I finally got a github invitation and used the opportunity to release another Shopify extractions.

Delayed::Job or DJ is a asynchronous priority queue which only relies on a simple database table. It doesn’t require you to run a dedicated server like many other systems do.

We use for a lot of longer running tasks in Shopify such as sending newsletters, uploading files to s3, downloading images from urls, indexing products to Solr and so on.

There are two ways to add jobs to the queue:

Jobs are simple ruby objects with a method called perform. Any object which responds to perform can be stuffed into the jobs table. Job objects are serialized to yaml so that they can later be resurrected by the job runner.

  class NewsletterJob < Struct.new(:text, :emails)
    def perform
      emails.each { |e| NewsletterMailer.deliver_text_to_email(text, e) }
    end    
  end  

  Delayed::Job.enqueue NewsletterJob.new('lorem ipsum...', Customers.find(:all).collect(&:email))

There is also a second way to get jobs in the queue: send_later.

  BatchImporter.new(Shop.find(1)).send_later(:import_massive_csv, massive_csv)                                                    

This will simply create a Delayed::PerformableMethod job in the jobs table which serializes all the parameters you pass to it. There are some special smarts for active record objects which are stored as their text representation and loaded from the database fresh when the job is actually run later.

The plugin can be found on github.