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An Engine with the responsibility of coordinating the whole boot process.

Initialization

Rails::Application is responsible for executing all railties and engines initializers. It also executes some bootstrap initializers (check Rails::Application::Bootstrap) and finishing initializers, after all the others are executed (check Rails::Application::Finisher).

Configuration

Besides providing the same configuration as Rails::Engine and Rails::Railtie, the application object has several specific configurations, for example enable_reloading, consider_all_requests_local, filter_parameters, logger, and so forth.

Check Rails::Application::Configuration to see them all.

Routes

The application object is also responsible for holding the routes and reloading routes whenever the files change in development.

Middlewares

The Application is also responsible for building the middleware stack.

Booting process

The application is also responsible for setting up and executing the booting process. From the moment you require config/application.rb in your app, the booting process goes like this:

  1. require "config/boot.rb" to set up load paths.

  2. require railties and engines.

  3. Define Rails.application as class MyApp::Application < Rails::Application.

  4. Run config.before_configuration callbacks.

  5. Load config/environments/ENV.rb.

  6. Run config.before_initialize callbacks.

  7. Run Railtie#initializer defined by railties, engines, and application. One by one, each engine sets up its load paths and routes, and runs its config/initializers/* files.

  8. Custom Railtie#initializers added by railties, engines, and applications are executed.

  9. Build the middleware stack and run to_prepare callbacks.

  10. Run config.before_eager_load and eager_load! if eager_load is true.

  11. Run config.after_initialize callbacks.

Namespace
Methods
C
D
E
F
G
I
K
M
N
R
S
V

Attributes

[RW] assets
[R] autoloaders
[W] config
[W] credentials
[R] executor
[R] reloader
[R] reloaders
[RW] sandbox
[RW] sandbox?
[W] secrets

Class Public methods

create(initial_variable_values = {}, &block)

Source: show 

# File railties/lib/rails/application.rb, line 82
def create(initial_variable_values = {}, &block)
  new(initial_variable_values, &block).run_load_hooks!
end

find_root(from)

Source: show 

# File railties/lib/rails/application.rb, line 86
def find_root(from)
  find_root_with_flag "config.ru", from, Dir.pwd
end

inherited(base)

Source: show 

# File railties/lib/rails/application.rb, line 71
def inherited(base)
  super
  Rails.app_class = base
  add_lib_to_load_path!(find_root(base.called_from))
  ActiveSupport.run_load_hooks(:before_configuration, base)
end

instance()

Source: show 

# File railties/lib/rails/application.rb, line 78
def instance
  super.run_load_hooks!
end

new(initial_variable_values = {}, &block)

Source: show 

# File railties/lib/rails/application.rb, line 107
def initialize(initial_variable_values = {}, &block)
  super()
  @initialized       = false
  @reloaders         = []
  @routes_reloader   = nil
  @app_env_config    = nil
  @ordered_railties  = nil
  @railties          = nil
  @key_generators    = {}
  @message_verifiers = nil
  @deprecators       = nil
  @ran_load_hooks    = false

  @executor          = Class.new(ActiveSupport::Executor)
  @reloader          = Class.new(ActiveSupport::Reloader)
  @reloader.executor = @executor

  @autoloaders = Rails::Autoloaders.new

  # are these actually used?
  @initial_variable_values = initial_variable_values
  @block = block
end

Instance Public methods

config_for(name, env: Rails.env)

Convenience for loading config/foo.yml for the current Rails env.

Examples:

# config/exception_notification.yml:
production:
  url: http://127.0.0.1:8080
  namespace: my_app_production

development:
  url: http://localhost:3001
  namespace: my_app_development

# config/environments/production.rb
Rails.application.configure do
  config.middleware.use ExceptionNotifier, config_for(:exception_notification)
end

# You can also store configurations in a shared section which will be
# merged with the environment configuration

# config/example.yml
shared:
  foo:
    bar:
      baz: 1

development:
  foo:
    bar:
      qux: 2

# development environment
Rails.application.config_for(:example)[:foo][:bar]
# => { baz: 1, qux: 2 }

Source: show 

# File railties/lib/rails/application.rb, line 269
def config_for(name, env: Rails.env)
  yaml = name.is_a?(Pathname) ? name : Pathname.new("#{paths["config"].existent.first}/#{name}.yml")

  if yaml.exist?
    require "erb"
    all_configs    = ActiveSupport::ConfigurationFile.parse(yaml).deep_symbolize_keys
    config, shared = all_configs[env.to_sym], all_configs[:shared]

    if shared
      config = {} if config.nil? && shared.is_a?(Hash)
      if config.is_a?(Hash) && shared.is_a?(Hash)
        config = shared.deep_merge(config)
      elsif config.nil?
        config = shared
      end
    end

    if config.is_a?(Hash)
      config = ActiveSupport::OrderedOptions.new.update(config)
    end

    config
  else
    raise "Could not load configuration. No such file - #{yaml}"
  end
end

console(&blk)

Sends any console called in the instance of a new application up to the console method defined in Rails::Railtie.

Source: show 

# File railties/lib/rails/application.rb, line 351
def console(&blk)
  self.class.console(&blk)
end

credentials()

Returns an ActiveSupport::EncryptedConfiguration instance for the credentials file specified by config.credentials.content_path.

By default, config.credentials.content_path will point to either config/credentials/#{environment}.yml.enc for the current environment (for example, config/credentials/production.yml.enc for the production environment), or config/credentials.yml.enc if that file does not exist.

The encryption key is taken from either ENV["RAILS_MASTER_KEY"], or from the file specified by config.credentials.key_path. By default, config.credentials.key_path will point to either config/credentials/#{environment}.key for the current environment, or config/master.key if that file does not exist.

Source: show 

# File railties/lib/rails/application.rb, line 493
def credentials
  @credentials ||= encrypted(config.credentials.content_path, key_path: config.credentials.key_path)
end

deprecators()

A managed collection of deprecators (ActiveSupport::Deprecation::Deprecators). The collection’s configuration methods affect all deprecators in the collection. Additionally, the collection’s silence method silences all deprecators in the collection for the duration of a given block.

Source: show 

# File railties/lib/rails/application.rb, line 228
def deprecators
  @deprecators ||= ActiveSupport::Deprecation::Deprecators.new.tap do |deprecators|
    deprecators[:railties] = Rails.deprecator
  end
end

eager_load!()

Eager loads the application code.

Source: show 

# File railties/lib/rails/application.rb, line 551
def eager_load!
  Rails.autoloaders.each(&:eager_load)
end

encrypted(path, key_path: "config/master.key", env_key: "RAILS_MASTER_KEY")

Returns an ActiveSupport::EncryptedConfiguration instance for an encrypted file. By default, the encryption key is taken from either ENV["RAILS_MASTER_KEY"], or from the config/master.key file.

my_config = Rails.application.encrypted("config/my_config.enc")

my_config.read
# => "foo:\n  bar: 123\n"

my_config.foo.bar
# => 123

Encrypted files can be edited with the bin/rails encrypted:edit command. (See the output of bin/rails encrypted:edit --help for more information.)

Source: show 

# File railties/lib/rails/application.rb, line 512
def encrypted(path, key_path: "config/master.key", env_key: "RAILS_MASTER_KEY")
  ActiveSupport::EncryptedConfiguration.new(
    config_path: Rails.root.join(path),
    key_path: Rails.root.join(key_path),
    env_key: env_key,
    raise_if_missing_key: config.require_master_key
  )
end

env_config()

Stores some of the Rails initial environment parameters which will be used by middlewares and engines to configure themselves.

Source: show 

# File railties/lib/rails/application.rb, line 298
def env_config
  @app_env_config ||= super.merge(
      "action_dispatch.parameter_filter" => filter_parameters,
      "action_dispatch.redirect_filter" => config.filter_redirect,
      "action_dispatch.secret_key_base" => secret_key_base,
      "action_dispatch.show_exceptions" => config.action_dispatch.show_exceptions,
      "action_dispatch.show_detailed_exceptions" => config.consider_all_requests_local,
      "action_dispatch.log_rescued_responses" => config.action_dispatch.log_rescued_responses,
      "action_dispatch.logger" => Rails.logger,
      "action_dispatch.backtrace_cleaner" => Rails.backtrace_cleaner,
      "action_dispatch.key_generator" => key_generator,
      "action_dispatch.http_auth_salt" => config.action_dispatch.http_auth_salt,
      "action_dispatch.signed_cookie_salt" => config.action_dispatch.signed_cookie_salt,
      "action_dispatch.encrypted_cookie_salt" => config.action_dispatch.encrypted_cookie_salt,
      "action_dispatch.encrypted_signed_cookie_salt" => config.action_dispatch.encrypted_signed_cookie_salt,
      "action_dispatch.authenticated_encrypted_cookie_salt" => config.action_dispatch.authenticated_encrypted_cookie_salt,
      "action_dispatch.use_authenticated_cookie_encryption" => config.action_dispatch.use_authenticated_cookie_encryption,
      "action_dispatch.encrypted_cookie_cipher" => config.action_dispatch.encrypted_cookie_cipher,
      "action_dispatch.signed_cookie_digest" => config.action_dispatch.signed_cookie_digest,
      "action_dispatch.cookies_serializer" => config.action_dispatch.cookies_serializer,
      "action_dispatch.cookies_digest" => config.action_dispatch.cookies_digest,
      "action_dispatch.cookies_rotations" => config.action_dispatch.cookies_rotations,
      "action_dispatch.cookies_same_site_protection" => coerce_same_site_protection(config.action_dispatch.cookies_same_site_protection),
      "action_dispatch.use_cookies_with_metadata" => config.action_dispatch.use_cookies_with_metadata,
      "action_dispatch.content_security_policy" => config.content_security_policy,
      "action_dispatch.content_security_policy_report_only" => config.content_security_policy_report_only,
      "action_dispatch.content_security_policy_nonce_generator" => config.content_security_policy_nonce_generator,
      "action_dispatch.content_security_policy_nonce_directives" => config.content_security_policy_nonce_directives,
      "action_dispatch.permissions_policy" => config.permissions_policy,
    )
end

generators(&blk)

Sends any generators called in the instance of a new application up to the generators method defined in Rails::Railtie.

Source: show 

# File railties/lib/rails/application.rb, line 357
def generators(&blk)
  self.class.generators(&blk)
end

initialized?()

Returns true if the application is initialized.

Source: show 

# File railties/lib/rails/application.rb, line 132
def initialized?
  @initialized
end

initializer(name, opts = {}, &block)

Sends the initializers to the initializer method defined in the Rails::Initializable module. Each Rails::Application class has its own set of initializers, as defined by the Initializable module.

Source: show 

# File railties/lib/rails/application.rb, line 339
def initializer(name, opts = {}, &block)
  self.class.initializer(name, opts, &block)
end

isolate_namespace(mod)

Sends the isolate_namespace method up to the class method.

Source: show 

# File railties/lib/rails/application.rb, line 368
def isolate_namespace(mod)
  self.class.isolate_namespace(mod)
end

key_generator(secret_key_base = self.secret_key_base)

Returns a key generator (ActiveSupport::CachingKeyGenerator) for a specified secret_key_base. The return value is memoized, so additional calls with the same secret_key_base will return the same key generator instance.

Source: show 

# File railties/lib/rails/application.rb, line 159
def key_generator(secret_key_base = self.secret_key_base)
  # number of iterations selected based on consultation with the google security
  # team. Details at https://github.com/rails/rails/pull/6952#issuecomment-7661220
  @key_generators[secret_key_base] ||= ActiveSupport::CachingKeyGenerator.new(
    ActiveSupport::KeyGenerator.new(secret_key_base, iterations: 1000)
  )
end

message_verifier(verifier_name)

Returns a message verifier object.

This verifier can be used to generate and verify signed messages in the application.

It is recommended not to use the same verifier for different things, so you can get different verifiers passing the verifier_name argument.

Parameters

  • verifier_name - the name of the message verifier.

Examples

message = Rails.application.message_verifier('sensitive_data').generate('my sensible data')
Rails.application.message_verifier('sensitive_data').verify(message)
# => 'my sensible data'

See the ActiveSupport::MessageVerifier documentation for more information.

Source: show 

# File railties/lib/rails/application.rb, line 220
def message_verifier(verifier_name)
  message_verifiers[verifier_name]
end

message_verifiers()

Returns a message verifier factory (ActiveSupport::MessageVerifiers). This factory can be used as a central point to configure and create message verifiers (ActiveSupport::MessageVerifier) for your application.

By default, message verifiers created by this factory will generate messages using the default ActiveSupport::MessageVerifier options. You can override these options with a combination of ActiveSupport::MessageVerifiers#clear_rotations and ActiveSupport::MessageVerifiers#rotate. However, this must be done prior to building any message verifier instances. For example, in a before_initialize block:

# Use `url_safe: true` when generating messages
config.before_initialize do |app|
  app.message_verifiers.clear_rotations
  app.message_verifiers.rotate(url_safe: true)
end

Message verifiers created by this factory will always use a secret derived from secret_key_base when generating messages. clear_rotations will not affect this behavior. However, older secret_key_base values can be rotated for verifying messages:

# Fall back to old `secret_key_base` when verifying messages
config.before_initialize do |app|
  app.message_verifiers.rotate(secret_key_base: "old secret_key_base")
end

Source: show 

# File railties/lib/rails/application.rb, line 195
def message_verifiers
  @message_verifiers ||=
    ActiveSupport::MessageVerifiers.new do |salt, secret_key_base: self.secret_key_base|
      key_generator(secret_key_base).generate_key(salt)
    end.rotate_defaults
end

rake_tasks(&block)

If you try to define a set of Rake tasks on the instance, these will get passed up to the Rake tasks defined on the application’s class.

Source: show 

# File railties/lib/rails/application.rb, line 332
def rake_tasks(&block)
  self.class.rake_tasks(&block)
end

reload_routes!()

Reload application routes regardless if they changed or not.

Source: show 

# File railties/lib/rails/application.rb, line 151
def reload_routes!
  routes_reloader.reload!
end

runner(&blk)

Sends any runner called in the instance of a new application up to the runner method defined in Rails::Railtie.

Source: show 

# File railties/lib/rails/application.rb, line 345
def runner(&blk)
  self.class.runner(&blk)
end

secret_key_base()

The secret_key_base is used as the input secret to the application’s key generator, which in turn is used to create all ActiveSupport::MessageVerifier and ActiveSupport::MessageEncryptor instances, including the ones that sign and encrypt cookies.

In development and test, this is randomly generated and stored in a temporary file in tmp/development_secret.txt.

You can also set ENV["SECRET_KEY_BASE_DUMMY"] to trigger the use of a randomly generated secret_key_base that’s stored in a temporary file. This is useful when precompiling assets for production as part of a build step that otherwise does not need access to the production secrets.

Dockerfile example: RUN SECRET_KEY_BASE_DUMMY=1 bundle exec rails assets:precompile.

In all other environments, we look for it first in ENV["SECRET_KEY_BASE"], then credentials.secret_key_base, and finally secrets.secret_key_base. For most applications, the correct place to store it is in the encrypted credentials file.

Source: show 

# File railties/lib/rails/application.rb, line 469
def secret_key_base
  if Rails.env.local? || ENV["SECRET_KEY_BASE_DUMMY"]
    secrets.secret_key_base ||= generate_development_secret
  else
    validate_secret_key_base(
      ENV["SECRET_KEY_BASE"] || credentials.secret_key_base || secrets.secret_key_base
    )
  end
end

secrets()

Source: show 

# File railties/lib/rails/application.rb, line 437
def secrets
  @secrets ||= begin
    secrets = ActiveSupport::OrderedOptions.new
    files = config.paths["config/secrets"].existent
    files = files.reject { |path| path.end_with?(".enc") } unless config.read_encrypted_secrets
    secrets.merge! Rails::Secrets.parse(files, env: Rails.env)

    # Fallback to config.secret_key_base if secrets.secret_key_base isn't set
    secrets.secret_key_base ||= config.secret_key_base

    secrets
  end
end

server(&blk)

Sends any server called in the instance of a new application up to the server method defined in Rails::Railtie.

Source: show 

# File railties/lib/rails/application.rb, line 363
def server(&blk)
  self.class.server(&blk)
end

Instance Protected methods

ensure_generator_templates_added()

Source: show 

# File railties/lib/rails/application.rb, line 639
def ensure_generator_templates_added
  configured_paths = config.generators.templates
  configured_paths.unshift(*(paths["lib/templates"].existent - configured_paths))
end

validate_secret_key_base(secret_key_base)

Source: show 

# File railties/lib/rails/application.rb, line 629
def validate_secret_key_base(secret_key_base)
  if secret_key_base.is_a?(String) && secret_key_base.present?
    secret_key_base
  elsif secret_key_base
    raise ArgumentError, "`secret_key_base` for #{Rails.env} environment must be a type of String`"
  else
    raise ArgumentError, "Missing `secret_key_base` for '#{Rails.env}' environment, set this string with `bin/rails credentials:edit`"
  end
end