[jira] [Closed] (TINKERPOP-2759) gremlinpython gives error "RuntimeError: Cannot run the event loop while another loop is running".

["Stephen Mallette (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TINKERPOP-2759?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Stephen Mallette closed TINKERPOP-2759.
---------------------------------------
    Fix Version/s:     (was: 3.6.0)
       Resolution: Duplicate

> gremlinpython gives error "RuntimeError: Cannot run the event loop while another loop is running".
> --------------------------------------------------------------------------------------------------
>
>                 Key: TINKERPOP-2759
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2759
>             Project: TinkerPop
>          Issue Type: Bug
>          Components: python
>    Affects Versions: 3.6.0
>         Environment: I am running the code inside Docker with Python 3.9 on Ubuntu 20.04 with relevant package versions as follows:
> gremlinpython==3.6.0
> uvicorn==0.17.6
> fastapi==0.78.0
>            Reporter: Gavin Aten
>            Priority: Major
>
> Im not sure if this is the correct place to post an issue. If not, I can redirect this elsewhere.
> I am trying to run a fastapi app with uvicorn but am struggling to run a gremlinpython query (run over AWS Neptune DB) inside. It seems like gremlinpython tries to start up a new event loop while one is already running. Is it possible to get gremlinpython to use the current event loop if there is one running?
> The following code snippet works when running with python3 but fails when running with uvicorn: 
>  
> {code:java}
> from gremlin_python.structure.graph import Graph
> from gremlin_python.driver.driver_remote_connection import DriverRemoteConnection
> from fastapi import FastAPI
> def run_query(conn_string, vertex_id):
>     graph = Graph()
>     remoteConn = DriverRemoteConnection(conn_string, 'g')
>     g = graph.traversal().withRemote(remoteConn)
>     details = g.V(vertex_id).valueMap(True).toList()
>     print(details)
>     remoteConn.close()
>     return FastAPI()
> conn_string = '<conn_string>'
> vertex_id = '<vertex_id>'
> app = run_query(conn_string, vertex_id)
> # running with:
> # uvicorn {file_name}:app{code}
>  
>  
> The error when running with uvicorn is as follows:
>  
> {{File "/code/./app/main2.py", line 20, in <module>}}
> {{    app = run_query(conn_string, vertex_id)}}
> {{  File "/code/./app/main2.py", line 11, in run_query}}
> {{    details = g.V(vertex_id).valueMap(True).toList()}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/process/traversal.py", line 62, in toList}}
> {{    return self.to_list()}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/process/traversal.py", line 65, in to_list}}
> {{    return list(iter(self))}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/process/traversal.py", line 48, in {_}{{_}}next{{_}}{_}}}
> {{    self.traversal_strategies.apply_strategies(self)}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/process/traversal.py", line 682, in apply_strategies}}
> {{    traversal_strategy.apply(traversal)}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/driver/remote_connection.py", line 78, in apply}}
> {{    remote_traversal = self.remote_connection.submit(traversal.bytecode)}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/driver/driver_remote_connection.py", line 102, in submit}}
> {{    result_set = self._client.submit(bytecode, request_options=self._extract_request_options(bytecode))}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/driver/client.py", line 148, in submit}}
> {{    return self.submit_async(message, bindings=bindings, request_options=request_options).result()}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/driver/client.py", line 180, in submit_async}}
> {{    return conn.write(message)}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/driver/connection.py", line 55, in write}}
> {{    self.connect()}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/driver/connection.py", line 45, in connect}}
> {{    self._transport.connect(self._url, self._headers)}}
> {{  File "/usr/local/lib/python3.9/dist-packages/gremlin_python/driver/aiohttp/transport.py", line 80, in connect}}
> {{    self._loop.run_until_complete(async_connect())}}
> {{  File "uvloop/loop.pyx", line 1495, in uvloop.loop.Loop.run_until_complete}}
> {{  File "uvloop/loop.pyx", line 1488, in uvloop.loop.Loop.run_until_complete}}
> {{  File "uvloop/loop.pyx", line 1377, in uvloop.loop.Loop.run_forever}}
> {{  File "uvloop/loop.pyx", line 515, in uvloop.loop.Loop._run}}
> {{RuntimeError: Cannot run the event loop while another loop is running}}
>  



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