Baskground task FastAPI

Question

I am attempting to send an email using a FastAPI background task, but the email is not being sent. There are no errors in the console, and the rest of the code is functioning correctly.

endpoint:

@user_router.post("/register", tags=["Auth"])
    async def register(user_data: UserCreate, service: UserService = Depends()):
    return await service.register_user(user_data)

register logic and task:

 async def register_user(self, data: dict) -> dict:
        ...
        result = await self.crud.create_model(self.INSTANCE, user_data)
        task = BackgroundTasks()
        task.add_task(self.email.send_email_verification, data.email)

send_email_verification method:

  async def send_email_verification(self, email: str):
        ...
        message = MessageSchema(
            recipients=[email],
            subject="Your email verification link",
            body=body,
            subtype="html",
        )

        await self.mail.send_message(message)

Thought maybe the issue was with the email function, so I replaced the task with a simple function to print text to the console. Therefore, the problem is likely related to asynchronous handling.

Answer 1

The issues arises from the fact that BackgroundTasks is not a parameter of your path operation function. BackgroundTasks is supposed to work through dependency injection.

Here is how you could adapt your code:

@user_router.post("/register", tags=["Auth"])
async def register(
    user_data: UserCreate,
    background_tasks: BackgroundTasks,
    service: UserService = Depends()
):
    return await service.register_user(user_data, background_tasks)

async def register_user(self, data: dict, background_tasks: BackgroundTasks) -> dict:
    ...
    result = await self.crud.create_model(self.INSTANCE, user_data)
    background_tasks.add_task(self.email.send_email_verification, data.email)