Versions: Perl 5.10, Apache 2.x, CentOS 6

(modified since originally posted, so that process A kicks off the scripts, rather than using an intermediary script to do it)

I have a Perl script (process A) which kicks off several other Perl scripts. Process A is kicked off via http.

I am trying to get process A to wait for x seconds after having executed the other scripts, which may have finished, or they may not have done; I don’t really care – I just need to wait x seconds in process A, and then continue.

I’ve tried several ways of doing this, but can’t seem to get it working as I want. Partly this is probably because I don’t really understand signals etc, etc properly. I used to have a way of making it work in Apache 1.3, but Apache 2.x has changed how it handles such things I think.

So, code which I can get to work as a single process (purloined from StackOverflow), as a test, is below:

#!/usr/bin/perl

use strict;

use My_Functions;

&print_myheader();

my $br=(-t)?"\n":'<br />';

use POSIX qw(:signal_h);

my $sigset_new = POSIX::SigSet->new();
my $sigset_old = POSIX::SigSet->new();

sigprocmask(SIG_BLOCK, $sigset_new, $sigset_old);

if ($sigset_old->ismember(SIGALRM)) {
  print "SIGALRM is being blocked!$br";
  $sigset_new->addset(SIGALRM);
  sigprocmask(SIG_UNBLOCK, $sigset_new);
} else {
  print "SIGALRM NOT being blocked$br";
}

$SIG{ALRM} = sub {print scalar(localtime()), " ALARM, leaving$br"; sig
+procmask(SIG_BLOCK, $sigset_new, $sigset_old); exit; };

alarm(5);

print scalar(localtime()), " Starting sleep...$br";

sleep (10);

print scalar(localtime()), " Exiting normally...$br";

[download]

This does as expected, and exits after five seconds.

However, I’m not sure if it’s because I am not implementing the code properly, but I just can’t seem to get it working, and I can get no http output until each of the kicked-off scripts has finished.

The relevant snippet of my code from process A looks like this:

[…. code …]

my $sigset_new = POSIX::SigSet->new();
my $sigset_old = POSIX::SigSet->new();

sigprocmask(SIG_BLOCK, $sigset_new, $sigset_old);

if ($sigset_old->ismember(SIGALRM))
{
$sigset_new->addset(SIGALRM);
sigprocmask(SIG_UNBLOCK, $sigset_new);
}
else
{
# do nothing
}

eval {

$SIG{ALRM}=sub{
   sigprocmask(SIG_BLOCK, $sigset_new, $sigset_old);
   exit;
};

alarm ($timer);

   for (@mylist)
   {
   my $cmd= "perl process_$_.pl args";  # tried with trailing & too
   system($cmd);
   }

alarm (0);
};

[ … more code …]

[download]

Any assistance would be greatly appreciated! Thanks.

In reply to Perl / Apache 2 / Alarms by DanielSpaniel

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