Overview

Uvicorn 0.21, released on March 9, 2023, introduces lifespan state allowing shared state between the application lifecycle and request handlers.

Main Features

Lifespan state

The state dictionary passed to the lifespan protocol is now injected into each request scope, making it easy to share DB connections, caches, and other resources initialized at startup.

python 
from contextlib import asynccontextmanager
from fastapi import FastAPI, Request

@asynccontextmanager
async def lifespan(app):
    # Startup: initialize resources
    app.state.db = await create_pool()
    yield
    # Shutdown: close resources
    await app.state.db.close()

app = FastAPI(lifespan=lifespan)

@app.get('/')
async def root(request: Request):
    pool = request.state.db
    return {'status': 'ok'}

Sources