Custom 404 & 500 Error Pages

application_controller.rb

class ApplicationController < ActionController::Base
  #...

  unless Rails.application.config.consider_all_requests_local
    rescue_from Exception, with: lambda { |exception| render_error 500, exception }
    rescue_from ActionController::RoutingError, ActionController::UnknownController, ::AbstractController::ActionNotFound, ActiveRecord::RecordNotFound, with: lambda { |exception| render_error 404, exception }
  end

  #...
  
  protected
  
  #...

    def not_found
      raise ActionController::RoutingError.new('Not Found')
    end

    def restrict_to_development
      head(:bad_request) unless Rails.env.development?
    end
  
  #...

  private
    def render_error(status, exception)
      if(status == 404)
        logger.info "Not Found: '#{request.fullpath}'.\n#{exception.class} error was raised for path .\n#{exception.message}"
      else
        logger.info "System Error: Tried to access '#{request.fullpath}'.\n#{exception.class} error was raised for path .\n#{exception.message}"
      end

      respond_to do |format|
        format.html { render template: "errors/error_#{status}", layout: 'layouts/application', status: status }
        format.all { render nothing: true, status: status }
      end
    end

  #...
  
end

errors_controller.rb

class ErrorsController < ApplicationController
  def error_404
    render status: 404
  end

  def error_500
    render status: 500
  end

  def not_found
    raise ActionController::RoutingError.new('Not Found')
  end
end

routes.rb

MyApp::Application.routes.draw do

  #...

  #Custom Error Generating controller
  get "/errors/not_found" => 'errors#not_found'
  get "/errors/server_error" => 'errors#server_error'

  unless Rails.application.config.consider_all_requests_local
    match '*not_found', to: 'errors#error_404'
  end
  
  #...
end