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I wrote a Link Checker, to check which Links are dead on a webpage. To get Server informations like Status Code and last modified Date, I used the head function of LWP::simple. Now this takes a lot of time. To speed up the process I’d like to run the processes simultaneous. I used the modul ForkManager and I am very impressed. It’s easy to use and fasten up the program. But it is not reliable. I have run the script multiple times to see the crash happens unregulary. Sometimes after 9 times of executions, then again after the first time, while in between it works fine and correct. The question is why?

The Program crashes with a windows msg opening, saying “Perl Command Line Interpreter has been stop working”.

If I click on show further informations, following Informations get shown:

Problem signature:
  Problem Event Name:     APPCRASH
    Application Name:    perl.exe
  Application Version:    5.16.3.1604
  Application Timestamp:    534c69c3
  Fault Module Name:    ntdll.dll
  Fault Module version:    6.1.7601.23864
  Fault Module Timestamp:    595fa942
  Exception Code:    c0000022
  Exception offset:    00000000000c8078
  OS version:    6.1.7601.2.1.0.272.7
  Locale ID:    1031
  Additional Information 1:    fdd8
  Additional Information 2:    fdd8457bc7039603b6dc9eb824e5dab9
  Additional Information 3:    8044
  Additional Information 4:    80447c7063d0a8ad48b87e45c4d37c4f
[download]

Though I assume this is an incompatibility problem with lwp::Simple head function, because if I wouldn’t include it in the parallising process, it doesn’t crash so far. But this is also the point in the script, which takes the most time in processing. So I wonder if there is an error in my script or any working alternative? ( I already tried HTTP::Async, which I couldn’t get work at all).

I use ActivePerl 64 bit (v5.16.3 built for MSWindows32-x64-multi-thread) on Windows Server 2008 R2 Standard.

#!d:\perl\bin\perl.exe
use LWP::Simple;
use strict;
use warnings;

use Parallel::ForkManager;

my $pm= new Parallel::ForkManager(8);  #didn’t matter if it’s 1 or 5 o
+r whatever else .. crash gets caused anyways  

foreach my $url (
  'http://us.a1.yimg.com/us.yimg.com/i/ww/m5v9.gif',
  'http://hooboy.no-such-host.int/',
  'http://www.yahoo.com',
  'http://www.ora.com/ask_tim/graphics/asktim_header_main.gif',
  'http://www.guardian.co.uk/',
  'http://www.pixunlimited.co.uk/siteheaders/Guardian.gif' ) {

  $pm->start and next;
  my ($type, $length, $mod) = head($url); 


  unless (defined $type) {
    print "$url is done \n"; ## I obviously reduced the output msgs 
    $pm->finish;
    next;
  }

  if ($mod) {
    print "$url is done \n";
    $pm->finish;
  } else {
    print "$url is done \n";
    $pm->finish;
   }
 $pm->finish;
}
$pm->wait_all_children;
[download]

Thanks for your time.

In reply to Crash with ForkManager on Windows by amitsq

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