Module ActionController::Rescue
In: vendor/rails/actionpack/lib/action_controller/rescue.rb

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_locally methods.

Methods

Classes and Modules

Module ActionController::Rescue::ClassMethods

Constants

LOCALHOST = '127.0.0.1'.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'

Protected Instance methods

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.

[Source]

     # File vendor/rails/actionpack/lib/action_controller/rescue.rb, line 169
169:       def local_request? #:doc:
170:         request.remote_addr == LOCALHOST && request.remote_ip == LOCALHOST
171:       end

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

[Source]

     # File vendor/rails/actionpack/lib/action_controller/rescue.rb, line 132
132:       def log_error(exception) #:doc:
133:         ActiveSupport::Deprecation.silence do
134:           if ActionView::TemplateError === exception
135:             logger.fatal(exception.to_s)
136:           else
137:             logger.fatal(
138:               "\n\n#{exception.class} (#{exception.message}):\n    " +
139:               clean_backtrace(exception).join("\n    ") +
140:               "\n\n"
141:             )
142:           end
143:         end
144:       end

Attempts to render a static error page based on the status_code thrown, or just return headers if no such file exists. For example, if a 500 error is being handled Rails will first attempt to render the file at public/500.html. If the file doesn‘t exist, the body of the response will be left empty.

[Source]

     # File vendor/rails/actionpack/lib/action_controller/rescue.rb, line 156
156:       def render_optional_error_file(status_code)
157:         status = interpret_status(status_code)
158:         path = "#{Rails.public_path}/#{status[0,3]}.html"
159:         if File.exist?(path)
160:           render :file => path, :status => status
161:         else
162:           head status
163:         end
164:       end

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

[Source]

     # File vendor/rails/actionpack/lib/action_controller/rescue.rb, line 114
114:       def rescue_action(exception)
115:         log_error(exception) if logger
116:         erase_results if performed?
117: 
118:         # Let the exception alter the response if it wants.
119:         # For example, MethodNotAllowed sets the Allow header.
120:         if exception.respond_to?(:handle_response!)
121:           exception.handle_response!(response)
122:         end
123: 
124:         if consider_all_requests_local || local_request?
125:           rescue_action_locally(exception)
126:         else
127:           rescue_action_in_public(exception)
128:         end
129:       end

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.s

[Source]

     # File vendor/rails/actionpack/lib/action_controller/rescue.rb, line 148
148:       def rescue_action_in_public(exception) #:doc:
149:         render_optional_error_file response_code_for_rescue(exception)
150:       end

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

[Source]

     # File vendor/rails/actionpack/lib/action_controller/rescue.rb, line 175
175:       def rescue_action_locally(exception)
176:         add_variables_to_assigns
177:         @template.instance_variable_set("@exception", exception)
178:         @template.instance_variable_set("@rescues_path", File.dirname(rescues_path("stub")))
179:         @template.send!(:assign_variables_from_controller)
180: 
181:         @template.instance_variable_set("@contents", @template.render_file(template_path_for_local_rescue(exception), false))
182: 
183:         response.content_type = Mime::HTML
184:         render_for_file(rescues_path("layout"), response_code_for_rescue(exception))
185:       end

Tries to rescue the exception by looking up and calling a registered handler.

[Source]

     # File vendor/rails/actionpack/lib/action_controller/rescue.rb, line 188
188:       def rescue_action_with_handler(exception)
189:         if handler = handler_for_rescue(exception)
190:           if handler.arity != 0
191:             handler.call(exception)
192:           else
193:             handler.call
194:           end
195:           true # don't rely on the return value of the handler
196:         end
197:       end

[Validate]