in reply to Forking Issues

Here's a skeleton from something I've used successfully for dealing with large numbers of processes by forking a limited number in parallel. 

# UNTESTED
# @srvrs is potentially LARGE array of servers to test
# $frk is maximum number of processes to fork at one time.

while ( @srvrs )
{
   SRVR:   
   for (1..$frk)
   {
       $x = shift @srvrs or last SRVR;

       $pid = fork; 
       if ( $pid )
       {       
            push @pids, $pid
       }       
       elsif ( defined $pid )
       {       
            # DO thing with $x you want parallelized  (testing servers
+) here
            exit;   
       }       
       else                                                           
+                                                                
       {
           die "fork failed\n";
       }       
   }

   waitpid($_, 0) for ( @pids );
}

[download]

--Bob Niederman, http://bob-n.com

Replies are listed 'Best First'.
Re: Re: Forking Issues
by Anonymous Monk on Aug 07, 2003 at 18:41 UTC
    Take a look at Parallel::ForkManager. It'll do most of this work for you, keeping track of N available process slots.
[reply]
      You are right- it is far easier.
      #!/usr/bin/perl -w strict

use strict;
use DBI;
use Parallel::ForkManager;

my $dbh = DBI->connect('DBI:mysql:noc', 'root', '') or die "Couldn't o
+pen database: $DBI::errstr; stopped";
my $fm = new Parallel::ForkManager(10);

while (1) {
my $sth = $dbh->prepare("select assetid,ip,snmpname from assets") or d
+ie "Couldn't prepare statement: $DBI::errstr; stopped";
$sth->execute() or die "Couldnt execute statement: $DBI::errsrt; stopp
+ed";
  my @ret;
  while ( my ($aid, $aip, $asnmp) = $sth->fetchrow_array() ) {
    $fm->start and next;
    ping_remote($aip,$aid,$asnmp);
    $fm->finish;
  }
  $fm->wait_all_children; 
  sleep(5);
  print "repeating\n";
} 

sub ping_remote {
  my $ip = shift;
  my $aid = shift;
  my $snmpname = shift;
  my @ret = undef;
  my @p = split(/(,)/,`ping -c 1 $ip | grep "0% loss"`);
  if ($p[4] eq " 0% loss") {
    my $a=`/etc/poller/snmptraffic.php "$ip" "$snmpname"`;
    my $u=`/etc/poller/snmpuptime.php "$ip" "$snmpname"`;
    my $f=`/etc/poller/snmpfirmware.php "$ip" "$snmpname"`;
    @ret = ($a,$u,$f);
  }
  if (@ret) {
    print "$ip\n";
    my $sth2 = $dbh->prepare("insert into history set assetid='$aid', 
+trafficload='$ret[1]'") or die "Couldn't prepare statement: $DBI::err
+str; stopped";    
    $sth2->execute() or die "Couldnt execute statement: $DBI::errsrt; 
+stopped";
    $sth2 = $dbh->prepare("update assets set firmware='$ret[2]', uptim
+e='$ret[1]', status='u', trafficload='$ret[0]' where assetid='$aid'")
+ or die "Couldn't prepare statement: $DBI::errstr; stopped";    
    $sth2->execute() or die "Couldnt execute statement: $DBI::errsrt; 
+stopped";
  } else {
    print "down - $ip\n";
    my $sth2 = $dbh->prepare("update assets set status='d' where asset
+id='$aid'") or die "Couldn't prepare statement: $DBI::errstr; stopped
+";    
    $sth2->execute() or die "Couldnt execute statement: $DBI::errsrt; 
+stopped";
  }
}

      [download]

      THANKS!
[reply]
[d/l]
        well, now to clean it up :P that that should give other people an idea as to how to do it... roughly :)
[reply]

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