Sunday, April 16, 2023

Re: Async views means dropping gunicorn gevent for uvicorn, affecting sync view performance

You can simply run gunicorn with unicorn workers... which is very performance using uvloop... test it performance against pure gunicorn... note that performance is not totally dependent on server used(a whole lot of things can affect performance like moddlewares, serialization etc)


On Sun, Apr 16, 2023 at 5:34 PM Chris Barber <barberchris01@gmail.com> wrote:
Hello

Production django app, currently 100% sync views, running under gunicorn with gevent worker class.

@andrewgodwin suggests here it is possible to migrate slowly, just run hybrid sync-async and add or convert views as desired

But to get a single async view one has to switch to uvicorn workers or similar, right? Now one is no longer getting the gevent patching for sync views, which could be a major impact on performance/scaling, and could trigger re-evaluation of the production deployment & tuning!

Questions:

1. How to approach this? It has me wondering if monkey.patch_all() should be ported to asyncio and tested under uvicorn. This would smooth the transition since the sync views should perform and scale roughly the same as before.

2. Also an important technical question on how sync views under ASGI work. By default they will run all in the same thread (per worker) which could be really bad for performance with tons of sync views, correct? If I enable DJANGO_ALLOW_ASYNC_UNSAFE, then the sync views will be run in more threads, right? How many threads?Should I expect to have to tune this?

In general, regardless of the approach, one could presumably A/B test in a live environment - run some workers / nodes under uvicorn, partition the traffic accordingly, and see how it compares. Tune, stress test, and then rolling transition.

-C

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