!/usr/bin/perl

use strict;
use warnings;
use Async;

my $workercount = 10;
my @workerqueue;
for my $i (1..$workercount) {
    my $proc = Async->new( sub { sleep($i*3); print "$i\n"; } );
    print "--> enqueue $proc->{PID}\n";
    push @workerqueue, $proc;
}

while (1) {
    sleep(1);
    my @unfinished;
    while (my $proc = shift @workerqueue) {
        if ($proc and $proc->ready) {
            print "--> $proc->{PID} is ready\n";
            if (my $e = $proc->error) {
                print "Something went wrong.  The error was: $e\n";
            }
            undef $proc;
        } else {
            push @unfinished, $proc;
        }
    }
    push @workerqueue, @unfinished;
    ## START refill queue block ##
    my $free = $workercount - @workerqueue;
    for my $i (1..$free) {
        my $proc = Async->new( sub { sleep($i*3); print "$i new\n"; } );
        print "--> enqueue $proc->{PID}\n";
        push @workerqueue, $proc;
    }
    ## END refill queue block ##
    print "mainloop\n";
}

##</code><code>##

--> enqueue 28304
--> enqueue 28305
--> enqueue 28306
--> enqueue 28307
--> enqueue 28308
--> enqueue 28309
--> enqueue 28310
--> enqueue 28311
--> enqueue 28312
--> enqueue 28313
mainloop
mainloop
1
--> 28304 is ready
mainloop
mainloop
mainloop
2
--> 28305 is ready
mainloop
mainloop
mainloop
3
--> 28306 is ready
mainloop
mainloop
mainloop
4
--> 28307 is ready
mainloop
mainloop
mainloop
5
--> 28308 is ready
mainloop
mainloop
mainloop
6
--> 28309 is ready
mainloop
mainloop
mainloop
7
--> 28310 is ready
...

##</code><code>##

--> enqueue 28319
--> enqueue 28320
--> enqueue 28321
--> enqueue 28322
--> enqueue 28323
--> enqueue 28324
--> enqueue 28325
--> enqueue 28326
--> enqueue 28327
--> enqueue 28328
mainloop
mainloop
1
--> 28319 is ready
--> enqueue 28329
mainloop
mainloop
mainloop
2
1 new
--> 28320 is ready
--> 28327 is ready
--> 28328 is ready
--> 28329 is ready
--> enqueue 28330
--> enqueue 28331
--> enqueue 28332
--> enqueue 28333
mainloop
--> 28321 is ready
--> 28322 is ready
--> 28323 is ready
--> 28324 is ready
--> 28325 is ready
--> 28326 is ready
--> enqueue 28334
--> enqueue 28335
--> enqueue 28336
--> enqueue 28337
--> enqueue 28338
--> enqueue 28339
mainloop
mainloop
1 new
--> 28330 is ready
--> enqueue 28340
...

##</code><code>##

kill 9 => $pid;  # I don't care.

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use threads;
use threads::shared;
use Data::Dumper;

my %state :shared;
my $workercount = 10;
my $run = 1;

$SIG{TERM} = sub { $run = 0; };
$SIG{INT} = sub { $run = 0; };

my @workerqueue;
for my $i (1..$workercount) {
    my $thr = threads->create(\&mysub, $i);
    my $id = $thr->tid();
    print "--> enqueue $id\n";
    $state{$id} = 'running';
    push @workerqueue, $thr;
}

while ($run) {
    sleep(1);
    my @unfinished;
    while (my $thr = shift @workerqueue) {
        my $id = $thr->tid();
        if ($thr and $state{$id} eq 'finished') {
            print "--> $id is ready\n";
            my $x = $thr->join();
            delete $state{$id};
            print Dumper $x; # do something useful with the data
        } else {
            push @unfinished, $thr;
        }
    }
    push @workerqueue, @unfinished;
    ## START refill queue block ##
    my $free = $workercount - @workerqueue;
    for my $i (1..$free) {
        my $thr = threads->create(\&mysub, $i);
        my $id = $thr->tid();
        print "--> enqueue $id\n";
        $state{$id} = 'running';
        push @workerqueue, $thr;
    }
    ## END refill queue block ##
    print "mainloop\n";
}

my @threads = threads->list();
foreach my $thr (@threads) {
    $thr->join();
}


sub mysub {
    my $i = shift;
    $i *= 3;
    sleep $i;
    my $id = threads->tid();
    print "$id : slept for $i sec\n";
    my $x = {
        'ID' => $id,
        'a' => [1,2,3],
        'B' => { 'a' => 'A', },
    };
    $state{$id} = 'finished';
    return $x;
}