Re: Re: How to run POE as a daemon

This is not a daemon:

while (1) {
  print "Enter a number: ";
  $Number = <STDIN>;
  chomp($Number);
   print "You entered - $Number.\n";
  }
[download]

yet you would have me believe it is.

When I said daemon, I meant having true daemon characteristics, not kinda sorta daemon-like. Fork and exit, setsid, chdir /, close or redirect STDIN, STDOUT, STDERR. Here's the example from Matt Sergeants' talk:

Daemonizing POE

We often write daemons with POE (network daemons, cron daemons, etc
But POE doesn't "background" automatically, so we need to write that:

use POE;
use POSIX;
$|++;
sub become_daemon {
my $child = fork;
die "Can't fork: $!" unless defined($child);
exit(0) if $child; # parent dies;
POSIX::setsid(); # become session leader
open(STDIN,"</dev/null");
open(STDOUT,">/dev/null");
open(STDERR, '>&STDOUT');
umask(0); # forget file mode creation mask
$ENV{PATH} = '/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin';
delete @ENV{'IFS', 'CDPATH', 'ENV', 'BASH_ENV'};
}
become_daemon(); # MUST do this before we create any sessions
POE::Session->create(
inline_states => {
_start => sub { $_[KERNEL]->yield("loop") },
loop => sub { $_[KERNEL]->delay_set("loop", 10) },
});
$poe_kernel->run();
exit(0);
[download]

This example fails in the same way: POE::Kernel's run() method was never called.

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Re: Re: Re: How to run POE as a daemon by Matts (Deacon) on Oct 02, 2002 at 13:16 UTC
It doesn't fail. The warning "POE::Kernel's run() method was never called" is from the fact that the parent exits without having ever called $poe_kernel->run(), which is absolutely fine because the child continues and does that. It's just a warning. Ignore it. That warning should be gone in POE 0.23.	[reply]
Re: Re: Re: How to run POE as a daemon by hossman (Prior) on Oct 02, 2002 at 00:39 UTC
This is not a daemon: `while (1) { print "Enter a number: "; $Number = <STDIN>; chomp($Number); print "You entered - $Number.\n"; }` [download] yet you would have me believe it is. No, I don't consider that a daemon because it's actively soliciting information on a handle (or port, or file, etc...) as soon as it starts. I would however consider this to be a very simple daemon... `while (1) { $Number = <STDIN>; chomp($Number); print "You entered - $Number.\n"; }` [download] ...because it passively waits for a connection on a handle (or port, etc...) before doing anything. it's not a very useful daemon because it's single threaded ... but lots of daemons can run as single threads. But none of this is really helping you achieve what you want, so i guess we'll just agree to disagree. In the mean time, perhaps Proc::Daemon would be of interest to you?	[reply] [d/l] [select]
Re: Re: Re: How to run POE as a daemon by Anonymous Monk on Oct 01, 2002 at 22:19 UTC
I have no idea what POE is but that code is already dodgy to begin with. Perhaps this is a usage I'm not familar with but I'd normally write `open(STDERR, '>&STDOUT');` as `STDERR = STDOUT` instead. There are no `or die "Couldn't open ...: $!"` tests on the open() calls. It'd be interesting if you'd stick some print() calls around that script and let us know which line it's cheffing on.	[reply] [d/l] [select]
Re: Re: Re: Re: How to run POE as a daemon by Matts (Deacon) on Oct 02, 2002 at 13:24 UTC
Please log in if you wish to comment on somebody's code looking "dodgy". Yes, this is a usage you're not familiar with. Please read perldoc -f open. The "or die" is skipped because this is for a presentation - it has to fit on a slide and be visual and understandable by the attendees in the few seconds that I have to show it to them. Plus if you can give me a reason they might fail on a unix system I'll be a lot more interested in your comment ;-)	[reply]