Alberto Grespan

Send emails in the background using sucker punch

July 13, 2013

Sucker punch gem

This gem was created by @brandonhilkert with a very specific use case in mind. I’m not sure what the use case was, but, I believe it’s something like; taking advantage of Heroku web dynos, without needing to pay extra for a worker dyno (this is what I’m using it for). If It’s not; I’m leaning towards simplicity. At this point with sucker_punch in it’s version 1.0.1 became dead simple to install and use, no configuration needed. I’m really grateful that this gem was created.

note: If you are looking for a massive background processing gem with persistence, etc. go with something like Sidekiq instead.

Why sucker punch?

Sending emails within a Rails application using sucker_punch

You already have a Rails application running and you want to send a contact form email or an email when the user registers. Let’s do this using asynchronous processing with sucker punch.

First install the sucker punch gem.

# Add this line to your Gemfile
$ gem 'sucker_punch', '~> 1.0.1'

# Run bundle
$ bundle install

Generate the mailer.

$ rails g mailer ContactMailer

This command will create all the files necessary to send emails within the rails application.

# app/mailers/contact_mailer.rb
class ContactMailer < ActionMailer::Base
  default from: ""

  # This method receives the data from the sucker punch job.
  def contact_form(contact)
    @contact = contact

    mail to: "",
         subject: contact.subject,

Create your email template.

# app/views/contact_mailer/contact_form.txt.erb
# This template receives the @contact variable from the
# app/mailers/contact_mailer.rb contact_form method.
<%= %>

<%= @contact.content %>

Let’s create the sucker punch job.

# app/jobs/contacts_email_job.rb
class ContactsEmailJob
  include SuckerPunch::Job

  # The perform method is in charge of our code execution when enqueued.
  def perform(contact)


Now let’s take a look at the controller.

# app/controllers/contacts_controller.rb
class ContactsController < ApplicationController
  def new
    @contact =

  def create
    @contact =[:contact])

    if @contact.valid?

      # We call our sucker punch job asynchronously using "async"
      flash[:success] = Your email has been send!
      redirect_to root_url
      render :action => 'new'

When the user hits contact form and click the submit button of the form, they are triggering the controller which instantiates a new job that will perform asynchronously so the user will not be hold down waiting for the email to be send. In the end using background jobs for doing this things reflects in a better user experience.

In conclusion doing complicated things like background jobs becomes really easy when using the right tools. In this case using sucker punch. We didn’t have to figure out how to install and configure persistence or configuring the job queues. It just works.