Custom error pages for 404, 500 but where is the default 500 error message coming from?

Question

Currently in production I'm getting this text:

500 Internal Server Error
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.

There isn't any HTML on that page. Where is this code situated? I don't have a public/500.html file.

In my routes I have:

  get "/404", :to => "errors#error_404"
  get "/422", :to => "errors#error_404"
  get "/500", :to => "errors#error_500"
  get "/505", :to => "errors#error_505"

ErrorsController:

class ErrorsController < ApplicationController

  def sub_layout
    "left"
  end

  def error_404
    render :status => 404, :formats => [:html], :layout => "white", :sub_layout => "left"
  end

  def error_422
    render :status => 422, :formats => [:html], :layout => "white", :sub_layout => "left"
  end

  def error_500
    render :status => 500, :formats => [:html], :layout => "white", :sub_layout => "left"
  end

  def error_505
    render :status => 505, :formats => [:html], :layout => "white", :sub_layout => "left"
  end

end

How do I make it load my custom errors always? On some errors, it just throws those two lines of text coming somewhere from the Ruby on Rails core. I want it to pickup my custom styled error pages every time!

Answer 1

The error you are experiencing is being thrown from

https://github.com/rails/rails/blob/4-0-stable/actionpack/lib/action_dispatch/middleware/show_exceptions.rb#L18-L22

This means the code your exceptions are getting rescued by are themselves throwing exceptions. You can check your logs for text:

Error during failsafe response:

to identify what the exceptions really are originating from and thus solve your problem.