[Doc]: error in retrieval_augmented_generation_with_langchain.py

[JiaYuanChng]

📚 The doc issue

Hello,

I've encountered an error after running the example of RAG with langchain:

raise MilvusException(
pymilvus.exceptions.MilvusException: <MilvusException: (code=2, message=Fail connecting to server on unix:/tmp/tmpq1f16sdm_milvus.db.sock, illegal connection params or server unavailable)>

Suggest a potential alternative/fix

No response

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[yankay]

@JiaYuanChng

Could you please elaborate on how to reproduce this issue?

Looking at the code, the Milvus URL is set to './milvus.db' in the example (https://github.com/vllm-project/vllm/blob/main/examples/online_serving/retrieval_augmented_generation_with_langchain.py#L156).

Could it be that your environment has Milvus configuration directing the URL to "unix:/tmp/tmp... " ?

[JiaYuanChng]

Hello,

Thanks for looking into this!

I have my Python environment in a container:

Bootstrap:docker
From:vllm/vllm-openai:latest

%post
   chmod 777 /tmp
   apt-get -y update
   apt install -y python3-pip
   python3 -m pip install jupyterlab pandas numpy pydantic tiktoken ipywidgets bitsandbytes pymilvus langchain-milvus langchain-openai langchain-community beautifulsoup4 langchain-text-splitters langchain-qdrant

Using this env, I ran the following on my university's HPC cluster (RHEL ops) with 1 L40s GPU:

from pymilvus import MilvusClient
import pymilvus

print(pymilvus.__version__)
milvus_client = MilvusClient(uri="./milvus.db")

Error:

2.5.11
2025-06-27 12:48:42,741 [ERROR][_create_connection]: Failed to create new connection using: 77ac5b224fc14a928c830166d8aab4dc (milvus_client.py:916)
---------------------------------------------------------------------------
MilvusException                           Traceback (most recent call last)
    [... skipping hidden 1 frame]

Cell In[12], line 1
----> 1 milvus_client = MilvusClient(uri="./milvus.db")

File /usr/local/lib/python3.12/dist-packages/pymilvus/milvus_client/milvus_client.py:64, in MilvusClient.__init__(self, uri, user, password, db_name, token, timeout, **kwargs)
     52 """A client for the common Milvus use case.
     53 
     54 This client attempts to hide away the complexity of using Pymilvus. In a lot ofcases what
   (...)     62         to None.
     63 """
---> 64 self._using = self._create_connection(
     65     uri, user, password, db_name, token, timeout=timeout, **kwargs
     66 )
     67 self.is_self_hosted = bool(utility.get_server_type(using=self._using) == "milvus")

File /usr/local/lib/python3.12/dist-packages/pymilvus/milvus_client/milvus_client.py:917, in MilvusClient._create_connection(self, uri, user, password, db_name, token, **kwargs)
    916     logger.error("Failed to create new connection using: %s", using)
--> 917     raise ex from ex
    918 else:

File /usr/local/lib/python3.12/dist-packages/pymilvus/milvus_client/milvus_client.py:914, in MilvusClient._create_connection(self, uri, user, password, db_name, token, **kwargs)
    913 try:
--> 914     connections.connect(using, user, password, db_name, token, uri=uri, **kwargs)
    915 except Exception as ex:

File /usr/local/lib/python3.12/dist-packages/pymilvus/orm/connections.py:465, in Connections.connect(self, alias, user, password, db_name, token, _async, **kwargs)
    463         kwargs["secure"] = True
--> 465 connect_milvus(**kwargs, user=user, password=password, token=token, db_name=db_name)
    466 return

File /usr/local/lib/python3.12/dist-packages/pymilvus/orm/connections.py:415, in Connections.connect.<locals>.connect_milvus(**kwargs)
    414 if not _async:
--> 415     gh._wait_for_channel_ready(timeout=timeout)
    417     if kwargs.pop("keep_alive", False):

File /usr/local/lib/python3.12/dist-packages/pymilvus/client/grpc_handler.py:159, in GrpcHandler._wait_for_channel_ready(self, timeout)
    158     self.close()
--> 159     raise MilvusException(
    160         code=Status.CONNECT_FAILED,
    161         message=f"Fail connecting to server on {self._address}, illegal connection params or server unavailable",
    162     ) from e
    163 except Exception as e:

MilvusException: <MilvusException: (code=2, message=Fail connecting to server on uni[x:/tmp/tmpstr3183r_milvus.db.sock](file:///X:/tmp/tmpstr3183r_milvus.db.sock), illegal connection params or server unavailable)>

The above exception was the direct cause of the following exception:

MilvusException                           Traceback (most recent call last)
    [... skipping hidden 1 frame]

Cell In[12], line 1
----> 1 milvus_client = MilvusClient(uri="./milvus.db")

File /usr/local/lib/python3.12/dist-packages/pymilvus/milvus_client/milvus_client.py:64, in MilvusClient.__init__(self, uri, user, password, db_name, token, timeout, **kwargs)
     52 """A client for the common Milvus use case.
     53 
     54 This client attempts to hide away the complexity of using Pymilvus. In a lot ofcases what
   (...)     62         to None.
     63 """
---> 64 self._using = self._create_connection(
     65     uri, user, password, db_name, token, timeout=timeout, **kwargs
     66 )
     67 self.is_self_hosted = bool(utility.get_server_type(using=self._using) == "milvus")

File /usr/local/lib/python3.12/dist-packages/pymilvus/milvus_client/milvus_client.py:917, in MilvusClient._create_connection(self, uri, user, password, db_name, token, **kwargs)
    916     logger.error("Failed to create new connection using: %s", using)
--> 917     raise ex from ex
    918 else:

File /usr/local/lib/python3.12/dist-packages/pymilvus/milvus_client/milvus_client.py:914, in MilvusClient._create_connection(self, uri, user, password, db_name, token, **kwargs)
    913 try:
--> 914     connections.connect(using, user, password, db_name, token, uri=uri, **kwargs)
    915 except Exception as ex:

File /usr/local/lib/python3.12/dist-packages/pymilvus/orm/connections.py:465, in Connections.connect(self, alias, user, password, db_name, token, _async, **kwargs)
    463         kwargs["secure"] = True
--> 465 connect_milvus(**kwargs, user=user, password=password, token=token, db_name=db_name)
    466 return

File /usr/local/lib/python3.12/dist-packages/pymilvus/orm/connections.py:415, in Connections.connect.<locals>.connect_milvus(**kwargs)
    414 if not _async:
--> 415     gh._wait_for_channel_ready(timeout=timeout)
    417     if kwargs.pop("keep_alive", False):

File /usr/local/lib/python3.12/dist-packages/pymilvus/client/grpc_handler.py:159, in GrpcHandler._wait_for_channel_ready(self, timeout)
    158     self.close()
--> 159     raise MilvusException(
    160         code=Status.CONNECT_FAILED,
    161         message=f"Fail connecting to server on {self._address}, illegal connection params or server unavailable",
    162     ) from e
    163 except Exception as e:

MilvusException: <MilvusException: (code=2, message=Fail connecting to server on uni[x:/tmp/tmpstr3183r_milvus.db.sock](file:///X:/tmp/tmpstr3183r_milvus.db.sock), illegal connection params or server unavailable)>

The above exception was the direct cause of the following exception:

MilvusException                           Traceback (most recent call last)
Cell In[12], line 1
----> 1 milvus_client = MilvusClient(uri="./milvus.db")

File /usr/local/lib/python3.12/dist-packages/pymilvus/milvus_client/milvus_client.py:64, in MilvusClient.__init__(self, uri, user, password, db_name, token, timeout, **kwargs)
     42 def __init__(
     43     self,
     44     uri: str = "http://localhost:19530/",
   (...)     50     **kwargs,
     51 ) -> None:
     52     """A client for the common Milvus use case.
     53 
     54     This client attempts to hide away the complexity of using Pymilvus. In a lot ofcases what
   (...)     62             to None.
     63     """
---> 64     self._using = self._create_connection(
     65         uri, user, password, db_name, token, timeout=timeout, **kwargs
     66     )
     67     self.is_self_hosted = bool(utility.get_server_type(using=self._using) == "milvus")

File /usr/local/lib/python3.12/dist-packages/pymilvus/milvus_client/milvus_client.py:917, in MilvusClient._create_connection(self, uri, user, password, db_name, token, **kwargs)
    915 except Exception as ex:
    916     logger.error("Failed to create new connection using: %s", using)
--> 917     raise ex from ex
    918 else:
    919     logger.debug("Created new connection using: %s", using)

File /usr/local/lib/python3.12/dist-packages/pymilvus/milvus_client/milvus_client.py:914, in MilvusClient._create_connection(self, uri, user, password, db_name, token, **kwargs)
    912 using = kwargs.pop("alias", None) or uuid4().hex
    913 try:
--> 914     connections.connect(using, user, password, db_name, token, uri=uri, **kwargs)
    915 except Exception as ex:
    916     logger.error("Failed to create new connection using: %s", using)

File /usr/local/lib/python3.12/dist-packages/pymilvus/orm/connections.py:465, in Connections.connect(self, alias, user, password, db_name, token, _async, **kwargs)
    462         if parsed_uri.scheme == "https":
    463             kwargs["secure"] = True
--> 465     connect_milvus(**kwargs, user=user, password=password, token=token, db_name=db_name)
    466     return
    468 # 2nd Priority, connection configs from env

File /usr/local/lib/python3.12/dist-packages/pymilvus/orm/connections.py:415, in Connections.connect.<locals>.connect_milvus(**kwargs)
    412 timeout = t if isinstance(t, (int, float)) else Config.MILVUS_CONN_TIMEOUT
    414 if not _async:
--> 415     gh._wait_for_channel_ready(timeout=timeout)
    417     if kwargs.pop("keep_alive", False):
    418         gh.register_state_change_callback(
    419             ReconnectHandler(self, alias, kwargs_copy).reconnect_on_idle
    420         )

File /usr/local/lib/python3.12/dist-packages/pymilvus/client/grpc_handler.py:159, in GrpcHandler._wait_for_channel_ready(self, timeout)
    157 except grpc.FutureTimeoutError as e:
    158     self.close()
--> 159     raise MilvusException(
    160         code=Status.CONNECT_FAILED,
    161         message=f"Fail connecting to server on {self._address}, illegal connection params or server unavailable",
    162     ) from e
    163 except Exception as e:
    164     self.close()

MilvusException: <MilvusException: (code=2, message=Fail connecting to server on uni[x:/tmp/tmpstr3183r_milvus.db.sock](file:///X:/tmp/tmpstr3183r_milvus.db.sock), illegal connection params or server unavailable)>