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fix: ignore closed log streams during shutdown #2222

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fix: ignore closed log streams during shutdown #2222

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13 changes: 8 additions & 5 deletions src/mcp/server/lowlevel/server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -414,11 +414,14 @@ async def _handle_message(
)
case Exception():
logger.error(f"Received exception from stream: {message}")
await session.send_log_message(
level="error",
data="Internal Server Error",
logger="mcp.server.exception_handler",
)
try:
await session.send_log_message(
level="error",
data="Internal Server Error",
logger="mcp.server.exception_handler",
)
except (anyio.BrokenResourceError, anyio.ClosedResourceError):
logger.debug("Skipping exception log message because the session write stream is closed")
if raise_exceptions:
raise message
case _:
Expand Down
14 changes: 14 additions & 0 deletions tests/server/test_lowlevel_exception_handling.py
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
from unittest.mock import AsyncMock, Mock

import anyio
import pytest

from mcp import types
Expand Down Expand Up @@ -52,6 +53,19 @@ async def test_exception_handling_with_raise_exceptions_false(exception_class: t
assert call_args.kwargs["logger"] == "mcp.server.exception_handler"


@pytest.mark.anyio
@pytest.mark.parametrize("stream_error", [anyio.ClosedResourceError(), anyio.BrokenResourceError()])
async def test_exception_handling_ignores_closed_log_stream(stream_error: Exception):
"""Logging an exception should not crash shutdown if the write stream is already gone."""
server = Server("test-server")
session = Mock(spec=ServerSession)
session.send_log_message = AsyncMock(side_effect=stream_error)

await server._handle_message(RuntimeError("Test error"), session, {}, raise_exceptions=False)

session.send_log_message.assert_called_once()


@pytest.mark.anyio
async def test_normal_message_handling_not_affected():
"""Test that normal messages still work correctly"""
Expand Down