On Nov 28, 2012, at 12:04 PM, Guido van Rossum <gu...@python.org> wrote:
>> Anyway, as for concrete requirements: The issue I have always seen with
>> various asynchronous libraries is their lack of composability. Everyone
>> writes their own application loop and event queue. Merely having a standard
>> spec and reference implementation of an application main loop object, and
>> main event queue object, in the spirit of WSGI, would possibly remedy this.
>> You could then hopefully assemble various different libraries in the same
>> application, including greenlet(*) based ones.
>
> Hm. I agree with the first part of this -- and indeed I am planning to
> make it so that tulip's event loop can easily be replaced by another
> one. I'm less sure about the yield-from-based scheduler, that's the
> kind of thing for which it doesn't really make sense to have multiple
> implementations. If greenlets can work with the standard event loop
> interface, good for them. (Either by providing a conforming
> implementation that also supports greenlets, or by just using the
> standard implementation.)
I'm really happy that you are building this in as a core feature of Tulip.
It's really important.
Very early on, Twisted attempted to avoid this lack of composability by
explicitly delegating to other application loops; it's one of my favorite
features of Twisted. Granted, no two loops we have attempted to use have
themselves been composable, but there's not much we can do about that :).
Still, code written on top of Twisted can always be plugged in to any other
loop by simply using the appropriate reactor. (There's also a plug-in
interface for the reactor and a plug-in discovery mechanism so that third
parties can easily provide their own reactors if they have an unusual main loop
that isn't supported by twisted itself.)
I would also like to bring up <https://github.com/lvh/async-pep> again. If
anyone really wants to dig in and enumerate the use-cases for the _lower-level_
event delivery portions of Tulip, something that would be compatible with
Twisted and Tornado and so on, that PEP already has a good skeleton and could
use some pull requests.
-glyph
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