Hi All, I'm very new to PERL threading.. and got a bit struck in implementing a ThreadPool. I saw the Thread::Pool module, but since that has the implementation for older thread model, I decided to try and implement one on my own(just an experiment). The idea is the same - put all the work in a queue and a fixed number of threads should work on it, till the queue is emptied.

my $pool = Custom::Utility::ThreadPool->new(maxThreads => 5);
$pool->enqueue(&func, $arg1, $arg2...);
$pool->start;
$pool->blockTillCompletion;
[download]

Here is my module :

package Custom::Utility::ThreadPool;

use strict;

use threads;
use threads::shared;

sub new {
  my $class = shift;
  my %params = @_;
  my $pool = {
    maxThreads => $params{maxThreads},
    workQueue => undef,
    jobs => undef,
  };
  bless($pool, $class);
  return $pool;
}

sub work {
  my $pool = shift;
  while(my @args = shift @{$pool->{workQueue}}) {
print "ID=" .threads->self()->tid()  ." : WorkQueue = " .@{$pool->{wor
+kQueue}} ."\n";  #problem here; every thread seems to have its own co
+py of @{$pool->{workQueue}}
    my $code = shift @args;
    &$code(@args);
  }
}

sub start {
  my $pool = shift;

  # ensure that start is executed only once on a ThreadPool instance
  return if $pool->{jobs};

  # make sure there undefs are enqueued to the workQueue so that child
+ threads can
  # complete the process rather than being blocked on Thread::Queue's 
+dequeue
  push @{$pool->{workQueue}}, ((undef) x $pool->{maxThreads});
  @{$pool->{jobs}} = map { threads->create(\&work, $pool) } 1..$pool->
+{maxThreads};
}

sub enqueue {
  my ($pool, $code, @args) = @_;

  # default the namespace to the caller's package if only a name is
  # specificed instead of a code or its reference
  $code = caller() ."::$code" if !ref($code) && $code !~ /::/;

  # push it to the workQueue list
  push @{$pool->{workQueue}}, [$code, @args];
}

sub blockTillCompletion {
  my $pool = shift;
  $_->join() for @{$pool->{jobs}};
}

1;
[download]

The problem I'm facing is - in the work subroutine, every thread is getting its own copy of $pool it seems. Say if there are 10 items in the workQueue, all threads executing work subroutine seems to get a copy of the workQueue and each proceeds to execute all 10 of them. The expected is the 10 work items must be shared and completed. I tried to share @{$pool->workQueue} but wasn't able to. PERL gave me compile errors saying 'invalid value for shared scalar'. I'm using PERL5.8.8. Can anybody help me in overcoming this, please.

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