Running Django 4.2.16 with Uvicorn

The error you're encountering (SynchronousOnlyOperation) is a common issue when running a traditional synchronous Django application with an ASGI server like Uvicorn. This happens because Uvicorn runs in an asynchronous context, but your Django application is trying to perform synchronous database operations.

Why This Happens

When you run Django with Uvicorn, the application is executed in an asynchronous context. However, Django's ORM operations are synchronous by default, which causes the conflict you're seeing.

Solutions

There are a few approaches to fix this issue:

1. Use Django's sync_to_async Utility

You can wrap your synchronous views with Django's sync_to_async decorator to make them compatible with the asynchronous context:

PYTHONCopied
from asgiref.sync import sync_to_async
from django.http import HttpResponse

@sync_to_async
def my_view(request):
    # Your synchronous code here
    return HttpResponse("Hello World")

2. Configure ASGI Application with ThreadPoolExecutor

A more comprehensive solution is to modify your asgi.py file to use a thread pool executor for handling synchronous views:

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import os
from django.core.asgi import get_asgi_application
from django.urls import path

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'cayank.settings')

# This will ensure synchronous views run in a thread pool
application = get_asgi_application()

3. Use Uvicorn with the --workers Flag

For a production-like setup, you can use Gunicorn with Uvicorn workers:

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python -m pip install uvicorn uvicorn-worker gunicorn
python -m gunicorn cayank.asgi:application -k uvicorn_worker.UvicornWorker

This approach is recommended for production environments as it provides process monitoring and automatic restarts.

Development Workflow

For development purposes, you can continue using:

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python -m uvicorn cayank.asgi:application --reload

The --reload flag will automatically restart the server when code changes are detected.

Conclusion

Yes, you can run existing Django applications with Uvicorn, but you need to handle the synchronous/asynchronous context transition properly. The simplest approach for an existing application is to modify your ASGI configuration to handle synchronous views correctly.

If you're planning to move toward a more asynchronous architecture, you might want to gradually refactor your views to use Django's async view capabilities, which are fully supported in Django 4.2.