Add existing rails project to heroku

Gemfile

# Ruby version has to be  1.9.3 or above, by default is 2.0
...
ruby '2.2.0'

# Heroku uses only supports Postgresql
# Check database.yml to make sure production is using postgresql
gem 'pg' #, group: :production # in case of using another db for development
gem 'rails', '4.2.0'
gem 'unicorn'
gem 'rails_12factor', group: :production
...

# bundle install

Procfle.md

This file should be at app's root level with no extension

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

Steps.md

Steps to upload a rails 4 project to Heroku

1.- Create the Heroku app where it will be uploaded.

2.- Download and install Heroku toolbelt if it is not installed already.

3.- In the terminal, login in to Heroku

  heroku login

4.- In the repository root folder, add the remote to the Heroku app previously created in step 1, replace the name fakeapp for your app.

  heroku git:remote -a fakeapp

5.- Add the changes in Gemfile, Procfile and unicorn.rb and commit the changes and push them to Heroku.

  git push heroku master

6.- Run the migrations.

  heroku run rake db:migrate

7.- Set variables if any.

  heroku config:set API_KEY=secret

8.- Restart Heroku app.

  heroku restart

9.- View app in browser from the Heroku server.

  heroku open

unicorn.rb

# # This file should be placed on the directory of 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