[need help]: gunicorn+fastapi+beanie raise RuntimeError

[hd10180]

i use fastapi + beanie, everything works perfect when running with uvicorn,
it raise RuntimeError(maybe cause by asyncio?) when using gunicorn to get more worker

i use uvicorn web_boost:app --host 127.0.0.1 --port 3344 --reload on dev env,
use gunicorn web_boost:app --workers 4 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:3344 when error raise

i use fastapi lifespan method to init model, here is my code:

@app.on_event("startup")
async def boost_beanie():
    from app.core.session import fetch_db

    _db = fetch_db()
    app.state.db = _db
    from app.models.entity import __beanie_models__

    await init_beanie(database=_db, document_models=__beanie_models__)

the error logs here:

ERROR    2022-04-24 11:15:28.052 - uvicorn.lifespan.on:send - Traceback (most recent call last):
  File "/home/zeara/miniconda3/envs/lunar/lib/python3.8/site-packages/starlette/routing.py", line 621, in lifespan
    async with self.lifespan_context(app):
  File "/home/zeara/miniconda3/envs/lunar/lib/python3.8/site-packages/starlette/routing.py", line 518, in __aenter__
    await self._router.startup()
  File "/home/zeara/miniconda3/envs/lunar/lib/python3.8/site-packages/starlette/routing.py", line 598, in startup
    await handler()
  File "/home/zeara/proj/platform/app/core/boost.py", line 85, in boost_beanie
    await init_beanie(database=_db, document_models=__beanie_models__)
  File "/home/zeara/miniconda3/envs/lunar/lib/python3.8/site-packages/beanie/odm/utils/general.py", line 76, in init_beanie
    await asyncio.gather(*collection_inits)
  File "/home/zeara/miniconda3/envs/lunar/lib/python3.8/site-packages/beanie/odm/documents.py", line 1126, in init_model
    await cls.init_settings(
  File "/home/zeara/miniconda3/envs/lunar/lib/python3.8/site-packages/beanie/odm/documents.py", line 1093, in init_settings
    cls._document_settings = await DocumentSettings.init(
  File "/home/zeara/miniconda3/envs/lunar/lib/python3.8/site-packages/beanie/odm/settings/general.py", line 17, in init
    collection_settings = await CollectionSettings.init(
  File "/home/zeara/miniconda3/envs/lunar/lib/python3.8/site-packages/beanie/odm/settings/collection.py", line 71, in init
    build_info = await database.command({"buildInfo": 1})
RuntimeError: Task <Task pending name='Task-3' coro=<Document.init_model() running at /home/zeara/miniconda3/envs/lunar/lib/python3.8/site-packages/beanie/odm/documents.py:1126> cb=[gather.<locals>._done_callback() at /home/zeara/miniconda3/envs/lunar/lib/python3.8/asyncio/tasks.py:769]> got Future <Future pending cb=[_chain_future.<locals>._call_check_cancel() at /home/zeara/miniconda3/envs/lunar/lib/python3.8/asyncio/futures.py:360]> attached to a different loop

ERROR    2022-04-24 11:15:28.052 - uvicorn.lifespan.on:startup - Application startup failed. Exiting.
[2022-04-24 11:15:28 +0800] [15190] [INFO] Worker exiting (pid: 15190)
[2022-04-24 11:15:28 +0800] [15185] [WARNING] Worker with pid 15189 was terminated due to signal 15
[2022-04-24 11:15:28 +0800] [15185] [WARNING] Worker with pid 15187 was terminated due to signal 15
[2022-04-24 11:15:28 +0800] [15185] [WARNING] Worker with pid 15190 was terminated due to signal 15

[hd10180]

problem solved!
i find this issue tiangolo/fastapi#3855 (comment) work for me.

# my case, in session.py
db: AsyncIOMotorClient = MotorMongo.make_conn(MongoConfig(**MONGODB_CONFIG))
db.get_io_loop = asyncio.get_event_loop

def fetch_db() -> AsyncIOMotorDatabase:
    return db[MONGODB_CONFIG["authSource"]]

# init beanie
@app.on_event("startup")
async def boost_beanie():
    from app.core.session import fetch_db

    _db = fetch_db()
    app.state.db = _db
    from app.models.entity import __beanie_models__

    await init_beanie(database=_db, document_models=__beanie_models__)