WebSockets in Rails: ActionCable

Transcript

1. WebSockets in Rails ActionCable Matic Jurglič @matixmatix codeandtechno.com
2. WebSockets • Communication protocol, introduced in 2010 • Holding the connection to the server open • Bi-directional persistent connection • HTTP handshake = Upgrade request
5. WS in developer console
7. Frames
8. Path to Real-Time Rails • Polling • Long polling • WebSocket servers: Faye, Firehose,… • External hosted services: Pusher, Firebase, PubNub,…
9. DHH (2015) Dealing with WebSockets is a pain in the a$$
10. ✨ Hello ActionCable ✨
11. ActionCable • Rails 5 feature • Seamless integration of WebSockets into Rails apps • Full-stack, all ends are covered • Simple to implement and use anywhere in the application
12. Action Cable Terminology • WebSocket connection => ActionCable::Connection • Connection client is called Consumer • Consumer can subscribe to multiple channels • When Consumer subscribes, they act as a subscriber • Channel is streaming broadcastings
13. My project: http://github-radar.xyz
14. Generator
15. App structure
16. Generated by default
17. Need authentication?
18. Radar channel stream
19. Montreal Barcelona Hamburg Phillipines Svalbarðsstrandarhreppur
20. Setting up the front-end • A port of ActionCable JavaScript library is also available for Ember, React, Vanilla JS,…
21. Browser (consumer) Action Cable server JavaScript Geocoder (Google maps API) Washington Sevnica Sevnica 14.505751. Washington 46.056946 38.889931 -77.009003
22. It goes both ways! Washington Sevnica 14.505751. 46.056946 38.889931 -77.009003
23. Sending a message from the front-end to back-end
24. Sending a message from the front-end to back-end
25. behind the curtains…
26. Redis! • Keeps messages synced across connections and instances of the application • Every broadcast is sent to Redis event queue first • Can also use PG • concurrent-ruby
27. Config
28. Running the Cable • ActionCable does not need a multi-threaded server (works with Unicorn, Puma, Passenger) • Action Cable uses the Rack socket hijacking API to take over control of connections from the application server • Action Cable then manages connections internally, in a multithreaded manner
29. Running the Cable • Option 1: Running In-App
30. Running the Cable • Option 2: Running Standalone
31. Bad parts
32. Bad parts • Memory leaks (?) • Single point of failure (Redis) • Latency • No ACK for publishing from client to server • No message ordering • Scaling (https://dockyard.com/blog/2016/08/09/ phoenix-channels-vs-rails-action-cable)
33. Matic Jurglič @matixmatix codeandtechno.com github.com/matixmatix/github_broadcast github.com/matixmatix/commit_radar