CODEWITHSUNDEEP
multithreadingperl
Ritesh Kumar Gupta
Ritesh Kumar Gupta

Reputation: 5191

Check number of alive threads

I was implementing a boss-worker crew thread model in Perl. Due to exceptions, worker thread exit abnormally.

Once all worker threads die(abnormal exit), jobs are stucked, as there are no thread to process the workers_fn and boss thread keep enquing the jobs.

Thread 2 terminated abnormally: Illegal division by zero at threading.pl line 20.
Thread 3 terminated abnormally: Illegal division by zero at threading.pl line 20.
Thread 4 terminated abnormally: Illegal division by zero at threading.pl line 20.
Thread 5 terminated abnormally: Illegal division by zero at threading.pl line 20.
Thread 6 terminated abnormally: Illegal division by zero at threading.pl line 20.
Thread 7 terminated abnormally: Illegal division by zero at threading.pl line 20.
Thread 8 terminated abnormally: Illegal division by zero at threading.pl line 20.
Thread 9 terminated abnormally: Illegal division by zero at threading.pl line 20.
Thread 10 terminated abnormally: Illegal division by zero at threading.pl line 20.
Thread 11 terminated abnormally: Illegal division by zero at threading.pl line 20.

At any point of time, how can I detect accurately, the number of alive workers thread?

#!/usr/bin/perl
use strict;
use warnings;
use Carp;
use diagnostics;

use threads;
use Thread::Queue;

use Data::Dumper;

use constant {
    WORKERS_CNT => 10,    
};

my $queue= new Thread::Queue();
sub workers_fn{

    #Producing exceptions DELIBERATELY as a test case 
    my $random_number = int(time);
    if($random_number %2==0 || $random_number %3==0 || $random_number %5==0){
        print "CRASHED:".5/($random_number %2);
        print "\n";
    }

    while (my $query = $queue->dequeue) {
        print "DEQ(".threads->tid.") :$query\n";
    }

}
sub master_fn(){
    my $TotalEntry=10000;
    while($TotalEntry -- > 0){
        my $query = localtime;
        $queue->enqueue($query);
        print "ENQ(".threads->tid.") :$query\n";
        sleep(1);

        #check which worker threads are alive
        {
          #HOW TO CHECK NUMBER OF ALIVE THREADS?????????????
        }

    }
}

my $master_th=threads->create(\&master_fn);
my  @worker_th=map threads->create(\&workers_fn), 1..WORKERS_CNT;
$master_th->join;
$queue->enqueue(undef) for 1..WORKERS_CNT;

for (@worker_th){
    $_->join;

Upvotes: 0

Views: 106

Answers (1)

ikegami
ikegami

Reputation: 385764

my $running = threads->list(threads::running);

$ perl -Mthreads -Mthreads::shared -MTime::HiRes=sleep -E'
   my $hold : shared;
   {
      lock($hold);

      async { sleep 1; die "ack" };
      async { lock($hold) };

      while (1) {
         my $running = threads->list(threads::running);
         say $running;
         last if $running < 2;
         sleep 0.1;
      }
   }

   $_->join for threads->list;
'
2
2
2
2
2
2
2
2
2
2
Thread 1 terminated abnormally: ack at -e line 6.
1

Upvotes: 4

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