Actions that fail to perform as expected throw exceptions. These exceptions can either be rescued for the public view (with a nice user-friendly explanation) or for the developers view (with tons of debugging information). The developers view is already implemented by the Action Controller, but the public view should be tailored to your specific application.

The default behavior for public exceptions is to render a static html file with the name of the error code thrown. If no such file exists, an empty response is sent with the correct status code.

You can override what constitutes a local request by overriding the local_request?method in your own controller. Custom rescue behavior is achieved by overriding the rescue_action_in_public and rescue_action_locallymethods.

Namespace
Methods
L
R
Constants
LOCALHOST = [/^127\.0\.0\.\d{1,3}$/, /^::1$/, /^0:0:0:0:0:0:0:1(%.*)?$/].freeze
 
DEFAULT_RESCUE_RESPONSE = :internal_server_error
 
DEFAULT_RESCUE_RESPONSES = { 'ActionController::RoutingError' => :not_found, 'ActionController::UnknownAction' => :not_found, 'ActiveRecord::RecordNotFound' => :not_found, 'ActiveRecord::StaleObjectError' => :conflict, 'ActiveRecord::RecordInvalid' => :unprocessable_entity, 'ActiveRecord::RecordNotSaved' => :unprocessable_entity, 'ActionController::MethodNotAllowed' => :method_not_allowed, 'ActionController::NotImplemented' => :not_implemented, 'ActionController::InvalidAuthenticityToken' => :unprocessable_entity }
 
DEFAULT_RESCUE_TEMPLATE = 'diagnostics'
 
DEFAULT_RESCUE_TEMPLATES = { 'ActionView::MissingTemplate' => 'missing_template', 'ActionController::RoutingError' => 'routing_error', 'ActionController::UnknownAction' => 'unknown_action', 'ActionView::TemplateError' => 'template_error' }
 
RESCUES_TEMPLATE_PATH = ActionView::Template::EagerPath.new_and_loaded( File.join(File.dirname(__FILE__), "templates"))
 
Instance Protected methods
local_request?()

True if the request came from localhost, 127.0.0.1. Override this method if you wish to redefine the meaning of a local request to include remote IP addresses or other criteria.

# File actionpack/lib/action_controller/rescue.rb, line 124
def local_request? #:doc:
  LOCALHOST.any?{ |local_ip| request.remote_addr =~ local_ip && request.remote_ip =~ local_ip }
end
log_error(exception)

Overwrite to implement custom logging of errors. By default logs as fatal.

# File actionpack/lib/action_controller/rescue.rb, line 79
def log_error(exception) #:doc:
  ActiveSupport::Deprecation.silence do
    if ActionView::TemplateError === exception
      logger.fatal(exception.to_s)
    else
      logger.fatal(
        "\n#{exception.class} (#{exception.message}):\n  " +
        clean_backtrace(exception).join("\n  ") + "\n\n"
      )
    end
  end
end
render_optional_error_file(status_code)

Attempts to render a static error page based on the status_codethrown, or just return headers if no such file exists. At first, it will try to render a localized static page. For example, if a 500 error is being handled Rails and locale is :da, it will first attempt to render the file at public/500.da.htmlthen attempt to render public/500.html. If none of them exist, the body of the response will be left empty.

# File actionpack/lib/action_controller/rescue.rb, line 107
def render_optional_error_file(status_code)
  status = interpret_status(status_code)
  locale_path = "#{Rails.public_path}/#{status[0,3]}.#{I18n.locale}.html" if I18n.locale
  path = "#{Rails.public_path}/#{status[0,3]}.html"
  if locale_path && File.exist?(locale_path)
    render :file => locale_path, :status => status, :content_type => Mime::HTML
  elsif File.exist?(path)
    render :file => path, :status => status, :content_type => Mime::HTML
  else
    head status
  end
end
rescue_action(exception)

Exception handler called when the performance of an action raises an exception.

# File actionpack/lib/action_controller/rescue.rb, line 72
def rescue_action(exception)
  rescue_with_handler(exception) ||
    rescue_action_without_handler(exception)
end
rescue_action_in_public(exception)

Overwrite to implement public exception handling (for requests answering false to local_request?). By default will call render_optional_error_file. Override this method to provide more user friendly error messages.

# File actionpack/lib/action_controller/rescue.rb, line 96
def rescue_action_in_public(exception) #:doc:
  render_optional_error_file response_code_for_rescue(exception)
end
rescue_action_locally(exception)

Render detailed diagnostics for unhandled exceptions rescued from a controller action.

# File actionpack/lib/action_controller/rescue.rb, line 130
def rescue_action_locally(exception)
  @template.instance_variable_set("@exception", exception)
  @template.instance_variable_set("@rescues_path", RESCUES_TEMPLATE_PATH)
  @template.instance_variable_set("@contents",
    @template.render(:file => template_path_for_local_rescue(exception)))
  response.content_type = Mime::HTML
  render_for_file(rescues_path("layout"),
    response_code_for_rescue(exception))
end
rescue_action_without_handler(exception)
# File actionpack/lib/action_controller/rescue.rb, line 141
def rescue_action_without_handler(exception)
  log_error(exception) if logger
  erase_results if performed?
  # Let the exception alter the response if it wants.
  # For example, MethodNotAllowed sets the Allow header.
  if exception.respond_to?(:handle_response!)
    exception.handle_response!(response)
  end
  if consider_all_requests_local || local_request?
    rescue_action_locally(exception)
  else
    rescue_action_in_public(exception)
  end
end