Abbacabba has asked for the wisdom of the Perl Monks concerning the following question:

I'm writing a daemon for a company production system and need to know if this will come back to bite my butt.

I was wanting a way to make sure this daemon sleeps properly so I don't chew up valuable CPU time.

I'm catching and using signals and found that sleep gets "woken up" whenever a child signals in.

When I want to sleep in my prog I do this now:
1. define a variable to keep track of actual time spent sleeping. ($slept)
2. in my main loop, reset $slept to 0
3. loop until my $slept is equal or greater than my specified sleep interval ($Interval)
4. wash, rinse, repeat



my $slept;
my $Interval = 120;  

while(1)
{
    check_signals();

    $slept = 0;
    while($slept <= $Interval)
    {
         $slept += sleep(60);
    }
}

[download]
The only thing I see here is that I might end up sleeping for $Interval + 59 seconds, which is fine with me. Does anyone feel uneasy about this code?

Replies are listed 'Best First'.
Re: Tracking actual time spent sleeping: Is this bad coding?
by dragonchild (Archbishop) on Feb 02, 2005 at 15:12 UTC
    I don't see a huge issue with that. You could improve it by changing the sleep(60) to sleep( $Interval - $slept + 1 ).

    But, that begs the question - why aren't you using your system's version of cron?

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[reply]

      Dunno about the OP but I have a daemonized process that monitors some hardware and sleeps a lot. I do not use cron though because the start up costs are high compared to the actual work it does.

      Cheers,
      R.

      Pereant, qui ante nos nostra dixerunt!
[reply]
        If you're worried about the startup costs of cron, I've had excellent experiences with Schedule::Cron. You can daemonize the process and tell it to run a coderef on schedule.
[reply]
        I'm unfamiliar with any start-up costs of cron. I use it quite frequently on most boxes I administer. Would you mind going into detail? Perhaps after your explanation I'll change my ways.

        - Justin
[reply]

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