background-jobs.md

Background jobs w/ Resque

Resque is a ruby library for creating background jobs, which are tasks that are placed in a queue and processed by a separate process than our running application. Resque is build upon Redis, redis is a key-value store, or referred to as a NoSQL database, the idea is basically that it's a database that stores hashes.

Install Redis

Resque depends on a redis server to be running.

brew update
brew install redis

To start the server, run:

redis-server

See Try Redis for more info.

Resque

Add the resque gem to the Gemfile

gem "resque"

Next we'll need to start an addition process to run in the background of our application. Resque provides a rake task to start this process, but first we need to include the tasks within our application, add the following to the Rakefile

require "resque/tasks"
task "resque:setup" => :environment

Then to start the process you can use

bundle exec rake resque:work QUEUE='*'

Resque uses the idea of Jobs to create items for the a queue. We'll start by creating a new class in a jobs dir.

mkdir app/jobs
touch app/jobs/email_job.rb

In the email_job.rb create a new class:

class EmailJob
end

Resque depends on two things, a @queue instance variable, and a class method called perform:

class EmailJob
  @queue = :email
  def self.perform
    puts "THIS IS A JOB"
  end
end

We can then use the Resque gem to add something to this queue, in the rails console

Resque.enqueue(EmailJob)

Mount the resque server to the rails app

require 'resque/server'
Golf::Application.routes.draw do
  mount Resque::Server, :at => "/resque"
  ...

Now we can replace the contents of the perform method to actually do logic, we can also accepts arguments on the perform method:

class EmailJob
  @queue = :email
  def self.perform(club_id)
    ClubMailer.join_us(club_id).deliver
  end
end

Be sure to restart the Resque rake task after changing any of the job classes. Now to enqueue this job, we will need to pass in an additional argument, which is the clubs id

Resque.enqueue(EmailJob, Club.last.id)

Now our mailer can be sent in a background job using Resque