"Resque Mailer says: Put your emails to background"

April 05, 2011

It's no secret that handling HTTP requests should be quick. Very quick. Your business' "to be or not to be" may depend on how "fast" is you site. "Fast" site for end-users is when they're clicking and they don't need to switch to other tabs to kill time while waiting for page to open.

How to make your site fast?

  • buy more RAM (and install Oracle) - it costs $$$
  • lazy load what you can after initial page - complicates the code
  • do any processing in background - that one is quick win!

Depending on the application there will always be need for some combination of above. Best practice however, is: Webserver should not do any heavy data processing when handling request. It should just process the request and return response as soon as possible.

It means that all you can do is:

  1. parsing params
  2. loading resource(s)
  3. changing state of resource(s)
  4. utilizing background processing workers for data grinding
  5. rendering response body from template
  6. returning response to client

All of the above steps except last one are optional but they're all usually required in most apps. Point 4 is the important here. Developers often forget about it or are just too lazy to implement it. But it makes huge difference! Waiting 10 seconds for page load because the controller needs to finish something... it's unacceptable.

Resque to the rescue! Very reliable, framework independent, fast "Redis-backed library for creating background jobs" by Github's defunkt. I use various Ruby web-frameworks to build my webapps, the choice is not always Rails but Resque can be used with anything. Good stuff.

Anyway, what is not that common is sending e-mails asynchronously. Yeah, some people never thought about it. But sending them right from controller costs. Building mail message and sending it involves creating lots of ruby objects, rendering templates, preparing mail headers and eventually passing it to local MTA or sometimes to remote SMTP server. Sounds like a lot of time, especially when you use remote SMTP server.

But who would want to create dedicated background worker for this task? Who would want to enqueue such a job instead of doing simple Notifications.signup(@user).deliver in the controller? Not me.

Enter ResqueMailer. Originally created for Rails 2 by Nick Plante, updated by me to work with both Rails 2.x and 3.x. ResqueMailer allows you to move processing of Rails mailers out of controller to an async Resque worker with minimal fuss.

Just put the gem into your Rails project Gemfile:

gem 'resque_mailer'

and then include the Resque::Mailer module into your Mailer class:

class Notifications < ActionMailer::Base
  include Resque::Mailer

  def signup(...)

Instaaant gratification!

This is it. Now start your worker and enjoy faster responses. For information on ResqueMailer's optional settings see project's github repository. For details about setting up Resque and running workers go to README of Resque project.

Read more about gem, rails, resque, ruby.
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