Await dont work in BackgroundTaks (Fastapi, Beanie, MongoDB)

[leaguidi]

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Example Code

from beanie import PydanticObjectId, Document
from fastapi import FastAPI, APIRouter, Request, BackgroundTasks
from time import time
from pydantic import BaseModel
from typing import Optional

app = FastAPI()
#router = APIRouter(prefix="/audit",tags=['Audit'])

class Audit(Document):
    account: Optional[str]
    company: Optional[str]
    user: Optional[str]
    module: str
    endpoint: str
    url_params: Optional[str]
    body_params: Optional[dict]
    reference_id: Optional[str]
    previous_state: Optional[bytes]
    posterior_state: Optional[bytes]
    date: int = time()

    class Settings:
        name = "audit"

async def review_audits() -> List[Audit]:
       audits = await Audit.find().limit(4).sort([("date", -1),]).to_list()
       print(audits)

@app.get("/query/", response_description="get audits to the database")
async def get_filter_audits(request: Request, background_tasks: BackgroundTasks) -> List[Audit]:
        desc = "We are working on it, you will be notified"
        reviews = {"hash":"12345678"}
        
        background_tasks.add_task(review_audits)
        
        return reviews

Description

when you call de endpoint return the result {"hash":"12345678"} but the background task dont print the result founded on mongodb.
I realized that the error occurs with version 0.85.0 but it works fine with version 0.78.0

Operating System

macOS

Operating System Details

No response

FastAPI Version

0.85.0

Python Version

3.10.9

Additional Context

No response

[iudeen]

You are not calling any function inside background Task.

@app.post("/send-notification/{email}")
async def send_notification(email: str, background_tasks: BackgroundTasks):
    background_tasks.add_task(write_notification, email, message="some notification")
    return {"message": "Notification sent in the background"}

[JarroVGIT]

background_tasks.add_task() doesn’t add any task.

[leaguidi]

Sorry i forgot, insiste o calling the function upside filter_audits El El vie, 16 de sep. de 2022 a la(s) 14:39, Jarro van Ginkel < ***@***.***> escribió:

background_tasks.add_task() doesn’t add any task. — Reply to this email directly, view it on GitHub <#5403 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHFJEFNS5FQTBWSZ2JGOQH3V6SWGDANCNFSM6AAAAAAQOQK35E> . You are receiving this because you authored the thread.Message ID: ***@***.***>

-- Lea Guidi.

[leaguidi]

the code is correct now, sorry for my English.

[JarroVGIT]

I cannot reproduce this using the following example:

import asyncio
from fastapi import BackgroundTasks, FastAPI

app = FastAPI()


async def get_items_from_db():
    print("Get some items from DB..")
    await asyncio.sleep(1)
    return [1, 2, 3, 4]


async def background_task_function():
    print("Background task is executing..")
    result = await get_items_from_db()
    print(f"Items collected: {result}")


@app.get("/")
async def root(bt: BackgroundTasks):
    print("Endpoint is called, now adding BG task..")
    bt.add_task(background_task_function)
    print("BG task added, returning response..")
    return {"hello": "world"}


if __name__ == "__main__":
    import uvicorn

    uvicorn.run(app, host="0.0.0.0", port=8000)

The above example will print correctly when calling localhost:8000:

INFO:     Started server process [14322]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://0.0.0.0:8000 (Press CTRL+C to quit)
Endpoint is called, now adding BG task..
BG task added, returning response..
INFO:     127.0.0.1:55946 - "GET / HTTP/1.1" 200 OK
Background task is executing..
Get some items from DB..
Items collected: [1, 2, 3, 4]

The issue might be the actual call to Audit. Try the following:

• Print something before you call Audit.find(), to assert that the background task is actually executing.
• Try to ensure that the Audit.find() actually returns something.

But to answer your issue title: you can certainly use await in a background task, and it should work. My money would be on the Audit.find() doesn't return anything.

[leaguidi]

could be possible, really i don't try to use another thing with await, the problem are in that line (Audit.find()) but, when i use another version of fastapi (0.78.0) works fine, the problem is finding in a mongodb database with beanie and fastapi version 0.85.0. El sáb, 17 sept 2022 a la(s) 12:29, Jarro van Ginkel ( ***@***.***) escribió:

…

I cannot reproduce this using the following example: import asynciofrom fastapi import BackgroundTasks, FastAPI app = FastAPI() async def get_items_from_db(): print("Get some items from DB..") await asyncio.sleep(1) return [1, 2, 3, 4] async def background_task_function(): print("Background task is executing..") result = await get_items_from_db() print(f"Items collected: {result}") @app.get("/")async def root(bt: BackgroundTasks): print("Endpoint is called, now adding BG task..") bt.add_task(background_task_function) print("BG task added, returning response..") return {"hello": "world"} if __name__ == "__main__": import uvicorn uvicorn.run(app, host="0.0.0.0", port=8000) The issue might be the actual call to Audit. Try the following: - Print something before you call Audit.find(), to assert that the background task is actually executing. - Try to ensure that the Audit.find() actually returns something. But to answer your issue title: you can certainly use await in a background task, and it should work. My money would be on the Audit.find() doesn't return anything. — Reply to this email directly, view it on GitHub <#5403 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHFJEFK2LBPMYN25ROEUHLTV6XPVLANCNFSM6AAAAAAQOQK35E> . You are receiving this because you modified the open/close state.Message ID: ***@***.***>

[leaguidi]

I am using versión 0.85.0 no 0.58, i write that tris error no occurs no versión 0.78.0 El El sáb, 17 de sep. de 2022 a la(s) 18:49, Irfanuddin Shafi Ahmed < ***@***.***> escribió:

0.58 is very old. Please update FastAPI :/ — Reply to this email directly, view it on GitHub <#5403 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AHFJEFPFHKQDMSZLN2XN5FLV6Y4IFANCNFSM6AAAAAAQOQK35E> . You are receiving this because you modified the open/close state.Message ID: ***@***.***>

-- Lea Guidi.

[Kludex]

the code is correct now, sorry for my English.

There are people on our discord server that can help you in Spanish: https://fastapi.tiangolo.com/help-fastapi/?h=discord#join-the-chat.

[vanishingESCkey]

@leaguidi if you use BaseHTTPMiddleware in your project then it may affect your BackgroundTasks, take a look at issues mentioned in encode/starlette#1715 (comment)

[thomasleveil]

@leaguidi @vanishingESCkey a fix for encode/starlette#1715 (comment) has been released in https://github.com/encode/starlette/releases/tag/0.21.0

Watch PR #5471