Custom Error Handling with Rails 4.0

Question

I'm building a Ruby on Rails api using Ruby 2.0 and Rails 4.0. My app is almost solely a JSON API, so if an error occurs (500, 404), I want to capture that error and return a nicely formatted JSON error message.

I've tried this and also:

rescue_from ActionController::RoutingError, :with => :error_render_method

def error_render_method
  puts "HANDLING ERROR"
  render :json => { :errors => "Method not found." }, :status => :not_found
  true
end

In my ApplicationController.

Neither of these do the trick (the exceptions are not captured at all). My Googling shows that this changed a lot between 3.1, 3.2, and I can't find any good documentation on how to do this in Rails 4.0.

Anybody know?

Edit Here's the stack trace when I go to a 404 page:

Started GET "/testing" for 127.0.0.1 at 2013-08-21 09:50:42 -0400

ActionController::RoutingError (No route matches [GET] "/testing"):
actionpack (4.0.0) lib/action_dispatch/middleware/debug_exceptions.rb:21:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.0) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `block in call'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.0.0) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/static.rb:64:in `call'
railties (4.0.0) lib/rails/engine.rb:511:in `call'
railties (4.0.0) lib/rails/application.rb:97:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/webrick/httpserver.rb:138:in `service'
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/webrick/httpserver.rb:94:in `run'
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/webrick/server.rb:295:in `block in start_thread'


Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.0ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/templates/routes/_route.html.erb (2.9ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/templates/routes/_route.html.erb (0.9ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/templates/routes/_table.html.erb (1.1ms)
Rendered /Library/Ruby/Gems/2.0.0/gems/actionpack-4.0.0/lib/action_dispatch/middleware/templates/rescues/routing_error.erb within rescues/layout (38.3ms)

I don't think I want it to ever get this far, something should catch it and return the appropriate json error response.

Answer 1

The request isn't even hitting your app.

You need to define a catchall route so Rails will send the request to your app rather than display an error (in development) or render the public/404.html page (in production)

Modify your routes.rb file to include the following

match "*path", to: "errors#catch_404", via: :all

And in your controller

class ErrorsController < ApplicationController

  def catch_404
    raise ActionController::RoutingError.new(params[:path])
  end
end

And your rescue_from should catch the error then.

Answer 2

After trying a few variations I've settle on this as the simplest way to handle the API 404s:

# Passing request spec
describe 'making a request to an unrecognised path' do
  before { host! 'api.example.com' }
    it 'returns 404' do
    get '/nowhere'
    expect(response.status).to eq(404)
  end
end

# routing
constraints subdomain: 'api' do
  namespace :api, path: '', defaults: { format: 'json' } do
    scope module: :v1, constraints: ApiConstraints.new(1) do
      # ... actual routes omitted ...
    end
    match "*path", to: -> (env) { [404, {}, ['{"error": "not_found"}']] }, via: :all
  end
end

Answer 3

this works in rails4, this way you can manage directly all errors: for example you can render error_info as json when an an error occurs from an api call..

application_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery


  # CUSTOM EXCEPTION HANDLING
  rescue_from StandardError do |e|
    error(e)
  end

  def routing_error
    raise ActionController::RoutingError.new(params[:path])
  end

  protected

  def error(e)
    #render :template => "#{Rails::root}/public/404.html"
    if env["ORIGINAL_FULLPATH"] =~ /^\/api/
    error_info = {
      :error => "internal-server-error",
      :exception => "#{e.class.name} : #{e.message}",
    }
    error_info[:trace] = e.backtrace[0,10] if Rails.env.development?
    render :json => error_info.to_json, :status => 500
    else
      #render :text => "500 Internal Server Error", :status => 500 # You can render your own template here
      raise e
    end
  end

  # ...

end

routes.rb

MyApp::Application.routes.draw do

  # ...

  # Any other routes are handled here (as ActionDispatch prevents RoutingError from hitting ApplicationController::rescue_action).
  match "*path", :to => "application#routing_error", :via => :all
end

Answer 4

I used the 404.html from public folder and this is in dev environment.
I actually got the answer from:

• https://stackoverflow.com/posts/20508445/revisions and
• https://coderwall.com/p/w3ghqq

However, I did a little experiment on what pieces of code actually made it work. Here's are the pieces of code that I only added.

config/routes.rb

Rails.application.routes.draw do
    // other routes
    match "*path", to: "application#catch_404", via: :all
end

app/controllers/application_controller.rb

class ApplicationController < ActionController::Base
    def catch_404
        render :file => 'public/404.html', :status => :not_found
    end
end

Will appreciate any comments and clarifications as to why some of the original are are needed. For instance, using this line of code

raise ActionController::RoutingError.new(params[:path])

and this

rescue_from ActionController::RoutingError, :with => :error_render_method

Because rescue_from and raise ActionController::RoutingError seem to be the popular answer from the older Rails versions.