Program Design Around Threads

[aeaton1843]

Hello Everyone

I ran across a problem and am pondering the best way to implement it. I have some working code but am not sure my path is a good one. I will put enough code here so that people can comment. If any of you have good reference material on program design around threads and PERL please post. I have done a chunk of work with threads but I can't say that I cared too much about synchronizing the output they produce.

The problem is that of not orchestrating a bunch of threads with a lot of code yet needing some synchronization. My problem is I need to get command output from several thousand network devices all of which are sitting behind a proxy. The basic program is take in a file of machines and a file of commands, run the commands and drop the responses into files.

The problem I am trying to solve is the printed order of the commands in the output file. I would like the command output to be in the order that is in the file. After a lot of tinkering and debugging of different ideas, I settled on creating a shared array that holds the order of thread creation. After the threads are populated with the information to print, I allow them to print in the order of their creation. It isn't very elegant and I am guessing there is a better way. It just hasn't hit me yet. So my question is what is a good way to handle the file creation with multiple threads spitting out files at the same time. I have seen some information out there about sharing filehandles between threads and the like but nothing about a good design to deal with something like this. Frankly, another design might be to have the threads print to separate files and the synch problem goes away. Not really what I wanted though.

use threads;
use threads::shared;

my $semaphore = new Thread::Semaphore;
my $live_threads :shared = 0;
my $thrwait_to_finish :shared = 5;
my $maximum_active_threads :shared = 10;
my @tid_array :shared;

my @commands = ("show ip interface brief | exclude unassigned",
        "show vlan",
        "show vrf");

my @machines = ('1.1.1.1', '2.2.2.2', '3.3.3.3');

foreach my $cmd (@commands)
{
    foreach my $machine_name (@machines)
    {
    my $url = "http://proxy:port/api/device/$machine_name/execute?cmd=
+$cmd";
    if ($live_threads >= $maximum_active_threads)
    {
        my $new_thread_num = wait_for_finish();
        $semaphore->down();
        $live_threads = $new_thread_num;
        $semaphore->up();
    }
    else
    {
        my $thread = threads->create('get_request', $cmd, $url, $machi
+ne_name);
        my $tid = $thread->tid();
        $semaphore->down();
        push (@tid_array, $tid);
        $live_threads++;
        $semaphore->up();
    }
    }
}
sub get_request
{
    sleep 1;
    my $cmd = $_[0];
    my $url = $_[1];
    my $machine_name = $_[2];
    my $thread_id = threads->tid();
    my $count = '0';
    ...
    $web_response = $response->content;
    ...
    while ($thread_id != $tid_array[0])
    {
        print "Thread_sleaping: $thread_id\n";
        sleep 1;
    }
    ...
    $semaphore->down();
    shift @tid_array;
    $semaphore->up();
    print $fh ($webresponse);
}