Dead simple task scheduling in Rails

I was working on a project where I needed to send out a daily digest email.  The emails needed to be sent out on a scheduled interval, not as the result of some user action.  This meant that it would need to be handled outside of the normal request/response cycle.

Typically in the Rails world, when someone mentions long-running, or background tasks, you think either BackgrounDrb or Starling/Workling.  Those tools are fine and all -- actually, don't get me started on BackgrounDrb -- but I wanted something a bit more simple.

I didn't need queueing, or jobs, or anything like that.  I had only one task to manage.  I just want something that will say, "Once a day, do [task]", and that's all.

Also, I really didn't want to have to monkey with deployment tasks, be it with Vlad or Capistrano or whatever.  I wanted to just deploy as usual, and have it all just work, no extra processes to start or tasks to run.

This seemed like a tall order, but I began my search anyway.  Google led me to a number of pages about a number of tools, all of which included one or more of the things I was trying to avoid.  Of all places, I finally ended up on this page from the Ruby On Rails wiki.

Despite having only a one line mention near the bottom of the page, I decided to check out rufus-scheduler, and it turned out to be exactly what I was looking for.  There was no database table, queueing mechanism, or separate process to manage.  Just a simple scheduler to call out to your existing ruby code.

It couldn't get any simpler.  Here's how I set it up...

First, install the gem.

sudo gem install rufus-scheduler

I also froze it into vendor/gems by declaring the gem in the initializer block of environment.rb and then running rake gems:unpack.

Then I created a file called task_scheduler.rb in my config/initializers directory.   Inside this file is where the magic happens.  This is where it all goes down.  Are you ready?  Here it is...

scheduler = Rufus::Scheduler.start_new

scheduler.every("1m") do
   DailyDigest.send_digest!
end 

Yeah, that's it. Seriously.

I was in disbelief myself until I started up the server and watched it send me an email.  In it's current state, it would send the digest every minute, which is not what I wanted.  Fortunately, the rufus-scheduler provides several ways to schedule your tasks.  Once I was ready, I changed it to more of a cron-style scheduler.

scheduler = Rufus::Scheduler.start_new

# Send the digest every day at noon
scheduler.cron("0 12 * * *") do
   DailyDigest.new.send_digest!
end 

You could also use scheduler.in or scheduler.at for one time tasks set to run at some point in the future.

So there you have it.  Dead simple task scheduling in Rails.  It really doesn't get any easier.