A high precision scheduler including timezone aware cron jobs

Tasker

A high precision scheduler for crystal lang. Allows you to schedule tasks to run in the future and obtain the results.

Usage

Grab an instance of the scheduler

    require "tasker"

    # Grab the default scheduler - really only need a single instance per application
    schedule = Tasker.instance

At a time in the future

    schedule.at(20.seconds.from_now) { perform_action }

    # If you would like the value of that result
    # returns value or raises error - a Concurrent::Future
    schedule.at(20.seconds.from_now) { perform_action }.get

After some period of time

    schedule.in(20.seconds) { perform_action }

Repeating every time period

    task = schedule.every(2.milliseconds) { perform_action }
    # Canceling stops the schedule from running
    task.cancel
    # Resume can be used to restart a canceled schedule
    task.resume

You can grab the values of repeating schedules too

    tick = 0
    task = schedule.every(2.milliseconds) { tick += 1; tick }

    # Calling get will pause until after the next schedule has run
    task.get == 1 # => true
    task.get == 2 # => true
    task.get == 3 # => true

    # It also works as an enumerable
    # NOTE:: this will only stop counting once the schedule is canceled
    task.each do |count|
      puts "The count is #{count}"
      task.cancel if count > 5
    end

Running a CRON job

    # Run a job at 7:30am every day
    schedule.cron("30 7 * * *") { perform_action }

    # For running in a job in a particular time zone:
    berlin = Time::Location.load("Europe/Berlin")
    schedule.cron("30 7 * * *", berlin) { perform_action }

    # Also supports pause, resume and enumeration