The Rails 5.0 Default Files

Rails 5 is here!

Published on:July 21, 2016

Rails 5 has been released! Below you will find a copy of each of the files generated during new application creation. This will assist you when upgrading. Below the tabs is some additional upgrade info you might find handy. Simply scroll down.

Notable changes to Rails 5.0 include:

  • Action Cable - An awesome framework for handling web sockets.
  • New Default Web Server: Puma - Puma is now the default development web server for Rails 5 applications.
  • Integrated Rails API - The Rails API gem is now integrated. Rails API enables you to quickly and easily build APIs using the Ruby On Rails framework.
  • One Command to Rule Them All - The rails command now handles all of your command line needs. Now you can do stuff like run rails db:migrate to migrate the database.
  • Ruby 2.2 REQUIRED - Rails now requires Ruby 2.2.2 and above.

Note that you can install Rails 5 by running gem install rails. I hope to go over some of the new Rails 5.0 features in future articles. For now, enjoy!

The contents of the Gemfile are listed below. Notable changes include the addition of the puma gem, the listen gem as well as the spring-watcher-listen gem. In addition, turbolinks and webconsole both receive major version updates.

source ''

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.0.0'
# Use sqlite3 as the database for Active Record
gem 'sqlite3'
# Use Puma as the app server
gem 'puma', '~> 3.0'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# See for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'
# Turbolinks makes navigating your web application faster. Read more:
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more:
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 3.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platform: :mri

group :development do
  # Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
  gem 'web-console'
  gem 'listen', '~> 3.0.5'
  # Spring speeds up development by keeping your application running in the background. Read more:
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

The config/application.rb file has been slimmed down.

require_relative 'boot'

require 'rails/all'

# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.

module Rails5ExampleApp
  class Application < Rails::Application
    # Settings in config/environments/* take precedence over those specified here.
    # Application configuration should go into files in config/initializers
    # -- all .rb files in that directory are automatically loaded.

Quite a bit going on in config/environments/development.rb. There is an if statement that looks for a tmp/caching-dev.txt file. If this file exists, caching is enabled. Also, a config.filewatcher setting has been added, allowing you to specify an evented file watcher, which is currently provided by the listen gem. Note that the setting listed for config.public_file_server.headers actually contains the former settings that were once a part of config.static_cache_control.

Rails.application.configure do
  # Settings specified here will take precedence over those in config/application.rb.

  # In the development environment your application's code is reloaded on
  # every request. This slows down response time but is perfect for development
  # since you don't have to restart the web server when you make code changes.
  config.cache_classes = false

  # Do not eager load code on boot.
  config.eager_load = false

  # Show full error reports.
  config.consider_all_requests_local = true

  # Enable/disable caching. By default caching is disabled.
  if Rails.root.join('tmp/caching-dev.txt').exist?
    config.action_controller.perform_caching = true

    config.cache_store = :memory_store
    config.public_file_server.headers = {
      'Cache-Control' => 'public, max-age=172800'
    config.action_controller.perform_caching = false

    config.cache_store = :null_store

  # Don't care if the mailer can't send.
  config.action_mailer.raise_delivery_errors = false

  config.action_mailer.perform_caching = false

  # Print deprecation notices to the Rails logger.
  config.active_support.deprecation = :log

  # Raise an error on page load if there are pending migrations.
  config.active_record.migration_error = :page_load

  # Debug mode disables concatenation and preprocessing of assets.
  # This option may cause significant delays in view rendering with a large
  # number of complex assets.
  config.assets.debug = true

  # Suppress logger output for asset requests.
  config.assets.quiet = true

  # Raises error for missing translations
  # config.action_view.raise_on_missing_translations = true

  # Use an evented file watcher to asynchronously detect changes in source code,
  # routes, locales, etc. This feature depends on the listen gem.
  config.file_watcher = ActiveSupport::EventedFileUpdateChecker

Some changes to config/environments/production.rb. The config.serve_static_files setting name has been changed (yet again) to config.public_file_server.enabled. Some enhancements have been added that allow you to easily enable STDOUT logging by simply setting the RAILS_LOG_TO_STDOUT environment variable to true. Finally, an initial configuration option called config.log_tags was included that allows you to tag log entries with extra information. This setting has actually been floating around for quite a while, but it's great to see that an example is included in production.rb.

Rails.application.configure do
  # Settings specified here will take precedence over those in config/application.rb.

  # Code is not reloaded between requests.
  config.cache_classes = true

  # Eager load code on boot. This eager loads most of Rails and
  # your application in memory, allowing both threaded web servers
  # and those relying on copy on write to perform better.
  # Rake tasks automatically ignore this option for performance.
  config.eager_load = true

  # Full error reports are disabled and caching is turned on.
  config.consider_all_requests_local       = false
  config.action_controller.perform_caching = true

  # Disable serving static files from the `/public` folder by default since
  # Apache or NGINX already handles this.
  config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?

  # Compress JavaScripts and CSS.
  config.assets.js_compressor = :uglifier
  # config.assets.css_compressor = :sass

  # Do not fallback to assets pipeline if a precompiled asset is missed.
  config.assets.compile = false

  # `config.assets.precompile` and `config.assets.version` have moved to config/initializers/assets.rb

  # Enable serving of images, stylesheets, and JavaScripts from an asset server.
  # config.action_controller.asset_host = ''

  # Specifies the header that your server uses for sending files.
  # config.action_dispatch.x_sendfile_header = 'X-Sendfile' # for Apache
  # config.action_dispatch.x_sendfile_header = 'X-Accel-Redirect' # for NGINX

  # Mount Action Cable outside main process or domain
  # config.action_cable.mount_path = nil
  # config.action_cable.url = 'wss://'
  # config.action_cable.allowed_request_origins = [ '', /http:\/\/example.*/ ]

  # Force all access to the app over SSL, use Strict-Transport-Security, and use secure cookies.
  # config.force_ssl = true

  # Use the lowest log level to ensure availability of diagnostic information
  # when problems arise.
  config.log_level = :debug

  # Prepend all log lines with the following tags.
  config.log_tags = [ :request_id ]

  # Use a different cache store in production.
  # config.cache_store = :mem_cache_store

  # Use a real queuing backend for Active Job (and separate queues per environment)
  # config.active_job.queue_adapter     = :resque
  # config.active_job.queue_name_prefix = "final5app_#{Rails.env}"
  config.action_mailer.perform_caching = false

  # Ignore bad email addresses and do not raise email delivery errors.
  # Set this to true and configure the email server for immediate delivery to raise delivery errors.
  # config.action_mailer.raise_delivery_errors = false

  # Enable locale fallbacks for I18n (makes lookups for any locale fall back to
  # the I18n.default_locale when a translation cannot be found).
  config.i18n.fallbacks = true

  # Send deprecation notices to registered listeners.
  config.active_support.deprecation = :notify

  # Use default logging formatter so that PID and timestamp are not suppressed.
  config.log_formatter =

  # Use a different logger for distributed setups.
  # require 'syslog/logger'
  # config.logger = 'app-name')

  if ENV["RAILS_LOG_TO_STDOUT"].present?
    logger           =
    logger.formatter = config.log_formatter
    config.logger =

  # Do not dump schema after migrations.
  config.active_record.dump_schema_after_migration = false

A few changes for config/environments/test.rb. Note again that that config.serve_static_assets has been changed to config.public_file_server.enabled. Hopefully this is the end of the identity crisis for this setting. The config/static_cache_control setting has been merged into config.public_file_server.headers. A new setting called config.action_mailer.perform_caching has been added, and finally the config.active_support.test_order setting has been removed.

Rails.application.configure do
  # Settings specified here will take precedence over those in config/application.rb.

  # The test environment is used exclusively to run your application's
  # test suite. You never need to work with it otherwise. Remember that
  # your test database is "scratch space" for the test suite and is wiped
  # and recreated between test runs. Don't rely on the data there!
  config.cache_classes = true

  # Do not eager load code on boot. This avoids loading your whole application
  # just for the purpose of running a single test. If you are using a tool that
  # preloads Rails for running tests, you may have to set it to true.
  config.eager_load = false

  # Configure public file server for tests with Cache-Control for performance.
  config.public_file_server.enabled = true
  config.public_file_server.headers = {
    'Cache-Control' => 'public, max-age=3600'

  # Show full error reports and disable caching.
  config.consider_all_requests_local       = true
  config.action_controller.perform_caching = false

  # Raise exceptions instead of rendering exception templates.
  config.action_dispatch.show_exceptions = false

  # Disable request forgery protection in test environment.
  config.action_controller.allow_forgery_protection = false
  config.action_mailer.perform_caching = false

  # Tell Action Mailer not to deliver emails to the real world.
  # The :test delivery method accumulates sent emails in the
  # ActionMailer::Base.deliveries array.
  config.action_mailer.delivery_method = :test

  # Print deprecation notices to the stderr.
  config.active_support.deprecation = :stderr

  # Raises error for missing translations
  # config.action_view.raise_on_missing_translations = true

For the people that still haven't upgraded.

          # Be sure to restart your server when you modify this file.

          # Your secret key is used for verifying the integrity of signed cookies.
          # If you change this key, all old signed cookies will become invalid!

          # Make sure the secret is at least 30 characters and all random,
          # no regular words or you'll be exposed to dictionary attacks.
          # You can use `rake secret` to generate a secure secret key.

          # Make sure the secrets in this file are kept private
          # if you're sharing your code publicly.

            secret_key_base: <A SECRET KEY>

            secret_key_base: <A SECRET KEY>

          # Do not keep production secrets in the repository,
          # instead read values from the environment.
            secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>


New Config Files

Wait! We aren't done yet. Rails 5 has added a couple new configuration files along with several new initializers. Let's take a look!

First up is the config/cable.yml file, which contains settings for Action Cable.


  adapter: async

  adapter: async

  adapter: redis
  url: redis://localhost:6379/1

Next up is config/puma.rb which contains some Rails specific Puma settings. Remember that Puma is the default development web server now!


# Puma can serve each request in a thread from an internal thread pool.
# The `threads` method setting takes two numbers a minimum and maximum.
# Any libraries that use thread pools should be configured to match
# the maximum value specified for Puma. Default is set to 5 threads for minimum
# and maximum, this matches the default thread size of Active Record.
threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }.to_i
threads threads_count, threads_count

# Specifies the `port` that Puma will listen on to receive requests, default is 3000.
port        ENV.fetch("PORT") { 3000 }

# Specifies the `environment` that Puma will run in.
environment ENV.fetch("RAILS_ENV") { "development" }

# Specifies the number of `workers` to boot in clustered mode.
# Workers are forked webserver processes. If using threads and workers together
# the concurrency of the application would be max `threads` * `workers`.
# Workers do not work on JRuby or Windows (both of which do not support
# processes).
# workers ENV.fetch("WEB_CONCURRENCY") { 2 }

# Use the `preload_app!` method when specifying a `workers` number.
# This directive tells Puma to first boot the application and load code
# before forking the application. This takes advantage of Copy On Write
# process behavior so workers use less memory. If you use this option
# you need to make sure to reconnect any threads in the `on_worker_boot`
# block.
# preload_app!

# The code in the `on_worker_boot` will be called if you are using
# clustered mode by specifying a number of `workers`. After each worker
# process is booted this block will be run, if you are using `preload_app!`
# option you will want to use this block to reconnect to any threads
# or connections that may have been created at application boot, Ruby
# cannot share connections between processes.
# on_worker_boot do
#   ActiveRecord::Base.establish_connection if defined?(ActiveRecord)
# end

# Allow puma to be restarted by `rails restart` command.
plugin :tmp_restart

Next up is config/initializers/new_framework_defaults.rb. This file contains settings that are used for backwards compatibility.

# Be sure to restart your server when you modify this file.
# This file contains migration options to ease your Rails 5.0 upgrade.
# Read the Rails 5.0 release notes for more info on each option.

# Enable per-form CSRF tokens. Previous versions had false.
Rails.application.config.action_controller.per_form_csrf_tokens = true

# Enable origin-checking CSRF mitigation. Previous versions had false.
Rails.application.config.action_controller.forgery_protection_origin_check = true

# Make Ruby 2.4 preserve the timezone of the receiver when calling `to_time`.
# Previous versions had false.
ActiveSupport.to_time_preserves_timezone = true

# Require `belongs_to` associations by default. Previous versions had false.
Rails.application.config.active_record.belongs_to_required_by_default = true

# Do not halt callback chains when a callback returns false. Previous versions had true.
ActiveSupport.halt_callback_chains_on_return_false = false

# Configure SSL options to enable HSTS with subdomains. Previous versions had false.
Rails.application.config.ssl_options = { hsts: { subdomains: true } }

Other New Files

Two new folders have been added to the app folder. The first is app/channels. This folder stores your Action Cable code. By default it contains only 1 folder called application_cable, which itself contains 2 files, channel.rb and connection.rb. The contents of these files are listed below.


# Be sure to restart your server when you modify this file. Action Cable runs in a loop that does not support auto reloading.
module ApplicationCable
  class Channel < ActionCable::Channel::Base

# Be sure to restart your server when you modify this file. Action Cable runs in a loop that does not support auto reloading.
module ApplicationCable
  class Connection < ActionCable::Connection::Base

The second new folder is calledjobs and is where you store your Active Job code. This folder was previously created whenever you created a new job, but now it exists by default. It contains a single application_job.rb file which is a global file your jobs can inherit from.


class ApplicationJob < ActiveJob::Base

There are also some other changes. The app/mailers gets an application_mailer.rb file that you can inherit from in your mailers. It's contents are listed below.


class ApplicationMailer < ActionMailer::Base
  default from: '[email protected]'
  layout 'mailer'

The app/models folder also gets an application_record.rb file that your models can inherit from. It's contents are listed below.


class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true

A folder has been added to app/assets called config, which contains a file called manifest.js It's contents are listed below.


//= link_tree ../images
//= link_directory ../javascripts .js
//= link_directory ../stylesheets .css

Two layouts have been added for ActionMailer under the app/views/layouts folder. They are called mailer.html.erb and mailer.text.erb. Their contents are listed below. These layouts are referenced by app/mailers/application_mailer.rb.


<!DOCTYPE html>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
      /* Email styles need to be inline */

    <%= yield %>


<%= yield %>

I hope this article helps you with upgrading to Rails 5.0. If you have any questions, comments, or concerns, please feel free to leave them in the comments section below. Thanks for reading!