Scheduler Daemon

Rails 3+ compatible scheduler daemon (see branches for older versions).

Replaces cron/rake pattern of periodically running rake tasks to perform maintenance
tasks in Rails apps. Scheduler Daemon is made specifically for your Rails app, and only
loads the environment once, no matter how many tasks run.

What’s so great about it? Well, I’m glad you asked!

• Only loads your Rails environment once on daemon start, not every time a task is run
• Allows you to easily deploy the scheduled tasks with your Rails app instead of depending on an administrator to update crontab
• Can be installed as a gem or a plugin (I suggest gem)
• It doesn’t use rake or cron!
• Gets you up and running with your own daemon in under 2 minutes
• Specially designed to work with your rails app!

Setup

Install as a gem or plugin.

As a gem, the old-fashioned way:

gem install scheduler_daemon

As a gem with bundler, add to your ./Gemfile:

gem 'scheduler_daemon'

I pretty much assume you chose this option below and prefix most commands with bundle exec

As a plugin (deprecated): (might be awkward to call the binary to start up the daemon…)

rails plugin install git://github.com/ssoroka/scheduler_daemon.git
# Install required gems
gem install daemons rufus-scheduler eventmachine chronic -s http://gemcutter.org

Optionally generate the default scheduler daemon task for your rails app:

rails generate scheduler_task MyNewTask

which will create a task named:

scheduled_tasks/my_new_task.rb

Usage

generate a new scheduled task:

rails generate scheduler_task MyTaskName

If you have problems with that, the template for new tasks is here

You can always copy it and make modifications, or see Manually create tasks

Tasks support their own special DSL; commands are:

environments :production, :staging             # run only in environments listed. (:all by default)
every '1d'                                     # run every day
every '1d', :first_at => Chronic.parse("2 am") # run every day, starting at 2 am (see caveat below)
at Cronic.parse('5 pm')                        # run *once* at 5 pm today
                                               #   (relative to scheduler start/restart time    )
                                               #   (happens every time scheduler starts/restarts)
                                               #   (see caveat below                            )
cron '* 4 * * *'                               # cron style (run every 4 am)
self.in '30s'                                  # run once, 30 seconds from scheduler start/restart
                                               # "self." is required--"in" is a keyword

fire up the daemon in console mode to test it out

bundle exec scheduler_daemon run

For production environments, add the daemon to the system start-up, and capistrano
deploy scripts, etc. Something like:

export RAILS_ENV=production
bundle exec scheduler_daemon start

Selectively run tasks like so:

bundle exec scheduler_daemon start -- --only=task_name1,task_name2 --except=not_me

Manually create tasks

If you don’t want to use this gem with Rails, you can manually create tasks in a
scheduled_tasks/ subdirectory and start the daemon with --skip-rails (though it’ll
figure it out anyway if there’s no config/environment.rb file in the launch directory
or --dir=/path)

Here’s an example task file.

class CleanUpTask < Scheduler::SchedulerTask
  every '2m'

  def run
    do_something
    log("I've done things")
  end
end

Specs

See this example spec
for an idea on how to write specs for your tasks.

To Do

Looking for suggestions!

Send requests to [email protected] or on twitter, @ssoroka

Bugs

Submit bugs here

Caveats

When using the cronic gem to parse dates, be careful of how it interprets your date, for
example:

every '24h', :first_at => Chronic.parse('noon')

will be once a day at noon, but the first time the server starts up (or restarts), noon
is relative to the current time of day. Before lunch, and it’s in the future. If the
daemon starts up after lunch, the date is in the past, and the task is immediately run
because it thinks it missed its last execution time. Depending on what your task is,
this may or may not be a problem. If you always want the date to resolve in the future
with terms like “noon”, “3 am” and “midnight”, prepend “next” to it. ie:

every '24h', :first_at => Chronic.parse('next noon')

Author

Steven Soroka

• @ssoroka
• My Github repo