1 Locations for Initialization Code
Rails offers four standard spots to place initialization code:
config/application.rb
- Environment-specific configuration files
- Initializers
- After-initializers
2 Running Code Before Rails
In the rare event that your application needs to run some code before Rails itself is loaded, put it above the call to require 'rails/all'
in config/application.rb
.
3 Configuring Rails Components
In general, the work of configuring Rails means configuring the components of Rails, as well as configuring Rails itself. The configuration file config/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 config/application.rb
file includes this setting:
config.time_zone = 'Central Time (US & Canada)'
This is a setting for Rails itself. If you want to pass settings to individual Rails components, you can do so via the same config
object in config/application.rb
:
config.active_record.schema_format = :ruby
Rails will use that particular setting to configure Active Record.
3.1 Rails General Configuration
These configuration methods are to be called on a Rails::Railtie
object, such as a subclass of Rails::Engine
or Rails::Application
.
-
config.after_initialize
takes a block which will be run after Rails has finished initializing the application. That includes the initialization of the framework itself, engines, and all the application's initializers inconfig/initializers
. Note that this block will be run for rake tasks. Useful for configuring values set up by other initializers:config.after_initialize do ActionView::Base.sanitized_allowed_tags.delete 'div' end
config.asset_host
sets the host for the assets. Useful when CDNs are used for hosting assets, or when you want to work around the concurrency constraints built-in in browsers using different domain aliases. Shorter version ofconfig.action_controller.asset_host
.config.autoload_once_paths
accepts an array of paths from which Rails will autoload constants that won't be wiped per request. Relevant ifconfig.cache_classes
is false, which is the case in development mode by default. Otherwise, all autoloading happens only once. All elements of this array must also be inautoload_paths
. Default is an empty array.config.autoload_paths
accepts an array of paths from which Rails will autoload constants. Default is all directories underapp
.config.cache_classes
controls whether or not application classes and modules should be reloaded on each request. Defaults to false in development mode, and true in test and production modes.config.action_view.cache_template_loading
controls whether or not templates should be reloaded on each request. Defaults to whatever is set forconfig.cache_classes
.config.beginning_of_week
sets the default beginning of week for the application. Accepts a valid week day symbol (e.g.:monday
).config.cache_store
configures which cache store to use for Rails caching. Options include one of the symbols:memory_store
,:file_store
,:mem_cache_store
,:null_store
, or an object that implements the cache API. Defaults to:file_store
if the directorytmp/cache
exists, and to:memory_store
otherwise.config.colorize_logging
specifies whether or not to use ANSI color codes when logging information. Defaults to true.config.consider_all_requests_local
is a flag. If true then any error will cause detailed debugging information to be dumped in the HTTP response, and theRails::Info
controller will show the application runtime context in/rails/info/properties
. True by default in development and test environments, and false in production mode. For finer-grained control, set this to false and implementlocal_request?
in controllers to specify which requests should provide debugging information on errors.-
config.console
allows you to set class that will be used as console you runrails console
. It's best to run it inconsole
block:console do # this block is called only when running console, # so we can safely require pry here require "pry" config.console = Pry end
config.eager_load
when true, eager loads all registeredconfig.eager_load_namespaces
. This includes your application, engines, Rails frameworks and any other registered namespace.config.eager_load_namespaces
registers namespaces that are eager loaded whenconfig.eager_load
is true. All namespaces in the list must respond to theeager_load!
method.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 theapp
directory of the application.config.enable_dependency_loading
: when true, enables autoloading, even if the application is eager loaded andconfig.cache_classes
is set as true. Defaults to false.config.encoding
sets up the application-wide encoding. Defaults to UTF-8.config.exceptions_app
sets the exceptions application invoked by the ShowException middleware when an exception happens. Defaults toActionDispatch::PublicExceptions.new(Rails.public_path)
.config.debug_exception_response_format
sets the format used in responses when errors occur in development mode. Defaults to:api
for API only apps and:default
for normal apps.config.file_watcher
is the class used to detect file updates in the file system whenconfig.reload_classes_only_on_change
is true. Rails ships withActiveSupport::FileUpdateChecker
, the default, andActiveSupport::EventedFileUpdateChecker
(this one depends on the listen gem). Custom classes must conform to theActiveSupport::FileUpdateChecker
API.config.filter_parameters
used for filtering out the parameters that you don't want shown in the logs, such as passwords or credit card numbers. By default, Rails filters out passwords by addingRails.application.config.filter_parameters += [:password]
inconfig/initializers/filter_parameter_logging.rb
. Parameters filter works by partial matching regular expression.config.force_ssl
forces all requests to be served over HTTPS by using theActionDispatch::SSL
middleware, and setsconfig.action_mailer.default_url_options
to be{ protocol: 'https' }
. This can be configured by settingconfig.ssl_options
- see the ActionDispatch::SSL documentation for details.config.log_formatter
defines the formatter of the Rails logger. This option defaults to an instance ofActiveSupport::Logger::SimpleFormatter
for all modes except production, where it defaults toLogger::Formatter
. If you are setting a value forconfig.logger
you must manually pass the value of your formatter to your logger before it is wrapped in anActiveSupport::TaggedLogging
instance, Rails will not do it for you.config.log_level
defines the verbosity of the Rails logger. This option defaults to:debug
for all environments. The available log levels are::debug
,:info
,:warn
,:error
,:fatal
, and:unknown
.config.log_tags
accepts a list of: methods that therequest
object responds to, aProc
that accepts therequest
object, or something that responds toto_s
. This makes it easy to tag log lines with debug information like subdomain and request id - both very helpful in debugging multi-user production applications.-
config.logger
is the logger that will be used forRails.logger
and any related Rails logging such asActiveRecord::Base.logger
. It defaults to an instance ofActiveSupport::TaggedLogging
that wraps an instance ofActiveSupport::Logger
which outputs a log to thelog/
directory. You can supply a custom logger, to get full compatibility you must follow these guidelines:- To support a formatter, you must manually assign a formatter from the
config.log_formatter
value to the logger. - To support tagged logs, the log instance must be wrapped with
ActiveSupport::TaggedLogging
. - To support silencing, the logger must include
LoggerSilence
andActiveSupport::LoggerThreadSafeLevel
modules. TheActiveSupport::Logger
class already includes these modules.
class MyLogger < ::Logger include ActiveSupport::LoggerThreadSafeLevel include LoggerSilence end mylogger = MyLogger.new(STDOUT) mylogger.formatter = config.log_formatter config.logger = ActiveSupport::TaggedLogging.new(mylogger)
- To support a formatter, you must manually assign a formatter from the
config.middleware
allows you to configure the application's middleware. This is covered in depth in the Configuring Middleware section below.config.reload_classes_only_on_change
enables or disables reloading of classes only when tracked files change. By default tracks everything on autoload paths and is set to true. Ifconfig.cache_classes
is true, this option is ignored.secrets.secret_key_base
is used for specifying a key which allows sessions for the application to be verified against a known secure key to prevent tampering. Applications getsecrets.secret_key_base
initialized to a random key present inconfig/secrets.yml
.config.public_file_server.enabled
configures Rails to serve static files from the public directory. This option defaults to true, but in the production environment it is set to false because the server software (e.g. NGINX or Apache) used to run the application should serve static files instead. If you are running or testing your app in production mode using WEBrick (it is not recommended to use WEBrick in production) set the option to true. Otherwise, you won't be able to use page caching and request for files that exist under the public directory.-
config.session_store
is usually set up inconfig/initializers/session_store.rb
and specifies what class to use to store the session. Possible values are:cookie_store
which is the default,:mem_cache_store
, and:disabled
. The last one tells Rails not to deal with sessions. Custom session stores can also be specified:config.session_store :my_custom_store
This custom store must be defined as
ActionDispatch::Session::MyCustomStore
. config.time_zone
sets the default time zone for the application and enables time zone awareness for Active Record.
3.2 Configuring Assets
config.assets.enabled
a flag that controls whether the asset pipeline is enabled. It is set to true by default.config.assets.raise_runtime_errors
Set this flag totrue
to enable additional runtime error checking. Recommended inconfig/environments/development.rb
to minimize unexpected behavior when deploying toproduction
.config.assets.compress
a flag that enables the compression of compiled assets. It is explicitly set to true inconfig/environments/production.rb
.config.assets.css_compressor
defines the CSS compressor to use. It is set by default bysass-rails
. The unique alternative value at the moment is:yui
, which uses theyui-compressor
gem.config.assets.js_compressor
defines the JavaScript compressor to use. Possible values are:closure
,:uglifier
and:yui
which require the use of theclosure-compiler
,uglifier
oryui-compressor
gems respectively.config.assets.gzip
a flag that enables the creation of gzipped version of compiled assets, along with non-gzipped assets. Set totrue
by default.config.assets.paths
contains the paths which are used to look for assets. Appending paths to this configuration option will cause those paths to be used in the search for assets.config.assets.precompile
allows you to specify additional assets (other thanapplication.css
andapplication.js
) which are to be precompiled whenrake assets:precompile
is run.config.assets.prefix
defines the prefix where assets are served from. Defaults to/assets
.config.assets.manifest
defines the full path to be used for the asset precompiler's manifest file. Defaults to a file namedmanifest-<random>.json
in theconfig.assets.prefix
directory within the public folder.config.assets.digest
enables the use of MD5 fingerprints in asset names. Set totrue
by default.config.assets.debug
disables the concatenation and compression of assets. Set totrue
by default indevelopment.rb
.config.assets.compile
is a boolean that can be used to turn on live Sprockets compilation in production.config.assets.logger
accepts a logger conforming to the interface of Log4r or the default RubyLogger
class. Defaults to the same configured atconfig.logger
. Settingconfig.assets.logger
to false will turn off served assets logging.
3.3 Configuring Generators
Rails allows you to alter what generators are used with the config.generators
method. This method takes a block:
config.generators do |g| g.orm :active_record g.test_framework :test_unit end
The full set of methods that can be used in this block are as follows:
-
assets
allows to create assets on generating a scaffold. Defaults totrue
. -
force_plural
allows pluralized model names. Defaults tofalse
. -
helper
defines whether or not to generate helpers. Defaults totrue
. -
integration_tool
defines which integration tool to use to generate integration tests. Defaults to:test_unit
. -
javascripts
turns on the hook for JavaScript files in generators. Used in Rails for when thescaffold
generator is run. Defaults totrue
. -
javascript_engine
configures the engine to be used (for eg. coffee) when generating assets. Defaults to:js
. -
orm
defines which orm to use. Defaults tofalse
and will use Active Record by default. -
resource_controller
defines which generator to use for generating a controller when usingrails generate resource
. Defaults to:controller
. -
resource_route
defines whether a resource route definition should be generated or not. Defaults totrue
. -
scaffold_controller
different fromresource_controller
, defines which generator to use for generating a scaffolded controller when usingrails generate scaffold
. Defaults to:scaffold_controller
. -
stylesheets
turns on the hook for stylesheets in generators. Used in Rails for when thescaffold
generator is run, but this hook can be used in other generates as well. Defaults totrue
. -
stylesheet_engine
configures the stylesheet engine (for eg. sass) to be used when generating assets. Defaults to:css
. -
scaffold_stylesheet
createsscaffold.css
when generating a scaffolded resource. Defaults totrue
. -
test_framework
defines which test framework to use. Defaults tofalse
and will use Minitest by default. -
template_engine
defines which template engine to use, such as ERB or Haml. Defaults to:erb
.
3.4 Configuring Middleware
Every Rails application comes with a standard set of middleware which it uses in this order in the development environment:
-
ActionDispatch::SSL
forces every request to be served using HTTPS. Enabled ifconfig.force_ssl
is set totrue
. Options passed to this can be configured by settingconfig.ssl_options
. -
ActionDispatch::Static
is used to serve static assets. Disabled ifconfig.public_file_server.enabled
isfalse
. Setconfig.public_file_server.index_name
if you need to serve a static directory index file that is not namedindex
. For example, to servemain.html
instead ofindex.html
for directory requests, setconfig.public_file_server.index_name
to"main"
. -
ActionDispatch::Executor
allows thread safe code reloading. Disabled ifconfig.allow_concurrency
isfalse
, which causesRack::Lock
to be loaded.Rack::Lock
wraps the app in mutex so it can only be called by a single thread at a time. -
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 anX-Runtime
header, containing the time (in seconds) taken to execute the request. -
Rails::Rack::Logger
notifies the logs that the request has begun. 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 ifconfig.consider_all_requests_local
is set totrue
. Ifconfig.action_dispatch.show_exceptions
is set tofalse
, exceptions will be raised regardless. -
ActionDispatch::RequestId
makes a unique X-Request-Id header available to the response and enables theActionDispatch::Request#uuid
method. -
ActionDispatch::RemoteIp
checks for IP spoofing attacks and gets validclient_ip
from request headers. Configurable with theconfig.action_dispatch.ip_spoofing_check
, andconfig.action_dispatch.trusted_proxies
options. -
Rack::Sendfile
intercepts responses whose body is being served from a file and replaces it with a server specific X-Sendfile header. Configurable withconfig.action_dispatch.x_sendfile_header
. -
ActionDispatch::Callbacks
runs the prepare callbacks before serving the request. -
ActiveRecord::ConnectionAdapters::ConnectionManagement
cleans active connections after each request, unless therack.test
key in the request environment is set totrue
. -
ActiveRecord::QueryCache
caches all SELECT queries generated in a request. If any 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 theconfig.action_controller.session_store
to an alternate value. Additionally, options passed to this can be configured by usingconfig.action_controller.session_options
. -
ActionDispatch::Flash
sets up theflash
keys. Only available ifconfig.action_controller.session_store
is set to a value. -
Rack::MethodOverride
allows the method to be overridden ifparams[:_method]
is set. This is the middleware which supports the PATCH, PUT, and DELETE HTTP method types. -
Rack::Head
converts HEAD requests to GET requests and serves them as so.
Besides these usual middleware, you can add your own by using the config.middleware.use
method:
config.middleware.use Magical::Unicorns
This will put the Magical::Unicorns
middleware on the end of the stack. You can use insert_before
if you wish to add a middleware before another.
config.middleware.insert_before Rack::Head, Magical::Unicorns
There's also insert_after
which will insert a middleware after another:
config.middleware.insert_after Rack::Head, Magical::Unicorns
Middlewares can also be completely swapped out and replaced with others:
config.middleware.swap ActionController::Failsafe, Lifo::Failsafe
They can also be removed from the stack completely:
config.middleware.delete Rack::MethodOverride
3.5 Configuring i18n
All these configuration options are delegated to the I18n
library.
config.i18n.available_locales
whitelists the available locales for the app. Defaults to all locale keys found in locale files, usually only:en
on a new application.config.i18n.default_locale
sets the default locale of an application used for i18n. Defaults to:en
.config.i18n.enforce_available_locales
ensures that all locales passed through i18n must be declared in theavailable_locales
list, raising anI18n::InvalidLocale
exception when setting an unavailable locale. Defaults totrue
. It is recommended not to disable this option unless strongly required, since this works as a security measure against setting any invalid locale from user input.config.i18n.load_path
sets the path Rails uses to look for locale files. Defaults toconfig/locales/*.{yml,rb}
.
3.6 Configuring Active Record
config.active_record
includes a variety of configuration options:
config.active_record.logger
accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then passed on to any new database connections made. You can retrieve this logger by callinglogger
on either an Active Record model class or an Active Record model instance. Set tonil
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 namedid
(and this configuration option doesn't need to be set.) There are two other choices:-
:table_name
would make the primary key for the Customer classcustomerid
. -
:table_name_with_underscore
would make the primary key for the Customer classcustomer_id
.
-
config.active_record.table_name_prefix
lets you set a global string to be prepended to table names. If you set this tonorthwest_
, then the Customer class will look fornorthwest_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 forcustomers_northwest
as its table. The default is an empty string.config.active_record.schema_migrations_table_name
lets you set a string to be used as the name of the schema migrations table.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 thecustomers
table. If set to false, then the Customer class will use thecustomer
table.config.active_record.default_timezone
determines whether to useTime.local
(if set to:local
) orTime.utc
(if set to:utc
) when pulling dates and times from the database. The default is:utc
.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.error_on_ignored_order_or_limit
specifies if an error should be raised if the order or limit of a query is ignored during a batch query. The options are true (raise error) or false (warn). Default is false.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.config.active_record.lock_optimistically
controls whether Active Record will use optimistic locking and is true by default.config.active_record.cache_timestamp_format
controls the format of the timestamp value in the cache key. Default is:nsec
.config.active_record.record_timestamps
is a boolean value which controls whether or not timestamping ofcreate
andupdate
operations on a model occur. The default value istrue
.config.active_record.partial_writes
is a boolean value and controls whether or not partial writes are used (i.e. whether updates only set attributes that are dirty). Note that when using partial writes, you should also use optimistic lockingconfig.active_record.lock_optimistically
since concurrent updates may write attributes based on a possibly stale read state. The default value istrue
.config.active_record.maintain_test_schema
is a boolean value which controls whether Active Record should try to keep your test database schema up-to-date withdb/schema.rb
(ordb/structure.sql
) when you run your tests. The default is true.config.active_record.dump_schema_after_migration
is a flag which controls whether or not schema dump should happen (db/schema.rb
ordb/structure.sql
) when you run migrations. This is set to false inconfig/environments/production.rb
which is generated by Rails. The default value is true if this configuration is not set.config.active_record.dump_schemas
controls which database schemas will be dumped when calling db:structure:dump. The options are:schema_search_path
(the default) which dumps any schemas listed in schema_search_path,:all
which always dumps all schemas regardless of the schema_search_path, or a string of comma separated schemas.config.active_record.belongs_to_required_by_default
is a boolean value and controls whether a record fails validation ifbelongs_to
association is not present.config.active_record.warn_on_records_fetched_greater_than
allows setting a warning threshold for query result size. If the number of records returned by a query exceeds the threshold, a warning is logged. This can be used to identify queries which might be causing memory bloat.config.active_record.index_nested_attribute_errors
allows errors for nested has_many relationships to be displayed with an index as well as the error. Defaults to false.
The MySQL adapter adds one additional configuration option:
-
ActiveRecord::ConnectionAdapters::Mysql2Adapter.emulate_booleans
controls whether Active Record will consider alltinyint(1)
columns as booleans. True by default.
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 unlessconfig.active_record.schema_format == :ruby
.
3.7 Configuring Action Controller
config.action_controller
includes a number of configuration settings:
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.perform_caching
configures whether the application should perform the caching features provided by the Action Controller component or not. Set to false in development mode, true in production.config.action_controller.default_static_extension
configures the extension used for cached pages. Defaults to.html
.config.action_controller.include_all_helpers
configures whether all view helpers are available everywhere or are scoped to the corresponding controller. If set tofalse
,UsersHelper
methods are only available for views rendered as part ofUsersController
. Iftrue
,UsersHelper
methods are available everywhere. The default configuration behavior (when this option is not explicitly set totrue
orfalse
) is that all view helpers are available to each controller.config.action_controller.logger
accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Action Controller. Set tonil
to disable logging.config.action_controller.request_forgery_protection_token
sets the token parameter name for RequestForgery. Callingprotect_from_forgery
sets it to:authenticity_token
by default.config.action_controller.allow_forgery_protection
enables or disables CSRF protection. By default this isfalse
in test mode andtrue
in all other modes.config.action_controller.forgery_protection_origin_check
configures whether the HTTPOrigin
header should be checked against the site's origin as an additional CSRF defense.config.action_controller.per_form_csrf_tokens
configures whether CSRF tokens are only valid for the method/action they were generated for.config.action_controller.relative_url_root
can be used to tell Rails that you are deploying to a subdirectory. The default isENV['RAILS_RELATIVE_URL_ROOT']
.config.action_controller.permit_all_parameters
sets all the parameters for mass assignment to be permitted by default. The default value isfalse
.config.action_controller.action_on_unpermitted_parameters
enables logging or raising an exception if parameters that are not explicitly permitted are found. Set to:log
or:raise
to enable. The default value is:log
in development and test environments, andfalse
in all other environments.config.action_controller.always_permitted_parameters
sets a list of whitelisted parameters that are permitted by default. The default values are['controller', 'action']
.
3.8 Configuring Action Dispatch
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.-
config.action_dispatch.default_headers
is a hash with HTTP headers that are set by default in each response. By default, this is defined as:config.action_dispatch.default_headers = { 'X-Frame-Options' => 'SAMEORIGIN', 'X-XSS-Protection' => '1; mode=block', 'X-Content-Type-Options' => 'nosniff' }
config.action_dispatch.default_charset
specifies the default character set for all renders. Defaults tonil
.config.action_dispatch.tld_length
sets the TLD (top-level domain) length for the application. Defaults to1
.config.action_dispatch.http_auth_salt
sets the HTTP Auth salt value. Defaults to'http authentication'
.config.action_dispatch.signed_cookie_salt
sets the signed cookies salt value. Defaults to'signed cookie'
.config.action_dispatch.encrypted_cookie_salt
sets the encrypted cookies salt value. Defaults to'encrypted cookie'
.config.action_dispatch.encrypted_signed_cookie_salt
sets the signed encrypted cookies salt value. Defaults to'signed encrypted cookie'
.config.action_dispatch.perform_deep_munge
configures whetherdeep_munge
method should be performed on the parameters. See Security Guide for more information. It defaults to true.config.action_dispatch.rescue_responses
configures what exceptions are assigned to an HTTP status. It accepts a hash and you can specify pairs of exception/status. By default, this is defined as:
config.action_dispatch.rescue_responses = { 'ActionController::RoutingError' => :not_found, 'AbstractController::ActionNotFound' => :not_found, 'ActionController::MethodNotAllowed' => :method_not_allowed, 'ActionController::UnknownHttpMethod' => :method_not_allowed, 'ActionController::NotImplemented' => :not_implemented, 'ActionController::UnknownFormat' => :not_acceptable, 'ActionController::InvalidAuthenticityToken' => :unprocessable_entity, 'ActionController::InvalidCrossOriginRequest' => :unprocessable_entity, 'ActionDispatch::ParamsParser::ParseError' => :bad_request, 'ActionController::BadRequest' => :bad_request, 'ActionController::ParameterMissing' => :bad_request, 'ActiveRecord::RecordNotFound' => :not_found, 'ActiveRecord::StaleObjectError' => :conflict, 'ActiveRecord::RecordInvalid' => :unprocessable_entity, 'ActiveRecord::RecordNotSaved' => :unprocessable_entity }
Any exceptions that are not configured will be mapped to 500 Internal Server Error.
ActionDispatch::Callbacks.before
takes a block of code to run before the request.ActionDispatch::Callbacks.to_prepare
takes a block to run afterActionDispatch::Callbacks.before
, but before the request. Runs for every request indevelopment
mode, but only once forproduction
or environments withcache_classes
set totrue
.ActionDispatch::Callbacks.after
takes a block of code to run after the request.
3.9 Configuring Action View
config.action_view
includes a small number of configuration settings:
-
config.action_view.field_error_proc
provides an HTML generator for displaying errors that come from Active Model. The default isProc.new do |html_tag, instance| %Q(<div class="field_with_errors">#{html_tag}</div>).html_safe end
config.action_view.default_form_builder
tells Rails which form builder to use by default. The default isActionView::Helpers::FormBuilder
. If you want your form builder class to be loaded after initialization (so it's reloaded on each request in development), you can pass it as aString
.config.action_view.logger
accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Action View. Set tonil
to disable logging.config.action_view.erb_trim_mode
gives the trim mode to be used by ERB. It defaults to'-'
, which turns on trimming of tail spaces and newline when using<%= -%>
or<%= =%>
. See the Erubis documentation for more information.config.action_view.embed_authenticity_token_in_remote_forms
allows you to set the default behavior forauthenticity_token
in forms withremote: true
. By default it's set to false, which means that remote forms will not includeauthenticity_token
, which is helpful when you're fragment-caching the form. Remote forms get the authenticity from themeta
tag, so embedding is unnecessary unless you support browsers without JavaScript. In such case you can either passauthenticity_token: true
as a form option or set this config setting totrue
.-
config.action_view.prefix_partial_path_with_controller_namespace
determines whether or not partials are looked up from a subdirectory in templates rendered from namespaced controllers. For example, consider a controller namedAdmin::ArticlesController
which renders this template:<%= render @article %>
The default setting is
true
, which uses the partial at/admin/articles/_article.erb
. Setting the value tofalse
would render/articles/_article.erb
, which is the same behavior as rendering from a non-namespaced controller such asArticlesController
. config.action_view.raise_on_missing_translations
determines whether an error should be raised for missing translations.config.action_view.automatically_disable_submit_tag
determines whether submit_tag should automatically disable on click, this defaults to true.config.action_view.debug_missing_translation
determines whether to wrap the missing translations key in a<span>
tag or not. This defaults to true.
3.10 Configuring Action Mailer
There are a number of settings available on config.action_mailer
:
config.action_mailer.logger
accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Action Mailer. Set tonil
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 thesendmail
delivery method. It accepts a hash of options, which can include any of these options:-
:location
- The location of the sendmail executable. Defaults to/usr/sbin/sendmail
. -
:arguments
- The command line arguments. Defaults to-i -t
.
-
config.action_mailer.raise_delivery_errors
specifies whether to raise an error if email delivery cannot be completed. It defaults to true.config.action_mailer.delivery_method
defines the delivery method and defaults to:smtp
. See the configuration section in the Action Mailer guide for more info.config.action_mailer.perform_deliveries
specifies whether mail will actually be delivered and is true by default. It can be convenient to set it to false for testing.-
config.action_mailer.default_options
configures Action Mailer defaults. Use to set options likefrom
orreply_to
for every mailer. These default to:mime_version: "1.0", charset: "UTF-8", content_type: "text/plain", parts_order: ["text/plain", "text/enriched", "text/html"]
Assign a hash to set additional options:
config.action_mailer.default_options = { from: "noreply@example.com" }
-
config.action_mailer.observers
registers observers which will be notified when mail is delivered.config.action_mailer.observers = ["MailObserver"]
-
config.action_mailer.interceptors
registers interceptors which will be called before mail is sent.config.action_mailer.interceptors = ["MailInterceptor"]
-
config.action_mailer.preview_path
specifies the location of mailer previews.config.action_mailer.preview_path = "#{Rails.root}/lib/mailer_previews"
-
config.action_mailer.show_previews
enable or disable mailer previews. By default this istrue
in development.config.action_mailer.show_previews = false
config.action_mailer.deliver_later_queue_name
specifies the queue name for mailers. By default this ismailers
.config.action_mailer.perform_caching
specifies whether the mailer templates should perform fragment caching or not. By default this is false in all environments.
3.11 Configuring Active Support
There are a few configuration options available in Active Support:
config.active_support.bare
enables or disables the loading ofactive_support/all
when booting Rails. Defaults tonil
, which meansactive_support/all
is loaded.config.active_support.test_order
sets the order that test cases are executed. Possible values are:random
and:sorted
. This option is set to:random
inconfig/environments/test.rb
in newly-generated applications. If you have an application that does not specify atest_order
, it will default to:sorted
, until Rails 5.0, when the default will become:random
.config.active_support.escape_html_entities_in_json
enables or disables the escaping of HTML entities in JSON serialization. Defaults totrue
.config.active_support.use_standard_json_time_format
enables or disables serializing dates to ISO 8601 format. Defaults totrue
.config.active_support.time_precision
sets the precision of JSON encoded time values. Defaults to3
.ActiveSupport.halt_callback_chains_on_return_false
specifies whether Active Record and Active Model callback chains can be halted by returningfalse
in a 'before' callback. When set tofalse
, callback chains are halted only when explicitly done so withthrow(:abort)
. When set totrue
, callback chains are halted when a callback returns false (the previous behavior before Rails 5) and a deprecation warning is given. Defaults totrue
during the deprecation period. New Rails 5 apps generate an initializer file calledcallback_terminator.rb
which sets the value tofalse
. This file is not added when runningrails app:update
, so returningfalse
will still work on older apps ported to Rails 5 and display a deprecation warning to prompt users to update their code.ActiveSupport::Logger.silencer
is set tofalse
to disable the ability to silence logging in a block. The default istrue
.ActiveSupport::Cache::Store.logger
specifies the logger to use within cache store operations.ActiveSupport::Deprecation.behavior
alternative setter toconfig.active_support.deprecation
which configures the behavior of deprecation warnings for Rails.ActiveSupport::Deprecation.silence
takes a block in which all deprecation warnings are silenced.ActiveSupport::Deprecation.silenced
sets whether or not to display deprecation warnings.
3.12 Configuring Active Job
config.active_job
provides the following configuration options:
-
config.active_job.queue_adapter
sets the adapter for the queueing backend. The default adapter is:async
. For an up-to-date list of built-in adapters see the ActiveJob::QueueAdapters API documentation.# Be sure to have the adapter's gem in your Gemfile # and follow the adapter's specific installation # and deployment instructions. config.active_job.queue_adapter = :sidekiq
-
config.active_job.default_queue_name
can be used to change the default queue name. By default this is"default"
.config.active_job.default_queue_name = :medium_priority
-
config.active_job.queue_name_prefix
allows you to set an optional, non-blank, queue name prefix for all jobs. By default it is blank and not used.The following configuration would queue the given job on the
production_high_priority
queue when run in production:config.active_job.queue_name_prefix = Rails.env
class GuestsCleanupJob < ActiveJob::Base queue_as :high_priority #.... end
-
config.active_job.queue_name_delimiter
has a default value of'_'
. Ifqueue_name_prefix
is set, thenqueue_name_delimiter
joins the prefix and the non-prefixed queue name.The following configuration would queue the provided job on the
video_server.low_priority
queue:# prefix must be set for delimiter to be used config.active_job.queue_name_prefix = 'video_server' config.active_job.queue_name_delimiter = '.'
class EncoderJob < ActiveJob::Base queue_as :low_priority #.... end
config.active_job.logger
accepts a logger conforming to the interface of Log4r or the default Ruby Logger class, which is then used to log information from Active Job. You can retrieve this logger by callinglogger
on either an Active Job class or an Active Job instance. Set tonil
to disable logging.
3.13 Configuring Action Cable
-
config.action_cable.url
accepts a string for the URL for where you are hosting your Action Cable server. You would use this option if you are running Action Cable servers that are separated from your main application. -
config.action_cable.mount_path
accepts a string for where to mount Action Cable, as part of the main server process. Defaults to/cable
. You can set this as nil to not mount Action Cable as part of your normal Rails server.
3.14 Configuring a Database
Just about every Rails application will interact with a database. You can connect to the database by setting an environment variable ENV['DATABASE_URL']
or by using a configuration file called config/database.yml
.
Using the config/database.yml
file you can specify all the information needed to access your database:
development: adapter: postgresql database: blog_development pool: 5
This will connect to the database named blog_development
using the postgresql
adapter. This same information can be stored in a URL and provided via an environment variable like this:
> puts ENV['DATABASE_URL'] postgresql://localhost/blog_development?pool=5
The config/database.yml
file contains sections for three different environments in which Rails can run by default:
- The
development
environment is used on your development/local computer as you interact manually with the application. - The
test
environment is used when running automated tests. - The
production
environment is used when you deploy your application for the world to use.
If you wish, you can manually specify a URL inside of your config/database.yml
development: url: postgresql://localhost/blog_development?pool=5
The config/database.yml
file can contain ERB tags <%= %>
. Anything in the tags will be evaluated as Ruby code. You can use this to pull out data from an environment variable or to perform calculations to generate the needed connection information.
You don't have to update the database configurations manually. If you look at the options of the application generator, you will see that one of the options is named --database
. This option allows you to choose an adapter from a list of the most used relational databases. You can even run the generator repeatedly: cd .. && rails new blog --database=mysql
. When you confirm the overwriting of the config/database.yml
file, your application will be configured for MySQL instead of SQLite. Detailed examples of the common database connections are below.
3.15 Connection Preference
Since there are two ways to configure your connection (using config/database.yml
or using an environment variable) it is important to understand how they can interact.
If you have an empty config/database.yml
file but your ENV['DATABASE_URL']
is present, then Rails will connect to the database via your environment variable:
$ cat config/database.yml $ echo $DATABASE_URL postgresql://localhost/my_database
If you have a config/database.yml
but no ENV['DATABASE_URL']
then this file will be used to connect to your database:
$ cat config/database.yml development: adapter: postgresql database: my_database host: localhost $ echo $DATABASE_URL
If you have both config/database.yml
and ENV['DATABASE_URL']
set then Rails will merge the configuration together. To better understand this we must see some examples.
When duplicate connection information is provided the environment variable will take precedence:
$ cat config/database.yml development: adapter: sqlite3 database: NOT_my_database host: localhost $ echo $DATABASE_URL postgresql://localhost/my_database $ bin/rails runner 'puts ActiveRecord::Base.configurations' {"development"=>{"adapter"=>"postgresql", "host"=>"localhost", "database"=>"my_database"}}
Here the adapter, host, and database match the information in ENV['DATABASE_URL']
.
If non-duplicate information is provided you will get all unique values, environment variable still takes precedence in cases of any conflicts.
$ cat config/database.yml development: adapter: sqlite3 pool: 5 $ echo $DATABASE_URL postgresql://localhost/my_database $ bin/rails runner 'puts ActiveRecord::Base.configurations' {"development"=>{"adapter"=>"postgresql", "host"=>"localhost", "database"=>"my_database", "pool"=>5}}
Since pool is not in the ENV['DATABASE_URL']
provided connection information its information is merged in. Since adapter
is duplicate, the ENV['DATABASE_URL']
connection information wins.
The only way to explicitly not use the connection information in ENV['DATABASE_URL']
is to specify an explicit URL connection using the "url"
sub key:
$ cat config/database.yml development: url: sqlite3:NOT_my_database $ echo $DATABASE_URL postgresql://localhost/my_database $ bin/rails runner 'puts ActiveRecord::Base.configurations' {"development"=>{"adapter"=>"sqlite3", "database"=>"NOT_my_database"}}
Here the connection information in ENV['DATABASE_URL']
is ignored, note the different adapter and database name.
Since it is possible to embed ERB in your config/database.yml
it is best practice to explicitly show you are using the ENV['DATABASE_URL']
to connect to your database. This is especially useful in production since you should not commit secrets like your database password into your source control (such as Git).
$ cat config/database.yml production: url: <%= ENV['DATABASE_URL'] %>
Now the behavior is clear, that we are only using the connection information in ENV['DATABASE_URL']
.
3.15.1 Configuring an SQLite3 Database
Rails comes with built-in support for SQLite3, which is a lightweight serverless database application. While a busy production environment may overload SQLite, it works well for development and testing. Rails defaults to using an SQLite database when creating a new project, but you can always change it later.
Here's the section of the default configuration file (config/database.yml
) with connection information for the development environment:
development: adapter: sqlite3 database: db/development.sqlite3 pool: 5 timeout: 5000
Rails uses an SQLite3 database for data storage by default because it is a zero configuration database that just works. Rails also supports MySQL (including MariaDB) and PostgreSQL "out of the box", and has plugins for many database systems. If you are using a database in a production environment Rails most likely has an adapter for it.
3.15.2 Configuring a MySQL or MariaDB Database
If you choose to use MySQL or MariaDB instead of the shipped SQLite3 database, your config/database.yml
will look a little different. Here's the development section:
development: adapter: mysql2 encoding: utf8 database: blog_development pool: 5 username: root password: socket: /tmp/mysql.sock
If your development database has a root user with an empty password, this configuration should work for you. Otherwise, change the username and password in the development
section as appropriate.
3.15.3 Configuring a PostgreSQL Database
If you choose to use PostgreSQL, your config/database.yml
will be customized to use PostgreSQL databases:
development: adapter: postgresql encoding: unicode database: blog_development pool: 5
Prepared Statements are enabled by default on PostgreSQL. You can disable prepared statements by setting prepared_statements
to false
:
production: adapter: postgresql prepared_statements: false
If enabled, Active Record will create up to 1000
prepared statements per database connection by default. To modify this behavior you can set statement_limit
to a different value:
production: adapter: postgresql statement_limit: 200
The more prepared statements in use: the more memory your database will require. If your PostgreSQL database is hitting memory limits, try lowering statement_limit
or disabling prepared statements.
3.15.4 Configuring an SQLite3 Database for JRuby Platform
If you choose to use SQLite3 and are using JRuby, your config/database.yml
will look a little different. Here's the development section:
development: adapter: jdbcsqlite3 database: db/development.sqlite3
3.15.5 Configuring a MySQL or MariaDB Database for JRuby Platform
If you choose to use MySQL or MariaDB and are using JRuby, your config/database.yml
will look a little different. Here's the development section:
development: adapter: jdbcmysql database: blog_development username: root password:
3.15.6 Configuring a PostgreSQL Database for JRuby Platform
If you choose to use PostgreSQL and are using JRuby, your config/database.yml
will look a little different. Here's the development section:
development: adapter: jdbcpostgresql encoding: unicode database: blog_development username: blog password:
Change the username and password in the development
section as appropriate.
3.16 Creating Rails Environments
By default Rails ships with three environments: "development", "test", and "production". While these are sufficient for most use cases, there are circumstances when you want more environments.
Imagine you have a server which mirrors the production environment but is only used for testing. Such a server is commonly called a "staging server". To define an environment called "staging" for this server, just create a file called config/environments/staging.rb
. Please use the contents of any existing file in config/environments
as a starting point and make the necessary changes from there.
That environment is no different than the default ones, start a server with rails server -e staging
, a console with rails console staging
, Rails.env.staging?
works, etc.
3.17 Deploy to a subdirectory (relative url root)
By default Rails expects that your application is running at the root
(eg. /
). This section explains how to run your application inside a directory.
Let's assume we want to deploy our application to "/app1". Rails needs to know this directory to generate the appropriate routes:
config.relative_url_root = "/app1"
alternatively you can set the RAILS_RELATIVE_URL_ROOT
environment
variable.
Rails will now prepend "/app1" when generating links.
3.17.1 Using Passenger
Passenger makes it easy to run your application in a subdirectory. You can find the relevant configuration in the Passenger manual.
3.17.2 Using a Reverse Proxy
Deploying your application using a reverse proxy has definite advantages over traditional deploys. They allow you to have more control over your server by layering the components required by your application.
Many modern web servers can be used as a proxy server to balance third-party elements such as caching servers or application servers.
One such application server you can use is Unicorn to run behind a reverse proxy.
In this case, you would need to configure the proxy server (NGINX, Apache, etc) to accept connections from your application server (Unicorn). By default Unicorn will listen for TCP connections on port 8080, but you can change the port or configure it to use sockets instead.
You can find more information in the Unicorn readme and understand the philosophy behind it.
Once you've configured the application server, you must proxy requests to it by configuring your web server appropriately. For example your NGINX config may include:
upstream application_server { server 0.0.0.0:8080 } server { listen 80; server_name localhost; root /root/path/to/your_app/public; try_files $uri/index.html $uri.html @app; location @app { proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Host $http_host; proxy_redirect off; proxy_pass http://application_server; } # some other configuration }
Be sure to read the NGINX documentation for the most up-to-date information.
4 Rails Environment Settings
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_ENV"]
defines the Rails environment (production, development, test, and so on) that Rails will run under.ENV["RAILS_RELATIVE_URL_ROOT"]
is used by the routing code to recognize URLs when you deploy your application to a subdirectory.ENV["RAILS_CACHE_ID"]
andENV["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.
5 Using Initializer Files
After loading the framework and any gems in your application, Rails turns to loading initializers. An initializer is any Ruby file stored under config/initializers
in your application. You can use initializers to hold configuration settings that should be made after all of the frameworks and gems are loaded, such as options to configure settings for these parts.
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.
If you have any ordering dependency in your initializers, you can control the load order through naming. Initializer files are loaded in alphabetical order by their path. For example, 01_critical.rb
will be loaded before 02_normal.rb
.
6 Initialization events
Rails has 5 initialization events which can be hooked into (listed in the order that they are run):
before_configuration
: This is run as soon as the application constant inherits fromRails::Application
. Theconfig
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 run for all Railties (including the application itself), but before eager loading and the middleware stack is built. More importantly, will run upon every request indevelopment
, but only once (during boot-up) inproduction
andtest
.before_eager_load
: This is run directly before eager loading occurs, which is the default behavior for theproduction
environment and not for thedevelopment
environment.after_initialize
: Run directly after the initialization of the application, after the application initializers inconfig/initializers
are run.
To define an event for these hooks, use the block syntax within a Rails::Application
, Rails::Railtie
or Rails::Engine
subclass:
module YourApp class Application < Rails::Application config.before_initialize do # initialization code goes here end end end
Alternatively, you can also do it through the config
method on the Rails.application
object:
Rails.application.config.before_initialize do # initialization code goes here end
Some parts of your application, notably routing, are not yet set up at the point where the after_initialize
block is called.
6.1 Rails::Railtie#initializer
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 set_helpers_path
initializer from Action Controller:
initializer "action_controller.set_helpers_path" do |app| ActionController::Helpers.helpers_path = app.helpers_paths end
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 run in the order they are defined in, with the exception of ones that use the :before
or :after
methods.
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 argument of the initializer
method is the instance of the application itself, and so we can access the configuration on it by using the config
method as done in the example.
Because Rails::Application
inherits from Rails::Railtie
(indirectly), you can use the initializer
method in config/application.rb
to define initializers for the application.
6.2 Initializers
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_environment_hook
: Serves as a placeholder so that:load_environment_config
can be defined to run before it.load_active_support
: Requiresactive_support/dependencies
which sets up the basis for Active Support. Optionally requiresactive_support/all
ifconfig.active_support.bare
is un-truthful, which is the default.initialize_logger
: Initializes the logger (anActiveSupport::Logger
object) for the application and makes it accessible atRails.logger
, provided that no initializer inserted before this point has definedRails.logger
.initialize_cache
: IfRails.cache
isn't set yet, initializes the cache by referencing the value inconfig.cache_store
and stores the outcome asRails.cache
. If this object responds to themiddleware
method, its middleware is inserted beforeRack::Runtime
in the middleware stack.set_clear_dependencies_hook
: This initializer - which runs only ifcache_classes
is set tofalse
- usesActionDispatch::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
: Ifconfig.cache_classes
is true, configuresActiveSupport::Dependencies.mechanism
torequire
dependencies rather thanload
them.bootstrap_hook
: Runs all configuredbefore_initialize
blocks.i18n.callbacks
: In the development environment, sets up ato_prepare
callback which will callI18n.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.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 forconfig.active_support.deprecation
then this initializer will prompt the user to configure this line in the current environment'sconfig/environments
file. Can be set to an array of values.active_support.initialize_time_zone
: Sets the default time zone for the application based on theconfig.time_zone
setting, which defaults to "UTC".active_support.initialize_beginning_of_week
: Sets the default beginning of week for the application based onconfig.beginning_of_week
setting, which defaults to:monday
.active_support.set_configs
: Sets up Active Support by using the settings inconfig.active_support
bysend
'ing the method names as setters toActiveSupport
and passing the values through.action_dispatch.configure
: Configures theActionDispatch::Http::URL.tld_length
to be set to the value ofconfig.action_dispatch.tld_length
.action_view.set_configs
: Sets up Action View by using the settings inconfig.action_view
bysend
'ing the method names as setters toActionView::Base
and passing the values through.action_controller.assets_config
: Initializes theconfig.actions_controller.assets_dir
to the app's public directory if not explicitly configured.action_controller.set_helpers_path
: Sets Action Controller'shelpers_path
to the application'shelpers_path
.action_controller.parameters_config
: Configures strong parameters options forActionController::Parameters
.action_controller.set_configs
: Sets up Action Controller by using the settings inconfig.action_controller
bysend
'ing the method names as setters toActionController::Base
and passing the values through.action_controller.compile_config_methods
: Initializes methods for the config settings specified so that they are quicker to access.active_record.initialize_timezone
: SetsActiveRecord::Base.time_zone_aware_attributes
to true, as well as settingActiveRecord::Base.default_timezone
to UTC. When attributes are read from the database, they will be converted into the time zone specified byTime.zone
.active_record.logger
: SetsActiveRecord::Base.logger
- if it's not already set - toRails.logger
.active_record.migration_error
: Configures middleware to check for pending migrations.active_record.check_schema_cache_dump
: Loads the schema cache dump if configured and available.active_record.warn_on_records_fetched_greater_than
: Enables warnings when queries return large numbers of records.active_record.set_configs
: Sets up Active Record by using the settings inconfig.active_record
bysend
'ing the method names as setters toActiveRecord::Base
and passing the values through.active_record.initialize_database
: Loads the database configuration (by default) fromconfig/database.yml
and establishes a connection for the current environment.active_record.log_runtime
: IncludesActiveRecord::Railties::ControllerRuntime
which is responsible for reporting the time taken by Active Record calls for the request back to the logger.active_record.set_reloader_hooks
: Resets all reloadable connections to the database ifconfig.cache_classes
is set tofalse
.active_record.add_watchable_files
: Addsschema.rb
andstructure.sql
files to watchable files.active_job.logger
: SetsActiveJob::Base.logger
- if it's not already set - toRails.logger
.active_job.set_configs
: Sets up Active Job by using the settings inconfig.active_job
bysend
'ing the method names as setters toActiveJob::Base
and passing the values through.action_mailer.logger
: SetsActionMailer::Base.logger
- if it's not already set - toRails.logger
.action_mailer.set_configs
: Sets up Action Mailer by using the settings inconfig.action_mailer
bysend
'ing the method names as setters toActionMailer::Base
and passing the values through.action_mailer.compile_config_methods
: Initializes methods for the config settings specified so that they are quicker to access.set_load_path
: This initializer runs beforebootstrap_hook
. Adds paths specified byconfig.load_paths
and all autoload paths to$LOAD_PATH
.set_autoload_paths
: This initializer runs beforebootstrap_hook
. Adds all sub-directories ofapp
and paths specified byconfig.autoload_paths
,config.eager_load_paths
andconfig.autoload_once_paths
toActiveSupport::Dependencies.autoload_paths
.add_routing_paths
: Loads (by default) allconfig/routes.rb
files (in the application and railties, including engines) and sets up the routes for the application.add_locales
: Adds the files inconfig/locales
(from the application, railties and engines) toI18n.load_path
, making available the translations in these files.add_view_paths
: Adds the directoryapp/views
from the application, railties and engines to the lookup path for view files for the application.load_environment_config
: Loads theconfig/environments
file for the current environment.prepend_helpers_path
: Adds the directoryapp/helpers
from the application, railties and engines to the lookup path for helpers for the application.load_config_initializers
: Loads all Ruby files fromconfig/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 are loaded.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 run.add_generator_templates
: Finds templates for generators atlib/templates
for the application, railties and engines and adds these to theconfig.generators.templates
setting, which will make the templates available for all generators to reference.ensure_autoload_once_paths_as_subset
: Ensures that theconfig.autoload_once_paths
only contains paths fromconfig.autoload_paths
. If it contains extra paths, then an exception will be raised.add_to_prepare_blocks
: The block for everyconfig.to_prepare
call in the application, a railtie or engine is added to theto_prepare
callbacks for Action Dispatch which will be run 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 forrails/info/properties
to the application routes. This route provides the detailed information such as Rails and Ruby version forpublic/index.html
in a default Rails application.build_middleware_stack
: Builds the middleware stack for the application, returning an object which has acall
method which takes a Rack environment object for the request.eager_load!
: Ifconfig.eager_load
is true, runs theconfig.before_eager_load
hooks and then callseager_load!
which will load allconfig.eager_load_namespaces
.finisher_hook
: Provides a hook for after the initialization of process of the application is complete, as well as running all theconfig.after_initialize
blocks for the application, railties and engines.set_routes_reloader
: Configures Action Dispatch to reload the routes file usingActionDispatch::Callbacks.to_prepare
.disable_dependency_loading
: Disables the automatic dependency loading if theconfig.eager_load
is set to true.
7 Database pooling
Active Record database connections are managed by ActiveRecord::ConnectionAdapters::ConnectionPool
which ensures that a connection pool synchronizes the amount of thread access to a limited number of database connections. This limit defaults to 5 and can be configured in database.yml
.
development: adapter: sqlite3 database: db/development.sqlite3 pool: 5 timeout: 5000
Since the connection pooling is handled inside of Active Record by default, all application servers (Thin, mongrel, Unicorn etc.) should behave the same. The database connection pool is initially empty. As demand for connections increases it will create them until it reaches the connection pool limit.
Any one request will check out a connection the first time it requires access to the database. At the end of the request it will check the connection back in. This means that the additional connection slot will be available again for the next request in the queue.
If you try to use more connections than are available, Active Record will block you and wait for a connection from the pool. If it cannot get a connection, a timeout error similar to that given below will be thrown.
ActiveRecord::ConnectionTimeoutError - could not obtain a database connection within 5.000 seconds (waited 5.000 seconds)
If you get the above error, you might want to increase the size of the
connection pool by incrementing the pool
option in database.yml
If you are running in a multi-threaded environment, there could be a chance that several threads may be accessing multiple connections simultaneously. So depending on your current request load, you could very well have multiple threads contending for a limited number of connections.
8 Custom configuration
You can configure your own code through the Rails configuration object with custom configuration. It works like this:
config.payment_processing.schedule = :daily config.payment_processing.retries = 3 config.super_debugger = true
These configuration points are then available through the configuration object:
Rails.configuration.payment_processing.schedule # => :daily Rails.configuration.payment_processing.retries # => 3 Rails.configuration.super_debugger # => true Rails.configuration.super_debugger.not_set # => nil
You can also use Rails::Application.config_for
to load whole configuration files:
# config/payment.yml: production: environment: production merchant_id: production_merchant_id public_key: production_public_key private_key: production_private_key development: environment: sandbox merchant_id: development_merchant_id public_key: development_public_key private_key: development_private_key # config/application.rb module MyApp class Application < Rails::Application config.payment = config_for(:payment) end end
Rails.configuration.payment['merchant_id'] # => production_merchant_id or development_merchant_id
9 Search Engines Indexing
Sometimes, you may want to prevent some pages of your application to be visible
on search sites like Google, Bing, Yahoo or Duck Duck Go. The robots that index
these sites will first analyze the http://your-site.com/robots.txt
file to
know which pages it is allowed to index.
Rails creates this file for you inside the /public
folder. By default, it allows
search engines to index all pages of your application. If you want to block
indexing on all pages of you application, use this:
User-agent: * Disallow: /
To block just specific pages, it's necessary to use a more complex syntax. Learn it on the official documentation.
10 Evented File System Monitor
If the listen gem is loaded Rails uses an
evented file system monitor to detect changes when config.cache_classes
is
false:
group :development do gem 'listen', '~> 3.0.4' end
Otherwise, in every request Rails walks the application tree to check if anything has changed.
On Linux and Mac OS X no additional gems are needed, but some are required for *BSD and for Windows.
Note that some setups are unsupported.
Feedback
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