I'm trying to use File::Temp to write out one file from each of 10-15 processes I've forked off. It seems that when I have more than 10 processes forked, I start getting error messages starting at temp file 11 about having to try too many times to generate a random filename.

The error looks like:

Error in tempfile() using /tmp/1yUjjuyGJn/sappyXXXXXXXX: Have exceeded the maximum number of attempts (10) to open temp file/dir at /home/sappy/dev/pfork.pl line 19

Apparently, File::Temp will only try 10 times to come up with a unique random filename, then gives up. When one forks off processes, File::Temp somehow comes up with the same "random" filenames for each process. Is this expected behavior, given how fork works, or is this a bug in File::Temp?

FWIW, I am on File::Temp 0.14, and I noticed the following in the ChangeLog entry for 0.15:

* Temp.pm: Increase maximum number of tries before aborting.
MAX_TRIES has been taken from 10 to 1000! Is this the only way to get around this problem, just have the module keep trying, or is there a more elegant solution?

I have a workaround, which is to include $$, the PID, in the template I pass to File::Temp for generating filenames. But I think this should be at least noted in the File::Temp documentation (which even has a section on forking).

Example code giving errors (derived, by the way, from code found in Parallel::ForkManager docs and/or Perlmonks): 

use strict;
use warnings;
use Parallel::ForkManager;
use HTTP::GHTTP;
use Time::HiRes qw[ time ];
use File::Temp qw(tempdir tempfile);
use File::Path;

my $start = time;
my $pm=new Parallel::ForkManager(15);
my $temp_dir = tempdir();

for my $link (map { chomp; $_ } <DATA>) {
  $pm->start and next;
  my $getter = HTTP::GHTTP->new;
  $getter->set_uri("http://$link/");
  $getter->process_request;
  my $page = $getter->get_body;
  my $fh = File::Temp->new(TEMPLATE => "sappyXXXXXXXX",
                           DIR => $temp_dir,
                           UNLINK => 0) or die "Could not make tempfil
+e: $!";
  print $fh $page or die "Could not print to tempfile: $!";
  close $fh or die "Could not close tempfile: $!";
  print "$link downloaded.\n";
  $pm->finish;
}
$pm->wait_all_children;

#rmtree([$temp_dir]);
print "Removed temp dir '$temp_dir'\n";


print 'Done in: ', time - $start, ' seconds.';

__DATA__
www.google.com
www.yahoo.com
www.amazon.com
www.ebay.com
www.perlmonks.com
news.yahoo.com
news.google.com
www.msn.com
www.slashdot.org
www.indymedia.org
www.sfgate.com
www.nytimes.com
www.cnn.com

[download]

Output, including errors: 

blah@blah [534] perl -wT /home/sappy/dev/pfork.pl
www.amazon.com downloaded.
www.yahoo.com downloaded.
news.google.com downloaded.
www.google.com downloaded.
news.yahoo.com downloaded.
www.slashdot.org downloaded.
www.indymedia.org downloaded.
www.ebay.com downloaded.
www.cnn.com downloaded.
www.sfgate.com downloaded.
Error in tempfile() using /tmp/1yUjjuyGJn/sappyXXXXXXXX: Have exceeded
+ the maximum number of attempts (10) to open temp file/dir at /home/s
+appy/dev/pfork.pl line 19
Error in tempfile() using /tmp/1yUjjuyGJn/sappyXXXXXXXX: Have exceeded
+ the maximum number of attempts (10) to open temp file/dir at /home/s
+appy/dev/pfork.pl line 19

[download]

To fix code, I change one line as such: 

  my $fh = File::Temp->new(TEMPLATE => "sappy" . $$ . "XXXXXXXX",
                           DIR => $temp_dir,
                           UNLINK => 0) or die "Could not make tempfil
+e: $!";

[download]

In reply to File::Temp randomness when forking by ryantate

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