With Rails4.2 I'm not able to handle Exceptions like RoutingError

Question

My application_controller.rb code is:

class ApplicationController < ActionController::Base# Prevent CSRF attacks by raising an exception.#For APIs, you may want to use: null_session instead.
  protect_from_forgery
  before_filter: set_current_user
  rescue_from ActionController::RoutingError, with: : render_error

  def render_error
    p "**************************************"
  end

  def set_current_user
    User.current_user = current_user
  end

 end

Now if I try to hit my home/xyz this exception should have captured but control is never coming to render_error method. Is there anything else which I have to do in order to capture this exception? or if there is any better way available for Rails 4.2 can someone guide me on those I have tried Exception Notificaiton Gem but that too not working it seems. Note : I'm using development environment.

My Error logs :

Started GET "/qweq"
for 172.24.106.197 at 2016 - 09 - 07 16: 03: 01 + 0530

ActionController::RoutingError(No route matches[GET]
    "/qweq"):
  actionpack(4.2.6) lib / action_dispatch / middleware / debug_exceptions.rb: 21: in `call'
  actionpack (4.2.6) lib/action_dispatch/middleware/show_exceptions.rb:30:in `
call '
  railties (4.2.6) lib/rails/rack/logger.rb:38:in `call_app'
railties(4.2.6) lib / rails / rack / logger.rb: 20: in `block in call'
  activesupport (4.2.6) lib/active_support/tagged_logging.rb:68:in `
block in tagged '
  activesupport (4.2.6) lib/active_support/tagged_logging.rb:26:in `tagged'
activesupport(4.2.6) lib / active_support / tagged_logging.rb: 68: in `tagged'
  railties (4.2.6) lib/rails/rack/logger.rb:20:in `
call '
  actionpack (4.2.6) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack(1.6.4) lib / rack / methodoverride.rb: 22: in `call'
  rack (1.6.4) lib/rack/runtime.rb:18:in `
call '
  activesupport (4.2.6) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
rack(1.6.4) lib / rack / lock.rb: 17: in `call'
  actionpack (4.2.6) lib/action_dispatch/middleware/static.rb:120:in `
call '
  rack (1.6.4) lib/rack/sendfile.rb:113:in `call'
railties(4.2.6) lib / rails / engine.rb: 518: in `call'
  railties (4.2.6) lib/rails/application.rb:165:in `
call '
  rack (1.6.4) lib/rack/lock.rb:17:in `call'
rack(1.6.4) lib / rack / content_length.rb: 15: in `call'
  rack (1.6.4) lib/rack/handler/webrick.rb:88:in `
service '
  /home/883562/.rvm/rubies/ruby-2.1.4/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service' / home / 883562 / .rvm / rubies / ruby - 2.1.4 / lib / ruby / 2.1.0 / webrick / httpserver.rb: 94: in `run'
  /home/883562/.rvm/rubies/ruby-2.1.4/lib/ruby/2.1.0/webrick/server.rb:295:in `
block in start_thread '

Answer 1

config/application.rb

module NameOfYourApp
  class Application < Rails::Application
    require Rails.root.join("lib/custom_public_exceptions")
    config.exceptions_app = CustomPublicExceptions.new(Rails.public_path)
  end
end

config/routes.rb

match "/404" => "errors#error404", via: [ :get, :post, :patch, :delete ]

lib/custom_public_exceptions.rb

class CustomPublicExceptions < ActionDispatch::PublicExceptions
  def call(env)
    status = env["PATH_INFO"][1..-1]

    if status == "404"
      Rails.application.routes.call(env)
    else
      super
    end
  end
end

app/controllers/errors_controller.rb

class ErrorsController < ApplicationController
  def error404
    render status: :not_found
  end
end

app/views/errors/error404.er

  <span> 404 </span>
  <p>Page Not Found<p>

You can make use of the ErrorsController for handling different errors and customizing corresponding view templates to provide better looking error pages

Answer 2

The reason why you can't handle routing errors with that code is because route is resolved before any controller is instantiated. If it is not resolved (matching controller/action is not found), then router itself raises this error. Naturally, application controller never sees it.

What you can do is define a "catch-all" route which will map to a controller/action and do your tracking in that action (or whatever it is you wanted to do).