=head1 NAME
Porting Apache:: Modules from mod_perl 1.0 to 2.0
=head1 Description
If you have released an C<Apache::Foo> module on CPAN you may wonder
what steps you should take to make your code working under mod_perl
2.0 while still preserving 1.0 compatibility. This document attempts
to answer some of the questions related to this issue.
API changes are listed in L<the back compatibility
document|docs::2.0::user::compat::compat/>.
=head1 Should the Module Name Be Changed?
While you can change the name of the module, it's the best to try to
preserve the name and use some workarounds if your module cannot be
ported to run under 1.0 and 2.0 at the same time.
Most of the CPAN C<Apache::> modules for mod_perl 1.0 should work with
mod_perl 2.0 without any change. Modules including XS code may or may
not work, depending on whether they use Apache API that have changed
in Apache 2.0.
Let's say that you have a module C<Apache::Friendly> whose release
version complient with mod_perl 1.0 is 1.57. You keep this version on
CPAN and release a new version 2.01 which is complient with 2.0 and
preserves the name of the module. It's possible that a user may need
to have both versions of the module on the same machine. Since the two
have the same name they obviously cannot live under the same tree. One
attempt to solve that problem is to use C<MP_INST_APACHE2>
I<Makefile.PL>'s option. If the module is configured as:
% perl Makefile.PL MP_INST_APACHE2=1
it'll be installed relative to the I<Apache2/> directory.
META: but of course this won't work in non-core mod_perl, since a
generic C<Makefile.PL> has no idea what to do about
MP_INST_APACHE2=1. Need to provide copy-n-paste recipe for this. Or
even add to the core a supporting module that will handle this
functionality.
The second step is to change the documentation of your 2.0 complient
module to say:
use Apache2 ();
in the code before the module is required or in I<startup.pl> or
PerlModule Apache2
in I<httpd.conf>. This will C<@INC> to look in the I<Apache2/>
directory first.
The introduction of I<Apache2/> directory is similar to how Perl
installs its modules in a version specific directory. For example:
lib/5.7.1
lib/5.7.2
=head1 Requiring a specific mod_perl version.
To require a module to run only under 2.0, simply add:
use mod_perl 2.0;
to your module. You can also use the variable C<$mod_perl::VERSION>.
In the configuration file you can use a special configuration "define"
symbol C<MODPERL2> which is enabled internally, as if the server had
been started with C<-DMODPERL2>.
<IfDefine MODPERL2>
# 2.0 configuration
</IfDefine>
<IfDefine !MODPERL2>
# else
</IfDefine>
From within Perl code this can be tested with
C<Apache::exists_config_define()>, for example:
if (Apache::exists_config_define("MODPERL2")) {
# some 2.0 specific code
}
=head1 Adjusting Modules to Work with 1.0 and 2.0.
It's possible to adjust your module to work with both 2.0 and
1.0. This is quite easy if your aren't using XS. Interfaces that are
deprecated in 2.0 can be enabled by adding:
use Apache::compat();
in the code or I<startup.pl>. The API changes are documented in L<the
back compatibility document|docs::2.0::user::compat::compat/>.
The variable C<$mod_perl::VERSION> should be used in conditionals to
use the appropriate code for 1.0 or 2.0. You can use it to load
C<Apache::compat> if running under mod_perl 2.0:
if ($mod_perl::VERSION >= 2.0) {
require Apache::compat;
}
META: while 2.0 is not released, use:
$mod_perl::VERSION >= 1.99
XS modules will need I<Makefile.PL>/C<#ifdef> logic to work with both
versions. But the applications that use them should not need to know
the difference.
META: example? probably the best to use some existing module that
co-exists with the two versions.
=head1 Thread Safety
META: to be written
#ifdef MP_THREADED
/* threads specific code goes here */
#endif
=head1 PerlIO
PerlIO layer has become usable only in perl 5.8.0, so if you plan on
working with PerlIO, you can use the C<PERLIO_LAYERS> constant. e.g.:
#ifdef PERLIO_LAYERS
#include "perliol.h"
#else
#include "iperlsys.h"
#endif
=head1 'make test' Suite
C<Apache::Test> testing framework that comes together with mod_perl
2.0 works with 1.0 and 2.0 mod_perl versions. Therefore you should
consider porting your test suite to use L<the Apache::Test
Framework|docs::general::testing::testing>.
=head1 Apache C Code Specific Notes
=head2 Apache Core Documentation
Most of documentation dedicated for migration to Apache 2.0 can be
found at: http://httpd.apache.org/docs-2.0/developer/
The Apache 2.0 API documentation now resides in the C header files,
which can be conveniently browsed via http://docx.webperf.org/.
The APR API documentation can be found here http://apr.apache.org/.
The new Apache and APR APIs include many new functions. Though certain
functions have been preserved, either as is or with a changed
prototype (for example to work with pools), others have been
renamed. So if you are porting your code and the function that you've
used doesn't seem to exist in Apache 2.0, first refer to the "compat"
header files, such as: I<include/ap_compat.h>,
I<srclib/apr/include/apr_compat.h>, and
I<srclib/apr-util/include/apu_compat.h>, which list functions whose
names have changed but which are otherwise the same. If failed,
proceed to look in other headers files in the following directories:
=over
=item *
I<ap_> functions in I<include/>
=item *
I<apr_> functions in I<srclib/apr/include/> and
I<srclib/apr-util/include/>
=back
=head2 ap_soft_timeout(), ap_reset_timeout(), ap_hard_timeout() and ap_kill_timeout()
If the C part of the module in 1.0 includes C<ap_soft_timeout()>,
C<ap_reset_timeout()>, C<ap_hard_timeout()> and C<ap_kill_timeout()>
functions simply remove these in 2.0. There is no replacement for
these functions because Apache 2.0 uses non-blocking I/O. As a
side-effect of this change, Apache 2.0 no longer uses C<SIGALRM>,
which has caused conflicts in mod_perl 1.0.
=head1 Maintainers
Maintainer is the person(s) you should contact with updates,
corrections and patches.
Stas Bekman E<lt>stas (at) stason.orgE<gt>
=head1 Authors
=over
=item *
Stas Bekman E<lt>stas (at) stason.orgE<gt>
=item *
Doug MacEachern E<lt>dougm (at) covalent.netE<gt>
=back
Only the major authors are listed above. For contributors see the
Changes file.
=cut
