Migration from FastAPI: Repeated Tasks function in litestar ?

[wifff]

Hi,
I am trying to migrate an app from FastAPI to litestar.
Is there a aquivalent of the @repeat_every(...) function ?

From the FastAPI docs:
..."When a function decorated with the @repeat_every(...) decorator is called, a loop is started, and the function is called periodically with a delay determined by the seconds argument provided to the decorator."...

Many thanks for your help
Wolfgang

[JacobCoffee]

Hi 👋🏽

There isn't a facility to do this natively, but our projects have had great success with SAQ

It is very lightweight and can do this OOTB.

example repo:
https://github.com/litestar-org/litestar-fullstack

[JacobCoffee]

Also, in searching around to make sure I still had the most up-to-date answers, I found this old Discord thread that confirms this is true for now:

https://discord.com/channels/919193495116337154/1077179278422196234

[JacobCoffee]

Loveless - OP
 — 02/20/2023 4:45 AM
In FastAPI there's a Utils package, that can be used to implement a @repeat_every decorator.
I was wondering if there's something like that for Starlite, or if there's a workaround to get something like it to work in Starlite as I'm trying to run something every hour or so.

provinzkraut — 02/20/2023 4:48 AM
There's no such functionality in Starlite but you can take a look at this project: https://github.com/topsport-com-au/starlite-saqlalchemy
GitHub
[GitHub - topsport-com-au/starlite-saqlalchemy: Starlite API boilerp...](https://github.com/topsport-com-au/starlite-saqlalchemy)
Starlite API boilerplate abstraction and utilities. - GitHub - topsport-com-au/starlite-saqlalchemy: Starlite API boilerplate abstraction and utilities.
GitHub - topsport-com-au/starlite-saqlalchemy: Starlite API boilerp...
It integrates saq (https://github.com/tobymao/saq) with starlite, which supports cron type jobs 
GitHub
[GitHub - tobymao/saq: Simple Async Queues](https://github.com/tobymao/saq)
Simple Async Queues. Contribute to tobymao/saq development by creating an account on GitHub.
GitHub - tobymao/saq: Simple Async Queues

Loveless
OP

 — 02/20/2023 4:50 AM
Looks promising, thank you for the suggestion.

Goldziher — 02/20/2023 8:41 AM
We can easily add this
Since we now have signals

provinzkraut — 02/20/2023 9:41 AM
Not that easy actually, at least not if we want to maintain compatibility with trio
Scheduled tasks require some sort of long running background task, which trio simply does not support out of principle
And the alternative trio wants you to use don't work in the context of an ASGI application
It's been a pain point and commonly raised issue with trio for a while now
(Actually this originated in curio, but that's no longer relevant really)
So the only solution would be spawning an actual subprocess / thread if we want to keep using trio
But we need to tackle this problem anyway if we want to allow inter-process signals
Since the common async message queues also require active polling / listening
I was thinking about dropping explicit trio support maybe? It's not that widely used and maybe we could support it in a "best effort" way? I.e. try to use patterns that will work in both asyncio / trio (mostly solved by anyio), but don't try to bend over backwards if something is really hard to do in trio and just mention that it's an asyncio-only feature

provinzkraut — 02/20/2023 9:58 AM
Here's a (somewhat) related discussion on their GitHub: https://github.com/python-trio/trio/issues/467
And this: https://github.com/python-trio/trio/issues/1141
https://stackoverflow.com/questions/48282841/in-trio-how-can-i-have-a-background-task-that-lives-as-long-as-my-object-does

provinzkraut — 02/20/2023 9:59 AM
This answer is by one of the trio maintainers

Goldziher — 02/20/2023 10:44 AM
Sure
Or we can state that using trio x, y and z are unavailable
Leave it to users to decide how to handle

provinzkraut — 02/20/2023 11:11 AM
Yah, that's what I was thinking