.review_apps: use app autoscaling to turn review apps off at night, w…

…eekends

AWS App Autoscaling allows us to scale AWS ECS services up and down on a
schedule. To save money, we want to turn them off at 6pm each day, and then
back on at 8am Monday to Friday.

The result should be them being turned off from 6pm to 8am Monday to Friday,
and all day on weekends.

.review_apps/app_autoscaling.tf

@@ -0,0 +1,38 @@
+resource "aws_appautoscaling_target" "review_app" {
+  service_namespace  = "ecs"
+  resource_id        = "service/${data.terraform_remote_state.review.outputs.ecs_cluster_id}/${aws_ecs_service.app.name}"
+  scalable_dimension = "ecs:service:DesiredCount"
+
+  max_capacity = 1
+  min_capacity = 1
+}
+
+resource "aws_appautoscaling_scheduled_action" "shutdown_at_night" {
+  name = "pr-${var.pull_request_number}-shutdown-at-night"
+
+  service_namespace  = aws_appautoscaling_target.review_app.service_namespace
+  resource_id        = aws_appautoscaling_target.review_app.resource_id
+  scalable_dimension = aws_appautoscaling_target.review_app.scalable_dimension
+
+  schedule = "cron(0 18 * * ? *)" # daily at 1800
+
+  scalable_target_action {
+    min_capacity = 0
+    max_capacity = 0
+  }
+}
+
+resource "aws_appautoscaling_scheduled_action" "startup_weekday_mornings" {
+  name = "pr-${var.pull_request_number}-startup-weekday-mornings"
+
+  service_namespace  = aws_appautoscaling_target.review_app.service_namespace
+  resource_id        = aws_appautoscaling_target.review_app.resource_id
+  scalable_dimension = aws_appautoscaling_target.review_app.scalable_dimension
+
+  schedule = "cron(0 8 ? * MON-FRI *)" # Monday-Friday at 0800
+
+  scalable_target_action {
+    min_capacity = 1
+    max_capacity = 1
+  }
+}