Chapter 13 · HTTP/2 and WebSocket

Chapter goals: Understand the advantages of HTTP/2 multiplexing, master httpx's HTTP/2 and WebSocket support.

13.1 HTTP/2 Multiplexing

HTTP/1.1 has head-of-line blocking issues - one slow request blocks all subsequent requests. HTTP/2 solves this through multiplexing:

pip install "httpx[http2]"

import httpx

# Enable HTTP/2
client = httpx.Client(h2=True)
resp = client.get('https://httpbin.org/get')

# Multiplexing: multiple requests share one TCP connection
with httpx.Client(h2=True) as client:
    resp1 = client.get('https://api.github.com/users/octocat')
    resp2 = client.get('https://api.github.com/users/torvalds')
    # Two requests transmitted concurrently on the same connection, not blocking each other

13.2 WebSocket Support

httpx has built-in WebSocket client:

import httpx
import asyncio

async def websocket_demo():
    uri = "wss://echo.websocket.org"
    
    async with httpx.AsyncClient() as client:
        async with client.websocket_connect(uri) as ws:
            await ws.send_text("Hello, WebSocket!")
            response = await ws.receive_text()
            print(f"Received: {response}")  # Echo "Hello, WebSocket!"

asyncio.run(websocket_demo())

13.3 Real-World Application Scenarios

import httpx
import asyncio

class RealtimeMonitor:
    """Real-time WebSocket data monitoring"""
    
    def __init__(self, url: str):
        self.url = url
        self.client = httpx.AsyncClient()
    
    async def connect(self):
        self.ws = await self.client.websocket_connect(self.url)
        await self.ws.send_text('subscribe: market_data')
    
    async def listen(self):
        async for message in self.ws.iter_text():
            print(f"Received: {message}")
            # Process real-time data...
    
    async def close(self):
        await self.ws.close()
        await self.client.aclose()

13.4 Chapter Summary

• HTTP/2 multiplexing improves concurrency performance, reducing connection count;
• httpx natively supports WebSocket without additional libraries;
• HTTP/2 requires extra installation: pip install "httpx[http2]".

🧪 随堂测验

点击你认为正确的选项。答错时会展示正确答案与原因解析。

1. What is the core advantage of HTTP/2 over HTTP/1.1?

2. What is needed to enable HTTP/2 in httpx?

3. At which layer does httpx WebSocket client belong?

4. What scenarios is WebSocket suitable for?

🛠️ Hands-on Practice

1. Compare HTTP/2 vs HTTP/1.1 concurrency performance with HTTP/2 enabled.
2. Implement a WebSocket echo client, send 10 messages and verify echo.
3. Create a real-time data subscriber that listens to WebSocket and processes messages.

Next chapter: Middleware and Event Hooks