diff --git a/main.tf b/main.tf
index 0deb3e3..171818a 100644
--- a/main.tf
+++ b/main.tf
@@ -29,9 +29,9 @@ resource "aws_ecs_service" "service" {
   dynamic "capacity_provider_strategy" {
     for_each = var.capacity_provider_strategies
     content {
-      base = capacity_provider_strategy.value.base
+      base              = capacity_provider_strategy.value.base
       capacity_provider = capacity_provider_strategy.value.capacity_provider
-      weight = capacity_provider_strategy.value.weight
+      weight            = capacity_provider_strategy.value.weight
     }
   }
 
@@ -81,7 +81,7 @@ resource "aws_ecs_task_definition" "task" {
     for_each = var.volumes
 
     content {
-      name     = volume.value["name"]
+      name      = volume.value["name"]
       host_path = lookup(volume.value, "host_path", null)
     }
   }
@@ -127,28 +127,28 @@ resource "aws_security_group" "service_security_group" {
 resource "aws_appautoscaling_target" "ecs_service_autoscaling_target" {
   for_each = var.use_autoscaling ? [1] : []
 
-  min_capacity = var.min_desired_count
-  max_capacity =  var.max_desired_count
+  min_capacity       = var.min_desired_count
+  max_capacity       = var.max_desired_count
   scalable_dimension = "ecs:service:DesiredCount"
-  service_namespace = "ecs"
-  resource_id = "service/${data.aws_ecs_cluster.cluster.cluster_name}/${aws_ecs_service.service.name}"
+  service_namespace  = "ecs"
+  resource_id        = "service/${data.aws_ecs_cluster.cluster.cluster_name}/${aws_ecs_service.service.name}"
 }
 
 resource "aws_appautoscaling_policy" "ecs_service_autoscaling_policy" {
-  name = "ecs-fargate-service-autoscaling-policy"
-  service_namespace = aws_appautoscaling_target.ecs_service_autoscaling_target.service_namespace
+  name               = "ecs-fargate-service-autoscaling-policy"
+  service_namespace  = aws_appautoscaling_target.ecs_service_autoscaling_target.service_namespace
   scalable_dimension = aws_appautoscaling_target.ecs_service_autoscaling_target.scalable_dimension
-  resource_id = aws_appautoscaling_target.ecs_service_autoscaling_target.resource_id
-  policy_type = "TargetTrackingScaling"
+  resource_id        = aws_appautoscaling_target.ecs_service_autoscaling_target.resource_id
+  policy_type        = "TargetTrackingScaling"
 
   target_tracking_scaling_policy_configuration {
     # Seconds
     scale_in_cooldown = 120
     # Seconds
     scale_out_cooldown = 30
-    target_value = var.scaling_target_value
+    target_value       = var.scaling_target_value
     predefined_metric_specification {
-      predefined_metric_type = "ALBRequestCountPerTarget"
+      predefined_metric_type = var.scaling_metric
     }
   }
 }
\ No newline at end of file
diff --git a/variables.tf b/variables.tf
index 2033b8d..66f52df 100644
--- a/variables.tf
+++ b/variables.tf
@@ -1,8 +1,8 @@
-variable name {
+variable "name" {
   description = "The name of the service. Used as a prefix for other resource names"
 }
 
-variable cluster_id {
+variable "cluster_id" {
   description = <<EOF
   The id of the ECS cluster this service belongs to.
 
@@ -11,46 +11,52 @@ variable cluster_id {
   EOF
 }
 
-variable desired_count {
+variable "desired_count" {
   type        = number
   description = "If not using Application Auto-scaling, the number of tasks to keep alive at all times"
-  default = null
+  default     = null
 }
 
-variable use_autoscaling {
-  type = bool
+variable "use_autoscaling" {
+  type        = bool
   description = "Use Application Auto-scaling to scale service"
-  default = false
+  default     = false
 }
 
-variable min_desired_count {
-  type = number
+variable "min_desired_count" {
+  type        = number
   description = "If using Application auto-scaling, minimum number of tasks to keep alive at all times"
-  default = null
+  default     = null
 }
 
-variable max_desired_count {
-  type = number
+variable "max_desired_count" {
+  type        = number
   description = "If using Application auto-scaling, maximum number of tasks to keep alive at all times"
-  default = null
+  default     = null
 }
 
 variable "scaling_target_value" {
-  type = number
+  type        = number
   description = "If using Application auto-scaling, the target value to hit for the Auto-scaling policy"
-  default = null
+  default     = null
+}
+
+variable "scaling_metric" {
+  type        = string
+  description = "If using Application auto-scaling, the pre-defined AWS metric to use for the Auto-scaling policy"
+  default     = "ALBRequestCountPerTarget"
 }
 
-variable vpc_id {
+variable "vpc_id" {
   description = "ID of the VPC the alb is in"
 }
 
-variable subnet_ids {
+variable "subnet_ids" {
   type        = list(string)
   description = "List of subnets tasks can be run in."
 }
 
-variable load_balancers {
+variable "load_balancers" {
   type = list(object({
     target_group_arn = string
     container_name   = string
@@ -69,91 +75,91 @@ variable load_balancers {
   EOF
 }
 
-variable service_registries {
+variable "service_registries" {
   description = "Allows you to register this service to a Cloud Map registry"
   type        = list(map(string))
   default     = []
 }
 
-variable tags {
+variable "tags" {
   type        = map(string)
   description = "Tags to set on all resources that support them"
 }
 
-variable cpu {
+variable "cpu" {
   default     = 512
   description = "How much CPU should be allocated to each app instance?"
 }
 
-variable memory {
+variable "memory" {
   default     = 1024
   description = "How much memory should be allocated to each app instance?"
 }
 
-variable container_definitions {
+variable "container_definitions" {
   type        = string
   description = "JSON encoded list of container definitions"
 }
 
-variable additional_task_policy_arns {
+variable "additional_task_policy_arns" {
   type        = list(string)
   description = "IAM Policy arns to be added to the tasks"
   default     = []
 }
 
-variable additional_task_policy_arns_count {
+variable "additional_task_policy_arns_count" {
   type        = number
   description = "The number of items in var.additional_task_policy_arns. Terraform is not quite smart enough to figure this out on its own."
   default     = 0
 }
 
-variable health_check_grace_period_seconds {
+variable "health_check_grace_period_seconds" {
   type        = number
   default     = 60
   description = "Seconds to ignore failing load balancer health checks on newly instantiated tasks to prevent premature shutdown, up to 2147483647. Only valid for services configured to use load balancers."
 }
 
-variable alb_security_group_ids {
+variable "alb_security_group_ids" {
   type        = list(string)
   description = "The ids of all security groups set on the ALB. We require that the tasks can only talk to the ALB"
 }
 
-variable execution_role_arn {
+variable "execution_role_arn" {
   type        = string
   description = "If present, this is the execution role that will be used for the ECS Tasks. If not present, a role will be created"
   default     = ""
 }
 
-variable security_group_id {
+variable "security_group_id" {
   type        = string
   description = "If present, this is the security group to apply to the ECS task. If not present, a security group will be created"
   default     = ""
 }
 
-variable volumes {
+variable "volumes" {
   type        = list(map(string))
   description = "List of volumes to make available to containers in this task."
   default     = []
 }
 
-variable deploy_env {
+variable "deploy_env" {
   type        = string
   description = "The environment resources are to be created in. Usually dev, staging, or prod"
 }
 
-variable aws_region {
+variable "aws_region" {
   type        = string
   description = "The AWS region to create resources in."
   default     = "eu-west-1"
 }
 
-variable capacity_provider_strategies {
+variable "capacity_provider_strategies" {
   type = list(object({
-    base = optional(number)
+    base              = optional(number)
     capacity_provider = string
-    weight = number
+    weight            = number
   }))
-  default = []
+  default     = []
   description = <<EOF
   Capacity provider strategy to use for the service
 
@@ -163,8 +169,8 @@ variable capacity_provider_strategies {
   EOF
 }
 
-variable ephemeral_storage_gib {
+variable "ephemeral_storage_gib" {
   description = "The total amount, in GiB, of ephemeral storage to set for the task. The minimum supported value is 20 GiB and the maximum supported value is 200 GiB."
-  type    = number
-  default = 20
+  type        = number
+  default     = 20
 }
\ No newline at end of file
diff --git a/versions.tf b/versions.tf
index cb8cd24..15513a6 100644
--- a/versions.tf
+++ b/versions.tf
@@ -1,10 +1,10 @@
 terraform {
   required_providers {
     aws = {
-      source = "hashicorp/aws"
+      source  = "hashicorp/aws"
       version = ">= 3.46.0"
     }
   }
   required_version = ">= 0.13"
-  experiments = [module_variable_optional_attrs]
+  experiments      = [module_variable_optional_attrs]
 }
\ No newline at end of file