fastmcp
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jlowin
issue on sse server and interrupted tool call
Description
Hi, I've developed a simple fastmcp server and using it via sse with LibreChat.
I have a simple tool for running commands (async):
proc = await asyncio.create_subprocess_shell(
cmd,
stdout=asyncio.subprocess.PIPE,
stderr=asyncio.subprocess.PIPE,
cwd="/aymcp",
)
try:
stdout, stderr = await proc.communicate()
except Exception:
return "Error executing this command"
if stdout:
return stdout.decode()
else:
return stderr.decode()
The tool works fine but if I:
- tell LibreChat model to use the tool
- interrupt (press the stop button on LibreChat) the tool while it's running I get this exception:
aymcp | ERROR: Exception in ASGI application
aymcp | Traceback (most recent call last):
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/uvicorn/protocols/http/h11_impl.py", line 403, in run_asgi
aymcp | result = await app( # type: ignore[func-returns-value]
aymcp | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in __call__
aymcp | return await self.app(scope, receive, send)
aymcp | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/applications.py", line 112, in __call__
aymcp | await self.middleware_stack(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/middleware/errors.py", line 187, in __call__
aymcp | raise exc
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/middleware/errors.py", line 165, in __call__
aymcp | await self.app(scope, receive, _send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/middleware/exceptions.py", line 62, in __call__
aymcp | await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
aymcp | raise exc
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
aymcp | await app(scope, receive, sender)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 714, in __call__
aymcp | await self.middleware_stack(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 734, in app
aymcp | await route.handle(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 288, in handle
aymcp | await self.app(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 76, in app
aymcp | await wrap_app_handling_exceptions(app, request)(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
aymcp | raise exc
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
aymcp | await app(scope, receive, sender)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 74, in app
aymcp | await response(scope, receive, send)
aymcp | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
aymcp | TypeError: 'NoneType' object is not callable
How can I avoid the exception inside the server? I'm running it with: uvicorn aymcp:app --host 0.0.0.0 --port 8000
tried also: fastmcp run aymcp/init.py:mcp --transport sse --host 0.0.0.0 --port 8000
but same issue.
Example Code
Version Information
[[package]]
name = "fastmcp"
version = "2.2.10"
Additional Context
No response
tried now with updated mcp and fastmcp releases:
aymcp | ERROR: Exception in ASGI application
aymcp | Traceback (most recent call last):
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/uvicorn/protocols/http/h11_impl.py", line 403, in run_asgi
aymcp | result = await app( # type: ignore[func-returns-value]
aymcp | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/uvicorn/middleware/proxy_headers.py", line 60, in __call__
aymcp | return await self.app(scope, receive, send)
aymcp | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/applications.py", line 112, in __call__
aymcp | await self.middleware_stack(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/middleware/errors.py", line 187, in __call__
aymcp | raise exc
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/middleware/errors.py", line 165, in __call__
aymcp | await self.app(scope, receive, _send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/fastmcp/server/http.py", line 59, in __call__
aymcp | await self.app(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/middleware/exceptions.py", line 62, in __call__
aymcp | await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
aymcp | raise exc
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
aymcp | await app(scope, receive, sender)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 714, in __call__
aymcp | await self.middleware_stack(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 734, in app
aymcp | await route.handle(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 288, in handle
aymcp | await self.app(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 76, in app
aymcp | await wrap_app_handling_exceptions(app, request)(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
aymcp | raise exc
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
aymcp | await app(scope, receive, sender)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/routing.py", line 74, in app
aymcp | await response(scope, receive, send)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/responses.py", line 150, in __call__
aymcp | await send(
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 39, in sender
aymcp | await send(message)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/_exception_handler.py", line 39, in sender
aymcp | await send(message)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/starlette/middleware/errors.py", line 162, in _send
aymcp | await send(message)
aymcp | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/uvicorn/protocols/http/h11_impl.py", line 513, in send
aymcp | raise RuntimeError(msg % message_type)
aymcp | RuntimeError: Unexpected ASGI message 'http.response.start' sent, after response already completed.
different error.
and now I moved to http streamable and:
aymcp | INFO: 192.168.112.7:53930 - "POST /mcp/ HTTP/1.1" 200 OK
aymcp | SSE response error
aymcp | + Exception Group Traceback (most recent call last):
aymcp | | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/mcp/server/streamable_http.py", line 511, in _handle_post_request
aymcp | | async with anyio.create_task_group() as tg:
aymcp | | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/anyio/_backends/_asyncio.py", line 772, in __aexit__
aymcp | | raise BaseExceptionGroup(
aymcp | | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
aymcp | +-+---------------- 1 ----------------
aymcp | | Traceback (most recent call last):
aymcp | | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/mcp/server/streamable_http.py", line 515, in _handle_post_request
aymcp | | await writer.send(session_message)
aymcp | | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/anyio/streams/memory.py", line 242, in send
aymcp | | self.send_nowait(item)
aymcp | | File "/root/.cache/pypoetry/virtualenvs/aymcp-aSnAZHCZ-py3.11/lib/python3.11/site-packages/anyio/streams/memory.py", line 211, in send_nowait
aymcp | | raise ClosedResourceError
aymcp | | anyio.ClosedResourceError
aymcp | +------------------------------------
aymcp | ERROR: ASGI callable returned without completing response.
