Bocadillo: How I Built A Python Async Web Framework And Became An Open Source Maintainer

Talk given at PyCon Web Munich 2019.

https://2019.pyconweb.com/talks/25-05-2019/bocadillo-or-how-i-built-an-open-source-async-web-framework.html

Transcript

1. Bocadillo, or how I built an open source Python async web framework @FlorimondManca | PyConWeb2019
2. @FlorimondManca
3. Q&A with myself Answers to 10 early-days questions @FlorimondManca
4. 1. What is async, why use it in a web framework, and why does it matter? @FlorimondManca
5. Synchronous Python import requests def fetch(url): resp = requests.get(url) return resp.text @FlorimondManca
6. Threaded synchronous Python → ?! import threading import requests def fetch(url): resp = requests.get(url) return resp.text def main(urls): result = {url: None for url in urls} def target(url, result): result[url] = fetch(url) threads = [] for url in urls: t = threading.Thread(target, [url, result]) t.start() threads.append(t) for t in threads: t.join() print(result) main(["https://python.org", "https://pyconweb.com"]) @FlorimondManca
7. Async = Single-threaded cooperative multitasking !"# @FlorimondManca
8. Asynchronous fetch import requests_async as requests async def fetch(url): resp = await requests.get(url)) return resp.text async def main(urls): result = await asyncio.gather(*map(fetch, urls)) print(result) import asyncio asyncio.run(main(["https://python.org", "https://pyconweb.com"])) @FlorimondManca
9. Tom Christie: "Why I think async is important, in one image" @FlorimondManca
10. The future is asynchronous @FlorimondManca
11. 2. Why build an async web framework? @FlorimondManca
12. Example innovation: native WebSocket! from bocadillo import App app = App() @app.websocket_route("/echo") async def echo(ws): async for message in ws: await ws.send(message) @FlorimondManca
13. 3. What even is a web framework? @FlorimondManca
14. Back to the basics: HTTP @FlorimondManca
15. WSGI def app(environ, start_response): data = b"Hello, World!\n" start_response("200 OK", [ ("Content-Type", "text/plain"), ]) return [data] @FlorimondManca
16. ASGI async def app(scope, receive, send): assert scope["type"] == "http" await send({ "type": "http.response.start", "status": 200, "headers": [[b"content-type", b"text/plain"]] }) await send({ "type": "http.response.body", "body": b"Hello, world!", }) @FlorimondManca
17. Async framework ≈ ASGI framework @FlorimondManca
18. 4. How easy is it to build a minimal* framework? *App, routing, views @FlorimondManca
19. Spoiler alert: very easy @FlorimondManca
20. Bocadillo v0.1 import bocadillo api = bocadillo.API() @api.route("/hello/{who}") async def greet(req, resp, who): resp.media = {"message": f"Hello, {who}"} if __name__ == "__main__": api.run() @FlorimondManca
21. 5. How about building a full-featured framework? @FlorimondManca
22. It's hard @FlorimondManca
23. Documentation-driven development @FlorimondManca
24. Response builder @app.route("/") async def home(req, res): res.text = "Hello, world!" @FlorimondManca
25. Response builder @app.route("/") async def home(req, res): res.text = "Hello, world!" # ! .content = "Hello, world!" @FlorimondManca
26. Response builder @app.route("/") async def home(req, res): res.text = "Hello, world!" # ! .content = "Hello, world!" # ! .headers["content-type"] = "plain/text" @FlorimondManca
27. Response builder @app.route("/") async def home(req, res): res.text = "Hello, world!" @app.route("/answer") async def get_answer(req, res): res.json = {"value": 42} @FlorimondManca
28. 6. Should I build from scratch, or reuse an existing framework? @FlorimondManca
29. Build upon existing components @FlorimondManca
30. @FlorimondManca
31. Connections from starlette import requests, websockets class Request(requests.Request): ... class WebSocket(websockets.WebSocket): ... @FlorimondManca
32. Middleware from bocadillo import App from starlette.middleware.cors import CORSMiddleware app = App() app.add_middleware(CORSMiddleware) @FlorimondManca
33. TypeSystem for JSON validation import typesystem as ts class Todo(ts.Schema): title = ts.String() done = ts.Boolean(default=False) @FlorimondManca
34. TypeSystem for JSON validation import typesystem as ts class Todo(ts.Schema): title = ts.String() done = ts.Boolean(default=False) @app.route("/todos") class Todos: async def post(self, req, res): # May raise a `ValidationError` todo = Todo.validate(**await req.json()) @FlorimondManca
35. Find new ways to solve problems @FlorimondManca
36. Accessing resources: global variables hell from starlette.applications import Starlette from databases import Database app = Starlette() db = Database("sqlite://sqlite.db") @app.route("/") async def todos(request): async with db: rows = await db.fetch_all(...) @FlorimondManca
37. Providers: async dependency injection from bocadillo import provider from databases import Database @provider async def db(): async with Database("sqlite://sqlite.db") as db: yield db @FlorimondManca
38. Providers: async dependency injection from bocadillo import App app = App() @app.route("/") # ! async def home(req, res, db): rows = await db.fetch_all(...) # ... @FlorimondManca
39. Fill in the gaps with ASGI @FlorimondManca
40. GraphQL over ASGI from tartiflette_starlette import TartifletteApp sdl = """ Query { hello(name: String): String } """ graphql_app = TartifletteApp(sdl=sdl) @FlorimondManca
41. GraphQL over ASGI from bocadillo import App from .graphql import graphql_app app = App() app.mount("/graphql", graphql_app) @FlorimondManca
42. 7. How should I promote my project? @FlorimondManca
43. Fact: I'm not a superstar @FlorimondManca
44. Branding & Marketing @FlorimondManca
45. @FlorimondManca
46. Promotion @FlorimondManca
47. 8. What else can I do to make people use my project? @FlorimondManca
48. Good documentation @FlorimondManca
49. @FlorimondManca
50. @FlorimondManca
51. 9. How to build a community? @FlorimondManca
52. tl;dr: Reduce friction for contributors See: Maintaining A Python Project When It's Not Your Job @FlorimondManca
53. README.md CHANGELOG.md LICENSE CONTRIBUTING.md CODE_OF_CONDUCT.md @FlorimondManca
54. 10. Will my daily life be affected by open source? @FlorimondManca
55. Of course! @FlorimondManca
56. OSS Maintainer Lifestyle 101 • Automate maintenance • Find support • Have fun! @FlorimondManca
57. Question @FlorimondManca
58. Why not start your own open source project today? @FlorimondManca
59. Thanks! { Twitter: @FlorimondManca } { Links: Blog / Bocadillo }