Setup Rails application for production

This guide will help you on how to setup a rails application(production) using heroku. This guide is useful for Rails 4.2+ but may work on lower versions.

Assumptions

• You have a heroku application linked to your project
• You have a Rails application to deploy

Steps

1. The first step is to add the following block to the Gemfile:

group :production do
  gem 'rails_12factor'
  gem 'pg' #ADD THIS IF YOU ARE NOT USING POSTGRES ON DEVELOPMENT
end

Run the bundle install command to install the gems

2. Next you need to add a Procfile on the root directory:

% touch Procfile

Using Unicorn

If you are using unicorn as the server, the Procfile content should look like:

web: bundle exec unicorn -p $PORT -c ./config/unicorn.rb

Using Puma

If you are using puma as the server, the Procfile content should look like:

web: bundle exec puma -C config/puma.rb

3. Once you have added the Procfile, you need to add a configuration file under config and the name here is important as they have to match the one on the Procfile

For unicorn.rb

# config/unicorn.rb
worker_processes Integer(ENV["WEB_CONCURRENCY"] || 3)
timeout 15
preload_app true

before_fork do |server, worker|
  Signal.trap 'TERM' do
    puts 'Unicorn master intercepting TERM and sending myself QUIT instead'
    Process.kill 'QUIT', Process.pid
  end

  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.connection.disconnect!
end

after_fork do |server, worker|
  Signal.trap 'TERM' do
    puts 'Unicorn worker intercepting TERM and doing nothing. Wait for master to send QUIT'
  end

  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.establish_connection
end

For puma.rb

workers Integer(ENV['WEB_CONCURRENCY'] || 2)
threads_count = Integer(ENV['RAILS_MAX_THREADS'] || 5)
threads threads_count, threads_count

preload_app!

rackup      DefaultRackup
port        ENV['PORT']     || 3000
environment ENV['RACK_ENV'] || 'development'

on_worker_boot do
  # Worker specific setup for Rails 4.1+
  # See: https://devcenter.heroku.com/articles/deploying-rails-applications-with-the-puma-web-server#on-worker-boot
  ActiveRecord::Base.establish_connection
end

Before pushing

Make sure to check out this list of points to ensure you are not missing any application configuration:

• Make sure you have the ruby version specified on the Gemfile
• Make sure the PG-Backups add on is enabled
• Make sure to add a logs providers
• Make sure you have [New Relic] for app monitoring
• Make sure to have every ENV variable necessary for the application

Deploy

In order to deploy you just need to place a commit and push it heroku:

% git add Gemfile
% git add Gemfile.lock
% git add Procfile
% git add config/puma.rb
% git commit -m "Adds production setup"
% git push heroku master

Resources

For more information you can always rely on Heroku's documentation

• https://devcenter.heroku.com/articles/deploying-rails-applications-with-the-puma-web-server
• https://devcenter.heroku.com/articles/rails-unicorn