I'm afraid that won't work for you.

Here's the implementation of P::FM::start (found by doing vi `perldoc -l Parallel::ForkManager`): 

sub start { my ($s,$identification)=@_;
  die "Cannot start another process while you are in the child process
+"
    if $s->{in_child};
  while ( ( keys %{ $s->{processes} } ) >= $s->{max_proc}) {
    $s->on_wait;
    $s->wait_one_child(defined $s->{on_wait_period} ? &WNOHANG : undef
+);
  };
  $s->wait_children;
  if ($s->{max_proc}) {
    my $pid=fork();
    die "Cannot fork: $!" if !defined $pid;
    if ($pid) {
      $s->{processes}->{$pid}=$identification;
      $s->on_start($pid,$identification);
    } else {
      $s->{in_child}=1 if !$pid;
    }
    return $pid;
  } else {
    $s->{processes}->{$$}=$identification;
    $s->on_start($$,$identification);
    return 0; # Simulating the child which returns 0
  }
}

[download]
If you look at the "} else {" branch, you'll see that if no processes are available (when $s->{max_proc}==0, what set_max_procs(0) does), the task is continued in the parent process.

That looks like a cool feature, actually, since you can test out your code in a single process loop before going parallel, if you like.

I think you should have your alarm sig set a flag, which you could check in your "my $data" loop: 

my $stopFlag=0;

$SIG{ARLM} = sub { $stopFlag=1; };

    alarm($MAX_TIME);
    foreach my $data (@all_data) {
        last if $stopFlag;

        my $pid = $pm->start and next;

        # Process or call processing routines 
        # for $data here

        $pm->finish;
    }
    $pm->wait_all_children;
    alarm(0);

[download]
Hmmm, I think that'd work... Not sure, though.
--
Mike

In reply to Re: Graceful shutdowns and Parallel::ForkManager by RMGir
in thread Graceful shutdowns and Parallel::ForkManager by atcroft

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