Re: How to make perl script work simltaneously on multiple objects

Hi,

I would go with the fork option. You seem to have a process running which detects new server instances. This would be your main loop (pseudocode):

my %found;
my %active;

# sighandler for sigchild
$SIG{'SIGCHLD'} = sub {
    my $pid = waitpid;
    delete $active{$pid};
};

while(running) {
    if(my $serverid = new_server_found()) {
        $found{$serverid} = {
            'name' => $servername,
            'otherinfo' => $otherinfo,
        };
        my $pid = fork;
        if(defined $pid) {
            # fork ok
            if($pid == 0) {
                 # this is in the child
                 do_all_stuff_necessary_for_hardening();
                 exit $rc;
            }
            else {
                # this is parent
                # You have the pid and you know that this
                # fork was concerning a server you found
                # probably you want to store this information
                $active{$pid} = $serverid;
            }
            
        else {
            # no fork => error handling
            die ("FATAL: Something went wrong");
        }

    }
    sleep(1);
}
[download]

BE AWARE: This is perlish pseudocode and should give only hints.

McA

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Re^2: How to make perl script work simltaneously on multiple objects by slayedbylucifer (Scribe) on Apr 01, 2013 at 04:10 UTC
Thanks McA. Sorry for late reply. I will evaluate fork usage and will see how it goes. I not sure how much code change would it take.	[reply]
Re^3: How to make perl script work simltaneously on multiple objects by McA (Priest) on Apr 01, 2013 at 06:43 UTC
Hi, if you fork a perl script which does have all to process the job it should be quite easy as you don't need to `exec` and you do have everything in hands. Anything you set up before fork is also accessible in the child. Be careful. Memory usage is multiplied. There a some points you have to be aware of: Childs inherit open io handles. If you don't need them close them in childs. If you have a DBI handle the childs inherit it. The DESTROY handler of DBI is shutting down the connection when childs exit. So look at manpage of DBI concerning DBI and forking. Make a SIGCHLD handler for reaping of just for setting flags to reap in parent. waitpid is your friend. Sometimes it's nice to call the non-blocking version of waitpid. Be aware that the SIGCHLD handler interrupts a `sleep()`, so that this sleep may be much less than the amount of seconds specified. McA	[reply] [d/l] [select]
Re^4: How to make perl script work simltaneously on multiple objects by slayedbylucifer (Scribe) on Apr 05, 2013 at 06:11 UTC
Hi McA, I had a developer colleague of mine help me on writing below fork code (after following your advice). #!/usr/bin/perl -w use strict; use POSIX; my @list=("server1","server2","server3","server4","server5","server6", +"server7","server8"); my $count = 0; my $pcount = 5; foreach (@list) { chomp ; my $real_host = $_; if( (my $pid = fork()) == 0) { print "Processing - $_ \n"; my $wait=ceil(rand(10)); print "Wait:$wait \n"; sleep($wait); print "Exit Status= $? \n"; if($? ==0) { print "$_ Exit successfully \n"; } else { print "$_ Does not Exit successfully \n"; } print "Completing - $_ \n"; exit; } $count++; while($count >= $pcount) { wait(); $count--; } } while(wait() != -1){} [download] I still don’t understand few parts of this code but I am OK with that. This test code is working perfectly. So I am planning to use the same logic in my orchestrator. Many thanks for your help.	[reply] [d/l]