cheek

cheek

cheek is a pico-sized declarative job scheduler designed to excel in a single-node environment. cheek aims to be lightweight, stand-alone and simple. It does not compete for robustness.

Getting started

Fetch the latest version for your system below.

darwin-arm64 | darwin-amd64 | linux-386 | linux-arm64 | linux-amd64

You can (for example) fetch it like below, make it executable and run it. Optionally put the cheek on your PATH.

curl https://storage.googleapis.com/cheek-scheduler/darwin/amd64/cheek -o cheek
chmod +x cheek
./cheek

Everything about how you want the scheduler to function is defined in a schedule specification written in YAML. Start by creating this specification using the below example. Note, this structure should be more or less self-explanatory, if it is not, create an issue.

tz_location: Europe/Brussels # optionally set timezone to adhere to
jobs:
  foo:
    command: date
    cron: "* * * * *" # a cron string to specify when to run
    on_success:
      trigger_job: # trigger something on run
        - bar
  bar:
    command: # command to run, use a list if you want to pass args
      - echo
      - $foo
    env: # you can pass env variables
      foo: bar
  other_workingdir:
    command: pwd
    working_directory: ../testdata # specify the working directory of the job
  coffee:
    command: this fails
    cron: "* * * * *"
    retries: 3
    on_error:
      notify_webhook: # notify something on error
        - https://webhook.site/4b732eb4-ba10-4a84-8f6b-30167b2f2762
      notify_slack_webhook: # notify slack via a slack compatible webhook
        - https://webhook.site/048ff47f-9ef5-43fb-9375-a795a8c5cbf5

If your command requires arguments, please make sure to pass them as an array like in foo_job.

Note that you can set tz_location if the system time of where you run your service is not to your liking.

Scheduler

The core of cheek consists of a scheduler that uses the schedule specs defined in your yaml file to trigger jobs when they are due.

You can launch the scheduler via:

cheek run ./path/to/my-schedule.yaml

Check out cheek run --help for configuration options.

Web UI

cheek ships with a web UI that by default gets launched on port 8081. You can define the port on which it is accessible via the --port flag.

main overview

job detail

You can access the UI by navigating to http://localhost:8081. When cheek is deployed you are recommended to NOT make this port publicly accessible, instead navigate to the UI via an SSH tunnel.

The UI allows to get a quick overview on jobs that have run, that error'd and their logs. It basically does this by fetching the state of the scheduler and by reading the logs that (per job) get written to $HOME/.cheek/. Note that you can ignore these logs, output of jobs will always go to stdout as well.

Note, cheek prior to version 0.3.0 originally used to boast a TUI, which has since been removed.

Configuration

All configuration options are available by checking out cheek --help or the help of its subcommands (e.g. cheek run --help).

Configuration can be passed as flags to the cheek CLI directly. All configuration flags are also possible to set via environment variables. The following environment variables are available, they will override the default and/or set value of their similarly named CLI flags (without the prefix): CHEEK_PORT, CHEEK_SUPPRESSLOGS, CHEEK_LOGLEVEL, CHEEK_PRETTY, CHEEK_HOMEDIR.

Events & Notifications

There are two types of event you can hook into: on_success and on_error. Both events materialize after an (attempted) job run. Three types of actions can be taken as a response: notify_webhook, notify_slack_webhook and trigger_job. See the example below. Definition of these event actions can be done on job level or at schedule level, in the latter case it will apply to all jobs.

on_success:
  notify_webhook:
    - https://webhook.site/e33464a3-1a4f-4f1a-99d3-743364c6b10f
jobs:
  coffee:
    command: this fails # this will create on_error event
    cron: "* * * * *"
    on_error:
      notify_webhook:
        - https://webhook.site/e33464a3-1a4f-4f1a-99d3-743364c6b10f
  beans:
    command: echo grind # this will create on_success event
    cron: "* * * * *"

Webhooks are a generic way to push notifications to a plethora of tools. There is a generic way to do this via the notify_webhook option or a Slack-compatible one via notify_slack_webhook.

The notify_webhook sends a JSON payload to your webhook url with the following structure:

{
	"status": 0,
	"log": "I'm a teapot, not a coffee machine!",
	"name": "TeapotTask",
	"triggered_at": "2023-04-01T12:00:00Z",
	"triggered_by": "CoffeeRequestButton",
	"triggered": ["CoffeeMachine"] // this job triggered another one
}

The notify_slack_webhook sends a JSON payload to your Slack webhook url with the following structure (which is Slack app compatible):

{
	"text": "TeapotTask (exitcode 0):\nI'm a teapot, not a coffee machine!"
}

Docker

Check out the Dockerfile.example for an example on how to use cheek within the context of a Docker container. Note that this builds upon a published Ubuntu-based image build that you can find in the base Dockerfile.

Prebuilt images are available at ghcr.io/datarootsio/cheek:latest where latest can be replaced by a version tag. Check out the available images for an overview on available tags.

Available versions

If you want to pin your setup to a specific version of cheek you can use the following template to fetch your cheek binary:

• latest version: https://storage.googleapis.com/cheek-scheduler/{os}/{arch}/cheek
• tagged version: https://storage.googleapis.com/cheek-scheduler/{os}/{arch}/cheek-{tag}
• main branch builds: https://storage.googleapis.com/cheek-scheduler/{os}/{arch}/cheek-{shortsha}

Where:

• os is one of linux, darwin
• arch is one of amd64, arm64, 386
• tag is one the available tags
• shortsha is a 7-char SHA and most commits on main will be available

Acknowledgements

cheek is building on top of many great OSS assets. Noteable thanks goes to:

• chota: for a pico sized css framework
• gronx: for allowing me not to worry about CRON strings.