fix: handle ClosedResourceError when logging errors to disconnected clients#2170
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giulio-leone wants to merge 1 commit intomodelcontextprotocol:mainfrom
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…lients Wrap send_log_message() in _handle_message's exception handler with a try/except for ClosedResourceError and BrokenResourceError. When a client disconnects during request processing, the server catches the stream exception but then crashes trying to send the error log back through the already-closed write stream. Closes modelcontextprotocol#2064 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Summary
Fixes #2064
When a client disconnects while a stateless streamable-HTTP server is processing a request, the exception handler in
_handle_messagetries tosend_log_message()back to the client. Since the session's write stream is already closed, this raisesClosedResourceError, which is unhandled and crashes the session with anExceptionGroup.Root Cause
_handle_message(lowlevel/server.py) has anExceptioncase that:session.send_log_message()to notify the client ❌ — crashes if the client is goneFix
Wrap the
send_log_message()call with a try/except foranyio.ClosedResourceErrorandanyio.BrokenResourceError. When the write stream is closed (client disconnected), the error is silently discarded with a debug log.Tests
All 475 server tests pass (2 consecutive clean runs).
ruff checkandruff formatclean.