On Thu, Jun 6, 2019 at 3:20 PM Pkl <chambon.pas...@gmail.com> wrote: > Hello, > > I'm a little late to the party, thanks for the big overview on this > complex matter. > > There are lots of thinks I still don't understand though, for example > regarding "what it unlocks". What asyncio structures would allow to run > several DB queries concurrently safely and easily, that can't be achieved > with some threadpool-like mechanism in nowadays' cod ? >
Python threads perform badly, as they force context-switches even when no work is pending; you can't sensibly run more than 20/30 threads before the overheads seriously start eating into your performance. > > Most importantly, I'm not getting why gevent/eventlet-style solutions are > systematically being dismissed in favor of asyncio. And the more I > read/talk about it, the less I understand what all that hype around asyncio > is. This is a whole new language, which forces people to trashbin half of > the Python ecosystem, and remake it with similar code but filled with > incompatible async/await statements. > > ... > > Granted, I have little experience with Geven and Asyncio, but all > experience feedbacks I've read so far mainly insist on minor limitations of > greenlets, and on the fact that "people are mainly going with asyncio" (a > self-fulfilling prophecy?). Considered the dramatic difference in workload > between the two, I'd really love to understand what killer-features justify > to go for the "recode everything" solution (or what greenlet limitations > would be show-stoppers on the long term). > I can't give you a full answer about why they are being dismissed, but the move is clearly systematic. My own personal experience is that writing with gevent in particular ends up being very difficult, as it is not very explicit about what is async, what causes a context switch, and so you end up wrapping a lot of your code in locks to even try and get code that isn't susceptible to nasty race conditions. I suspect asyncio fits much more with the Zen of Python - you know exactly when a context switch might occur (when you see an await), and modules explicitly add support for it rather than having it monkey-patched in. In addition, most people I know in the Python community who are actively working on async libraries are doing so against asyncio. You could make the same argument with trio - it's arguably a better, cleaner async implementation. But, again, it's not where Python is at. This change is already big enough that it's very important we keep consistency with Python core to lower the workload. If Python core turned around and blessed greenlets and gevent as the chosen async solution, I'd change my mind, but I haven't seen any evidence of that over many years. Andrew -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-developers+unsubscr...@googlegroups.com. To post to this group, send email to django-developers@googlegroups.com. Visit this group at https://groups.google.com/group/django-developers. To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/CAFwN1uqgUUwL_%3DXS%2Be6tzieycn%3DjDZK6wFCKzHKxRtfukacfQw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
