2016 - Ramesh Sampath - Building a Tic-Tac-Toe Two-Player Game using Tornado over Websockets

Transcript

1. Tic-Tac-Toe App with Tornado & WebSockets By Ramesh Sampath APP: http://games.sampathweb.com
2. Ramesh Sampath • Engineer ◦ Build Applications ◦ Build Machine Learning models ◦ Deploy @sampathweb (github / twitter / linkedin)
3. Objective Build and Deploy a Tic-Tac-Toe App that we can play with Friends.
4. Audience • New to WebSockets • May have built some Webapps • Want to built a Game / Chat App
5. Agenda • Tic-Tac-Toe - Single Player • Two Player Game • WebSockets • Tornado • Deploy • Scaling
6. Tic-Tac-Toe App (Command Line)
7. Tic Tac Toe Source: Wikipedia
8. Demo Command Line Version
9. Tic-Tac-Toe - Play with Human
10. Two Player Version Web Server Want to Play Other
11. Web App Clients Web Server Request Response Web App (Python)
12. Web App • Request / Response • Scale to lots of connections ◦ Short lived ◦ Isolated • Flask / Django over WSGI / Gunicorn & Nginx
13. Two Player Version Web Server Want to Play Other
14. Web App • Ajax Long Polling ◦ Latency ◦ Polling Frequency ◦ Server cannot initiate Push • Blocking - One Request at a Time.
15. WebSockets
16. WebSockets WebSocket is a protocol providing full-duplex communication channels over a single TCP connection. (RFC 6455)
17. WebSockets • Tunnel Data (String, Blob, ArrayBuffer) ◦ JSON ◦ XML / HTML ◦ Images, Sound, Video
18. WebSockets API • Open ◦ var ws = new WebSocket(ws://<endpoint>) • Send Message ◦ ws.send() • Receive Message ◦ ws.onmessage()
19. WebSockets Handler Open Socket Connection • Send Message • Receive Messages • Close Connection Handler Handler Handler Handler Application G A M E S T A T E
20. WebSockets • Persistent Connection • Two-way communication • Handle Lots of Connections • Non-Blocking (Async)
21. Async Stack Credits: Anton Caceres - Better asynchronous code with Tornado and Python 3 [EuroPython 2015]
22. Tornado • Web Framework • Single Threaded • Non-Blocking I/O Concurrency • Thousands of Requests
23. Tornado - When to use it • Building REST APIs (GET / POST) • Micro Services • Slow database queries • Communicating with external resources • Need to handle large number of connections
24. Demo!
25. Code Walkthrough Open Text Editor
26. Things to Lookout For • Async entire code ◦ Database Calls - Momoko over SqlAlchemy ◦ External HTTP Calls - AsyncHTTP ◦ Non Async Libraries ▪ Wrapped in coroutines / Threadpool
27. Deploy to AWS
28. Deploy Steps • Deploy Notes in the “README.md” file of repo. https://github.com/sampathweb/board-games-app
29. Deployment Handler Application S T A T E Handler Handler Handler Supervisor Process
30. Scaling App Handler Application S T A T E Handler Handler Handler Handler Application S T A T E Handler Handler Handler Not Connected
31. Problems • Single Instance of App ◦ Latency ◦ Number of connections • Source: Singleton Manager to maintain State
32. Scale with Pub/Sub Load Balancer (Nginx) Clients Tornado Process #1 Tornado Process #2 Tornado Process #3 Tornado Process #4 Supervisor Process Pub / Sub (Redis)
33. Thank You! Slides: https://goo.gl/NKzuZB @sampathweb (Github / Twitter / Linkedin)
34. WebSockets Web Server Web App (Python) Client Client Client Client Starts with HTTP Handshake