Hello Folks, I have a question regarding the use of Parallel::ForkManager I am trying to use in tandem with XML::Smart. I am trying to use Parallel::ForkManager to spawn off kids to collect information from hosts. From the documentation of Parallel::ForkManager, it says I can return a reference to a scalar, array, or hash. Here is the code:

my $maxProcesses=2;
my $pm = Parallel::ForkManager->new($maxProcesses, $tempDir);

# This has to be declared first.
$pm->run_on_finish(

  sub {
    my ($pid, $exit_code, $ident, $exit_signal, $core_dump, $data_stru
+cture_reference) = @_;
    my $reftype = ref($data_structure_reference);
    $log->info(qq/PID:$pid,EXIT_CODE=$exit_code,IDENT=$ident,EXIT_SIGN
+AL=$exit_signal,CORE_DUMP=$core_dump,DATA=$data_structure_reference(R
+EF_TYPE=$reftype)/);
    if (defined($data_structure_reference)) {  # children are not forc
+ed to send anything
      my $string = ${$data_structure_reference};  # child passed a str
+ing reference
      print "$string\n";
    } else {  # problems occuring during storage or retrieval will thr
+ow a warning
      print qq|No message received from child process $pid!\n|;
    }
  } # End sub
    
);

[download]

This exactly the same as what is documented in the link I provided above. Now for the loop:

use strict;
use XML::Smart;
use Parallel::ForkManager;

my $xmlin = XML::Smart->new($xmlInputFile); # Read in our input file d
+efined in $xmlInputFile
# For the example posted here, I walk through the XML file where <rows
+> is the root node, and there are multiple 'row' elements containing 
+various bits of data.
# I also use Log4perl to perform the logging, hence the the $log->info
+() calls.

foreach my $row (@{$xmlin->{'rows'}->{'row'}} ) {
    
  # Fork our children...
  $pm->start() and next;

  # Grab the hostname.
  my $host = $row->{HostName};
  $log->info(qq/[$i] Checking host: $host / . ref($host));
  # Do stuff...
  $log->info(qq/[$i] Finished checking host: $host /);
  $pm->finish(0, \$host );
}

[download]

What I see on the output is:

2013-09-13_07:29:13 | INFO | main:: | [0] Checking host: a01719 XML::S
+mart
2013-09-13_07:29:13 | INFO | main:: | [0] Finished checking host: a017
+19
2013-09-13_07:29:13 | INFO | main::__ANON__ | PID:2166,EXIT_CODE=0,IDE
+NT=,EXIT_SIGNAL=0,CORE_DUMP=0,DATA=(REF_TYPE=)
No message received from child process 2166!
2013-09-13_07:29:13 | INFO | main:: | [0] Checking host: a01719 XML::S
+mart
2013-09-13_07:29:13 | INFO | main:: | [0] Finished checking host: a017
+19
2013-09-13_07:29:13 | INFO | main::__ANON__ | PID:2167,EXIT_CODE=0,IDE
+NT=,EXIT_SIGNAL=0,CORE_DUMP=0,DATA=(REF_TYPE=)
No message received from child process 2167!

[download]

Note the line that prints out what the "ref" is says "XML::Smart". Since Parallel::ForkManager; says it only accepts a reference to a scalar, array, or hash, it may not be able to deal with a "XML::Smart" data structure. Fine. But what confuses me is where I explicitly say:

my $host = $row->{HostName};

I thought this would be simply a scalar, not a "XML::Smart" object. Do I have to "force" $host to be a scalar? If so, how? Why am I even getting a ref of type XML::Smart? I think it should be a simple scalar?

Advice is thankfully accepted in advance.

Cheers.

In reply to Using Parralel::ForkManager with XML::Smart ? by PropellerHead

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