Websockets in Rails

by Vineet Ahirkar - @vinzee93

TCP IPBasic communication protocol

of the Internet.

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

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

Network

1. Dude, i’m a web socket, make way for me!

2. Yes, Sure.

3. Yo communicate Yo

4. I’m done, Cya.

● 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

Problems faced !

● Blocking IO● Green vs Native threads● GIL !● Server Request caching

Actor Pattern Reactor Pattern

Actor Pattern

● Celluloid (previously used in Sidekiq)

● Erlang, Elixir, Scala, etc

Reactor Pattern

● Event Machine (used in Thin)● Node JS

● 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.

● Fiber’s execution can be controlled by user, while thread’s 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.

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 doesn’t support

websockets.● Websockets -> Server Sent Events -> XHR long polling -> CORS long polling ->

JSONP.

● 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.

TubeSock - (Rack Hijack, native Ruby threads)

Action Cable

Now what’s this new thing ?

● 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

Link to Git Repo

Components -

Future

● Truely concurrent MRI ruby

● JRuby, Rubinius

● WebRTC ● HTTP 2.0

Any questions ?

Thank you

● http://confreaks.tv/videos/rubyconfindia2014-let-s-get-real-time-server-sent-events-websockets-and-webrtc-for-the-soul

● http://merbist.com/2011/02/22/concurrency-in-ruby-explained/● http://javieracero.com/blog/starting-with-eventmachine-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/multithreading-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-mechanical-sympathy-lets.html● https://blogs.oracle.com/slc/entry/introduction_to_bayeux_protocol● https://www.websocket.org/● Books - High performance browser networking

References