaler asg (#1262)

## Description
Add an option to specify instance requirements instead of a using a
fixed list of instance types to provide greater flexibility and cost
optimization. This option allows ASG to dynamically select the best
instance types based on availability, price, and performance criteria
rather than being restricted to a predefined list and ensures better
spot instance allocation.

You can either use types as before:
```
runner_worker_docker_autoscaler_asg = {
    subnet_ids                               = module.vpc.private_subnets
    types                                    = ["t3a.micro", "t3a.small", "t3.micro", "t3.small"]
    enable_mixed_instances_policy            = true
    on_demand_percentage_above_base_capacity = 0
    spot_allocation_strategy                 = "price-capacity-optimized"
}
```
Or you can use instance requirements:
```
runner_worker_docker_autoscaler_asg = {
    subnet_ids                               = module.vpc.private_subnets
    default_instance_type                    = "t3.small"
    enable_mixed_instances_policy            = true
    on_demand_percentage_above_base_capacity = 0
    spot_allocation_strategy                 = "price-capacity-optimized"

    instance_requirements = [{
       allowed_instance_types = ["t*"]
       cpu_manufacturers = ["intel"]
       burstable_performance = "included"
       memory_mib = {
         max = 8192
         min = 1024
       }
       vcpu_count = {
         max = 4
         min = 2
       }
   }]
}
```

---------

Co-authored-by: Matthias Kay <matthias.kay@hlag.com>
Co-authored-by: Matthias Kay <github@matthiaskay.de>

Author: mmoutama09

.cspell.json

@@ -64,6 +64,7 @@
     "trivy",
     "usermod",
     "userns",
+    "vcpu",
     "xanzy",
     "xvda"
   ],
@@ -74,6 +75,7 @@
     "backports",
     "blockquotes",
     "bluegreen",
+    "burstable",
     "codeowners",
     "cpu",
     "cpus",

docker_autoscaler.tf

@@ -12,7 +12,7 @@ resource "aws_launch_template" "this" {
   name          = "${local.name_runner_agent_instance}-worker-launch-template"
   user_data     = base64gzip(var.runner_worker_docker_autoscaler_instance.start_script)
   image_id      = length(var.runner_worker_docker_autoscaler_ami_id) > 0 ? var.runner_worker_docker_autoscaler_ami_id : data.aws_ami.docker_autoscaler_by_filter[0].id
-  instance_type = var.runner_worker_docker_autoscaler_asg.types[0]
+  instance_type = length(var.runner_worker_docker_autoscaler_asg.types) > 0 ? var.runner_worker_docker_autoscaler_asg.types[0] : var.runner_worker_docker_autoscaler_asg.default_instance_type
   key_name      = aws_key_pair.autoscaler[0].key_name
   ebs_optimized = var.runner_worker_docker_autoscaler_instance.ebs_optimized
 
@@ -103,12 +103,39 @@ resource "aws_autoscaling_group" "autoscaler" {
           launch_template_id = aws_launch_template.this[0].id
           version            = aws_launch_template.this[0].latest_version
         }
+
         dynamic "override" {
           for_each = var.runner_worker_docker_autoscaler_asg.types
           content {
             instance_type = override.value
           }
         }
+
+        dynamic "override" {
+          for_each = var.runner_worker_docker_autoscaler_asg.instance_requirements
+          content {
+            instance_requirements {
+              allowed_instance_types = override.value.allowed_instance_types
+              cpu_manufacturers      = override.value.cpu_manufacturers
+              instance_generations   = override.value.instance_generations
+              burstable_performance  = override.value.burstable_performance
+              dynamic "memory_mib" {
+                for_each = [override.value.memory_mib]
+                content {
+                  max = memory_mib.value.max
+                  min = memory_mib.value.min
+                }
+              }
+              dynamic "vcpu_count" {
+                for_each = [override.value.vcpu_count]
+                content {
+                  max = vcpu_count.value.max
+                  min = vcpu_count.value.min
+                }
+              }
+            }
+          }
+        }
       }
     }
   }

variables.tf

@@ -803,8 +803,10 @@ variable "runner_worker_docker_autoscaler_asg" {
     spot_allocation_strategy = How to allocate capacity across the Spot pools. 'lowest-price' to optimize cost, 'capacity-optimized' to reduce interruptions.
     spot_instance_pools = Number of Spot pools per availability zone to allocate capacity. EC2 Auto Scaling selects the cheapest Spot pools and evenly allocates Spot capacity across the number of Spot pools that you specify.
     subnet_ids = The list of subnet IDs to use for the Runner Worker when the fleet mode is enabled.
+    default_instance_type = Default instance type for the launch template
     types = The type of instance to use for the Runner Worker. In case of fleet mode, multiple instance types are supported.
     upgrade_strategy = Auto deploy new instances when launch template changes. Can be either 'bluegreen', 'rolling' or 'off'.
+    instance_requirements = Override the instance type in the Launch Template with instance types that satisfy the requirements.
   EOT
   type = object({
     enabled_metrics                          = optional(list(string), [])
@@ -818,10 +820,28 @@ variable "runner_worker_docker_autoscaler_asg" {
     spot_allocation_strategy                 = optional(string, "lowest-price")
     spot_instance_pools                      = optional(number, 2)
     subnet_ids                               = optional(list(string), [])
-    types                                    = optional(list(string), ["m5.large"])
+    default_instance_type                    = optional(string, "m5.large")
+    types                                    = optional(list(string), [])
     upgrade_strategy                         = optional(string, "rolling")
+    instance_requirements = optional(list(object({
+      allowed_instance_types = optional(list(string), [])
+      cpu_manufacturers      = optional(list(string), [])
+      instance_generations   = optional(list(string), [])
+      burstable_performance  = optional(string)
+      memory_mib = optional(object({
+        min = optional(number, null)
+      max = optional(number, null) }), {})
+      vcpu_count = optional(object({
+        min = optional(number, null)
+      max = optional(number, null) }), {})
+    })), [])
   })
   default = {}
+
+  validation {
+    condition     = length(var.runner_worker_docker_autoscaler_asg.types) == 0 || length(var.runner_worker_docker_autoscaler_asg.instance_requirements) == 0
+    error_message = "AWS does not allow setting both 'types' and 'instance_requirements' at the same time. Set only one."
+  }
 }
 
 variable "runner_worker_docker_machine_role" {