1. Publish / Subscribe
in Ruby
Adrien Siami - Dimelo
@Intrepidd

2. What’s Pub / Sub ?
• Bidirectional communication between server and
clients
• Clients subscribe to channels
• Server or client pushes events to some channels
• Clients are notified in realtime!

3. Use case
• Private messaging
• Broadcasting
• Server-sent events

4. Possible Solutions (in ruby)
• Pusher
• PubNub
• Faye

5. Pusher
Pros
• SaaS
• Batteries Included (Auth, Presence)
Cons
• SaaS

6. PubNub
Pros
• SaaS
• Batteries Included (Auth, Presence)
Cons
• SaaS
• One event = one channel

7. Faye
Pros
• Built with ! (And Javascript)
• Open Source and self hosted
• Extensible
• Server level hooks
• Globbing (/users/*)
• Great Maintainer (@jcoglan)
Cons
• Les batteries included

9. Benchmarks
Websocket Json-p Cors Failure rate
Faye 84.68% 5.46% 9.81% 0.62%
Pusher 88.4% 6,67% 4,94% 3.7%

10. Faye Overview - Javascript
var client = new Faye.Client('http://foo.bar/faye');
!
client.subscribe('/user/123', function(message) {
console.log(message.content);
});
!
client.publish('/user/999', {content: 'Hey dude wassup?'});

11. Faye Overview - Ruby
require 'faye'
require 'eventmachine'
!
EM.run {
!
client = Faye::Client.new('http://foo.bar/faye')
!
client.subscribe('/user/123') do |message|
puts message.content
end
!
client.publish('/user/999', {content: 'Hey dude wassup?'})
}

12. Faye Hosting
• It’s a Rack system ! I Know this.
• EventMachine, one thread, tons of connections
• In-Memory by default
• Faye engines, e.g faye-redis, for multiple process
architecture

13. Benchmarks
Server
Without redis!
(1 worker)!
With redis!
(1 worker)
with redis !
(4 workers)
Passenger
+ nginx
43 sec 1m 25 sec 53 sec
Node!
1m 18 sec 1m 42 sec
Thin 38 sec 1m 28 sec
Puma 30 sec 1m 28 sec 43 sec
• Connect 10k clients
• Subscribe
• send some messages
• disconnect

14. Gotchas
• Tune your file descriptors
• Use EM.epoll
• PhusionPassenger.advertised_concurrency_level = 0
• passenger_max_requests 0;

15. DIY !
• Authentication
• Presence

16. Faye Authentication
• JWT based signature, generated by the Rails
Server when allowed
• Inserted into the faye request through a plugin
executing an Ajax Call
• Check at the faye server level
dimelo/faye-authentication

17. Faye Authentication
In a controller app (route /faye/auth):
def auth
if can?(:read, params[:message].try(:channel))
render :json => {signature: Faye::Authentication.sign(params[:message], 'faye
secret')}
else
render :text => "Forbidden", :status => '403'
end
In your JS :
client.addExtension(new FayeAuthentication(client));

18. Faye Authentication
On the faye server (config.ru):
server = Faye::RackAdapter.new mount: '/faye'
server.add_extension Faye::Authentication::ServerExtension.new('faye secret')
run server

19. Faye Presence
• Keep track of several clients per user
• Notify connection / disconnection
• Keep infos about the session (away / available)

20. Faye Presence
{
"event": "user-disconnected",
"user": {
"id": 42,
"infos" : {
"status": "away"
}
}
}

21. Thank you.

22. Dimelo contest!
• Submit a pull request on a 20+ stars ruby Github repository
• Have it merged
• Have a chance to win a Xbox One or a PS4
• http://contest.dimelo.com
• http://jobs.dimelo.com