Fastapi/Tortoise early model init

I have the following implementation with fastapi.

My current problem is that I can’t for the life of me do an early init on the tortoise models to get the relationship back in the schema.

I’ve tried dumping the following line basically everywhere and it just doesn’t seem to work.

Tortoise.init_models(["models.user", "models.group"], "models")

i’ve also tried using prefetch_related this way but that doesn’t work either

GetGroup.from_queryset(Group.get(id=3).prefetch_related('owner'))

I’ve been googling around for hours and haven’t found a concrete answer/way to get this to properly work.

Folder structure:

app
│   main.py
└───database
│   │   database.py
└───models
|    │   user.py
|    │   group.py
└───routers
|   │   user_router.py
|   │   group_router.py
└───services
|   │   auth.py

main.py

from fastapi import FastAPI
from database.database import init_db
from routers.user_router import router as UserRouter
from routers.group_router import router as GroupRouter

# Instantiate the Application
app = FastAPI(title="test", root_path="/api/")

# Include the Routers
app.include_router(UserRouter, tags=["User"], prefix="/user")
app.include_router(GroupRouter, tags=["Group"], prefix="/group")


# Start DB Connection on Startup
@app.on_event("startup")
async def startup_event():
    init_db(app)

database/database.py

from decouple import config
from fastapi import FastAPI
from tortoise import Tortoise
from tortoise.contrib.fastapi import register_tortoise


def init_db(app: FastAPI) -> None:
    Tortoise.init_models(["models.user", "models.group"], "models")
    register_tortoise(
        app,
        db_url=f"mysql://{config('MYSQL_USER')}:{config('MYSQL_PASSWORD')}@{config('MYSQL_HOST')}:{config('MYSQL_EXPOSE')}/{config('MYSQL_DB')}",
        modules={"models": ["models.user",
                            "models.group",
                            ]},
        generate_schemas=False,
        add_exception_handlers=True,
    )


TORTOISE_ORM = {
    "connections": {"default": f"mysql://{config('MYSQL_USER')}:{config('MYSQL_PASSWORD')}@{config('MYSQL_HOST')}:{config('MYSQL_EXPOSE')}/{config('MYSQL_DB')}"},
    "apps": {
        "models": {
            "models": ["models.user",
                       "models.group",
                       "aerich.models"],
            "default_connection": "default",
        },
    },
}

models/user.py

from tortoise import fields
from tortoise.models import Model
from tortoise.contrib.pydantic import pydantic_model_creator
from models.group import Group


class User(Model):
    # ##### Define Readonly Fields ##### #
    id = fields.BigIntField(pk=True)
    # ##### Define Normal Fields ##### #
    first_name = fields.CharField(max_length=50)
    last_name = fields.CharField(max_length=50)
    username = fields.CharField(max_length=50, unique=True)
    email = fields.CharField(max_length=50, unique=True)
    password = fields.CharField(max_length=128)
    # ##### Define O2M ##### #
    owned_groups: fields.ReverseRelation[Group]
    # ##### Define M2M ##### #
    groups: fields.ManyToManyRelation[Group]
    # ##### Define Time_Stamps ###### #
    created_at = fields.DatetimeField(auto_now_add=True)
    modified_at = fields.DatetimeField(auto_now=True)

    class Meta:
        table: str = 'users'


AuthData = pydantic_model_creator(User)
CreateUser = pydantic_model_creator(User, name="CreateUser", exclude_readonly=True)
UpdateUser = pydantic_model_creator(User, name="UpdateUser", exclude_readonly=True, exclude=['password'])
GetUser = pydantic_model_creator(User, name="GetUser", exclude=['password'])
ChangeUserPassword = pydantic_model_creator(User, name="ChangeUserPassword", exclude_readonly=True, include=['password'])

models/group.py

from tortoise import fields
from tortoise.models import Model
from tortoise.contrib.pydantic import pydantic_model_creator


class Group(Model):
    # ##### Define Readonly Fields ##### #
    id = fields.BigIntField(pk=True)
    # ##### Define Normal Fields ##### #
    name = fields.CharField(max_length=50, unique=True)
    # ##### Define O2M ##### #
    owner = fields.ForeignKeyField("models.User", related_name="owned_groups")
    # ##### Define M2M ##### #
    members = fields.ManyToManyField("models.User", related_name="groups")
    # ##### Define Time_Stamps ###### #
    created_at = fields.DatetimeField(auto_now_add=True)
    modified_at = fields.DatetimeField(auto_now=True)

    class Meta:
        table: str = 'groups'


CreateGroup = pydantic_model_creator(Group, name="CreateGroup", exclude_readonly=True, exclude=['members'])
UpdateGroup = pydantic_model_creator(Group, name="UpdateGroup", exclude_readonly=True, exclude=['members'])
GetGroup = pydantic_model_creator(Group, name="GetGroup")

routers/group_router.py

from typing import List
import json
from fastapi import HTTPException, APIRouter, Depends, status
from models.user import User
from models.group import Group, CreateGroup, UpdateGroup, GetGroup
from tortoise.contrib.fastapi import HTTPNotFoundError
from services.auth import current_user

# Intialize Router
router = APIRouter()


# ###################### Define Routes ###################### #

# Create A Group
@router.post("/", dependencies=[Depends(current_user)])
async def create_group(group: CreateGroup, user: User = Depends(current_user)):
    user = await user
    try:
        await Group.create(**group.dict(exclude_unset=True), owner_id=user.id)
    except Exception:
        raise HTTPException(
            status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
            detail="Group Name Already Exists"
        )
    return {"Group Created Successfully"}


# Update A Group
@router.put("/{group_id}", dependencies=[Depends(current_user)], responses={404: {"model": HTTPNotFoundError}})
async def update_group(group_id: int, group: UpdateGroup, user: User = Depends(current_user)):
    user = await user
    group = await GetGroup.from_queryset_single(Group.get(id=group_id))
    return group
    if user.id == group.id:
        await Group.filter(id=group_id).update(**group.dict(exclude_unset=True))
        return {"Group Successfully Updated"}
    else:
        raise HTTPException(
            status_code=status.HTTP_406_NOT_ACCEPTABLE,
            detail="You can't edit a group unless you're the owner"
        )


# Get All Groups
@router.get("/", dependencies=[Depends(current_user)])
async def get_groups():
    return GetGroup.schema()

As you can see that last line GetGroup.schema(), never returns the relationship.

I tried capturing the logs while the container is starting and got the following

[2021-04-24 19:59:53 +0000] [1255] [INFO] Started server process [1255]
[2021-04-24 19:59:53 +0000] [1255] [INFO] Waiting for application startup.
[2021-04-24 19:59:53 +0000] [1255] [ERROR] Traceback (most recent call last):
File "/usr/local/lib/python3.8/site-packages/tortoise/__init__.py", line 358, in _discover_models
module = importlib.import_module(models_path)
File "/usr/local/lib/python3.8/importlib/__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
File "<frozen importlib._bootstrap>", line 991, in _find_and_load
File "<frozen importlib._bootstrap>", line 973, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'a'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/usr/local/lib/python3.8/site-packages/starlette/routing.py", line 526, in lifespan
async for item in self.lifespan_context(app):
File "/usr/local/lib/python3.8/site-packages/starlette/routing.py", line 467, in default_lifespan
await self.startup()
File "/usr/local/lib/python3.8/site-packages/starlette/routing.py", line 502, in startup
await handler()
File "/app/main.py", line 17, in startup_event
init_db(app)
File "/app/database/database.py", line 8, in init_db
Tortoise.init_models("app.models.user", "models")
File "/usr/local/lib/python3.8/site-packages/tortoise/__init__.py", line 415, in init_models
app_models += cls._discover_models(models_path, app_label)
File "/usr/local/lib/python3.8/site-packages/tortoise/__init__.py", line 360, in _discover_models
raise ConfigurationError(f'Module "{models_path}" not found')
tortoise.exceptions.ConfigurationError: Module "a" not found
[2021-04-24 19:59:53 +0000] [1255] [ERROR] Application startup failed. Exiting.

mind you it does that for a few seconds and then the application starts correctly, i’ve also tried separating the pydantic models creation in a separate folder called ‘schema’ and that didn’t do anything either

Answer

so i’ve finally found an answer and i’m gonna leave it here in case some poor soul stumbles upon this question

the trick was to move

from database.database import init_db

to the top of the main.py file

and add

Tortoise.init_models(["models.user", "models.group"], "models")

below the init_db() function so that it’s called upon before the register_tortoise function executes and all the models are initialized

Info source: https://stackoverflow.com/a/65881146/13637905