From 9f01f15b3fd72f52082d9d526809034b763bbde7 Mon Sep 17 00:00:00 2001
From: Ash Davies <3853061+DrizzlyOwl@users.noreply.github.com>
Date: Fri, 21 Jun 2024 11:57:52 +0100
Subject: [PATCH] Set up a scale-in window

---
 scheduled-scaling.tf | 39 +++++++++++++++++++++++++++++++++++++++
 variables.tf         | 42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 scheduled-scaling.tf

diff --git a/scheduled-scaling.tf b/scheduled-scaling.tf
new file mode 100644
index 0000000..517fd55
--- /dev/null
+++ b/scheduled-scaling.tf
@@ -0,0 +1,39 @@
+locals {
+  today_date        = formatdate("YYYY-MM-DD", timestamp())
+  start_time_window = var.scale_down_start_time != "" ? "${local.today_date}T${var.scale_down_start_time}Z" : "${local.today_date}T23:00:00Z"
+  end_time_window   = var.scale_down_end_time != "" ? "${local.today_date}T${var.scale_down_end_time}Z" : "${local.today_date}T06:00:00Z"
+}
+
+resource "aws_autoscaling_schedule" "off" {
+  count = var.scale_down_out_of_hours_enabled ? 1 : 0
+
+  scheduled_action_name  = "asg-${aws_launch_template.ecs.name}-schedule-down"
+  min_size               = var.scale_down_min_servers
+  max_size               = var.scale_down_max_servers
+  desired_capacity       = var.scale_down_servers
+  recurrence             = var.scale_down_recurrance
+  start_time             = local.start_time_window
+  autoscaling_group_name = aws_autoscaling_group.ecs.name
+  time_zone              = "Europe/London"
+
+  lifecycle {
+    ignore_changes = [start_time]
+  }
+}
+
+resource "aws_autoscaling_schedule" "on" {
+  count = var.scale_down_out_of_hours_enabled ? 1 : 0
+
+  scheduled_action_name  = "asg-${aws_launch_template.ecs.name}-schedule-up"
+  min_size               = var.min_servers
+  max_size               = var.max_servers
+  desired_capacity       = var.servers
+  start_time             = local.end_time_window
+  recurrence             = var.scale_down_recurrance
+  autoscaling_group_name = aws_autoscaling_group.ecs.name
+  time_zone              = "Europe/London"
+
+  lifecycle {
+    ignore_changes = [start_time]
+  }
+}
diff --git a/variables.tf b/variables.tf
index 69d9975..b9d87f0 100644
--- a/variables.tf
+++ b/variables.tf
@@ -183,3 +183,45 @@ variable "max_instance_lifetime" {
   type        = string
   default     = "0"
 }
+
+variable "scale_down_out_of_hours_enabled" {
+  description = "Should the ECS cluster scale down outside of normal working hours"
+  type        = bool
+  default     = false
+}
+
+variable "scale_down_min_servers" {
+  description = "Minimum size to scale down to within the reduced scaling window"
+  type        = number
+  default     = 0
+}
+
+variable "scale_down_max_servers" {
+  description = "Maximum size to scale up to within the reduced scaling window"
+  type        = number
+  default     = 0
+}
+
+variable "scale_down_servers" {
+  description = "The desired capacity must be equal to or greater than the minimum group size, and equal to or less than the maximum group size"
+  type        = number
+  default     = 0
+}
+
+variable "scale_down_recurrance" {
+  description = "Cron expression for when to apply the scaling window. Defaults to 'Daily'"
+  type        = string
+  default     = "0 12 * * *"
+}
+
+variable "scale_down_start_time" {
+  description = "The time for the recurring schedule to start. Defaults to '23:00'"
+  type        = string
+  default     = ""
+}
+
+variable "scale_down_end_time" {
+  description = "The time for the recurring schedule to end. Defaults to '06:00'"
+  type        = string
+  default     = ""
+}