work::mod_perl-2.0.11::docs::api::ModPerl::RegistryLoader(3)

NAME
ModPerl::RegistryLoader - Compile ModPerl::RegistryCooker scripts at server startup

Synopsis
  # in startup.pl
  use ModPerl::RegistryLoader ();
  use File::Spec ();

  # explicit uri => filename mapping
  my $rlbb = ModPerl::RegistryLoader->new(
      package => 'ModPerl::RegistryBB',
      debug   => 1, # default 0
  );

  $rlbb->handler($uri, $filename);

  ###
  # uri => filename mapping using a helper function
  sub trans {
      my $uri = shift;
      $uri =~ s|^/registry/|cgi-bin/|;
      return File::Spec->catfile(Apache2::ServerUtil::server_root, $uri);
  }
  my $rl = ModPerl::RegistryLoader->new(
      package => 'ModPerl::Registry',
      trans   => \&trans,
  );
  $rl->handler($uri);

  ###
  $rlbb->handler($uri, $filename, $virtual_hostname);

Description
This modules allows compilation of scripts, running under packages derived from "ModPerl::RegistryCooker", at server startup. The script's handler routine is compiled by the parent server, of which children get a copy and thus saves some memory by initially sharing the compiled copy with the parent and saving the overhead of script's compilation on the first request in every httpd instance.

This module is of course useless for those running the "ModPerl::PerlRun" handler, because the scripts get recompiled on each request under this handler.

Methods

new()
    When creating a new "ModPerl::RegistryLoader" object, one has to specify which of the "ModPerl::RegistryCooker" derived modules to use. For example if a script is going to run under "ModPerl::RegistryBB" the object is initialized as:

      my $rlbb = ModPerl::RegistryLoader->new(
          package => 'ModPerl::RegistryBB',
      );

    If the package is not specified "ModPerl::Registry" is assumed:

      my $rlbb = ModPerl::RegistryLoader->new();

    To turn the debugging on, set the debug attribute to a true value:

      my $rlbb = ModPerl::RegistryLoader->new(
          package => 'ModPerl::RegistryBB',
          debug   => 1,
      );

    Instead of specifying explicitly a filename for each uri passed to handler(), a special attribute trans can be set to a subroutine to perform automatic remapping.

      my $rlbb = ModPerl::RegistryLoader->new(
          package => 'ModPerl::RegistryBB',
          trans   => \&trans,
      );

    See the handler() item for an example of using the trans attribute.

handler()
      $rl->handler($uri, [$filename, [$virtual_hostname]]);

    The handler() method takes argument of "uri" and optionally of "filename" and of "virtual_hostname".

    URI to filename translation normally doesn't happen until HTTP request time, so we're forced to roll our own translation. If the filename is supplied it's used in translation.

    If the filename is omitted and a "trans" subroutine was not set in new(), the loader will try using the "uri" relative to the "ServerRoot" configuration directive. For example:

      httpd.conf:
      -----------
      ServerRoot /usr/local/apache
      Alias /registry/ /usr/local/apache/cgi-bin/

      startup.pl:
      -----------
      use ModPerl::RegistryLoader ();
      my $rl = ModPerl::RegistryLoader->new(
          package => 'ModPerl::Registry',
      );
      # preload /usr/local/apache/cgi-bin/test.pl
      $rl->handler(/registry/test.pl);

    To make the loader smarter about the URI->filename translation, you may provide the "new()" method with a "trans()" function to translate the uri to filename.

    The following example will pre-load all files ending with .pl in the cgi-bin directory relative to "ServerRoot".

      httpd.conf:
      -----------
      ServerRoot /usr/local/apache
      Alias /registry/ /usr/local/apache/cgi-bin/

      startup.pl:
      -----------
      {
          # test the scripts pre-loading by using trans sub
          use ModPerl::RegistryLoader ();
          use File::Spec ();
          use DirHandle ();
          use strict;

          my $dir = File::Spec->catdir(Apache2::ServerUtil::server_root,
                                      "cgi-bin");

          sub trans {
              my $uri = shift;
              $uri =~ s|^/registry/|cgi-bin/|;
              return File::Spec->catfile(Apache2::ServerUtil::server_root,
                                         $uri);
          }

          my $rl = ModPerl::RegistryLoader->new(
              package => "ModPerl::Registry",
              trans   => \&trans,
          );
          my $dh = DirHandle->new($dir) or die $!;

          for my $file ($dh->read) {
              next unless $file =~ /\.pl$/;
              $rl->handler("/registry/$file");
          }
      }

    If $virtual_hostname argument is passed it'll be used in the creation of the package name the script will be compiled into for those registry handlers that use namespace_from_uri() method. See also the notes on $ModPerl::RegistryCooker::NameWithVirtualHost in the "ModPerl::RegistryCooker" documentation.

    Also explained in the "ModPerl::RegistryLoader" documentation, this only has an effect at run time if $ModPerl::RegistryCooker::NameWithVirtualHost is set to true, otherwise the $virtual_hostname argument is ignored.

Implementation Notes
"ModPerl::RegistryLoader" performs a very simple job, at run time it loads and sub-classes the module passed via the package attribute and overrides some of its functions, to emulate the run-time environment. This allows to preload the same script into different registry environments.

Authors
The original "Apache2::RegistryLoader" implemented by Doug MacEachern.

Stas Bekman did the porting to the new registry framework based on "ModPerl::RegistryLoader".

SEE ALSO
"ModPerl::RegistryCooker", "ModPerl::Registry", "ModPerl::RegistryBB", "ModPerl::PerlRun", Apache(3), mod_perl(3)