Clint

Original attempt by me, but most credit goes to Browseruk.

#! perl -slw
use strict;
use threads;
use Thread::Queue;

$| = 1; #$OUTPUT_AUTOFLUSH

our $KIDS ||= 10;
our $WORK ||= 500;
our $SLEEP||= 5;

sub kid {
    my( $Q ) = shift;
    my $tid = threads->tid;
    my $count=0;
    printf "Kid: %02d started\n", $tid;

    ## Pick a work item of the queue and process it
    while( my $work = $Q->dequeue ) {
        printf "Kid: %02d processing work item '%s'\n", $tid, $work;
        $count ++;

        ## Replace the sleep with the code to process teh work items
        rand > 0.7 and sleep rand( $SLEEP );
    }
    print "kid: $tid ending after processing $count items.\n";
}

## A queue for communications
my $Q = new Thread::Queue;

## Start the kids
my @kids = map{ threads->create( \&kid, $Q ) } 1 .. $KIDS;

## Wait till they're all up and running
sleep 1 until @{[ threads->list ]} == $KIDS;

## Feed the queue with work
## The limit just ensure we don't fill lots of memory
for my $workitem ( 1 .. $WORK ) {
    sleep 1 while $Q->pending > $KIDS *10;
    print "Queueing work item $workitem";
    $Q->enqueue( $workitem );
}

## Tell them to stop
$Q->enqueue( (undef) x $KIDS );

## And wait for them to do so.
$_->join for @kids;
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Greetings ewhitt,

Forking is nice, but when I need data back to the parent, I like using threads instead. The communication between source and thread is simple, only once at the end, but it usually does what I need, and it's pretty intuative.

If you need communication before the end of the thread, you can set that up with shared data structures with threads::shared.

#!/usr/bin/perl
use strict;
use warnings;
use threads;
use IO::File;
use Net::SSH 'sshopen2';
use DBI;

# username@hostname connect strings
my @servers = qw( gryphon@hornet gryphon@kursk gryphon@garfield );

# startup a thread for each server
my @threads = map {
    threads->new(
        sub {
            my ($server) = $_[0];
            my ( $reader, $writer ) = ( IO::File->new(), IO::File->new
+() );

            # ssh to the server and run "ls"
            sshopen2( $server, $reader, $writer, 'ls' ) or die "ssh fa
+iled $!";

            my @rv;
            while ( <$reader> ) {
                chomp();
                push @rv, $_;
            }

            # return the server name and an array ref of filenames
            return $server, \@rv;
        },
        $_,
    );
} (@servers);

# usual DBI stuff
my $dbh = DBI->connect(
    'DBI:mysql:database=DATABASENAME;host=localhost;port=3306',
    'USERNAME', 'PASSWORD', { 'RaiseError' => 1, 'AutoCommit' => 1 },
) or die $DBI::errstr;

my $sth = $dbh->prepare('INSERT INTO results (server, filename) VALUES
+ (?,?)');

# wait for threads to complete; insert data into db
foreach (@threads) {
    my ( $server, $files ) = $_->join();
    $sth->execute( $server, $_ ) foreach ( @{ $files } );
}

$dbh->disconnect();
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