Scheduling

A scheduler Lambda starts and stops instances on the windows you define. It reconciles every 15 minutes and at each window boundary.

Windows

module "workspace" {
  source  = "douklar/agent-workspace/aws"
  version = "~> 2.0"

  instance_schedule_windows = [
    {
      name       = "evenings"
      timezone   = "Europe/Berlin"
      days       = ["MON", "TUE", "WED", "THU", "FRI"]
      start_time = "18:30"
      stop_time  = "23:00"
    },
    {
      name       = "weekends"
      timezone   = "Europe/Berlin"
      days       = ["SAT", "SUN"]
      start_time = "11:00"
      stop_time  = "22:00"
    }
  ]
}

Rules for windows:

• An instance is on if any window of its cohort matches; otherwise it is stopped.
• Each window has its own IANA timezone.
• start_time must be earlier than stop_time. To run across midnight, split into two windows, for example 22:00–23:59 and 00:00–06:00.
• 00:00 to 23:59 runs all day.

Modes: the scheduler tag

Each instance's scheduler tag decides what the scheduler does. Change it at runtime; Terraform will not revert it. Set the starting value with scheduler_mode.

aws ec2 create-tags --resources i-0123456789abcdef0 --tags Key=scheduler,Value=on-demand

If the scheduler cannot evaluate a schedule, for example because of an unknown timezone, it leaves the instance running instead of stopping it.

Cohorts and other instances

Windows can carry a mode name, which makes a cohort; an instance whose tag names that cohort follows those windows. Any EC2 instance in the Region with a scheduler tag can join, and the Lambda's IAM permissions are scoped to instances that carry the tag.