[Stackless] Select() on channels?

Tim Kientzle tim at metaweb.com
Fri Sep 14 20:07:44 CEST 2007

Christian Tismer wrote:
>> Is there any way to wait on a set of channels
>> for the first one to become available?
> No. *)

> The other side of the coin is how to generalize waiting for data
> on multiple I/O channels simultaneously to a very high scale ...
>   http://www.kegel.com/c10k.html 

Yes, Dan Kegel's paper has certainly inspired a lot of
my own thinking along these lines.  (Although supporting c10k
in any interpreted language still seems quite ambitious.)

> An inefficient but probably working solution is this silly idea:
> - For each of the n channels to be waited on, create a tasklet
>   that blocks reading on this channel.
> - it runs code like this after the receive:
>   - kill the other extra tasklets
>   - send the result on the multi-channel
> Instead of killing, also a dummy value could be sent, that tells
> the other tasklets to do no action.

In my case, I can probably work around it with a simple
"aggregator" channel.  There's a tasklet for each
channel that does the equivalent of:

def feed_tasklet(ch, aggregator):
      while True:
          v = ch.receive()
          aggregator.send((ch, v))

Then the main tasklet can just receive from the
aggregator channel to get a list of events in whatever
order they occur.

Tim Kientzle

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