adding multiple servers using the ClientSessionGroup, an error occurs when closing the connection

[gaojun1212]

Describe the bug
When adding multiple servers using the Client Session Group, an error occurs when closing the connection

No problem when adding only one server

code

async def test_connect_to_server():
    async with ClientSessionGroup() as clinet_session_group:
        for server in ["stream_law", "sse_kb"]:
            server_param = server_config_group.get_server_param(server)
            print(f"connect to server: {server_param}")
            print("----------------------------------------")
            await clinet_session_group.connect_to_server(server_param)

        await asyncio.sleep(3)
        print("*****************list tools********************")

        for name, tool in clinet_session_group.tools.items():
            print(f"tool_name: {name}")
            print("----------------------------------------")

        await asyncio.sleep(3)
        print("*****************disconnect********************")

        for session in clinet_session_group.sessions:
            print(f"disconnect session: {session}")
            await clinet_session_group.disconnect_from_server(session)
            await asyncio.sleep(2)

logs

connect to server: url='http://x.x.x.x:8080/mcp' headers={} timeout=datetime.timedelta(seconds=30) sse_read_timeout=datetime.timedelta(seconds=300) terminate_on_close=True
----------------------------------------
connect to server: url='http://x.x.x.x:9000/sse/' headers={} timeout=30.0 sse_read_timeout=300.0
----------------------------------------
*****************list tools********************
tool_name: search_ft
----------------------------------------
tool_name: search_fg
----------------------------------------
tool_name: search_law_xl
----------------------------------------
tool_name: writ_search
----------------------------------------
tool_name: law_search
----------------------------------------
tool_name: paper_search
----------------------------------------
tool_name: web_search
----------------------------------------
*****************disconnect********************
disconnect session: <mcp.client.session.ClientSession object at 0x0000022AAAF1C050>
  + Exception Group Traceback (most recent call last):
  |   File "C:\project\python\work\mcp\mcp-client\main.py", line 107, in <module>
  |     asyncio.run(test_connect_to_server())
  |   File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 195, in run
  |     return runner.run(main)
  |            ^^^^^^^^^^^^^^^^
  |   File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 118, in run
  |     return self._loop.run_until_complete(task)
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |   File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\asyncio\base_events.py", line 691, in run_until_complete
  |     return future.result()
  |            ^^^^^^^^^^^^^^^
  |   File "C:\project\python\work\mcp\mcp-client\main.py", line 31, in test_connect_to_server
  |     async with ClientSessionGroup() as clinet_session_group:
  |                ^^^^^^^^^^^^^^^^^^^^
  |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\mcp\client\session_group.py", line 149, in __aexit__
  |     async with anyio.create_task_group() as tg:
  |                ^^^^^^^^^^^^^^^^^^^^^^^^^
  |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\anyio\_backends\_asyncio.py", line 772, in __aexit__
  |     raise BaseExceptionGroup(
  | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
    | Exception Group Traceback (most recent call last):
    |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\anyio\_backends\_asyncio.py", line 772, in __aexit__
    |     raise BaseExceptionGroup(
    | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
    +-+---------------- 1 ----------------
      | Traceback (most recent call last):
      |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\mcp\client\sse.py", line 154, in sse_client
      |     yield read_stream, write_stream
      |   File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 737, in __aexit__
      |     cb_suppress = await cb(*exc_details)
      |                   ^^^^^^^^^^^^^^^^^^^^^^
      |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\mcp\shared\session.py", line 220, in __aexit__
      |     return await self._task_group.__aexit__(exc_type, exc_val, exc_tb)
      |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\anyio\_backends\_asyncio.py", line 783, in __aexit__
      |     return self.cancel_scope.__exit__(exc_type, exc_val, exc_tb)
      |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\anyio\_backends\_asyncio.py", line 457, in __exit__
      |     raise RuntimeError(
      | RuntimeError: Attempted to exit cancel scope in a different task than it was entered in
      +------------------------------------
    | 
    | During handling of the above exception, another exception occurred:
    | 
    | Traceback (most recent call last):
    |   File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 696, in aclose
    |     await self.__aexit__(None, None, None)
    |   File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 754, in __aexit__
    |     raise exc_details[1]
    |   File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 737, in __aexit__
    |     cb_suppress = await cb(*exc_details)
    |                   ^^^^^^^^^^^^^^^^^^^^^^
    |   File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 231, in __aexit__
    |     await self.gen.athrow(value)
    |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\mcp\client\sse.py", line 53, in sse_client
    |     async with anyio.create_task_group() as tg:
    |                ^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\anyio\_backends\_asyncio.py", line 778, in __aexit__
    |     if self.cancel_scope.__exit__(type(exc), exc, exc.__traceback__):
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |   File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\anyio\_backends\_asyncio.py", line 457, in __exit__
    |     raise RuntimeError(
    | RuntimeError: Attempted to exit cancel scope in a different task than it was entered in
    +------------------------------------

进程已结束，退出代码为 1

·
Only one server is OK

code

async def test_connect_to_server():
    async with ClientSessionGroup() as clinet_session_group:
        for server in ["stream_law"]:
            server_param = server_config_group.get_server_param(server)
            print(f"connect to server: {server_param}")
            print("----------------------------------------")
            await clinet_session_group.connect_to_server(server_param)

        await asyncio.sleep(3)
        print("*****************list tools********************")

        for name, tool in clinet_session_group.tools.items():
            print(f"tool_name: {name}")
            print("----------------------------------------")

        await asyncio.sleep(3)
        print("*****************disconnect********************")

        for session in clinet_session_group.sessions:
            print(f"disconnect session: {session}")
            await clinet_session_group.disconnect_from_server(session)
            await asyncio.sleep(2)

logs

connect to server: url='http://x.x.x.x:8080/mcp' headers={} timeout=datetime.timedelta(seconds=30) sse_read_timeout=datetime.timedelta(seconds=300) terminate_on_close=True
----------------------------------------
*****************list tools********************
tool_name: search_ft
----------------------------------------
tool_name: search_fg
----------------------------------------
tool_name: search_law_xl
----------------------------------------
*****************disconnect********************
disconnect session: <mcp.client.session.ClientSession object at 0x000001F6ABF8E180>

进程已结束，退出代码为 0

[mkeid]

Merged a fix with #787

It should be part of the next release. Let me know if it works.

[gaojun1212]

Merged a fix with #787

It should be part of the next release. Let me know if it works.

It worked, when i use it like this below, but another problem occurred, when using the disconnect_from_server method

async def test_connect_to_server():
    async with ClientSessionGroup() as clinet_session_group:
        for server in ["stream_law", "stream_case"]:
            server_param = server_config_group.get_server_param(server)
            print(f"connect to server: {server_param}")
            print("----------------------------------------")
            session = await clinet_session_group.connect_to_server(server_param)

        await asyncio.sleep(3)
        print("*****************list tools********************")
        for name, tool in clinet_session_group.tools.items():
            print(f"tool_name: {name}")

logs

connect to server: url='http://x.x.x.x:9090/server/hyyd_law/mcp' timeout=datetime.timedelta(seconds=30) sse_read_timeout=datetime.timedelta(seconds=300) terminate_on_close=True
----------------------------------------
connect to server: url='http://x.x.x.x:9090/server/hyyd_case/mcp' timeout=datetime.timedelta(seconds=30) sse_read_timeout=datetime.timedelta(seconds=300) terminate_on_close=True
----------------------------------------
*****************list tools********************
tool_name: search_ft
tool_name: search_fg
tool_name: search_law_xl
tool_name: search_ptal
tool_name: search_qwal
tool_name: search_case_xl

another problem occurred, when using the disconnect_from_server method

code

async def test_disconnect_to_server():
    async with ClientSessionGroup() as clinet_session_group:
        sessions: list[ClientSession] = []
        for server in ["stream_law", "stream_case"]:
            server_param = server_config_group.get_server_param(server)
            print(f"connect to server: {server_param}")
            print("----------------------------------------")
            session = await clinet_session_group.connect_to_server(server_param)
            sessions.append(session)

        await asyncio.sleep(3)

        print(f"disconnect session: {sessions[0]}")
        await clinet_session_group.disconnect_from_server(sessions[0])

        await asyncio.sleep(5)

logs

connect to server: url='http://x.x.x.x:9090/server/hyyd_law/mcp' timeout=datetime.timedelta(seconds=30) sse_read_timeout=datetime.timedelta(seconds=300) terminate_on_close=True
----------------------------------------
connect to server: url='http://x.x.x.x:9090/server/hyyd_case/mcp'  timeout=datetime.timedelta(seconds=30) sse_read_timeout=datetime.timedelta(seconds=300) terminate_on_close=True
----------------------------------------
disconnect session: <mcp.client.session.ClientSession object at 0x000001B4A587E4B0>
Traceback (most recent call last):
  File "C:\project\python\work\mcp\mcp-client\main.py", line 112, in <module>
    asyncio.run(test_disconnect_to_server())
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 195, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\asyncio\runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\asyncio\base_events.py", line 691, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\main.py", line 47, in test_disconnect_to_server
    async with ClientSessionGroup() as clinet_session_group:
               ^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\mcp\client\session_group.py", line 150, in __aexit__
    await self._exit_stack.aclose()
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 696, in aclose
    await self.__aexit__(None, None, None)
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 754, in __aexit__
    raise exc_details[1]
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 737, in __aexit__
    cb_suppress = await cb(*exc_details)
                  ^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 754, in __aexit__
    raise exc_details[1]
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 737, in __aexit__
    cb_suppress = await cb(*exc_details)
                  ^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\contextlib.py", line 217, in __aexit__
    await anext(self.gen)
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\mcp\client\streamable_http.py", line 464, in streamablehttp_client
    async with anyio.create_task_group() as tg:
               ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\anyio\_backends\_asyncio.py", line 776, in __aexit__
    raise exc_val
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\mcp\client\streamable_http.py", line 499, in streamablehttp_client
    await transport.terminate_session(client)
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\mcp\client\streamable_http.py", line 412, in terminate_session
    response = await client.delete(self.url, headers=headers)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpx\_client.py", line 1966, in delete
    return await self.request(
           ^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpx\_client.py", line 1540, in request
    return await self.send(request, auth=auth, follow_redirects=follow_redirects)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpx\_client.py", line 1629, in send
    response = await self._send_handling_auth(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpx\_client.py", line 1657, in _send_handling_auth
    response = await self._send_handling_redirects(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpx\_client.py", line 1694, in _send_handling_redirects
    response = await self._send_single_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpx\_client.py", line 1730, in _send_single_request
    response = await transport.handle_async_request(request)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpx\_transports\default.py", line 394, in handle_async_request
    resp = await self._pool.handle_async_request(req)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpcore\_async\connection_pool.py", line 256, in handle_async_request
    raise exc from None
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpcore\_async\connection_pool.py", line 236, in handle_async_request
    response = await connection.handle_async_request(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpcore\_async\http_proxy.py", line 206, in handle_async_request
    return await self._connection.handle_async_request(proxy_request)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpcore\_async\connection.py", line 101, in handle_async_request
    raise exc
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpcore\_async\connection.py", line 76, in handle_async_request
    async with self._request_lock:
               ^^^^^^^^^^^^^^^^^^
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\httpcore\_synchronization.py", line 77, in __aenter__
    await self._anyio_lock.acquire()
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\anyio\_backends\_asyncio.py", line 1792, in acquire
    await AsyncIOBackend.checkpoint_if_cancelled()
  File "C:\project\python\work\mcp\mcp-client\.venv\Lib\site-packages\anyio\_backends\_asyncio.py", line 2341, in checkpoint_if_cancelled
    await sleep(0)
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\asyncio\tasks.py", line 656, in sleep
    await __sleep0()
  File "C:\Users\gaojun\AppData\Local\Programs\Python\Python312\Lib\asyncio\tasks.py", line 650, in __sleep0
    yield
asyncio.exceptions.CancelledError: Cancelled by cancel scope 1b4a59471d0

[xtang2010]

Have same problem, found somehow the disconnect order is important. Ie:

async with ClientSessionGroup() as group:
    session1 = await group.connect_to_server(server_params_list["filesystem"])
    session2 = await group.connect_to_server(server_params_list["excel"])

    await group.disconnect_from_server(session2)
    await group.disconnect_from_server(session1)

This works fine, but if change the disconnect order, ie:

    ....
    await group.disconnect_from_server(session1)
    await group.disconnect_from_server(session2)

This will cause the problem.

Hope this info helps.

-xtang

[gaojun1212]

Have same problem, found somehow the disconnect order is important. Ie:

async with ClientSessionGroup() as group:
    session1 = await group.connect_to_server(server_params_list["filesystem"])
    session2 = await group.connect_to_server(server_params_list["excel"])

    await group.disconnect_from_server(session2)
    await group.disconnect_from_server(session1)

This works fine, but if change the disconnect order, ie:

    ....
    await group.disconnect_from_server(session1)
    await group.disconnect_from_server(session2)

This will cause the problem.

Hope this info helps.

-xtang

thanks for your suggest
I just tested your suggestion and it works

[xtang2010]

Some further debug showed this related to how BaseSession is using anyio.create_task_group(). I don't think it has anything to do with ClientSessionGroup, thus I created issue#922

[mkeid]

Thanks for the find @xtang2010 - can you close this out, @gaojun1212 ?