Perl Reading from Thread::Queue with timeout - multithreading

Question

I am working in a boss worker crew multithreaded scenario with Thread::Queue in Perl.
The boss enqueues tasks and the workers dequeue from the queue.
I need to achieve that the worker crew sends downstream ping messages in case the boss does not send a task via the queue for x seconds.
Unfortunately there seems to be no dequeue method with a timeout.
Have I missed something or would you recommend a different approach/different data structure?

Answer 1

You can add the functionality yourself, knowing that a Thread::Queue object is a blessed reference to a shared array (which I believe is the implementation from 5.8 through 5.16):
package Thread::Queue::TimedDequeue;
use parent 'Thread::Queue';
use threads::shared qw(lock cond_timedwait);
sub timed_dequeue {
my ($q, $patience) = #_; # XXX revert to $q->dequeue() if $patience is negative?
# $q->dequeue_nb() if $patience is zero?
my $timelimit = time() + $patience;
lock(#$q);
until (#$q) {
last if !cond_timedwait(#$q, $timelimit);
}
return shift if #$q; # We got an element
# else we timed out.
}
1;
Then you'd do something like:
# main.pl
use threads;
use strict; use warnings;
use Thread::Queue::TimedDequeue;
use constant WORKER_PATIENCE => 10; # 10 seconds
my $queue = Thread::Queue::TimedDequeue->new();
...
sub worker {
my $item = $queue->dequeue(WORKER_PATIENCE);
timedout() unless $item;
...
}
Note that the above approach assumes you do not enqueue undef or an otherwise false value.

Answer 2

There is nothing wrong with your approach/structure, you just need to add some timeout control over your "Thread::Queue". That is either:
create some "yield" based loop to check your queue from the child side while using a time reference to detect timeout.
use the "Thread::Queue::Duplex" or "Thread::Queue::Multiplex" modules which might be a bit overill but do implement timeout controls.