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Bob the Scheduler

Bob the Scheduler is program used to schedule tasks. It plays nicely with Docker (or any other containers) and integrates with file-based configurations.

Bob's mission is to provide application developers a convenient way to schedule repeating jobs. It is intended to be run as PID 1 in container and spawn jobs.

If you need more advanced tasks like running tasks in other container, check Ofelia or K8S cronjobs.

How to use

Create directory /etc/bob-the-scheduler/tasks with jobs described as YAML files The job description should be saved with .yml or .yaml extension.

# task-01.yaml
task_name:  task-01
schedule: "@daily"
command: touch /var/data/timestamp
enabled: no

save_output: on-failure,on-success

# generate-images.yml
task_name: update-images
schedule: "CRON_TZ=Europe/Bratislava 12 01-07 * * *"
command: php /usr/local/www/cronjobs/update-images.php

How to start

bob-the-scheduler -c /etc/bob-the-scheduler -o /var/spool/bob-the-scheduler/ -p 8080 -v

Bob will periodically check new files in the config directory a and schedule its job.

Used command line parameters

  • -c says where the tasks directory with YAML files is located,
  • -o where to save the jobs output.
  • -p provides healthcheck endpoint on http://localhost:8000/healhtz
  • -v increase verbosity

The scheduling is done in UTC, but you can use CRON_TZ syntax to schedule in any other zone.

All the jobs are started with UID/GID of the calling user.

Job run

  • When the job is going to be started, Bob creates /var/spool/bob-the-scheduler/task-name/ directory.
  • The job will get timestamp.
  • Bob will create/overwrite file /task-name/last-start containing timestamp
  • It will create /task-name/stdout-timestamp.running file and redirects job command stdout there.
  • Jobs stderr is not going to be redirected
  • After successfull run, file /task-name/last-success is created/overwritten (containing timestamp)
  • After successfull run stdout file is moved to stdout-timestamp.succeeded
  • After failed run, file /task-name/last-failure is created/overwritten (containing timestamp)
  • After failed run stdout file is moved to stdout-timestamp.failed

Job parameters

  • task_name: ob name to use in file names. Defaults to job file name without
  • schedule: (required). Job schedule according to robfig's cron. Re
  • command: (required). Command to run
  • enabled: should the job be run? Defaults to True.
  • save_output: Should we keep the job output on success or failure? Default on-success,on-failure

What Bob does not do?

  • Mail reports on failures.
  • Enforce resource constraints (CPU/memory).
  • Report tasks' state through HTTP API.
  • Change UID/GID on execution.
  • Cleanup its files.

Patches are welcome.