require 'active_support/core_ext/exception'
require 'active_support/notifications'
require 'action_dispatch/http/request'
module ActionDispatch
# This middleware rescues any exception returned by the application and renders
# nice exception pages if it's being rescued locally.
#
# Every time an exception is caught, a notification is published, becoming a good API
# to deal with exceptions. So, if you want send an e-mail through ActionMailer
# everytime this notification is published, you just need to do the following:
#
# ActiveSupport::Notifications.subscribe "action_dispatch.show_exception" do |name, start, end, instrumentation_id, payload|
# ExceptionNotifier.deliver_exception(start, payload)
# end
#
# The payload is a hash which has to pairs:
#
# * :env - Contains the rack env for the given request;
# * :exception - The exception raised;
#
class ShowExceptions
LOCALHOST = '127.0.0.1'.freeze
RESCUES_TEMPLATE_PATH = File.join(File.dirname(__FILE__), 'templates')
cattr_accessor :rescue_responses
@@rescue_responses = Hash.new(:internal_server_error)
@@rescue_responses.update({
'ActionController::RoutingError' => :not_found,
'AbstractController::ActionNotFound' => :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
})
cattr_accessor :rescue_templates
@@rescue_templates = Hash.new('diagnostics')
@@rescue_templates.update({
'ActionView::MissingTemplate' => 'missing_template',
'ActionController::RoutingError' => 'routing_error',
'AbstractController::ActionNotFound' => 'unknown_action',
'ActionView::Template::Error' => 'template_error'
})
FAILSAFE_RESPONSE = [500, {'Content-Type' => 'text/html'},
["<html><body><h1>500 Internal Server Error</h1>" <<
"If you are the administrator of this website, then please read this web " <<
"application's log file and/or the web server's log file to find out what " <<
"went wrong.</body></html>"]]
def initialize(app, consider_all_requests_local = false)
@app = app
@consider_all_requests_local = consider_all_requests_local
end
def call(env)
@app.call(env)
rescue Exception => exception
ActiveSupport::Notifications.instrument 'action_dispatch.show_exception',
:env => env, :exception => exception do
raise exception if env['action_dispatch.show_exceptions'] == false
render_exception(env, exception)
end
end
private
def render_exception(env, exception)
log_error(exception)
request = Request.new(env)
if @consider_all_requests_local || local_request?(request)
rescue_action_locally(request, exception)
else
rescue_action_in_public(exception)
end
rescue Exception => failsafe_error
$stderr.puts "Error during failsafe response: #{failsafe_error}"
FAILSAFE_RESPONSE
end
# Render detailed diagnostics for unhandled exceptions rescued from
# a controller action.
def rescue_action_locally(request, exception)
template = ActionView::Base.new([RESCUES_TEMPLATE_PATH],
:request => request,
:exception => exception
)
file = "rescues/#{@@rescue_templates[exception.class.name]}.erb"
body = template.render(:file => file, :layout => 'rescues/layout.erb')
render(status_code(exception), body)
end
# Attempts to render a static error page based on the
# <tt>status_code</tt> thrown, 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 <tt>public/500.da.html</tt>
# then attempt to render <tt>public/500.html</tt>. If none of them exist,
# the body of the response will be left empty.
def rescue_action_in_public(exception)
status = status_code(exception)
locale_path = "#{public_path}/#{status}.#{I18n.locale}.html" if I18n.locale
path = "#{public_path}/#{status}.html"
if locale_path && File.exist?(locale_path)
render(status, File.read(locale_path))
elsif File.exist?(path)
render(status, File.read(path))
else
render(status, '')
end
end
# True if the request came from localhost, 127.0.0.1.
def local_request?(request)
request.remote_addr == LOCALHOST && request.remote_ip == LOCALHOST
end
def status_code(exception)
Rack::Utils.status_code(@@rescue_responses[exception.class.name])
end
def render(status, body)
[status, {'Content-Type' => 'text/html', 'Content-Length' => body.length.to_s}, [body]]
end
def public_path
defined?(Rails.public_path) ? Rails.public_path : 'public_path'
end
def log_error(exception)
return unless logger
ActiveSupport::Deprecation.silence do
if ActionView::Template::Error === 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
def clean_backtrace(exception)
defined?(Rails) && Rails.respond_to?(:backtrace_cleaner) ?
Rails.backtrace_cleaner.clean(exception.backtrace) :
exception.backtrace
end
def logger
defined?(Rails.logger) ? Rails.logger : Logger.new($stderr)
end
end
end
