[jira] [Updated] (TINKERPOP-2755) 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-2755?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Stephen Mallette updated TINKERPOP-2755:
----------------------------------------
    Fix Version/s:     (was: 3.6.0)

> gremlinpython gives error "RuntimeError: Cannot run the event loop while another loop is running".
> --------------------------------------------------------------------------------------------------
>
>                 Key: TINKERPOP-2755
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2755
>             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 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
>  
> ```
> 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
> # python3 \{file_name}
> ```
> 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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