[Python-ideas] Async API

[Yury Selivanov]

On 2012-10-23, at 7:00 PM, Sam Rushing <sam-pydeas at rushing.nightmare.com> wrote:

> On 10/23/12 3:05 PM, Yury Selivanov wrote:
>> Sam,
>> 
>> BTW, kudos for shrapnel!
> Thanks!
>> 
>> For basic library functions that will work.  And that's already a huge win.
>> But developing a complicated library will become twice as hard, as you'll need
>> to maintain two versions of API - sync & async all the way through the code.
> 
> This is really difficult, if you want to see a great example of trying
> to make all parties happy, look at Pika (an AMQP implementation).

Thanks, will take a look!

> Actually this reminds me, it would be really great if there was a
> standardized with_timeout()API.  It's better than adding timeout args to
> all the functions.  I'm sure that systems like Twisted & gevent could
> also implement it (if they don't already have it):
> 
> In shrapnel it is simply:
> 
>    coro.with_timeout (<seconds>, <fun>, *args, **kwargs)
> 
> Timeouts are caught thus:
> 
>   try:
>      coro.with_timeout (...)
>   except coro.TimeoutError:
>      ...

You're right--if we want to ship some "standard" async API in python,
API for timeouts is a must.  We will at least need to handle timeouts
in async code in the stdlib, won't we...

A question:

How do you protect finally statements in shrapnel?  If we have a following 
coroutine (greenlet style):

   def foo():
       connection = open_connection()
       try:
           spam()
       finally:
           [some code]
           connection.close()
           
What happens if you run 'foo.with_timeout(1)' and timeout occurs at 
"[some code]" point?  Will you just abort 'foo', possibly preventing
'connection' from being closed?

-
Yury