aws-overseer

Scheduled starting and stopping of EC2 instances with cron jobs.

If you are looking into this role then you might be trying to save some money by stopping non-critical EC2 instances during off hours. Why leave EC2 instances running if they are only used during specific time intervals and can be safely stopped? This role simply requires adding a couple tags to any instance that you want managed by a start_stop_schedule. It is also an experiment of using linux tools like ansible, cron and at for all functionality. There are some weird templated-out ansible playbooks if you examine further, but they work well.

The tags are:

Overseer: the name of the overseer that manages this instance (set to Ignore to be ignored by overseer)
StartStopSchedule: the name of the schedule to use for this instance

Instances are only stopped or started if a start_stop_schedule has been configured on the overseer host using this role.

Tip: Create an IAM user just for overseer so that you can use CloudTrail to view all start-stop history

Note:

Example Playbook

  ---
  - name: Configure the overseer host.
    hosts: overseer
    gather_facts: yes
    sudo: yes

    roles:
      - role: aws-overseer
        overseer_name: us-east-1-dev
        overseer_aws_region: us-east-1
        overseer_enforce: yes
        overseer_start_stop_schedules:
          - schedule_name: raleigh-business-hours
            start_cron_expression: "* 6 * * 1,2,3,4,5"
            stop_cron_expression: "* 18 * * 1,2,3,4,5"
            timezone: America/New_York
          - schedule_name: sao-paulo-business-hours
            start_cron_expression: "* 6 * * 1,2,3,4,5"
            stop_cron_expression: "* 18 * * 1,2,3,4,5"
            timezone: America/Sao_Paulo

      - role: aws-overseer
        overseer_name: us-west-2-dev
        overseer_aws_region: us-west-2
        overseer_start_stop_schedules:
          - schedule_name: san-francisco-business-hours
            start_cron_expression: "* 4 * * 1,2,3,4,5,6,7"
            stop_cron_expression: "* 20 * * 1,2,3,4,5,6,7"
            timezone: America/Los_Angeles

In this example the us-east-1-dev overseer will start and stop instances using two schedules:

raleigh-business-hours: starts instances every M-F at 6 AM Raleigh time and stops them every M-F at 6 PM
sao-paulo-business-hours: starts instances every M-F at 6 AM Sao Paulo time and stops them every M-F at 6PM

The us-east-1-dev overseer defaults to no enforcement, so instances that aren't tagged with an Overseer tag will keep on going, with no stops. The us-west-2-dev overseer will start and stop instances using one schedule:

san-francisco-business-hours: starts instances every day of the week at 4 AM and stops them every day at 8 PM

...it does have enforcement turned on. Instances that don't have the Overseer tag will simply be stopped within the first billable hour they are started.

Enforcement

If overseer_enforce is turned on then a cron job will run every 10 minutes that will check for instances that do not have an Overseer tag and have been running for more than 50 minutes after launch. For each of the instances that the cron finds it will schedule stopping it 5 minutes in the future. The reason for the delay is that I intend on adding a notification based on tag in the future to give somebody time to fix their instance if need be.

If previously enabled then the job is removed when disabled.

Requirements

The host operating system must be one of the following:

Debian
Ubuntu
CentOS
Red Hat Enterprise Linux
Amazon Linux

Role Variables

variable	required / optional	default	description
overseer_aws_region	required		the AWS region this overseer works in
overseer_aws_access_key	required		the AWS access key for the aws account this overseer works in
overseer_aws_secret_key	required		the AWS secret key for the aws account this overseer works in
overseer_home	optional	`/opt/overseer`	the path of the home directory for overseer configuration
overseer_name	optional	`Default`	the name to give this overseer
overseer_enforce	optional	`no`	stop any instances without an `Overseer` tag
overseer_start_stop_schedules	optional	[]	an array of `start_stop_schedule` descriptions (below)

An instance can be tagged with Overseer=Ignore to make it ignored by all overseer jobs, including enforcement.

start_stop_schedule description

property	required / optional	default	description
schedule_name	required		the name to give this schedule
start_cron_expression	required		a cron expression for the start instance job
stop_cron_expression	required		a cron expression for the stop instance job
timezone	optional	UTC	the timezone to use for the overseer cron table

Any start_stop_schedule jobs are removed if they are not in the configuration. This makes sure old start_stop_schedules aren't going to accumulate over time in /etc/cron.d

Dependencies

None

License

MIT