Mark Martinec writes:
> > Almost. One of the biggest problems I see is that one can't register a
> > socket with AsyncLoop.pm. Thereby, when DNS lookups are finished, the whole
> > loop stops regardless of outstanding non-DNS-based lookups.
> >
> > See sub complete_lookups in AsyncLoop.pm:
> > my $nfound = $self->{main}->{resolver}->poll_responses($timeout);
> > $nfound ||= 'no';
> > dbg ("async: select found $nfound socks ready");
> > foreach my $key (keys %{$pending}) {
> > my $ent = $pending->{$key};
> >
> > poll_responsens is in DnsResolver.pm and yield 0 when DNS queries are
> > finished. This causes the complete_lookups call to terminate all the
> > outstanding lookups, even the non-DNS-based ones.
>
> Not really (at least not in the current trunk I'm looking at).
> As long as there are any (non timed-out) requests in %$pending,
> it does not terminate, even if poll returns empty-handed.
> And 'a request' is a rather general term. Currently it covers
> DNS requests, but in principle could be other kind of 'requests'.
> There are routines for submitting and terminating requests.
>
> I'd be interested too if more general usage emerges, perhaps
> along with a somewhat cleaned/generalized API. My wish is
> to provide a mechanism for Plugins (such as DKIM, SPF, Razor2)
> to use the same async services and avoid doing their network
> lookups synchronously on their own. Suggestions welcome.
+1 agreed.
> If only Perl could have a way of expressing co-routines,
> then one could build a simple task scheduler, with task queues
> on blocked resources, etc.
Bear in mind that perl's extremely flexible closure support
is a great help here. e.g. you can write
sub start_request {
my $request = ...;
my $foo = ...;
my $bar = do_something();
call_back_once_complete ($request, sub { # line A
proc_response($foo, $bar);
});
}
in other words the closure can act as a kind of "second half" coroutine;
it helps if you think of line A as a "yield" statement ;)
I'm sure there are clean patterns around to express this... also I
know Matt Sergeant spent some time looking into it.
> > Does anybody knows which is the API to the async stuff? Maybe
> > I didn't get it at all and I'm attempting to use it the wrong way...
>
> Not much docs about API, but see comments on subroutines in
> AsyncLoop.pm, and their typical usage by Dns.pm.
Also there's some usage by bundled plugins in lib/Mail/SpamAssassin/Plugin/.
--j.
