getting task attached to a different loop runtime error when using fastapi with gunicron and motor

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Example Code

# mongo
from motor import motor_asyncio

mongo_uri = "mongodb://mongoUser:***/?authSource=admin"
mongo_client = motor_asyncio.AsyncIOMotorClient(mongo_uri)

def get_users_db() -> motor_asyncio.AsyncIOMotorDatabase:
    return mongo_client.devdb

# user_routes
import fastapi
import mongo
from bson import objectid

db = mongo.get_users_db()
router = fastapi.APIRouter()


@router.get("/{user_id}")
async def get_user_by_id(user_id: str):
    user = await db.users.find_one({"_id": objectid.ObjectId(user_id)})
    if user:
        user["_id"] = str(user["_id"])
        return user
    return {"error": "no user found"}

# main.py
import fastapi
import user_routes

app = fastapi.FastAPI()

app.include_router(user_routes.router)

Description

i am trying to create an app with mongodb client motor and fastapi. I created seperate routes and a seperate file to setup mongodb client. Running this with uvicorn works fine and i get results after querying the database but when i deploy the app with gunicorn and again use the route, i get the following error.

I tried bunch of methods, like assigning a loop to motor client, changing uvworker to use asyncio loop etc. i don’t know where to post this error but here i am

• expected: json of user with given id from database or no user found error
• got: Runtime error

Operating System

Linux

Operating System Details

Debian 11

FastAPI Version

0.68.1

Python Version

Python 3.9.2

Additional Context

motor==2.2.6 gunicorn==20.1

this issue only happens with gunicorn as server and only when accessing mongodb from a fastapi route (i checked running db query in the mongo file and it works)

this my first ever time creating an issue, so please guide me i did something wrong.

[CanD42]

That is the problem: https://github.com/encode/starlette/issues/1315

client = AsyncIOMotorClient()
client.get_io_loop = asyncio.get_event_loop

works for me

[miladvayani]

you should define in start up , like this :

app = FastAPI()
app.add_event_handler("startup", start_app) 


async def start_app():
    await Mongo().get_connection()


from motor.motor_asyncio import AsyncIOMotorClient
from config import CONNECTION_STRING, DB_NAME


class Mongo:
    client = None
    db = None

    async def get_connection(self) -> AsyncIOMotorClient:
        if not Mongo.client:
            Mongo.client = AsyncIOMotorClient(CONNECTION_STRING)

now you can use mongo client every where you want!!!