Hello again monks,
I have been toying with threads lately and wanted to know a good method for monitoring threads. If they die, I want to restart them. I ideally want to figure out why a thread dies.

I have done some research on perlmonks and just haven't found the information I am seeking for this topic.

Basically, the code below (StartJobRequest subroutine) is the thread being launched within my code that dies. I don't have all the code here because there are other threads, but none of them seem to be having a problem. I have all kinds of logging happening in my real code to find any problems, but nothing is being identified. So, I am putting the basic thread routine here and asking for help. I am pretty new to threads, so any pointers would be most appreciated. I think it would be great to start a thread that monitors the other threads, and when one dies, start it back up, and hopefully logging will help me find what the issue is.
========================================================
UPDATE: Since I have posted this message, I have successfully been able to relaunch a thread after it completes. I don't know if this works the same as a thread that dies. I was able to create a monitoring thread, but I wonder what prevents the monitor thread from dieing. And I have been able to start a thread back up from the main program, but in order to do that, I had to have all threads complete. Is this the way that is suppose to work? I have read the cpan page for threads, and there are good examples there, as before I posted this message, but there are some unclear items (as listed with this message) that just aren't too clear to this thread novice. thanks.
========================================================
#!/usr/bin/perl -w

use strict;
use warnings;

use threads;
use threads::shared;
use Thread::Queue;
use IO::Socket;

our $alock:shared;
our @uri_list:shared;

my $Server_IP = "172.168.0.1";
my $Server_IP_tcp_request_port = 40000;

#Set up the queue for playing
my $Q = Thread::Queue->new();

#Start the thread that keeps the queue full of jobs
my $thr1 = threads->create(\&StartJobRequest,1);

#Start a thread that checks the queue for jobs
#This is only a filler for this code on perlmonks (no provided code fo
+r StartPicker is provided, in order to reduce code space)
#This code takes queued jobs and performs them, as it completes, it pu
+lls from queue for next job.
#The actual code has many different Job pickers
my $thr2 = threads->create(\&StartPicker, 2);

#Join the threads
$thr1->join();
$thr2->join();

sub StartPicker{
        #Cool stuff goes on here.  ;-)
}

sub StartJobRequest{
    my $desired_q_level = 25;
    my $thid = threads->tid();
    #let's start a never ending process
    for(;;){
        my $pending = $Q->pending();
        #Check to see if we need to get a task from server.
        #Only to be done if queue has less than 25 jobs
        if ( $pending <= $desired_q_level ){
            my $collect = $desired_q_level - $pending;
            for(my $a=0; $a<$pending; $a++){
                my $socket = IO::Socket::INET->new(
                    PeerAddr    => $Server_IP,
                    PeerPort    => $Server_IP_tcp_request_port,
                    Proto       => 'tcp',
                    Reuse       => 1,
                    ) or warn "Can not open socket for client to $Serv
+er_IP on port $Server_IP_tcp_request_port\nReason: $!\n\n";
                if ($@ ){
                    #Set $a to exit loop after this
                    $a=$collect;
                    my $warn_sleep = int rand 10;
                    print "Can not connect to server $Server_IP on por
+t $Server_IP_tcp_request_port\nSleeping for $warn_sleep seconds\n";
                }
                else{
                    my $payload = "Need_Job";
                    $socket->autoflush(1);
                    print $socket $payload;
                    my $line = <$socket>;
                    if ($line =~ /^JOB:/){
                        $line=~ s/\n//;
                        write_log_entry("Job received: $line\n");
                        lock($alock);
                        $Q->enqueue($line);
                    }
                    elsif( $line=~ /=EMPTY=/){
                        #set $a to exit loop after this
                        $a=$collect;
                        sleep(3);
                    }
                    else{
                        print "Unknown returned info from Server: $lin
+e\n";
                        #set $a to end loop
                        $a=$collect;
                    }
                }
                close($socket);
            }
        }
    }
}

[download]


Thank you in advance for your help.

In reply to Monitoring Threads and keeping them alive/reviving them by r1n0

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