PubSub at Rails

Action Cable is a Rails component that helps to incorporate real-time features into your Rails application. We will talk about how Action Cable implements PubSub using WebSocket protocol, whether WebSocket protocol is always a good choice, and what are alternatives to it.

Transcript

1. PubSub in Rails @just_lest
2. Real-time features
4. Real-time features → Collaboration → Asynchronous tasks → Keeping UI in sync
5. Action Cable Action Cable seamlessly integrates WebSockets with the rest of your Rails application. http://guides.rubyonrails.org/ action_cable_overview.html
6. Besides WebSocket protocol → Polling → Long-polling → EventSource
7. WebSocket protocol → Full-duplex → Low overhead
8. WebSocket protocol var socket = new WebSocket('ws://www.example.com/socketserver') socket.onopen = function () { websocket.send('Hello') } socket.onmessage = function (msg) { console.log(msg) }
9. Action Cable ApplicationCable::Connection is a WebSocket connection ApplicationCable::Channel is a unit of work inside a connection
10. Action Cable Action Cable uses Pub/Sub to communicate between the server and many clients. http://guides.rubyonrails.org/ action_cable_overview.html
11. What is PubSub?
12. What is PubSub? → Publishers → Subscribers
14. Message reliability
15. Losing messages → Flaky internet connection → Swithing Wi-Fi networks → Closing your laptop's lid
16. Message reliability Messaging reliability is far more important than WebSockets. WebSockets are an implementation detail, not a feature. Sam Saffron https://samsaffron.com/archive/2015/12/29/ websockets-caution-required
17. Message reliability Twitter use HTTP/2 + polling, Facebook and Gmail use Long Polling. Sam Saffron https://samsaffron.com/archive/2015/12/29/ websockets-caution-required
18. HTTP/2
19. HTTP/2 There is no websockets for HTTP/2. By this, I mean that there’s no way to negotiate or upgrade a connection to websockets over HTTP/2 like there is for HTTP/1.1 as expressed by RFC 6455. Daniel Stenberg https://daniel.haxx.se/blog/2016/06/15/no- websockets-over-http2/
20. HTTP/2 Open 20 tabs with a WebSocket based application and you are risking 20 connections unless the client/server mitigates. Sam Saffron https://samsaffron.com/archive/2015/12/29/ websockets-caution-required
21. HTTP/2 HTTP comes with a lot of goodies, and by moving away from HTTP we'll lose it all. Caching, routing, multiplexing, gzipping and lot more. You could reimplement all of these things in Action Cable, but why? Nate Berkopec https://www.nateberkopec.com/2015/09/30/action- cable.html
22. Possible issues → Proxies when using unsecured HTTP → Load balancing
23. What to do then?
24. message_bus A reliable, robust messaging bus for Ruby processes and web clients. https://github.com/SamSaffron/message_bus
25. message_bus https://www.discourse.org
26. message_bus → Provides reliable queue → Supports both server-to-client and server-to- server communication
27. message_bus → Long-polling with chunked encoding (streaming) → Long-polling → Polling
28. But when to use WebSockets? → To utilize full-duplex connection → To minimize latency and overhead
29. Thank you!