[Python-ideas] async objects

[Nick Coghlan]

On 7 October 2016 at 16:42, Nathaniel Smith <njs at pobox.com> wrote:
> For folks who prefer the
> gevent API, is it really easier to port libraries to asyncio than to
> port them to gevent?

It's definitely *not* easier, as gevent lets you suspend execution
inside arbitrary CPython magic method calls. That's why you can still
use SQL Alchemy's ORM layer with gevent - greenlet can swap the stack
even with the extra C call frames on there.

If you're running in vanilla CPython (or recent non-Windows versions
of PyPy2), on a relatively mainstream architecture like x86_64 or ARM,
then gevent/greenlet will be fine as an applications
synchronous/asyncrhonous bridge.

However, if you're running in a context that embeds CPython inside a
larger application (e.g. mod_wsgi inside Apache), then gevent's
assumptions about how the C thread states are managed may be wrong,
and hence you may be in for some "interesting" debugging sessions. The
same goes for any library that implements callbacks that end up
executing a greenlet switch when they weren't expecting it (e.g. while
holding a threading lock - that will protect you from other OS
threads, but not from other greenlets in the same thread)

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia