Any plan to suppprt BackgroundTask from Starlette? about fastapi HOT 14 CLOSED

@madkote if your processing is in an async function (let's say, created with async def process_something(): ...), you can use an async function for your path operation too, and inside of it, use await process_something().

from starlette.concurrency import run_in_threadpool

@app.get("/items"/)
async def read_items():
    result = await process_something("argument 1", keyword_arg2="keyword argument")
    return result

If it's a normal function, you can use run_in_threadpool from Starlette, pass your standard function and await it, something like:

from starlette.concurrency import run_in_threadpool

@app.get("/items"/)
async def read_items():
    result = await run_in_threadpool(process_something, "argument 1", keyword_arg2="keyword argument")
    return result

If that doesn't solve your problem, please create a new issue for it so we can continue the discussion there.

As the original issue should be solved now with the support for BackgroundTasks, I'll close it now. But feel free to add more comments or create new issues.

from fastapi.

Wow - that's a lot more intuitive and will avoid the - "it's not working because you didn't return the JSONResponse()" issue from Starlette - thank you!

from fastapi.

@tiangolo thanks for the reply, I ended up adding more features to my project just to justify celery :D

from fastapi.

from fastapi.

You can already do this since it's built on Starlette - make sure you return JSONResponse() otherwise it won't start the background tasks.

Example:

from starlette.background import BackgroundTasks
from starlette.responses import UJSONResponse, JSONResponse

@router.post("/nanopubs/flushtosearch", tags=["Nanopubs"])
def flushtosearch():
    """
    Flush all nanopubs to search endpoint
    """

    tasks = BackgroundTasks()
    tasks.add_task(services.search.elasticsearch_index_all_nanopubs)

    message = "Reset Index and Flush to search submitted"
    return JSONResponse(message, background=tasks)

from fastapi.

Again, thanks for your help here guys @euri10 and @wshayes !

It is now integrated into FastAPI in a (probably) more intuitive way (in version 0.10.0).

The new docs are here: https://fastapi.tiangolo.com/tutorial/background-tasks/

In short:

from fastapi import BackgroundTasks, FastAPI

app = FastAPI()


def write_notification(email: str, message=""):
    with open("log.txt", mode="w") as email_file:
        content = f"notification for {email}: {message}"
        email_file.write(content)


@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"}

from fastapi.

Awesome! I'm glad to hear you like the design/interface.

from fastapi.

hi all, one similar question:

• let assume I would like to have a background task, which should NOT be executed after the response has been sent. but before?
• e.g. in REST, I receive the first chunk of data (multipart/form-data) and would like to start process it in background (e.g. thread - since it is blocking). After a final chunk, I would to await for the result from the executor and return the response to the client.

Is it possible with fastapi?

from fastapi.

Hi!
Is it possible to use BackgroundTasks before HTTPException?
I have a scenario in which I need to send a email when an exception occurs, but BackgroundTasks doesn't seem to work when a HTTPException is raised

from fastapi.

@outofnames I guess I would use celery in this scenario.

from fastapi.

Doesn't using celery only for sending emails seems overkill?

from fastapi.

@outofnames well, otherwise you would need to extend HttpExceptino to be able to run background tasks, which might be difficult. Maybe, additionally, I would ask at starlette project directly.
If you find a solution, please share - I would very appreciate that!

from fastapi.

@outofnames you can probably also use asyncio.ensure_future(awaitable_send_email()) inside of the exception handler, without needing to plug a background task.

https://docs.python.org/3/library/asyncio-future.html#asyncio.ensure_future

from fastapi.

Assuming the original need was handled, this will be automatically closed now. But feel free to add more comments or create new issues or PRs.

from fastapi.