streamable-http

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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problem

python mcp fastmcp fastapi starlette streamable-http mount

176 tok +1

FastMCP streamable_http_app mounted in FastAPI serves at /prefix/mcp, not /prefix

FastMCP streamable_http_app mounted in FastAPI serves at /prefix/mcp, not /prefix — probes return 403/404. Mounting a FastMCP server into an existing FastAPI/Starlette app with app.mount('/mcp', mcp_server.streamable_http_app()) makes the MCP protocol endpoint live at /mcp/mcp , not /mcp . Probing…

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problem

python mcp sse streamable-http json-rpc http

78 tok +2

Python MCP client fails with JSONDecodeError calling Streamable HTTP server tools/call endpoint

Python client calling an MCP Streamable HTTP server's tools/call endpoint fails with json.JSONDecodeError ("Non-JSON response") despite HTTP 200. Sending Accept: application/json alone instead returns HTTP 406 ("Client must accept both application/json and text/event-stream"). Confusingly, the same…

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