Sync style code with non-blocking I/O? about django-ninja HOT 7 CLOSED

Hi @Adamantish

I'm not really expert on gunicorn and do not know how it patches django, but in general if you use regular sync operations from django-ninja nothing is really different from regular django views, so I guess my answer is yes - nothing to worry about.

My usual approach is to write all in sync mode, and once some operation is getting high concurrency and does some IO - then it a good candidate to switch it to async mode.

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Thanks @vitalik, I had I look around to try to understand why this is the case and I think this question on FastApi was essentially the same as mine but more clearly formed and aso answered itself.

When you don't define a view as async in FastAPI it will be sent to run in a pool of OS threads, much like gunicorn in threaded mode. I took a little look and once I got to here in ninja it seems like confirmation that this doesn't do something similar. i.e. is it true that views not declared with async will block the process while waiting on I/O? Because that would be very different to normal django use.

from django-ninja.

is it true that views not declared with async will block the process while waiting on I/O?

Not really

if you define our ninja "view" as async - the AsyncOperation will be used.

Both are just wrappers for regular django views which internally follow this logic

• in async mode all async views are using event loop
• sync views will be executed in threads

Generally django-ninja is just a wrapper around django views, it does not bring any threading/event-loop features on top

read more about django async support here:

https://docs.djangoproject.com/en/3.1/topics/async/#async-views

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Ah so sync views will be done in threads? The reason I ask is that with standard Django the app is single threaded and it's the web server such as gunicorn that's responsible for multithreading / gevent loop. Uvicorn, on the other hand, I couldn't find a threaded feature for which is why FastAPI uses asyncio's ThreadPoolExecutor via run_in_executor.

Is there somewhere in ninja that does similar?

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I kind of repeat my self - but django-ninja is not involved in any sync/async/thread behaviour - it just a validation/openapi wrapper

All the execution logic is described here:

https://docs.djangoproject.com/en/3.1/topics/async/#async-views

I cannot guaranty this 100% - but my guess is that if you run django 3.1+ project under asgi (uvicorn or dafne) - sync views are executed under asgiref.sync_to_async (see https://github.com/django/asgiref/blob/master/asgiref/sync.py )

and it look like the execution is actually happening in threadpool executor

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Ah thank you very much. This makes a lot more sense and seems a sensible separation. Forgive my ignorance, I had the weird assumption that Django didn't have anything built-in to use an ASGI server.

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Hey @Adamantish , how did this work out for you?

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