TCP Transport RuntimeError with Python 3.13 + uvloop

TCP Transport RuntimeError with Python 3.13 + uvloop

Summary

uvloop is causing RuntimeError: unable to perform operation on <TCPTransport closed=True> errors when used with Python 3.13. Switching to --loop asyncio fixes the issue.

Environment

• Python: 3.13.3
• uvloop: (latest)
• Starlette: 0.46.2
• FastAPI: 0.115.14

Reproduction

1. Use Python 3.13
2. Run uvicorn with --loop uvloop
3. Make concurrent HTTP requests (e.g., browser loading static files)
4. Client disconnects/refreshes during response

Workaround

Use --loop asyncio instead of uvloop.

Expected

uvloop should handle closed connections gracefully like asyncio does.

Edit

I had a stray uvicorn process that had wracked up 9hrs of CPU time, this could potentially be the issue?

まず、Python 3.13.3、uvloop、uvicorn を使い、同時リクエストとクライアントの切断またはリフレッシュによって失敗を再現し、--loop asyncio の場合と比較します。TCPTransport closed=True RuntimeError を追跡し、報告されている残留 uvicorn プロセスについて説明できるようにします。再現時に uvloop の設定がこのエラーを発生させずに閉じた接続を処理できれば完了です。