Hello everyone,

I have a CSV file with a large list of domains and need to do DNS lookups against it. The input file is like this:

1,host1.foo.bar 2,host2.foo.bar n,hostn.foo.bar

I basically need to check if the domains are resolvable - with a 1 second timeout per DNS lookup and a list of 50,000 domains, this can take quite a while. I haven't used Perl threads before but think this would be a good candidate for it. Here is my code:

my $dns = new Net::DNS::Resolver;
$dns->tcp_timeout( 1 );
$dns->udp_timeout( 1 );

my $my_file = $ARGV[0];

open(INFILE, $my_file) || die ("I refuse to open your file!");

my @my_data=<INFILE>;

close(INFILE);

foreach my $line(@my_data) {
    ## Parse the file
    chop($line);
    my ($number,$domain)=split(/,/,$line);
    testDns($number,$domain,$dns);
}

sub testDns {
    my ($line_number, $domain_to_test, $default_resolver) = @_;

    my $ns = $default_resolver->query( $domain_to_test, 'NS' );
    if ($ns) {
        foreach my $rr ($ns->answer) {
            if ($rr->type eq "NS") {
                my @auth_nameservers = $rr->nsdname;
                foreach my $auth_nameserver (@auth_nameservers) {
                    print "$line_number,$domain_to_test,$auth_nameserv
+er\n";
            }
        }
    }
    else { print "$line_number,$domain_to_test,error\n"; }
}

[download]

How can I implement multiple threads in the above code?

Thanks, George

In reply to Multithreaded processing of a CSV file by costanza

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