faye-rails

faye-rails is a Ruby gem which handles embedding Faye's rack-based server into the rails stack and providing it with access to controllers and views based on bindings and observers.

A very small demonstration app is available for your perusal on Heroku. The source is here on Github.

Heroku Add-on

If you're planning on running Faye on Heroku you're probably going to have a bad time. Take a look at MessageRocket as an alternative, and help support the author to maintain more great open source projects.

Embedded server

Due to the limitations of most Rack-based web servers available Faye can only be run on Thin, however if you are using thin, then you can add as many Faye servers as you want to the Rails middleware stack like so:

# application.rb
config.middleware.use FayeRails::Middleware, mount: '/faye', :timeout => 25

You can also pass a block to faye_server which will be executed in the context of the Faye server, thus you can call any methods on Faye::RackAdapter from within the block:

config.middleware.use FayeRails::Middleware, mount: '/faye', :timeout => 25 do
  # can be defined anywhere, like app/faye_extensions/mock_extension.rb 
  class MockExtension
    def incoming(message, callback)
      callback.call(message)
    end
  end

  add_extension(MockExtension.new)
end

If you really want to, you can ask Faye to start it's own listening Thin server on an arbitrary port:

config.middleware.use FayeRails::Middleware, mount: '/faye', :timeout => 25 do
  listen(9292)  
end

You can also do some rudimentary routing using the map method:

config.middleware.use FayeRails::Middleware, mount: '/faye', :timeout => 25 do
  map '/widgets/**' => WidgetsController  
  map :default => :block
end

You can find more details on the #map method in the rdoc

Controller

faye-rails includes a controller for handling the binding between model events and channels with it's own DSL for managing channel-based events.

class WidgetController < FayeRails::Controller
end

Model observers

You can subscribe to changes in models using the controller's observer DSL:

class WidgetController < FayeRails::Controller
  observe Widget, :after_create do |new_widget|
    WidgetController.publish('/widgets', new_widget.attributes)
  end
end

The available callbacks are derived from the ActiveRecord callback stack. See ActiveRecord::Callbacks for more information regarding the callback queue.

See the rdoc for more information.

Channel DSL

The controller DSL elegantly wraps channel-based aspects of the Faye API so that you can easily group code based on specific channels.

Monitoring

You can make use of Faye's monitoring API by adding calls to monitor within the channel block. You are able to monitor :subscribe, :unsubscribe and :publish events. Blocks are executed within the context of a FayeRails::Controller::Monitor instance which will give you access to #client_id, #channel and #data (#data only having a value on :publish events).

class WidgetController < FayeRails::Controller
  channel '/widgets' do
    monitor :subscribe do
      puts "Client #{client_id} subscribed to #{channel}."
    end
    monitor :unsubscribe do
      puts "Client #{client_id} unsubscribed from #{channel}."
    end
    monitor :publish do
      puts "Client #{client_id} published #{data.inspect} to #{channel}."
    end
  end
end

Filtering

You can quickly and easily filter incoming and outgoing messages for your specific channel using the controller's filter API, which wraps Faye's extensions API in a concise and channel-specific way.

class WidgetController < FayeRails::Controller
  channel '/widgets' do
    filter :in do
      puts "Inbound message #{message}."
      pass
    end
  end
end

You can add filters for :in, :out and :any, which will allow you to filter messages entering the server, exiting the server or both. The block passed to the filter is executed in the context of a FayeRails::Filter::DSL instance, which gives you access to the #message method, which contains the entire message payload from the client (including meta information you wouldn't see other ways). You also have access to the #pass, #modify, #block and #drop methods which are sugar around Faye's callback system - which is accessible via the #callback method if you want to do it that way. Check out the FayeRails::Filter::DSL rdoc for more information. Please note that all filters must call callback.call either via the sugar methods or directly to ensure that requests are not lost (not to mention potential memory leaks).

Subscribing

You can easily subscribe to a channel using the 'subscribe' method inside your channel block, like so:

class WidgetController < FayeRails::Controller
  channel '/widgets' do
    subscribe do
      puts "Received on channel #{channel}: #{message.inspect}"
    end
  end
end

Non-server environments

Often you'll find yourself running the Rails environment without the server running - eg when doing background job processing, or running the console. If you have any actions which use Faye then you'll need to make sure that you have the EventMachine reactor running. The easiest solution to this is to create an initialiser in config/initializers which calls Faye.ensure_reactor_running!. For workers in production you probably also want to make sure that you are using the Redis engine for Faye to ensure that multiple server instances see the same data.

config.middleware.use FayeRails::Middleware, mount: '/faye', engine: {type: Faye::Redis, host: 'localhost'}, :timeout => 25 do
  map '/announce/**' => SomeController  
end

See more details in this issue on GitHub.

Running on Phusion Passenger

If you want to run faye-rails on passenger, make sure you are using passenger 4.0 standalone or passenger 4.0 on nginx 1.4+ for nginx with websocket support. Passenger on apache is not supported. Because passenger uses a multi-process model, you must use the faye redis backend. Add gem 'faye-redis' to your Gemfile and configure your routes like this:

config.middleware.use FayeRails::Middleware, mount: '/faye', :timeout => 25, server: 'passenger', engine: {type: Faye::Redis, host: 'localhost'}

Thanks.

Thanks to James Coglan for the excellent Faye Bayeux implementetation and great support for Faye users.

lightyrs / faye-rails