fix: gracefully terminate active sessions on shutdown#2181
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giulio-leone wants to merge 1 commit intomodelcontextprotocol:mainfrom
Open
fix: gracefully terminate active sessions on shutdown#2181giulio-leone wants to merge 1 commit intomodelcontextprotocol:mainfrom
giulio-leone wants to merge 1 commit intomodelcontextprotocol:mainfrom
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During StreamableHTTPSessionManager shutdown, iterate through all active transports and call terminate() before cancelling the task group. This allows SSE connections to receive a proper HTTP response instead of being abruptly dropped, which caused Uvicorn to log 'ASGI callable returned without completing response'. Fixes modelcontextprotocol#2150 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Summary
When shutting down a
StreamableHTTPSessionManager(e.g. CTRL+C) while clients have active streaming connections, Uvicorn logs:The error occurs because the
run()shutdown path cancels the task group without first gracefully terminating active SSE/streaming connections.Fix
Before cancelling the task group in
run()'sfinallyblock, iterate through all active_server_instancesand callterminate()on each transport. This gives each transport a chance to close its SSE connections properly, so clients receive a proper HTTP response instead of an abrupt disconnect.Tests
Added
test_shutdown_terminates_active_sessions— injects a mock transport and verifiesterminate()is called during shutdown.Fixes #2150