Pune Ruby Meetup - November 2015

1
Websockets in Rails

• by Vineet Ahirkar - _at_vinzee93

2
TCP IP

1. HTTP 1.1 ?
2. Server Sent Events ?
3. WebSockets ?

• Basic communication protocol
• of the Internet.

3
Options we have

• Long Polling

• Server Sent Events

• Web Sockets

• Uni - directional
• no multimedia support
• HTTP dependant
• Native implementation
• 3-5 bytes
• Eg - ActionController-live

• Bi - directional
• multimedia support
• HTTP compatible but not dependant
• Native implementation
• 3-5 bytes
• Eg - Action Cable

• Uni - directional
• multimedia support.
• HTTP dependant
• Native and non-native implementations
• 663 bytes
• Eg - Comet

4
Network
Dude, im a web socket, make way for me!

Yes, Sure.

Yo communicate Yo

Im done, Cya.

5
websocket-ruby - abstraction layer over the
WebSocket API, handshakes, frame handling, etc.
Redis - A pub sub mechanism
Events, Threads, Fibers, Forks - way to handle
concurrent requests
Implementation in Ruby
6
Problems faced !

Blocking IO
Green vs Native threads
GIL !
Server Request caching
7
Actor Pattern
Reactor Pattern
8
Actor Pattern
Reactor Pattern

• Each actor can be a thread or a Fiber which is
  spawned each time.
• A Fiber is thread which run in the user space and
  are faster with a lower memory space.
• Fibers execution can be controlled by user,
  while threads cannot.

• Continuously running thread called as Event loop,
  blocks all resources.
• Demultiplexer sends the resource to the
  Dispatcher, when it is possible to start a
  synchronous operation on a resource without
  blocking.

• Celluloid (previously used in Sidekiq)
• Erlang, Elixir, Scala, etc

• Event Machine (used in Thin)
• Node JS

9
Faye (event machine em-http-request)

• Based on Reactor Pattern
• One of the best options for implementation of
  websockets in rails.
• based on the bayeux protocol - channel
  management, subscription based messaging,
  multiple decoupled conversations on top of a
  single HTTP connection.
• Runs on a separate thread (Event machine).
• Provides easy client side integration.
• Light coupled modules, support for extensions.
• Awesome fallback mechanisms if the browser,
  network, server doesnt support websockets.
• Websockets -gt Server Sent Events -gt XHR long
  polling -gt CORS long polling -gt JSONP.

10
TubeSock - (Rack Hijack, native Ruby threads)

• It provides a module for Rails controllers and a
  wrapper method to hijack the rack connection.
  Then it wraps the ruby gem websocket to handle
  WebSocket handshakes and frames.
• Lets you use websockets from rack and rails 4 by
  using Rack's new hijack interface to access the
  underlying socket connection.
• No reactor, no eventmachine.
• Instead, it leverages Rails 4's new full-stack
  concurrency support. This means you must use a
  concurrent server.
• Use ruby Threads inside your Rails app to hold
  websocket connections open without bogging down
  our server.
• Rack Hijack (Rack 1.5)
• Hey Rack, give me your sockets.
• Gives access the underlying socket of a Rack
  connection in order to bidirectionally
  communicate with the client.

11
Action Cable
Components -

• Faye-Websocket - websocket driver event machine
• celluloid - efficient thread management in ruby
• em-hiredis - EM based wrapper over redis for
  better performance
• redis - Pub Sub service
• puma - multi threaded server

• Now whats this new thing ?

Link to Git Repo
12
Future

• Truely concurrent MRI ruby
• JRuby, Rubinius
• WebRTC
• HTTP 2.0

13
Thank you

• Any questions ?

14
References

• http//confreaks.tv/videos/rubyconfindia2014-let-s
  -get-real-time-server-sent-events-websockets-and-w
  ebrtc-for-the-soul
• http//merbist.com/2011/02/22/concurrency-in-ruby-
  explained/
• http//javieracero.com/blog/starting-with-eventmac
  hine-i
• http//old.blog.phusion.nl/2013/01/23/the-new-rack
  -socket-hijacking-api/
• http//c7.se/intro-to-celluloid/
• http//www.csinaction.com/2014/10/10/multithreadin
  g-in-the-mri-ruby-interpreter/
• http//railscasts.com/episodes/260-messaging-with-
  faye
• http//railscasts.com/episodes/367-celluloid
• http//tpierrain.blogspot.in/2013/09/some-web-mech
  anical-sympathy-lets.html
• https//blogs.oracle.com/slc/entry/introduction_to
  _bayeux_protocol
• https//www.websocket.org/
• Books - High performance browser networking