[Soaplite-devel] XML-RPC on mod_perl

[Byrne R. <by...@ma...>]

Ok, so I am writing not as a developer, but as a user. I was hoping that 
even though I have the programming skilz, that someone might help me out 
- after all, these days I am more of a product manager, then I am an 
engineer.

Here is an excerpt from a bug with Movable Type (the product I am the PM 
for) - the bug being described is that XML-RPC will NOT work under 
mod_perl or FastCGI. :-(. I am looking for help in addressing the root 
cause of this problem, in addition to guidance on the best short term 
workaround.

 From lib/MT/XMLRPCServer.pm, line 21 (the line where the error occurs):

    $main::server->serializer->encoding('UTF-8');

When running under mod_perl, the $main::server variable is undefined 
(does not exist) for a number of reasons:

1. Scripts run under mod_perl are not run under package "main".

2. Under mod_perl, the mt-xmlrpc.cgi script is never executed.  The 
mt-xmlrpc.cgi script defines a public $server variable when XMLRPC is 
run as a CGI script; mod_perl creates and initializes a $server instance 
through the Apache::XMLRPC::Lite perl module.

3. The Apache::XMLRPC::Lite perl module does not expose its $server 
variable, making it inaccessible to any code outside of the 
Apache::XMLRPC::Lite perl module.

Because there is no $server variable available or accessible when 
Movable Type is configured to run XMLRPC under mod_perl, the code at 
line 21 in XMLRPCServer.pm makes it impossible to run Movable Type's 
XMLRPC under mod_perl.

There appears to be a number of ways this issue could be addressed, but 
I am not sure if any of them are particularly good nor which one might 
be the best:

1. The Apache::XMLRPC::Lite code could be modified so that the $server 
variable it defines is a public variable rather than a private one.  
 From /extlib/Apache/XMLRPC/Lite.pm, line 20:

my $server = __PACKAGE__->new;

This variable could be made a public one, in the same way the $server 
variable defined in the mt-xmlrpc.cgi script is defined as a public 
variable:

use vars qw($server);
$server = __PACKAGE__->new;

With above change in the Apache::XMLRPC::Lite code, the code at line 21 
in XMLRPCServer.pm could then be modified to allow the encoding to be 
set for the $server instance under both CGI and mod_perl:

    if ($ENV{MOD_PERL}) {
        $Apache::XMLRPC::Lite::server->serializer->encoding('UTF-8');
    } else {
        $main::server->serializer->encoding('UTF-8');
    }

2. If it is not desirable to modify the Apache::XMLRPC::Lite code, the 
Apache::XMLRPC::Lite class could be subclassed in the XMLRPCServer.pm 
module and within the subclass, define a $server variable which would be 
publicly available to other classes.

Because the Apache::XMLRPC::Lite perl module contains so little code, it 
takes about the same amount of code to subclass Apache::XMLRPC::Lite as 
it does to just reimplement it in XMLRPCServer.pm.

I added the following code at the beginning of XMLRPCServer.pm to 
reimplement the functionality provided by Apache::XMLRPC::Lite, and 
allow the $server variable to be accessible to other classes:

package MT::XMLRPCServer::Lite;
use strict;
use XMLRPC::Transport::HTTP;
use base qw( XMLRPC::Transport::HTTP::Apache );

use vars qw($server);
$server = __PACKAGE__->new;

sub handler {
  $server->configure(@_);
  $server->SUPER::handler(@_);
}

The mod_perl configuration was modified in the Apache httpd.conf file to 
use the new MT::XMLRPC::Lite class instead of Apache::XMLRPC::Lite:

PerlModule MT::XMLRPCServer
<Location /mt/xmlrpc>
    SetHandler perl-script
    PerlHandler MT::XMLRPCServer::Lite
    PerlSetVar dispatch_to "blogger, metaWeblog, mt"
    PerlSetVar MTConfig 'C:/Apache/www/MT-4.01-en/mt-config.cgi'
    PerlSetEnv MT_CONFIG 'C:/Apache/www/MT-4.01-en/mt-config.cgi'
</Location>

With above changes to XMLRPCServer.pm and the mod_perl configuration in 
the Apache httpd.conf file, the code at line 21 in XMLRPCServer.pm could 
then be modified to allow the encoding to be set for the $server 
instance under both CGI and mod_perl:

    if ($ENV{MOD_PERL}) {
        $MT::XMLRPCServer::Lite::server->serializer->encoding('UTF-8');
    } else {
        $main::server->serializer->encoding('UTF-8');
    }