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Fix: Prevent session manager shutdown on individual session crash (#841)

Browse source 
Co-authored-by: Felix Weinberger <fweinberger@anthropic.com>
Co-authored-by: Inna Harper <inna.hrpr@gmail.com>
This commit is contained in:
Brian Soby 2025-07-09 08:43:21 -06:00 • committed by GitHub
commit 7b1078b515
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GPG key ID: B5690EEEBB952194
2 changed files with 165 additions and 13 deletions
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5
src/mcp/server/streamable_http.py
View file

@ -173,6 +173,11 @@ class StreamableHTTPServerTransport:
] = {}
self._terminated = False
@property
def is_terminated(self) -> bool:
"""Check if this transport has been explicitly terminated."""
return self._terminated
def _create_error_response(
self,
error_message: str,

47
src/mcp/server/streamable_http_manager.py
View file

@ -52,7 +52,6 @@ class StreamableHTTPSessionManager:
json_response: Whether to use JSON responses instead of SSE streams
stateless: If True, creates a completely fresh transport for each request
with no session tracking or state persistence between requests.
"""
def __init__(
@ -173,12 +172,15 @@ class StreamableHTTPSessionManager:
async with http_transport.connect() as streams:
read_stream, write_stream = streams
task_status.started()
await self.app.run(
read_stream,
write_stream,
self.app.create_initialization_options(),
stateless=True,
)
try:
await self.app.run(
read_stream,
write_stream,
self.app.create_initialization_options(),
stateless=True,
)
except Exception:
logger.exception("Stateless session crashed")
# Assert task group is not None for type checking
assert self._task_group is not None
@ -233,12 +235,31 @@ class StreamableHTTPSessionManager:
async with http_transport.connect() as streams:
read_stream, write_stream = streams
task_status.started()
await self.app.run(
read_stream,
write_stream,
self.app.create_initialization_options(),
stateless=False, # Stateful mode
)
try:
await self.app.run(
read_stream,
write_stream,
self.app.create_initialization_options(),
stateless=False, # Stateful mode
)
except Exception as e:
logger.error(
f"Session {http_transport.mcp_session_id} crashed: {e}",
exc_info=True,
)
finally:
# Only remove from instances if not terminated
if (
http_transport.mcp_session_id
and http_transport.mcp_session_id in self._server_instances
and not http_transport.is_terminated
):
logger.info(
"Cleaning up crashed session "
f"{http_transport.mcp_session_id} from "
"active instances."
)
del self._server_instances[http_transport.mcp_session_id]
# Assert task group is not None for type checking
assert self._task_group is not None