qron

Queue and cron.

A stupid Ruby cron thread that wakes up from time to time to perform according to what's written in a crontab.

Given etc/qrontab_dev:

  @reboot       p [ :hello, "just started" ]
  * * * * *     p [ :hello, :min, Time.now ]
  * * * * * *   p [ :hello, :sec, Time.now ]

and

require 'qron'

q = Qron.new(tab: 'etc/qrontab_dev')
q.join

[:hello, :sec, 2025-03-23 15:39:56.558783631 +0900]
[:hello, :sec, 2025-03-23 15:39:57.368985197 +0900]
[:hello, :sec, 2025-03-23 15:39:58.308865845 +0900]
[:hello, :sec, 2025-03-23 15:39:59.209102149 +0900]
[:hello, :min, 2025-03-23 15:40:00.149162785 +0900]
[:hello, :sec, 2025-03-23 15:40:00.149290935 +0900]
[:hello, :sec, 2025-03-23 15:40:01.039228675 +0900]
(...)

Uses fugit for cron parsing and stagnum as its worker pool.

A little brother to rufus-scheduler.

Specifying reload: true when initializing tells the Qron instance to reload its crontab file at every tick.

(Qron ticks usually every minute, unless it has one or more second precision crons specified, in which case it ticks every second).

require 'qron'

q = Qron.new(tab: 'etc/qrontab_dev', reload: true)

It's OK to use timezones in the qrontab file:

  30 * * * *     Asia/Tokyo        p [ :tokyo, :min, Time.now ]
  30 4 1,15 * 5  Europe/Budapest   p [ :budapest, :min, Time.now ]

A qrontab file accepts, cron and commands but also "settings" that set variables in the context passed to commands:

  #
  # settings

  a = 1 + 2
  b = Time.now

  #
  # actual crons

  * * * * * *  pp [ :ctx, ctx ]

where the puts might output something like:

[ :ctx,
  { time: 'Time instance...',
    cron: 'Fugit::Cron instance...',
    command: 'pp [ :ctx, ctx ]',
    qron: 'The Qron instance...',
    a: 3,
    b: 'Time instance...' } ]

A context is instantied and prepare for each command when it triggers.

MIT, see LICENSE.txt