mod_perl and CGI behavior

[naChoZ]

crossposted at stackoverflow here.

This has got to be something silly I'm doing wrong. It's such a newbie type problem.

The original script is something that sits and waits for a 3rd party to connect and POST some xml to it, it takes that xml, does some validation, and stores it in a db. That part is fine. The problem is my response. I'm trying to use the header() function from CGI and it's just not behaving. It comes up blank. Obviously I could just do this manually and just print the header string, but now I'm really curious why this is behaving so strangely.

Here is a stripped down test version of the cgi script:

#!/perl/bin/perl

use strict;
use warnings;

use Data::Dumper::Names;
use CGI qw(:standard);

use Apache2::Connection ();
use Apache2::RequestRec ();

$| = 1;

# Grab the request object provided by mod_perl.
#
our $request_obj = shift;
our $connection  = $request_obj->connection;
our $remote_ip   = $connection->client_ip();


my $cgi = CGI->new($request_obj->args());

print STDERR Dumper($cgi);

my $input = $cgi->param('POSTDATA');

print STDERR Dumper($input);

my $cgi_header = $cgi->header();

print STDERR Dumper($cgi_header);

#my $cgi_full_header = $cgi->header(-type => 'application/xml', -statu
+s => '400 Bad Request' );
my $cgi_full_header = $cgi->header(-type => 'application/xml');

print STDERR Dumper($cgi_full_header);




my $q = CGI->new({});

print STDERR Dumper($q);

my $q_header = $q->header();

print STDERR Dumper($q_header);

#my $q_full_header = $q->header(-type => 'application/xml', -status =>
+ '400 Bad Request' );
my $q_full_header = $q->header(-type => 'application/xml' );

print STDERR Dumper($q_full_header);


exit;

And the output:

$cgi = bless( {
                '.r' => bless( do{\(my $o = '94118860562256')}, 'Apach
+e2::RequestRec' ),
                'param' => {
                             'POSTDATA' => [
                                             'test'
                                           ],
                             'XForms:Model' => [
                                                 'test'
                                               ]
                           },
                'use_tempfile' => 1,
                '.fieldnames' => {},
                '.charset' => 'ISO-8859-1',
                'escape' => 1,
                '.parameters' => [
                                   'XForms:Model',
                                   'POSTDATA'
                                 ]
              }, 'CGI' );
$input = 'test';
$cgi_header = '';
$cgi_full_header = '';
$q = bless( {
              '.parameters' => [
                                 'XForms:Model',
                                 'POSTDATA'
                               ],
              'escape' => 1,
              '.fieldnames' => {},
              '.charset' => 'ISO-8859-1',
              'use_tempfile' => 1,
              '.r' => bless( do{\(my $o = '94118860562256')}, 'Apache2
+::RequestRec' ),
              'param' => {
                           'POSTDATA' => [
                                           ''
                                         ],
                           'XForms:Model' => [
                                               ''
                                             ]
                         }
            }, 'CGI' );
$q_header = '';
$q_full_header = '';

And here is the simple test script I'm using to send the POST.

#!/perl/bin/perl
use strict;
use warnings;

use DBI;
use URI;
use LWP::UserAgent;
use Data::Dumper::Names;


my $ua  = LWP::UserAgent->new;

$ua->max_size( 131072 );
$ua->agent('test_xml_pusher');
$ua->ssl_opts(verify_hostname => 0);

my $url = URI->new;
$url->scheme('https');
$url->host('xxxxxxxxxxxxxxxxxxxxxxxxx');
$url->port(443);
$url->path_segments('test.cgi');


# Yes, I know...  it's not valid xml...  don't care for the purposes o
+f this test.
#
my $xml = 'test';

my $response = $ua->post( $url, Content => $xml, 'Content-Type' => 'ap
+plication/xml' );


print Dumper($response);

my $status_line = $response->status_line;

print Dumper($status_line);

my $content = $response->content;

print Dumper($content);

So why is $cgi_header empty? And why does $q end up being a reference to the same thing as $cgi even though I tried initializing it as my $q = CGI->new({});? (I also tried empty quotes instead of empty brackets.)

Any thoughts?

Thanks!

My environment is a centos 7 server running apache httpd 2.4.34 with mod_perl 2.0.11 and perl 5.22.4. (httpd is installed from from SCL, but perl and mod_perl are installed from source.)

[choroba]

Crossposted to StackOverflow. Crossposting isn't bad, but it's considered polite to inform about crossposting to prevent unnecessary work: people not attending both sites might spend a lot of time solving a problem already solved at the other end of the internets.

[naChoZ]

Roger that. Updated.

[davebaker]

Haven't tested this yet as to whether it makes a difference, but I see you've imported various "standard" functions from CGI.pm by including :standard in the "use CGI qw(:standard);" statement. Because you're using CGI.pm in its object-oriented style (my $cgi = CGI->new() etc.), you don't need to do that, and you might be better off with "use CGI;" instead.

[naChoZ]

Unfortunately it seems deeper than that.

Looking at the code over on github here, you can see that the ->new method checks if mod_perl is being used and, if it is, gives you back an object with the request attached to it, and all that stuff...

But, regardless, I dumbed down the script to just...

#!/perl/bin/perl

use strict;
use warnings;

use Data::Dumper::Names;
use CGI;

use Apache2::Connection ();
use Apache2::RequestRec ();


$| = 1;

my $header = CGI::header();

print STDERR Dumper($header);

...and it still outputs just...

$header = '';

[davebaker]

Yes, something going on at line 1617 of CGI.pm at github, inside sub "header" --

if (($MOD_PERL >= 1) && !$nph) {
        $self->r->send_cgi_header($header);
        return '';
}

which explains the empty set being returned, after it's invoked a "send_cgi_header" mod_perl method that seems to be designed to take the place of sub "header" as a practical matter.

[trwww]

Theres a few problems here, but the most glaring one is you're printing your script's output to STDERR. Where did you get this pattern?

[Anonymous Monk]

Read the guide and get coping, it's cgi 101. Also CGI.pm is aware of mod_perl. For debugging use DebugCGI