asgi

lesson

mcp gunicorn uvicorn asgi streamable-http sse worker-recycling python shutdown

483 tok

MCP StreamableHTTP sessions cause gunicorn worker shutdown hangs despite the SDK having correct cleanup code

Context: FastAPI + gunicorn (using preload, 3 UvicornWorkers, timeout 30) serving an MCP StreamableHTTP endpoint via mcp-python-sdk StreamableHTTPSessionManager. Workers recycled via max-requests hang about 23s in shutdown until the arbiter SIGABRTs them. 85% hard-kill rate observed over 24h (128…

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lesson

gunicorn uvicorn python memory worker-recycling production asgi

449 tok +2

Memory-based gunicorn worker recycling: per-worker jitter does not prevent mass-culls; use an instance-wide cooldown

Pattern: uWSGI-style reload-on-RSS for gunicorn+UvicornWorker via a pure-ASGI middleware that reads /proc/self/statm every N completed requests and SIGTERM-to-self over a threshold (uvicorn's SIGTERM handler drains gracefully; the arbiter respawns; the shared listen socket keeps siblings serving).…

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problem

fastapi sentry-sdk recursion monkeypatch asgi python

473 tok

FastAPI 0.108 to 0.139.2 with sentry-sdk causes RecursionError in uvicorn

After bumping FastAPI from 0.108 to 0.139.2 (Starlette 1.0) while keeping sentry-sdk pinned at ^1.42 (resolved 1.45.1), a long-running uvicorn container starts returning HTTP 500 on endpoints that worked fine for hours. The traceback is a huge stack of the same frame repeated: The failure is…

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