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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
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)

# File railties/lib/rails/application.rb, line 81
def create(initial_variable_values = {}, &block)
  new(initial_variable_values, &block).run_load_hooks!
end

find_root(from)

# File railties/lib/rails/application.rb, line 85
def find_root(from)
  find_root_with_flag "config.ru", from, Dir.pwd
end

inherited(base)

# File railties/lib/rails/application.rb, line 70
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()

# File railties/lib/rails/application.rb, line 77
def instance
  super.run_load_hooks!
end

new(initial_variable_values = {}, &block)

# File railties/lib/rails/application.rb, line 106
def initialize(initial_variable_values = {}, &block)
  super()
  @initialized       = false
  @reloaders         = []
  @routes_reloader   = nil
  @app_env_config    = nil
  @ordered_railties  = nil
  @railties          = nil
  @message_verifiers = {}
  @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 }
# File railties/lib/rails/application.rb, line 221
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.

# File railties/lib/rails/application.rb, line 303
def console(&blk)
  self.class.console(&blk)
end

credentials()

Decrypts the credentials hash as kept in config/credentials.yml.enc. This file is encrypted with the Rails master key, which is either taken from ENV["RAILS_MASTER_KEY"] or from loading config/master.key. If specific credentials file exists for current environment, it takes precedence, thus for production environment look first for config/credentials/production.yml.enc with master key taken from ENV["RAILS_MASTER_KEY"] or from loading config/credentials/production.key. Default behavior can be overwritten by setting config.credentials.content_path and config.credentials.key_path.

# File railties/lib/rails/application.rb, line 432
def credentials
  @credentials ||= encrypted(config.credentials.content_path, key_path: config.credentials.key_path)
end

eager_load!()

Eager loads the application code.

# File railties/lib/rails/application.rb, line 497
def eager_load!
  Rails.autoloaders.each(&:eager_load)
end

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

Shorthand to decrypt any encrypted configurations or files.

For any file added with rails encrypted:edit call read to decrypt the file with the master key. The master key is either stored in config/master.key or ENV["RAILS_MASTER_KEY"].

Rails.application.encrypted("config/mystery_man.txt.enc").read
# => "We've met before, haven't we?"

It's also possible to interpret encrypted YAML files with config.

Rails.application.encrypted("config/credentials.yml.enc").config
# => { next_guys_line: "I don't think so. Where was it you think we met?" }

Any top-level configs are also accessible directly on the return value:

Rails.application.encrypted("config/credentials.yml.enc").next_guys_line
# => "I don't think so. Where was it you think we met?"

The files or configs can also be encrypted with a custom key. To decrypt with a key in the ENV, use:

Rails.application.encrypted("config/special_tokens.yml.enc", env_key: "SPECIAL_TOKENS")

Or to decrypt with a file, that should be version control ignored, relative to Rails.root:

Rails.application.encrypted("config/special_tokens.yml.enc", key_path: "config/special_tokens.key")
# File railties/lib/rails/application.rb, line 463
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.

# File railties/lib/rails/application.rb, line 250
def env_config
  @app_env_config ||= super.merge(
      "action_dispatch.parameter_filter" => config.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.

# File railties/lib/rails/application.rb, line 309
def generators(&blk)
  self.class.generators(&blk)
end

initialized?()

Returns true if the application is initialized.

# File railties/lib/rails/application.rb, line 129
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.

# File railties/lib/rails/application.rb, line 291
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.

# File railties/lib/rails/application.rb, line 320
def isolate_namespace(mod)
  self.class.isolate_namespace(mod)
end

key_generator()

Returns the application's KeyGenerator

# File railties/lib/rails/application.rb, line 153
def key_generator
  # number of iterations selected based on consultation with the google security
  # team. Details at https://github.com/rails/rails/pull/6952#issuecomment-7661220
  @caching_key_generator ||= 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.

# File railties/lib/rails/application.rb, line 179
def message_verifier(verifier_name)
  @message_verifiers[verifier_name] ||= begin
    secret = key_generator.generate_key(verifier_name.to_s)
    ActiveSupport::MessageVerifier.new(secret)
  end
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.

# File railties/lib/rails/application.rb, line 284
def rake_tasks(&block)
  self.class.rake_tasks(&block)
end

reload_routes!()

Reload application routes regardless if they changed or not.

# File railties/lib/rails/application.rb, line 148
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.

# File railties/lib/rails/application.rb, line 297
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.

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.

# File railties/lib/rails/application.rb, line 415
def secret_key_base
  if Rails.env.development? || Rails.env.test?
    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()

# File railties/lib/rails/application.rb, line 389
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.

# File railties/lib/rails/application.rb, line 315
def server(&blk)
  self.class.server(&blk)
end

Instance Protected methods

validate_secret_key_base(secret_key_base)

# File railties/lib/rails/application.rb, line 575
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