[Python-ideas] The async API of the future
shibturn at gmail.com
Sat Oct 20 12:56:41 CEST 2012
On 20/10/2012 1:33am, Greg Ewing wrote:
> That's been bothering me, too. It seems like an interface
> accommodating the completion-based style will have to be
> *extremely* fat.
> That's not just a burden for anyone implementing the
> interface, it's a problem for any library wanting to *wrap*
> it as well.
> For example, to maintain separation between the async
> layer and the generator layer, we will probably want to
> have an AsyncSocket object in the async layer, and a
> separate GeneratorSocket in the generator layer that wraps
> an AsyncSocket.
> If the AsyncSocket needs to provide methods for all the
> possible I/O operations that one might want to perform on
> a socket, then GeneratorSocket needs to provide its own
> versions of all those methods as well.
> Multiply that by the number of different kinds of I/O
> objects (files, sockets, message queues, etc. -- there
> seem to be quite a lot of them on Windows) and that's
> a *lot* of stuff to be wrapped.
I don't see why a completion api needs to create wrappers for sockets. See
for an implementation of a completion api implemented for Unix (plus a
stupid reactor class and some example server/client code).
The AsyncIO class is independent of reactors, futures etc. The methods
for starting an operation are
recv(key, sock, nbytes, flags=0)
send(key, sock, buf, flags=0)
connect(key, sock, address)
The "key" argument is used as an identifier for the operation. You wait
for something to complete using
which returns a list of tuples of the form "(key, success, value)"
representing completed operations. "key" is the identifier used when
starting the operation, "success" is a boolean indicating whether an
error occurred, and "value" is the return/exception value. To check
whether there are any outstanding operations, use
(To make the AsyncIO class usable without a reactor one should probably
implement a "filtered" wait so that you can restrict the keys you want
to wait for.)
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