Re: Crash with ForkManager on Windows

[Discipulus]

Hello amitsq,

I'm not at all a parallel monk and here there are, very skilled.

> my $pm= new Parallel::ForkManager(8); #didn’t matter if it’s 1 or 5 or whatever else

your original program crash here too and in the same way, but with 1 does not.

I have borrowed the below modifying it a little from example from P::FM docs and the resulting code runs with no crashes. At least something to start with:

  use Parallel::ForkManager;
  use LWP::Simple;

  my $pm = Parallel::ForkManager->new(10);

  LINKS:
  for my $link ('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 LINKS;    

      my ($content_type, $document_length, $modified_time, $expires, $
+server) = head($link);
      print "$link fetched: declared lenght $document_length, \n";   

    $pm->finish;
  };

# output

http://hooboy.no-such-host.int/ fetched: declared lenght ,
http://us.a1.yimg.com/us.yimg.com/i/ww/m5v9.gif fetched: declared leng
+ht 5611,
http://www.guardian.co.uk/ fetched: declared lenght 628397,
http://www.ora.com/ask_tim/graphics/asktim_header_main.gif fetched: de
+clared lenght ,
http://www.pixunlimited.co.uk/siteheaders/Guardian.gif fetched: declar
+ed lenght ,
http://www.yahoo.com fetched: declared lenght 12,

L*

[amitsq]

i tried your reduced code, 100% copy - no change and it crashes. I might run it 20 times with no crashes, but then the crashes happened like before.

Even once i got a very strange error message on the terminal:

http://us.a1.yimg.com/us.yimg.com/i/ww/m5v9.gif  1354074654,
Number found where operator expected at D:/Perl64/lib/File/Glob.pm lin
+e 13, near "over 4"
        (Do you need to predeclare over?)
Semicolon seems to be missing at D:/Perl64/lib/File/Glob.pm line 16.
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 17, near "<GLOB_NOSORT> is"
        (Missing operator before is?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 18, near ") rather"
        (Missing operator before rather?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 24, near ") returns"
        (Missing operator before returns?)
Can't locate object method "_init_implementor" via package "URI::http"
+ at D:/Perl64/lib/URI.pm line 137.
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 25, near "&File::Glob::GLOB_ERROR will"
        (Missing operator before will?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 26, near "&File::Glob::GLOB_ERROR is"
        (Missing operator before is?)
Number found where operator expected at D:/Perl64/lib/File/Glob.pm lin
+e 29, near "over 4"
        (Do you need to predeclare over?)
Semicolon seems to be missing at D:/Perl64/lib/File/Glob.pm line 32.
Semicolon seems to be missing at D:/Perl64/lib/File/Glob.pm line 36.
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 41, near ") has"
        (Missing operator before has?)
Operator or semicolon missing before &File::Glob::ERROR at D:/Perl64/l
+ib/File/Glob.pm line 43.
Ambiguous use of & resolved as operator & at D:/Perl64/lib/File/Glob.p
+m line 43.
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 45, near ") deviates"
        (Missing operator before deviates?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 45, near ") behaviour"
        (Missing operator before behaviour?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 46, near ") will"
        (Missing operator before will?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 47, near "continue processing"
        (Do you need to predeclare continue?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 47, near "<GLOB_ERR> flag"
        (Missing operator before flag?)
Number found where operator expected at D:/Perl64/lib/File/Glob.pm lin
+e 54, near "over 4"
        (Do you need to predeclare over?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 60, near ") isn't"
        (Missing operator before isn't?)
Semicolon seems to be missing at D:/Perl64/lib/File/Glob.pm line 66.
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 67, near "use of backslash"
        (Do you need to predeclare use?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 68, near ") solution"
        (Missing operator before solution?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 68, near "use forward slashes"
        (Do you need to predeclare use?)
String found where operator expected at D:/Perl64/lib/File/Glob.pm lin
+e 70, near "match "normal practice""
        (Do you need to predeclare match?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 70, near ""normal practice" on"
        (Missing operator before on?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 71, near ") only"
        (Missing operator before only?)
String found where operator expected at D:/Perl64/lib/File/Glob.pm lin
+e 72, near "metacharacters '['"
        (Do you need to predeclare metacharacters?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 77, near "use the real"
        (Do you need to predeclare use?)
Array found where operator expected at D:/Perl64/lib/File/Glob.pm line
+ 89, at end of line
Semicolon seems to be missing at D:/Perl64/lib/File/Glob.pm line 90.
Array found where operator expected at D:/Perl64/lib/File/Glob.pm line
+ 91, at end of line
Array found where operator expected at D:/Perl64/lib/File/Glob.pm line
+ 92, at end of line
Array found where operator expected at D:/Perl64/lib/File/Glob.pm line
+ 93, at end of line
Semicolon seems to be missing at D:/Perl64/lib/File/Glob.pm line 93.
Number found where operator expected at D:/Perl64/lib/File/Glob.pm lin
+e 96, near ") 1989"
        (Missing operator before 1989?)
Bareword found where operator expected at D:/Perl64/lib/File/Glob.pm l
+ine 96, near "1993 The"

No idea where that pop up from. It only happened once in all the times trying.

[marioroy]

When seeing errors (Bareword found where operator expected), try pre-loading the module before running parallel. See, this post.

use LWP::Simple;

# On the Windows platform, pre-loading essential modules
# (required at runtime) may be necessary for extra stability.

if ( $INC{'LWP/UserAgent.pm'} && !$INC{'Net/HTTP.pm'} ) {
   require IO::Handle;
   require Net::HTTP;
   require Net::HTTPS;
}

# run parallel

...