Getting `AssertionError: DatabaseBackend is not running` for Postgres

Describe the bug I used the sample code from README to connect to a sqlite DB and query items and it worked fine (See https://github.com/mei-li/tsougkrizo/blob/persistency/persistence.py). When I switched to a Postgres DB the schema initialisation worked, but when I query the items I get:

  File "./main.py", line 139, in websocket_host
    game = await game_manager.get_game(game_id)
  File "./main.py", line 82, in get_game
    game = await Game.objects.get(uuid=game_id)
  File "/home/olkos/.pyenv/versions/3.8.2/envs/tsougkrizo/lib/python3.8/site-packages/ormar/queryset/queryset.py", line 829, in get
    return await self.filter(*args, **kwargs).get()
  File "/home/olkos/.pyenv/versions/3.8.2/envs/tsougkrizo/lib/python3.8/site-packages/ormar/queryset/queryset.py", line 845, in get
    rows = await self.database.fetch_all(expr)
  File "/home/olkos/.pyenv/versions/3.8.2/envs/tsougkrizo/lib/python3.8/site-packages/databases/core.py", line 139, in fetch_all
    async with self.connection() as connection:
  File "/home/olkos/.pyenv/versions/3.8.2/envs/tsougkrizo/lib/python3.8/site-packages/databases/core.py", line 219, in __aenter__
    await self._connection.acquire()
  File "/home/olkos/.pyenv/versions/3.8.2/envs/tsougkrizo/lib/python3.8/site-packages/databases/backends/postgres.py", line 148, in acquire
    assert self._database._pool is not None, "DatabaseBackend is not running"
AssertionError: DatabaseBackend is not running

To Reproduce Steps to reproduce the behavior:

1. Go to https://github.com/mei-li/tsougkrizo/tree/persistency (only persistence.py and the sample url /demo_ormar_issue in main.py matter)
2. Create and install environment of the project with python 3.8
3. Export an existing postgres DB url eg. export DATABASE_URL=postgresql://dev:test@localhost/egg_db
4. Run python create_db.py # this works and creates the DB schema
5. Run uvicorn main:app --reload
6. Click on http://127.0.0.1:8000/demo_ormar_issue
7. See error

(Note: this should be a complete and concise piece of code that allows reproduction of an issue)

Expected behavior I expect the query to objects in the DB to work without this error

Versions (please complete the following information):

• Database backend used (mysql/sqlite/postgress)
• Python version 3.8.2
• ormar version 0.10.4
• pydantic version 1.8
• if applicable fastapi version 0.54.1

[collerek]

For all backends except sqlite you need to connect the database to use it.

You use fastapi so you should follow example in fastapi section of the ormar documentation. Basically you need to add connect and disconnect to fastapi instance events.

@app.on_event("startup")
async def startup() -> None:
    database_ = app.state.database
    if not database_.is_connected:
        await database_.connect()


@app.on_event("shutdown")
async def shutdown() -> None:
    database_ = app.state.database
    if database_.is_connected:
        await database_.disconnect()

As described in https://github.com/collerek/ormar/blob/master/docs/fastapi.md#database-connection

[ppostnov]

For all backends except sqlite you need to connect the database to use it.

You use fastapi so you should follow example in fastapi section of the ormar documentation. Basically you need to add connect and disconnect to fastapi instance events.

@app.on_event("startup")
async def startup() -> None:
    database_ = app.state.database
    if not database_.is_connected:
        await database_.connect()


@app.on_event("shutdown")
async def shutdown() -> None:
    database_ = app.state.database
    if database_.is_connected:
        await database_.disconnect()

As described in https://github.com/collerek/ormar/blob/master/docs/fastapi.md#database-connection

Thanks a lot !