Re: Creating active timers within callbacks

[John Christian]

Hi There,

Ok, here's the gist of what I'm doing, a lot of excess code snipped off, 
hopefully it's
legible enough to illustrate what I'm trying to do, I've added 
additional comments
to describe what's happening:

(The server code is split up into several modules but still in one file, 
and methods
are shared by @ISA relationships):

# file: Server.pm

package SCUMD::Server;

use Event;

@ISA = qw/SCUMD::Server::Jobs ... /;

@EXPORT = qw/new run/;

[ ... ]

# new just loads configs and creates a blessed reference

sub arm {
   my($h);
   $h = shift @_;
   Event->signal(signal => 'HUP',
                 cb     => [ $h, '_cb_hup'],
         desc   => 'HUP signal handler');
   # init_socket, returns plain server socket:
   # through the server socket can come requests
   # which can result in the creation of Event::timer objects
   # while in the event loop:
   Event->io(fd   => $h->init_socket(),
         cb   => [ $h, 'io_callback' ],
         desc => 'server socket watcher');
}
# run: besides "new", it's the only method Exported to be called
# by driver code:
sub run {
   my($h);
   $h = shift @_;
   $h->log_info("arming default event handlers");

   $h->arm();

   $h->log_info("entering standard server state");

   # enter event loop:
   Event::loop();
}
[ ... ]

package SCUMD::Server::Jobs;

use Event;

# job_create: this subroutine gets called as a method by a protocol 
handler, which
# is in turn called by the io callback:

sub job_create {
   my($h, %p, $time, $unit, $tmp, $jid, $iter, $interval, $abstime, $now,
      $set, $timer);
   ($h, %p) = @_;

[ ... ]

   # create a timer to push jobs onto the queue:
   # $abstime is computed using DateTime::Event::Cron, which returns
   # an interval with is added to the current time:
   # BUT ... even when testing this callback with a hardcoded interval
   # of a few seconds ... it's NEVER executed!
   $timer = Event->timer(at => $abstime,
             desc => "recurring job performing $p{task}",
             cb => sub {
                 print STDERR "job timer callback!\n";
                 $h->log_info("enqueuing job jid $jid for $p{who}");
                 $h->enqueue(%p);
                
                 # reset timer interval to next interation:
                 $interval = ($iter->next - DateTime->now)->seconds;
                 $now      = int timelocal(0,0,0,(localtime)[3,4,5]);
                 $abstime  = $interval + $now;
                 $h->log_info("resetting timer with absolute time 
$abstime (in ".$interval.
                      " seconds");
                 $timer->at($abstime);
             });

   $h->log_info("arming test timer (10 sec interval)");

   # test timer to see if stuff is actually happening ... it's callback 
never seems to get executed, as well:

   Event->timer(
        interval => 10,
        desc     => "test timer producing output every 10 seconds",
        prio     => &PRIO_HIGH,
        cb       => sub {
            $h->log_info("callback for test timer called!!!");
        });
   $tmp = {
   who   => $p{who},
   info  => { %p },
   jid   => $jid,
   timer => $timer
   };
   # push(@Jobs, $tmp);
   $JobsByJID{$jid} = $tmp;
   # at this point, if I call Event::all_watchers, it does return
   # watchers for timers and the io callback, reporting them all
   # as active.  I'd think this would allay any suspicion that it's
   # a scoping issue.
}

The file in its entirety can be seen at : 
http://cvs.sourceforge.net/viewcvs.py/*checkout*/scumd/scumd/lib/SCUMD/Server.pm?content-type=text%2Fplain&rev=1.5

Jochen Stenzel wrote:

Hello, John,

JC> The timer watchers created are returned when I do a
JC> all_watchers(), but their callbacks are NEVER subsequently
JC> executed (even with PRIO_HIGH and a hardcoded short interval).
JC> Is there anything more I may need to do for the timers to be active?

you just have to build the (active) watchers. Could you send a piece
of code to the list to demonstrate your algorithm?
I'm wondering that you mention all_watchers(), but I don't know the
code, so it would be interesting. I'd suggest to call Event's timer()
method from within the callback of the io watcher.
 

Right, that's what I'm trying, but the timers I've created are curiously 
never executed, all_watchers()
just (presumably) confirms that they are present and active within 
Event's internal watcher list.

JC> Also, if there is more documentation available in addition to the 
JC> perldoc, that would be very helpful.

There's a tutorial coming with the Event package, in PDF format.

Greetings

        Jochen

        

 

So I take it I am supposed to be able to create timers while in the 
event loop?  To me, that seemed like
that most likely culprit to my troubles here, but the Pod docs for Event 
really don't specifically say.

Any input appreciated.

Thanks,
John