In general, the work of configuring Rails means configuring the components of Rails, as well as configuring Rails itself. The +application.rb+ and environment-specific configuration files (such as +config/environments/production.rb+) allow you to specify the various settings that you want to pass down to all of the components. For example, the default Rails 3.0 +application.rb+ file includes this setting:
* +config.after_initialize+ takes a block which will be ran _after_ Rails has finished initializing. Useful for configuring values set up by other initializers:
* +config.allow_concurrency+ should be set to +true+ to allow concurrent (threadsafe) action processing. Set to +false+ by default. You probably don't want to call this one directly, though, because a series of other adjustments need to be made for threadsafe mode to work properly. Can also be enabled with +threadsafe!+.
* +config.asset_host+ sets the host for the assets. Useful when CDNs are used for hosting assets rather than the application server itself. Shorter version of +config.action_controller.asset_host+.
* +config.autoload_once_paths+ accepts an array of paths from which Rails will automatically load from only once. All elements of this array must also be in +autoload_paths+.
* +config.autoload_paths+ accepts an array of additional paths to prepend to the load path. By default, all app, lib, vendor and mock paths are included in this list.
* +config.cache_classes+ controls whether or not application classes should be reloaded on each request. Defaults to _true_ in development, _false_ in test and production. Can also be enabled with +threadsafe!+.
* +config.cache_store+ configures which cache store to use for Rails caching. Options include +:memory_store+, +:file_store+, +:mem_cache_store+ or the name of your own custom class. Defaults to +:file_store+.
* +config.consider_all_requests_local+ is generally set to +true+ during development and +false+ during production; if it is set to +true+, then any error will cause detailed debugging information to be dumped in the HTTP response. For finer-grained control, set this to +false+ and implement +local_request?+ in controllers to specify which requests should provide debugging information on errors.
* +config.dependency_loading+ enables or disables dependency loading during the request cycle. Setting dependency_loading to _true_ will allow new classes to be loaded during a request and setting it to _false_ will disable this behavior. Can also be enabled with +threadsafe!+.
* +config.eager_load_paths+ accepts an array of paths from which Rails will eager load on boot if cache classes is enabled. Defaults to every folder in the +app+ directory of the application. All elements of this array must also be in +load_paths+.
* +config.log_level+ defines the verbosity of the Rails logger. In production mode, this defaults to +:info+. In development mode, it defaults to +:debug+.
* +config.logger+ accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class, which is then used to log information from Action Controller. Set to nil to disable logging.
* +config.plugins+ accepts the list of plugins to load. If this is set to nil, all plugins will be loaded. If this is set to [], no plugins will be loaded. Otherwise, plugins will be loaded in the order specified.
* +config.preload_frameworks+ enables or disables preloading all frameworks at startup. Can also be enabled with +threadsafe!+. Defaults to +nil+, so is disabled.
* +config.secret_token+ used for specifying a key which allows sessions for the application to be verified against a known secure key to prevent tampering.
* +config.serve_static_assets+ configures Rails to serve static assets. Defaults to _true_, but in the production environment is turned off. The server software used to run the application should be used to serve the assets instead.
* +config.session_store+ is usually set up in +config/initializers/session_store.rb+ and specifies what class to use to store the session. Custom session stores can be specified like so:
<ruby>
config.session_store = :my_custom_store
</ruby>
This custom store must be defined as +ActionDispatch::Session::MyCustomStore+.
WARNING: Threadsafe operation is incompatible with the normal workings of development mode Rails. In particular, automatic dependency loading and class reloading are automatically disabled when you call +config.threadsafe!+.
* +scaffold_controller+ different from +resource_controller+, defines which generator to use for generating a _scaffolded_ controller when using +rails generate scaffold+. Defaults to +:scaffold_controller+.
* +stylesheets+ turns on the hook for stylesheets in generators. Used in Rails for when the +scaffold+ generator is ran, but this hook can be used in other generates as well.
* +test_framework+ defines which test framework to use. Defaults to _nil_, so will use Test::Unit by default.
* +template_engine+ defines which template engine to use, such as ERB or Haml. Defaults to +:erb+.
Every Rails application comes with a standard set of middleware which it uses in this order in the development environment:
* +ActionDispatch::Static+ is used to serve static assets. Disabled if +config.serve_static_assets+ is _true_.
* +Rack::Lock+ Will wrap the app in mutex so it can only be called by a single thread at a time. Only enabled if +config.action_controller.allow_concurrency+ is set to _false_, which it is by default.
* +ActiveSupport::Cache::Strategy::LocalCache+ Serves as a basic memory backed cache. This cache is not thread safe and is intended only for serving as a temporary memory cache for a single thread.
* +Rack::Runtime+ Sets an +X-Runtime+ header, containing the time (in seconds) taken to execute the request.
* +Rails::Rack::Logger+ Will notify the logs that the request has began. After request is complete, flushes all the logs.
* +ActionDispatch::ShowExceptions+ rescues any exception returned by the application and renders nice exception pages if the request is local or if +config.consider_all_requests_local+ is set to _true_. If +config.action_dispatch.show_exceptions+ is set to _false_, exceptions will be raised regardless.
* +ActionDispatch::RemoteIp+ checks for IP spoofing attacks. Configurable with the +config.action_dispatch.ip_spoofing_check+ and +config.action_dispatch.trusted_proxies+ settings.
* +Rack::Sendfile+ The Sendfile middleware intercepts responses whose body is being served from a file and replaces it with a server specific X-Sendfile header. Configurable with +config.action_dispatch_
* +ActionDispatch::Callbacks+ Runs the prepare callbacks before serving the request.
* +ActiveRecord::ConnectionAdapters::ConnectionManagement+ cleans active connections after each request, unless the +rack.test+ key in the request environment is set to _true_.
* +ActiveRecord::QueryCache+ caches all +SELECT+ queries generated in a request. If an +INSERT+ or +UPDATE+ takes place then the cache is cleaned.
* +ActionDispatch::Cookies+ sets cookies for the request.
* +ActionDispatch::Session::CookieStore+ is responsible for storing the session in cookies. An alternate middleware can be used for this by changing the +config.action_controller.session_store+ to an alternate value. Additionally, options passed to this can be configured by using +config.action_controller.session_options+.
* +ActionDispatch::Flash+ sets up the +flash+ keys. Only available if +config.action_controller.session_store+ is set to a value.
* +ActionDispatch::ParamsParser+ parses out parameters from the request into +params+
* +Rack::MethodOverride+ allows the method to be overridden if +params[:_method]+ is set. This is the middleware which supports the PUT and DELETE HTTP method types.
* +ActionDispatch::Head+ converts HEAD requests to GET requests and serves them as so.
* +ActionDispatch::BestStandardsSupport+ enables "best standards support" so that IE8 renders some elements correctly.
* +config.active_record.logger+ accepts a logger conforming to the interface of Log4r or the default Ruby 1.8.x Logger class, which is then passed on to any new database connections made. You can retrieve this logger by calling +logger+ on either an Active Record model class or an Active Record model instance. Set to nil to disable logging.
* +config.active_record.primary_key_prefix_type+ lets you adjust the naming for primary key columns. By default, Rails assumes that primary key columns are named +id+ (and this configuration option doesn't need to be set.) There are two other choices:
* +config.active_record.table_name_prefix+ lets you set a global string to be prepended to table names. If you set this to +northwest_+, then the Customer class will look for +northwest_customers+ as its table. The default is an empty string.
* +config.active_record.table_name_suffix+ lets you set a global string to be appended to table names. If you set this to +_northwest+, then the Customer class will look for +customers_northwest+ as its table. The default is an empty string.
* +config.active_record.pluralize_table_names+ specifies whether Rails will look for singular or plural table names in the database. If set to +true+ (the default), then the Customer class will use the +customers+ table. If set to +false+, then the Customers class will use the +customer+ table.
* +config.active_record.default_timezone+ determines whether to use +Time.local+ (if set to +:local+) or +Time.utc+ (if set to +:utc+) when pulling dates and times from the database. The default is +:local+.
* +config.active_record.schema_format+ controls the format for dumping the database schema to a file. The options are +:ruby+ (the default) for a database-independent version that depends on migrations, or +:sql+ for a set of (potentially database-dependent) SQL statements.
* +config.active_record.timestamped_migrations+ controls whether migrations are numbered with serial integers or with timestamps. The default is +true+, to use timestamps, which are preferred if there are multiple developers working on the same application.
The MySQL adapter adds one additional configuration option:
* +ActiveRecord::ConnectionAdapters::MysqlAdapter.emulate_booleans+ controls whether ActiveRecord will consider all +tinyint(1)+ columns in a MySQL database to be booleans. By default this is +true+.
The schema dumper adds one additional configuration option:
* +ActiveRecord::SchemaDumper.ignore_tables+ accepts an array of tables that should _not_ be included in any generated schema file. This setting is ignored unless +config.active_record.schema_format == :ruby+.
* +config.action_controller.asset_host+ sets the host for the assets. Useful when CDNs are used for hosting assets rather than the application server itself.
* +config.action_controller.asset_path+ takes a block which configures where assets can be found. Shorter version of +config.action_controller.asset_path+.
* +config.action_controller.page_cache_directory+ should be the document root for the web server and is set using <tt>Base.page_cache_directory = "/document/root"</tt>. For Rails, this directory has already been set to +Rails.public_path+ (which is usually set to <tt>Rails.root + "/public"</tt>). Changing this setting can be useful to avoid naming conflicts with files in <tt>public/</tt>, but doing so will likely require configuring your web server to look in the new location for cached files.
* +config.action_controller.perform_caching+ configures whether the application should perform caching or not. Set to _false_ in development mode, _true_ in production.
* +config.action_controller.logger+ accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class, which is then used to log information from Action Controller. Set to nil to disable logging.
* +config.action_controller.request_forgery_protection_token+ sets the token parameter name for RequestForgery. Calling +protect_from_forgery+ sets it to +:authenticity_token+ by default.
* +config.action_controller.allow_forgery_protection+ enables or disables CSRF protection. By default this is +false+ in test mode and +true+ in all other modes.
* +config.action_controller.relative_url_root+ can be used to tell Rails that you are deploying to a subdirectory. The default is +ENV['RAILS_RELATIVE_URL_ROOT']+.
* +ActionController::Base.page_cache_directory+ sets the directory where Rails will create cached pages for your web server. The default is +Rails.public_path+ (which is usually set to <tt>Rails.root + "/public"</tt>).
* +ActionController::Base.page_cache_extension+ sets the extension to be used when generating pages for the cache (this is ignored if the incoming request already has an extension). The default is +.html+.
* +config.action_dispatch.session_store+ sets the name of the store for session data. The default is +:cookie_store+; other valid options include +:active_record_store+, +:mem_cache_store+ or the name of your own custom class.
* +ActionDispatch::Callbacks.to_prepare+ takes a block to run after +ActionDispatch::Callbacks.before+, but before the request. Runs for every request in +development+ mode, but only once for +production+ or environments with +cache_classes+ set to +true+.
* +config.action_view.debug_rjs+ specifies whether RJS responses should be wrapped in a try/catch block that alerts the caught exception (and then re-raises it). The default is +false+.
* +config.action_view.field_error_proc+ provides an HTML generator for displaying errors that come from Active Record. The default is <tt>Proc.new{ |html_tag, instance| %Q(%<div class="field_with_errors">#{html_tag}</div>).html_safe }</tt>
* +config.action_view.logger+ accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class, which is then used to log information from Action Mailer. Set to nil to disable logging.
* +config.action_view.erb_trim_mode+ gives the trim mode to be used by ERB. It defaults to +'-'+. See the "ERB documentation":http://www.ruby-doc.org/stdlib/libdoc/erb/rdoc/ for more information.
* +config.action_view.javascript_expansions+ is a hash containing expansions that can be used for the JavaScript include tag. By default, this is defined as:
* +config.action_view.stylesheet_expansions+ works in much the same way as +javascript_expansions+, but has no default key. Keys defined for this hash can be referenced in the view like such:
* +ActionView::Helpers::AssetTagHelper::AssetPaths.cache_asset_ids+ With the cache enabled, the asset tag helper methods will make fewer expensive file system calls (the default implementation checks the file system timestamp). However this prevents you from modifying any asset files while the server is running.
* +config.action_mailer.logger+ accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class, which is then used to log information from Action Mailer. Set to nil to disable logging.
* +config.action_mailer.smtp_settings+ allows detailed configuration for the +:smtp+ delivery method. It accepts a hash of options, which can include any of these options:
** +:address+ - Allows you to use a remote mail server. Just change it from its default "localhost" setting.
** +:port+ - On the off chance that your mail server doesn't run on port 25, you can change it.
** +:domain+ - If you need to specify a HELO domain, you can do it here.
** +:user_name+ - If your mail server requires authentication, set the username in this setting.
** +:password+ - If your mail server requires authentication, set the password in this setting.
** +:authentication+ - If your mail server requires authentication, you need to specify the authentication type here. This is a symbol and one of +:plain+, +:login+, +:cram_md5+.
* +config.action_mailer.sendmail_settings+ allows detailed configuration for the +sendmail+ delivery method. It accepts a hash of options, which can include any of these options:
* +config.action_mailer.perform_deliveries+ specifies whether mail will actually be delivered. By default this is +true+; it can be convenient to set it to +false+ for testing.
* +config.active_resource.logger+ accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class, which is then used to log information from Active Resource. Set to nil to disable logging.
* +config.active_support.bare+ enables or disables the loading of +active_support/all+ when booting Rails. Defaults to +nil+, which means +active_support/all+ is loaded.
Some parts of Rails can also be configured externally by supplying environment variables. The following environment variables are recognized by various parts of Rails:
* +ENV["RAILS_ASSET_ID"]+ will override the default cache-busting timestamps that Rails generates for downloadable assets.
* +ENV["RAILS_CACHE_ID"]+ and +ENV["RAILS_APP_VERSION"]+ are used to generate expanded cache keys in Rails' caching code. This allows you to have multiple separate caches from the same application.
* +before_configuration+: This is run as soon as the application constant inherits from +Rails::Application+. The +config+ calls are evaluated before this happens.
* +before_initialize+: This is run directly before the initialization process of the application occurs with the +:bootstrap_hook+ initializer near the beginning of the Rails initialization process.
* +to_prepare+: Run after the initializers are ran for all Railties (including the application itself), but before eager loading and the middleware stack is built.
* +before_eager_load+: This is run directly before eager loading occurs, which is the default behaviour for the _production_ environment and not for the +development+ enviroment.
Rails has several initializers that run on startup that are all defined by using the +initializer+ method from +Rails::Railtie+. Here's an example of the +initialize_whiny_nils+ initializer from Active Support:
The +initializer+ method takes three arguments with the first being the name for the initializer and the second being an options hash (not shown here) and the third being a block. The +:before+ key in the options hash can be specified to specify which initializer this new initializer must run before, and the +:after+ key will specify which initializer to run this initializer _after_.
Initializers defined using the +initializer+ method will be ran in the order they are defined in, with the exception of ones that use the +:before+ or +:after+ methods.
WARNING: You may put your initializer before or after any other initializer in the chain, as long as it is logical. Say you have 4 initializers called "one" through "four" (defined in that order) and you define "four" to go _before_ "four" but _after_ "three", that just isn't logical and Rails will not be able to determine your initializer order.
The block's argument of the +initialize+ is the instance of the application itself, and so we can access the configuration on it by using the +config+ method as this initializer does.
Because +Rails::Application+ inherits from +Rails::Railtie+ (indirectly), you can use the +initializer+ method in +config/application.rb+ to define initializers for the application.
Below is a comprehensive list of all the initializers found in Rails in the order that they are defined (and therefore run in, unless otherwise stated).
*+load_active_support+* Requires +active_support/dependencies+ which sets up the basis for Active Support. Optionally requires +active_support/all+ if +config.active_support.bare+ is un-truthful, which is the default.
*+preload_frameworks+* Will load all autoload dependencies of Rails automatically if +config.preload_frameworks+ is +true+ or "truthful". By default this configuration option is disabled. In Rails, when internal classes are referenced for the first time they are autoloaded. +:preload_frameworks+ loads all of this at once on initialization.
*+initialize_logger+* Initializes the logger (an +ActiveSupport::BufferedLogger+ object) for the application and makes it accessible at +Rails.logger+, providing that there's no initializer inserted before this point that has defined +Rails.logger+.
*+initialize_cache+* If +RAILS_CACHE+ isn't yet set, initializes the cache by referencing the value in +config.cache_store+ and stores the outcome as +RAILS_CACHE+. If this object responds to the +middleware+ method, its middleware is inserted before +Rack::Runtime+ in the middleware stack.
*+set_clear_dependencies_hook+* Provides a hook for +active_record.set_dispatch_hooks+ to use, which will run before this initializer. This initializer -- which runs only if +cache_classes+ is set to +false+ -- uses +ActionDispatch::Callbacks.after+ to remove the constants which have been referenced during the request from the object space so that they will be reloaded during the following request.
*+initialize_dependency_mechanism+* If +config.cache_classes+ is set to +true+, configures +ActiveSupport::Dependencies.mechanism+ to +require+ dependencies rather than +load+ them.
*+i18n.callbacks+* In the development environment, sets up a +to_prepare+ callback which will call +I18n.reload!+ if any of the locales have changed since the last request. In production mode this callback will only run on the first request.
*+active_support.initialize_whiny_nils+* Will require +active_support/whiny_nil+ if +config.whiny_nils+ is set to +true+. This file will output errors such as:
*+active_support.deprecation_behavior+* Sets up deprecation reporting for environments, defaulting to +log+ for development, +notify+ for production and +stderr+ for test. If a value isn't set for +config.active_support.deprecation+ then this initializer will prompt the user to configure this line in the current environment's +config/environments+ file.
*+active_support.initialize_time_zone+* Sets the default time zone for the application based off the +config.time_zone+ setting, which defaults to "UTC".
*+action_view.cache_asset_ids+* Will set +ActionView::Helpers::AssetTagHelper::AssetPaths.cache_asset_ids+ to +false+ when Active Support loads, but only if +config.cache_classes+ is too.
*+action_view.javascript_expansions+* Registers the expansions set up by +config.action_view.javascript_expansions+ and +config.action_view.stylesheet_expansions+ to be recognised by Action View and therefore usable in the views.
*+action_view.set_configs+* Sets up Action View by using the settings in +config.action_view+ by +send+'ing the method names as setters to +ActionView::Base+ and passing the values through.
*+action_controller.set_configs+* Sets up Action Controller by using the settings in +config.action_controller+ by +send+'ing the method names as setters to +ActionController::Base+ and passing the values through.
*+active_record.initialize_timezone+* Sets +ActiveRecord::Base.time_zone_aware_attributes+ to true, as well as setting +ActiveRecord::Base.default_timezone+ to UTC. When attributes are read from the database, they will be converted into the time zone specified by +Time.zone+.
*+active_record.set_configs+* Sets up Active Record by using the settings in +config.active_record+ by +send+'ing the method names as setters to +ActiveRecord::Base+ and passing the values through.
*+active_record.initialize_database+* Loads the database configuration (by default) from +config/database.yml+ and establishes a connection for the current environment.
*+active_record.log_runtime+* Includes +ActiveRecord::Railties::ControllerRuntime+ which is responsible for reporting the length of time Active Record calls took for the request back to the logger.
*+action_mailer.set_configs+* Sets up Action Mailer by using the settings in +config.action_mailer+ by +send+'ing the method names as setters to +ActionMailer::Base+ and passing the values through.
*+active_resource.set_configs+* Sets up Active Resource by using the settings in +config.active_resource+ by +send+'ing the method names as setters to +ActiveResource::Base+ and passing the values through.
*+set_load_path+* This initializer runs before +bootstrap_hook+. Adds the +vendor+, +lib+, all directories of +app+ and any paths specified by +config.load_paths+ to +$LOAD_PATH+.
*+set_autoload_path+* This initializer runs before +bootstrap_hook+. Adds all sub-directories of +app+ and paths specified by +config.autoload_paths+ to +ActiveSupport::Dependencies.autoload_paths+.
*+add_routing_paths+* Loads (by default) all +config/routes.rb+ files (in the application and railties, including engines) and sets up the routes for the application.
*+add_locales+* Adds the files in +config/locales+ (from the application, railties and engines) to +I18n.load_path+, making available the translations in these files.
*+append_asset_paths+* Finds asset paths for the application and all attached railties and keeps a track of the available directories in +config.static_asset_paths+.
*+prepend_helpers_path+* Adds the directory +app/helpers+ from the application, railties and engines to the lookup path for helpers for the application.
*+load_config_initializers+* Loads all Ruby files from +config/initializers+ in the application, railties and engines. The files in this directory can be used to hold configuration settings that should be made after all of the frameworks and plugins are loaded.
NOTE: You can use subfolders to organize your initializers if you like, because Rails will look into the whole file hierarchy from the +initializers+ folder on down.
TIP: If you have any ordering dependency in your initializers, you can control the load order by naming. For example, +01_critical.rb+ will be loaded before +02_normal.rb+.
*+engines_blank_point+* Provides a point-in-initialization to hook into if you wish to do anything before engines are loaded. After this point, all railtie and engine initializers are ran.
*+add_generator_templates+* Finds templates for generators at +lib/templates+ for the application, railities and engines and adds these to the +config.generators.templates+ setting, which will make the templates available for all generators to reference.
*+ensure_autoload_once_paths_as_subset+* Ensures that the +config.autoload_once_paths+ only contains paths from +config.autoload_paths+. If it contains extra paths, then an exception will be raised.
*+add_to_prepare_blocks+* The block for every +config.to_prepare+ call in the application, a railtie or engine is added to the +to_prepare+ callbacks for Action Dispatch which will be ran per request in development, or before the first request in production.
*+add_builtin_route+* If the application is running under the development environment then this will append the route for +rails/info/properties+ to the application routes. This route provides the detailed information such as Rails and Ruby version for +public/index.html+ in a default Rails application.
*+build_middleware_stack+* Builds the middleware stack for the application, returning an object which has a +call+ method which takes a Rack environment object for the request.
*+eager_load!+* If +config.cache_classes+ is +true+, runs the +config.before_eager_load+ hooks and then calls +eager_load!+ which will load all the Ruby files from +config.eager_load_paths+.
*+finisher_hook+* Provides a hook for after the initialization of process of the application is complete, as well as running all the +config.after_initialize+ blocks for the application, railties and engines.
