# RuntimeError: 事件循环已关闭。

- **ID:** `python/starlette-event-loop-closed`
- **领域:** python
- **类别:** runtime_error
- **验证级别:** ai_generated
- **修复率:** 80%

## 根因

在某个事件循环中创建的异步资源（如 aiohttp/httpx 客户端、数据库连接池）在该循环关闭后被复用，常见于测试用例或热重载。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| 0.30+ | active | — | — |

## 解决方案

1. **** (92% 成功率)
   ```
   from contextlib import asynccontextmanager
@asynccontextmanager
async def lifespan(app):
    app.state.client = httpx.AsyncClient()
    yield
    await app.state.client.aclose()
app = FastAPI(lifespan=lifespan)
   ```
2. **** (90% 成功率)
   ```
   async with httpx.AsyncClient() as client:
    r = await client.get(url)
   ```

## 无效尝试

- **** — Replaces loop but leaves stale client bound to old loop. (80% 失败率)
- **** — Buffering setting irrelevant to event loop lifecycle. (95% 失败率)