This guide covers the configuration and initialization features available to Rails applications.
After reading this guide, you will know:
load_defaults
Rails offers four standard spots to place initialization code:
config/application.rb
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
.
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, you could add this setting to config/application.rb
file:
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.
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 in config/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 of config.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 if config.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 in autoload_paths
. Default is an empty array.
config.autoload_paths
accepts an array of paths from which Rails will autoload constants. Default is all directories under app
. It is no longer recommended to adjust this. See Autoloading and Reloading Constants
config.add_autoload_paths_to_load_path
says whether autoload paths have to be added to $LOAD_PATH
. This flag is true
by default, but it is recommended to be set to false
in :zeitwerk
mode early, in config/application.rb
. Zeitwerk uses absolute paths internally, and applications running in :zeitwerk
mode do not need require_dependency
, so models, controllers, jobs, etc. do not need to be in $LOAD_PATH
. Setting this to false
saves Ruby from checking these directories when resolving require
calls with relative paths, and saves Bootsnap work and RAM, since it does not need to build an index for them.
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.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
, :redis_cache_store
, or an object that implements the cache API. Defaults to :file_store
.
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 the Rails::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 implement local_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 run rails console
. It's best to run it in console
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.disable_sandbox
controls whether or not someone can start a console in sandbox mode. This is helpful to avoid a long running session of sandbox console, that could lead a database server to run out of memory. Defaults to false.
config.eager_load
when true
, eager loads all registered config.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 when config.eager_load
is true
. All namespaces in the list must respond to the eager_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 the app
directory of the application.
config.enable_dependency_loading
: when true, enables autoloading, even if the application is eager loaded and config.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 to ActionDispatch::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 when config.reload_classes_only_on_change
is true
. Rails ships with ActiveSupport::FileUpdateChecker
, the default, and ActiveSupport::EventedFileUpdateChecker
(this one depends on the listen gem). Custom classes must conform to the ActiveSupport::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. It also filters out sensitive values of database columns when call #inspect
on an Active Record object. By default, Rails filters out passwords by adding Rails.application.config.filter_parameters += [:password]
in config/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 the ActionDispatch::SSL
middleware, and sets config.action_mailer.default_url_options
to be { protocol: 'https' }
. This can be configured by setting config.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 of ActiveSupport::Logger::SimpleFormatter
for all modes. If you are setting a value for config.logger
you must manually pass the value of your formatter to your logger before it is wrapped in an ActiveSupport::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 the request
object responds to, a Proc
that accepts the request
object, or something that responds to to_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 for Rails.logger
and any related Rails logging such as ActiveRecord::Base.logger
. It defaults to an instance of ActiveSupport::TaggedLogging
that wraps an instance of ActiveSupport::Logger
which outputs a log to the log/
directory. You can supply a custom logger, to get full compatibility you must follow these guidelines:
config.log_formatter
value to the logger.ActiveSupport::TaggedLogging
.ActiveSupport::LoggerSilence
module. The ActiveSupport::Logger
class already includes these modules.class MyLogger < ::Logger include ActiveSupport::LoggerSilence end mylogger = MyLogger.new(STDOUT) mylogger.formatter = config.log_formatter config.logger = ActiveSupport::TaggedLogging.new(mylogger)
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
. If config.cache_classes
is true
, this option is ignored.
config.credentials.content_path
configures lookup path for encrypted credentials.
config.credentials.key_path
configures lookup path for encryption key.
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 get a random generated key in test and development environments, other environments should set one in config/credentials.yml.enc
.
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
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. Defaults to a cookie store with application name as the session key. 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.
config.autoloader
sets the autoloading mode. This option defaults to :zeitwerk
if 6.0
is specified in config.load_defaults
. Applications can still use the classic autoloader by setting this value to :classic
after loading the framework defaults:
config.load_defaults "6.0" config.autoloader = :classic
config.assets.enabled
a flag that controls whether the asset pipeline is enabled. It is set to true
by default.
config.assets.css_compressor
defines the CSS compressor to use. It is set by default by sass-rails
. The unique alternative value at the moment is :yui
, which uses the yui-compressor
gem.
config.assets.js_compressor
defines the JavaScript compressor to use. Possible values are :closure
, :uglifier
and :yui
which require the use of the closure-compiler
, uglifier
or yui-compressor
gems respectively.
config.assets.gzip
a flag that enables the creation of gzipped version of compiled assets, along with non-gzipped assets. Set to true
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 than application.css
and application.js
) which are to be precompiled when rake assets:precompile
is run.
config.assets.unknown_asset_fallback
allows you to modify the behavior of the asset pipeline when an asset is not in the pipeline, if you use sprockets-rails 3.2.0 or newer. Defaults to false
.
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 named manifest-<random>.json
in the config.assets.prefix
directory within the public folder.
config.assets.digest
enables the use of SHA256 fingerprints in asset names. Set to true
by default.
config.assets.debug
disables the concatenation and compression of assets. Set to true
by default in development.rb
.
config.assets.version
is an option string that is used in SHA256 hash generation. This can be changed to force all files to be recompiled.
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 Ruby Logger
class. Defaults to the same configured at config.logger
. Setting config.assets.logger
to false
will turn off served assets logging.
config.assets.quiet
disables logging of assets requests. Set to true
by default in development.rb
.
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 to true
.force_plural
allows pluralized model names. Defaults to false
.helper
defines whether or not to generate helpers. Defaults to true
.integration_tool
defines which integration tool to use to generate integration tests. Defaults to :test_unit
.system_tests
defines which integration tool to use to generate system tests. Defaults to :test_unit
.orm
defines which orm to use. Defaults to false
and will use Active Record by default.resource_controller
defines which generator to use for generating a controller when using rails generate resource
. Defaults to :controller
.resource_route
defines whether a resource route definition should be generated or not. Defaults to true
.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 run, but this hook can be used in other generates as well. Defaults to true
.stylesheet_engine
configures the stylesheet engine (for eg. sass) to be used when generating assets. Defaults to :css
.scaffold_stylesheet
creates scaffold.css
when generating a scaffolded resource. Defaults to true
.test_framework
defines which test framework to use. Defaults to false
and will use minitest 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::SSL
forces every request to be served using HTTPS. Enabled if config.force_ssl
is set to true
. Options passed to this can be configured by setting config.ssl_options
.ActionDispatch::Static
is used to serve static assets. Disabled if config.public_file_server.enabled
is false
. Set config.public_file_server.index_name
if you need to serve a static directory index file that is not named index
. For example, to serve main.html
instead of index.html
for directory requests, set config.public_file_server.index_name
to "main"
.ActionDispatch::Executor
allows thread safe code reloading. Disabled if config.allow_concurrency
is false
, which causes Rack::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 an X-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 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::RequestId
makes a unique X-Request-Id header available to the response and enables the ActionDispatch::Request#uuid
method.ActionDispatch::RemoteIp
checks for IP spoofing attacks and gets valid client_ip
from request headers. Configurable with the config.action_dispatch.ip_spoofing_check
, and config.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 with config.action_dispatch.x_sendfile_header
.ActionDispatch::Callbacks
runs the prepare callbacks before serving the request.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.Rack::MethodOverride
allows the method to be overridden if params[:_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
Or you can insert a middleware to exact position by using indexes. For example, if you want to insert Magical::Unicorns
middleware on top of the stack, you can do it, like so:
config.middleware.insert_before 0, 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
All these configuration options are delegated to the I18n
library.
config.i18n.available_locales
defines the permitted 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 the available_locales
list, raising an I18n::InvalidLocale
exception when setting an unavailable locale. Defaults to true
. 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 to config/locales/*.{yml,rb}
.
config.i18n.fallbacks
sets fallback behavior for missing translations. Here are 3 usage examples for this option:
true
for using default locale as fallback, like so:config.i18n.fallbacks = true
config.i18n.fallbacks = [:tr, :en]
:tr
for :az
and :de
, :en
for :da
as fallbacks, you can do it, like so:config.i18n.fallbacks = { az: :tr, da: [:de, :en] } #or config.i18n.fallbacks.map = { az: :tr, da: [:de, :en] }
config.active_model.i18n_customize_full_message
is a boolean value which controls whether the full_message
error format can be overridden at the attribute or model level in the locale files. This is false
by default.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 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:
:table_name
would make the primary key for the Customer class customerid
.:table_name_with_underscore
would make the primary key for the Customer class customer_id
.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.schema_migrations_table_name
lets you set a string to be used as the name of the schema migrations table.
config.active_record.internal_metadata_table_name
lets you set a string to be used as the name of the internal metadata table.
config.active_record.protected_environments
lets you set an array of names of environments where destructive actions should be prohibited.
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 Customer 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 :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
specifies if an error should be raised if the order 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 :usec
.
config.active_record.record_timestamps
is a boolean value which controls whether or not timestamping of create
and update
operations on a model occur. The default value is true
.
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 locking config.active_record.lock_optimistically
since concurrent updates may write attributes based on a possibly stale read state. The default value is true
.
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 with db/schema.rb
(or db/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
or db/structure.sql
) when you run migrations. This is set to false
in config/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 if belongs_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 a 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
.
config.active_record.use_schema_cache_dump
enables users to get schema cache information from db/schema_cache.yml
(generated by rails db:schema:cache:dump
), instead of having to send a query to the database to get this information. Defaults to true
.
config.active_record.collection_cache_versioning
enables the same cache key to be reused when the object being cached of type ActiveRecord::Relation
changes by moving the volatile information (max updated at and count) of the relation's cache key into the cache version to support recycling cache key. Defaults to false
.
The MySQL adapter adds one additional configuration option:
ActiveRecord::ConnectionAdapters::Mysql2Adapter.emulate_booleans
controls whether Active Record will consider all tinyint(1)
columns as booleans. Defaults to true
.The PostgreSQL adapter adds one additional configuration option:
ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.create_unlogged_tables
controls whether database tables created should be "unlogged," which can speed up performance but adds a risk of data loss if the database crashes. It is highly recommended that you do not enable this in a production environment. Defaults to false
in all environments.The schema dumper adds two additional configuration options:
ActiveRecord::SchemaDumper.ignore_tables
accepts an array of tables that should not be included in any generated schema file.
ActiveRecord::SchemaDumper.fk_ignore_pattern
allows setting a different regular expression that will be used to decide whether a foreign key's name should be dumped to db/schema.rb or not. By default, foreign key names starting with fk_rails_
are not exported to the database schema dump. Defaults to /^fk_rails_[0-9a-f]{10}$/
.
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. If it's not specified, the default will be true
.
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 to false
, UsersHelper
methods are only available for views rendered as part of UsersController
. If true
, UsersHelper
methods are available everywhere. The default configuration behavior (when this option is not explicitly set to true
or false
) 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 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.forgery_protection_origin_check
configures whether the HTTP Origin
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.default_protect_from_forgery
determines whether forgery protection is added on ActionController:Base
. This is false by default.
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']
.
config.action_controller.permit_all_parameters
sets all the parameters for mass assignment to be permitted by default. The default value is false
.
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, and false
in all other environments.
config.action_controller.always_permitted_parameters
sets a list of permitted parameters that are permitted by default. The default values are ['controller', 'action']
.
config.action_controller.enable_fragment_cache_logging
determines whether to log fragment cache reads and writes in verbose format as follows:
Read fragment views/v1/2914079/v1/2914079/recordings/70182313-20160225015037000000/d0bdf2974e1ef6d31685c3b392ad0b74 (0.6ms) Rendered messages/_message.html.erb in 1.2 ms [cache hit] Write fragment views/v1/2914079/v1/2914079/recordings/70182313-20160225015037000000/3b4e249ac9d168c617e32e84b99218b5 (1.1ms) Rendered recordings/threads/_thread.html.erb in 1.5 ms [cache miss]
By default it is set to false
which results in following output:
``` Rendered messages/_message.html.erb in 1.2 ms [cache hit] Rendered recordings/threads/_thread.html.erb in 1.5 ms [cache miss] ```
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', 'X-Download-Options' => 'noopen', 'X-Permitted-Cross-Domain-Policies' => 'none', 'Referrer-Policy' => 'strict-origin-when-cross-origin' }
config.action_dispatch.default_charset
specifies the default character set for all renders. Defaults to nil
.
config.action_dispatch.tld_length
sets the TLD (top-level domain) length for the application. Defaults to 1
.
config.action_dispatch.ignore_accept_header
is used to determine whether to ignore accept headers from a request. Defaults to false
.
config.action_dispatch.x_sendfile_header
specifies server specific X-Sendfile header. This is useful for accelerated file sending from server. For example it can be set to 'X-Sendfile' for Apache.
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.authenticated_encrypted_cookie_salt
sets the authenticated encrypted cookie salt. Defaults to 'authenticated encrypted
cookie'
.
config.action_dispatch.encrypted_cookie_cipher
sets the cipher to be used for encrypted cookies. This defaults to "aes-256-gcm"
.
config.action_dispatch.signed_cookie_digest
sets the digest to be used for signed cookies. This defaults to "SHA1"
.
config.action_dispatch.cookies_rotations
allows rotating secrets, ciphers, and digests for encrypted and signed cookies.
config.action_dispatch.use_authenticated_cookie_encryption
controls whether signed and encrypted cookies use the AES-256-GCM cipher or the older AES-256-CBC cipher. It defaults to true
.
config.action_dispatch.use_cookies_with_metadata
enables writing cookies with the purpose and expiry metadata embedded. It defaults to true
.
config.action_dispatch.perform_deep_munge
configures whether deep_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::Http::Parameters::ParseError' => :bad_request, 'ActionController::BadRequest' => :bad_request, 'ActionController::ParameterMissing' => :bad_request, 'Rack::QueryParser::ParameterTypeError' => :bad_request, 'Rack::QueryParser::InvalidParameterError' => :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.
config.action_dispatch.return_only_media_type_on_content_type
change the return value of ActionDispatch::Response#content_type
to the Content-Type header without modification. Defaults to false
.
ActionDispatch::Callbacks.before
takes a block of code to run before the request.
ActionDispatch::Callbacks.after
takes a block of code to run after the request.
config.action_view
includes a small number of configuration settings:
config.action_view.cache_template_loading
controls whether or not templates should be reloaded on each request. Defaults to whatever is set for config.cache_classes
.
config.action_view.field_error_proc
provides an HTML generator for displaying errors that come from Active Model. The default is
Proc.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 is ActionView::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 a String
.
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 to nil
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 for authenticity_token
in forms with remote:
true
. By default it's set to false
, which means that remote forms will not include authenticity_token
, which is helpful when you're fragment-caching the form. Remote forms get the authenticity from the meta
tag, so embedding is unnecessary unless you support browsers without JavaScript. In such case you can either pass authenticity_token: true
as a form option or set this config setting to true
.
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 named Admin::ArticlesController
which renders this template:
<%= render @article %>
The default setting is true
, which uses the partial at /admin/articles/_article.erb
. Setting the value to false
would render /articles/_article.erb
, which is the same behavior as rendering from a non-namespaced controller such as ArticlesController
.
config.action_view.raise_on_missing_translations
determines whether an error should be raised for missing translations. This defaults to false
.
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
.
config.action_view.form_with_generates_remote_forms
determines whether form_with
generates remote forms or not. This defaults to true
.
config.action_view.form_with_generates_ids
determines whether form_with
generates ids on inputs. This defaults to false
.
config.action_view.default_enforce_utf8
determines whether forms are generated with a hidden tag that forces older versions of Internet Explorer to submit forms encoded in UTF-8. This defaults to false
.
config.action_mailbox
provides the following configuration options:
config.action_mailbox.logger
contains the logger used by Action Mailbox. It accepts a logger conforming to the interface of Log4r or the default Ruby Logger class. The default is Rails.logger
.config.action_mailbox.logger = ActiveSupport::Logger.new(STDOUT)
config.action_mailbox.incinerate_after
accepts an ActiveSupport::Duration
indicating how long after processing ActionMailbox::InboundEmail
records should be destroyed. It defaults to 30.days
.# Incinerate inbound emails 14 days after processing. config.action_mailbox.incinerate_after = 14.days
config.action_mailbox.queues.incineration
accepts a symbol indicating the Active Job queue to use for incineration jobs. It defaults to :action_mailbox_incineration
.
config.action_mailbox.queues.routing
accepts a symbol indicating the Active Job queue to use for routing jobs. It defaults to :action_mailbox_routing
.
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 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
.:enable_starttls_auto
- Detects if STARTTLS is enabled in your SMTP server and starts to use it. It defaults to true
.:openssl_verify_mode
- When using TLS, you can set how OpenSSL checks the certificate. This is useful if you need to validate a self-signed and/or a wildcard certificate. This can be one of the OpenSSL verify constants, :none
or :peer
-- or the constant directly OpenSSL::SSL::VERIFY_NONE
or OpenSSL::SSL::VERIFY_PEER
, respectively.:ssl/:tls
- Enables the SMTP connection to use SMTP/TLS (SMTPS: SMTP over direct TLS connection).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:
:location
- The location of the sendmail executable. Defaults to /usr/sbin/sendmail
.:arguments
- The command line arguments. Defaults to -i
.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 like from
or reply_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: "[email protected]" }
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_interceptors
registers interceptors which will be called before mail is previewed.
config.action_mailer.preview_interceptors = ["MyPreviewMailInterceptor"]
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 is true
in development.
config.action_mailer.show_previews = false
config.action_mailer.deliver_later_queue_name
specifies the queue name for mailers. By default this is mailers
.
config.action_mailer.perform_caching
specifies whether the mailer templates should perform fragment caching or not. If it's not specified, the default will be true
.
config.action_mailer.delivery_job
specifies delivery job for mail. Defaults to ActionMailer::DeliveryJob
.
There are a few configuration options available in Active Support:
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.
config.active_support.test_order
sets the order in which the test cases are executed. Possible values are :random
and :sorted
. Defaults to :random
.
config.active_support.escape_html_entities_in_json
enables or disables the escaping of HTML entities in JSON serialization. Defaults to true
.
config.active_support.use_standard_json_time_format
enables or disables serializing dates to ISO 8601 format. Defaults to true
.
config.active_support.time_precision
sets the precision of JSON encoded time values. Defaults to 3
.
config.active_support.use_sha1_digests
specifies whether to use SHA-1 instead of MD5 to generate non-sensitive digests, such as the ETag header. Defaults to false.
config.active_support.use_authenticated_message_encryption
specifies whether to use AES-256-GCM authenticated encryption as the default cipher for encrypting messages instead of AES-256-CBC. This is false by default.
ActiveSupport::Logger.silencer
is set to false
to disable the ability to silence logging in a block. The default is true
.
ActiveSupport::Cache::Store.logger
specifies the logger to use within cache store operations.
ActiveSupport::Deprecation.behavior
alternative setter to config.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. The default is false
.
config.active_job
provides the following configuration options:
config.active_job.queue_adapter
sets the adapter for the queuing 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 '_'
. If queue_name_prefix
is set, then queue_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 calling logger
on either an Active Job class or an Active Job instance. Set to nil
to disable logging.
config.active_job.custom_serializers
allows to set custom argument serializers. Defaults to []
.
config.active_job.return_false_on_aborted_enqueue
change the return value of #enqueue
to false instead of the job instance when the enqueuing is aborted. Defaults to false
.
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.You can find more detailed configuration options in the Action Cable Overview.
config.active_storage
provides the following configuration options:
config.active_storage.variant_processor
accepts a symbol :mini_magick
or :vips
, specifying whether variant transformations will be performed with MiniMagick or ruby-vips. The default is :mini_magick
.
config.active_storage.analyzers
accepts an array of classes indicating the analyzers available for Active Storage blobs. The default is [ActiveStorage::Analyzer::ImageAnalyzer, ActiveStorage::Analyzer::VideoAnalyzer]
. The former can extract width and height of an image blob; the latter can extract width, height, duration, angle, and aspect ratio of a video blob.
config.active_storage.previewers
accepts an array of classes indicating the image previewers available in Active Storage blobs. The default is [ActiveStorage::Previewer::PDFPreviewer, ActiveStorage::Previewer::VideoPreviewer]
. The former can generate a thumbnail from the first page of a PDF blob; the latter from the relevant frame of a video blob.
config.active_storage.paths
accepts a hash of options indicating the locations of previewer/analyzer commands. The default is {}
, meaning the commands will be looked for in the default path. Can include any of these options:
:ffprobe
- The location of the ffprobe executable.:mutool
- The location of the mutool executable.:ffmpeg
- The location of the ffmpeg executable.config.active_storage.paths[:ffprobe] = '/usr/local/bin/ffprobe'
config.active_storage.variable_content_types
accepts an array of strings indicating the content types that Active Storage can transform through ImageMagick. The default is %w(image/png image/gif image/jpg image/jpeg image/pjpeg image/tiff image/vnd.adobe.photoshop image/vnd.microsoft.icon)
.
config.active_storage.content_types_to_serve_as_binary
accepts an array of strings indicating the content types that Active Storage will always serve as an attachment, rather than inline. The default is %w(text/html
text/javascript image/svg+xml application/postscript application/x-shockwave-flash text/xml application/xml application/xhtml+xml)
.
config.active_storage.queues.analysis
accepts a symbol indicating the Active Job queue to use for analysis jobs. When this option is nil
, analysis jobs are sent to the default Active Job queue (see config.active_job.default_queue_name
).
config.active_storage.queues.analysis = :low_priority
config.active_storage.queues.purge
accepts a symbol indicating the Active Job queue to use for purge jobs. When this option is nil
, purge jobs are sent to the default Active Job queue (see config.active_job.default_queue_name
).config.active_storage.queues.purge = :low_priority
config.active_storage.logger
can be used to set the logger used by Active Storage. Accepts a logger conforming to the interface of Log4r or the default Ruby Logger class.config.active_storage.logger = ActiveSupport::Logger.new(STDOUT)
config.active_storage.service_urls_expire_in
determines the default expiry of URLs generated by: ActiveStorage::Blob#service_url
ActiveStorage::Blob#service_url_for_direct_upload
ActiveStorage::Variant#service_url
The default is 5 minutes.
config.active_storage.routes_prefix
can be used to set the route prefix for the routes served by Active Storage. Accepts a string that will be prepended to the generated routes.config.active_storage.routes_prefix = '/files'
The default is /rails/active_storage
.
config.active_storage.replace_on_assign_to_many
determines whether assigning to a collection of attachments declared with has_many_attached
replaces any existing attachments or appends to them. The default is true
.load_defaults
config.action_controller.per_form_csrf_tokens
: true
config.action_controller.forgery_protection_origin_check
: true
ActiveSupport.to_time_preserves_timezone
: true
config.active_record.belongs_to_required_by_default
: true
config.ssl_options
: { hsts: { subdomains: true } }
config.assets.unknown_asset_fallback
: false
config.action_view.form_with_generates_remote_forms
: true
config.active_record.cache_versioning
: true
action_dispatch.use_authenticated_cookie_encryption
: true
config.active_support.use_authenticated_message_encryption
: true
config.active_support.use_sha1_digests
: true
config.action_controller.default_protect_from_forgery
: true
config.action_view.form_with_generates_ids
: true
config.autoloader
: :zeitwerk
config.action_view.default_enforce_utf8
: false
config.action_dispatch.use_cookies_with_metadata
: true
config.action_dispatch.return_only_media_type_on_content_type
: false
config.action_mailer.delivery_job
: "ActionMailer::MailDeliveryJob"
config.active_job.return_false_on_aborted_enqueue
: true
config.active_storage.queues.analysis
: :active_storage_analysis
config.active_storage.queues.purge
: :active_storage_purge
config.active_storage.replace_on_assign_to_many
: true
config.active_record.collection_cache_versioning
: true
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:
development
environment is used on your development/local computer as you interact manually with the application.test
environment is used when running automated tests.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.
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 $ rails runner 'puts ActiveRecord::Base.configurations' #<ActiveRecord::DatabaseConfigurations:0x00007fd50e209a28> $ rails runner 'puts ActiveRecord::Base.configurations.inspect' #<ActiveRecord::DatabaseConfigurations:0x00007fc8eab02880 @configurations=[ #<ActiveRecord::DatabaseConfigurations::UrlConfig:0x00007fc8eab020b0 @env_name="development", @spec_name="primary", @config={"adapter"=>"postgresql", "database"=>"my_database", "host"=>"localhost"} @url="postgresql://localhost/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 $ rails runner 'puts ActiveRecord::Base.configurations' #<ActiveRecord::DatabaseConfigurations:0x00007fd50e209a28> $ rails runner 'puts ActiveRecord::Base.configurations.inspect' #<ActiveRecord::DatabaseConfigurations:0x00007fc8eab02880 @configurations=[ #<ActiveRecord::DatabaseConfigurations::UrlConfig:0x00007fc8eab020b0 @env_name="development", @spec_name="primary", @config={"adapter"=>"postgresql", "database"=>"my_database", "host"=>"localhost", "pool"=>5} @url="postgresql://localhost/my_database"> ]
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 $ rails runner 'puts ActiveRecord::Base.configurations' #<ActiveRecord::DatabaseConfigurations:0x00007fd50e209a28> $ rails runner 'puts ActiveRecord::Base.configurations.inspect' #<ActiveRecord::DatabaseConfigurations:0x00007fc8eab02880 @configurations=[ #<ActiveRecord::DatabaseConfigurations::UrlConfig:0x00007fc8eab020b0 @env_name="development", @spec_name="primary", @config={"adapter"=>"sqlite3", "database"=>"NOT_my_database"} @url="sqlite3: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']
.
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.
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: utf8mb4 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.
If your MySQL version is 5.5 or 5.6 and want to use the utf8mb4
character set by default, please configure your MySQL server to support the longer key prefix by enabling innodb_large_prefix
system variable.
Advisory Locks are enabled by default on MySQL and are used to make database migrations concurrent safe. You can disable advisory locks by setting advisory_locks
to false
:
production: adapter: mysql2 advisory_locks: false
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
By default Active Record uses database features like prepared statements and advisory locks. You might need to disable those features if you're using an external connection pooler like PgBouncer:
production: adapter: postgresql prepared_statements: false advisory_locks: 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.
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
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:
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.
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 -e staging
, Rails.env.staging?
works, etc.
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.
Passenger makes it easy to run your application in a subdirectory. You can find the relevant configuration in the Passenger manual.
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.
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"]
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.
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.
There is no guarantee that your initializers will run after all the gem initializers, so any initialization code that depends on a given gem having been initialized should go into a config.after_initialize
block.
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.
While Rails supports numbering of initializer file names for load ordering purposes, a better technique is to place any code that need to load in a specific order within the same file. This reduces file name churn, makes dependencies more explicit, and can help surface new concepts within your application.
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 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 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 in development
, but only once (during boot-up) in production
and test
.
before_eager_load
: This is run directly before eager loading occurs, which is the default behavior for the production
environment and not for the development
environment.
after_initialize
: Run directly after the initialization of the application, after the application initializers in config/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.
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.
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
: 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.
initialize_logger
: Initializes the logger (an ActiveSupport::Logger
object) for the application and makes it accessible at Rails.logger
, provided that no initializer inserted before this point has defined Rails.logger
.
initialize_cache
: If Rails.cache
isn't set yet, 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
: 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 true, configures ActiveSupport::Dependencies.mechanism
to require
dependencies rather than load
them.
bootstrap_hook
: Runs all configured before_initialize
blocks.
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.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. Can be set to an array of values.
active_support.initialize_time_zone
: Sets the default time zone for the application based on the config.time_zone
setting, which defaults to "UTC".
active_support.initialize_beginning_of_week
: Sets the default beginning of week for the application based on config.beginning_of_week
setting, which defaults to :monday
.
active_support.set_configs
: Sets up Active Support by using the settings in config.active_support
by send
'ing the method names as setters to ActiveSupport
and passing the values through.
action_dispatch.configure
: Configures the ActionDispatch::Http::URL.tld_length
to be set to the value of config.action_dispatch.tld_length
.
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.assets_config
: Initializes the config.actions_controller.assets_dir
to the app's public directory if not explicitly configured.
action_controller.set_helpers_path
: Sets Action Controller's helpers_path
to the application's helpers_path
.
action_controller.parameters_config
: Configures strong parameters options for ActionController::Parameters
.
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.
action_controller.compile_config_methods
: Initializes methods for the config settings specified so that they are quicker to access.
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.logger
: Sets ActiveRecord::Base.logger
- if it's not already set - to Rails.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 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 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 if config.cache_classes
is set to false
.
active_record.add_watchable_files
: Adds schema.rb
and structure.sql
files to watchable files.
active_job.logger
: Sets ActiveJob::Base.logger
- if it's not already set - to Rails.logger
.
active_job.set_configs
: Sets up Active Job by using the settings in config.active_job
by send
'ing the method names as setters to ActiveJob::Base
and passing the values through.
action_mailer.logger
: Sets ActionMailer::Base.logger
- if it's not already set - to Rails.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.
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 before bootstrap_hook
. Adds paths specified by config.load_paths
and all autoload paths to $LOAD_PATH
.
set_autoload_paths
: This initializer runs before bootstrap_hook
. Adds all sub-directories of app
and paths specified by config.autoload_paths
, config.eager_load_paths
and config.autoload_once_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.
add_view_paths
: Adds the directory app/views
from the application, railties, and engines to the lookup path for view files for the application.
load_environment_config
: Loads the config/environments
file for the current environment.
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 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 at lib/templates
for the application, railties, 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 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 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.eager_load
is true
, runs the config.before_eager_load
hooks and then calls eager_load!
which will load all config.eager_load_namespaces
.
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.
set_routes_reloader_hook
: Configures Action Dispatch to reload the routes file using ActiveSupport::Callbacks.to_run
.
disable_dependency_loading
: Disables the automatic dependency loading if the config.eager_load
is set to true
.
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, Puma, 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.
You can configure your own code through the Rails configuration object with custom configuration under either the config.x
namespace, or config
directly. The key difference between these two is that you should be using config.x
if you are defining nested configuration (ex: config.x.nested.hi
), and just config
for single level configuration (ex: config.hello
).
config.x.payment_processing.schedule = :daily config.x.payment_processing.retries = 3 config.super_debugger = true
These configuration points are then available through the configuration object:
Rails.configuration.x.payment_processing.schedule # => :daily Rails.configuration.x.payment_processing.retries # => 3 Rails.configuration.x.payment_processing.not_set # => nil Rails.configuration.super_debugger # => true
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
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 your 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.
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', '>= 3.0.5', '< 3.2' end
Otherwise, in every request Rails walks the application tree to check if anything has changed.
On Linux and macOS no additional gems are needed, but some are required for *BSD and for Windows.
Note that some setups are unsupported.
You're encouraged to help improve the quality of this guide.
Please contribute if you see any typos or factual errors. To get started, you can read our documentation contributions section.
You may also find incomplete content or stuff that is not up to date. Please do add any missing documentation for master. Make sure to check Edge Guides first to verify if the issues are already fixed or not on the master branch. Check the Ruby on Rails Guides Guidelines for style and conventions.
If for whatever reason you spot something to fix but cannot patch it yourself, please open an issue.
And last but not least, any kind of discussion regarding Ruby on Rails documentation is very welcome on the rubyonrails-docs mailing list.
© 2004–2019 David Heinemeier Hansson
Licensed under the Creative Commons Attribution-ShareAlike 4.0 International License.