libapa...:compat(3pm)

📦
version 2.0.13 · 12 versions
, in ubuntu stonking

💖 NAME 💖

ok so bestie, welcome to libapa...:compat(3pm) — the User Contributed Perl Documentation's very own page for Apache2::compat — aka the 1.0 backward compatibility functions that got deprecated in 2.0. yes it's literally a time machine, no cap 💅

✨ SYNOPSIS ✨

  # either add at the very beginning of startup.pl
  use Apache2::compat;
  # or httpd.conf
  PerlModule Apache2::compat

  # override and restore compat functions colliding with mp2 API
  Apache2::compat::override_mp2_api('Apache2::Connection::local_addr');
  my ($local_port, $local_addr) = sockaddr_in($c->local_addr);
  Apache2::compat::restore_mp2_api('Apache2::Connection::local_addr');

🌸 DESCRIPTION 🌸

Apache2::compat hands you a whole mod_perl 1.0 compatibility layer so your transition to mod_perl 2.0 doesn't have to be a whole breakdown 🫶

It's got functions whose API changed, or that straight up got yeeted in mod_perl 2.0. If your code touches any of them, you should load this module at server startup and — fingers crossed — everything works exactly like it did back in 1.0. If it doesn't, please report the bug, but before you do that, please make absolutely sure your code actually works properly under mod_perl 1.0 first, okay? do your homework bestie 📝

but remember, babes: this is implemented in pure Perl, not C. so its functionality is not optimized, and honestly the best move is to port your code so it stops using deprecated functions and stop using the compatibility layer altogether. it's giving "training wheels" energy, and we love her for it, but you gotta ride the bike eventually 🚲✨

😭 Compatibility Functions Colliding with mod_perl 2.0 API 😭

Most of the functions Apache2::compat gives you don't interfere with the mod_perl 2.0 API at all. However — and this is the tea ☕ — there are several functions with the same name in mod_perl 1.0 and mod_perl 2.0, that accept the same number of arguments, but either the arguments themselves aren't the same or the return values are different. messy, right? 💀

For example, this mod_perl 1.0 code:

  require Socket;
  my $sockaddr_in = $c->local_addr;
  my ($local_port, $local_addr) = Socket::sockaddr_in($sockaddr_in);

should be adjusted to be:

  require Apache2::Connection;
  require APR::SockAddr;
  my $sockaddr = $c->local_addr;
  my ($local_port, $local_addr) = ($sockaddr->port, $sockaddr->ip_get);

to work under mod_perl 2.0.

As you can see, in the mod_perl 1.0 API local_addr() was returning a SOCKADDR_IN object (see the Socket perl manpage), while in the mod_perl 2.0 API it returns an APR::SockAddr object, which is a totally different beast. If Apache2::compat overrides the function local_addr() to be back-compatible with the mod_perl 1.0 API, then any code relying on that function to work as it should under mod_perl 2.0 will be broken. 😬

So the solution is not to override local_addr() by default. Instead there's a special API that overrides colliding functions only when needed, and that can be restored when no longer needed. iconic behaviour, honestly 👑

So for example if you have code from mod_perl 1.0:

  my ($local_port, $local_addr) = Socket::sockaddr_in($c->local_addr);

and you aren't ready to port it to to use the mp2 API:

  my ($local_port, $local_addr) = ($c->local_addr->port,
                                   $c->local_addr->ip_get);

you could do the following:

  Apache2::compat::override_mp2_api('Apache2::Connection::local_addr');
  my ($local_port, $local_addr) = Socket::sockaddr_in($c->local_addr);
  Apache2::compat::restore_mp2_api('Apache2::Connection::local_addr');
Notice that you need to restore the API as soon as possible. like, immediately. don't leave it hanging, bestie 🙈

Both override_mp2_api() and restore_mp2_api() accept a list of functions to operate on. (multiple at once, slay)

🌈 Available Overridable Functions 🌈

At the moment the following colliding functions are available for overriding:

  • Apache2::RequestRec::notes
  • Apache2::RequestRec::filename
  • Apache2::RequestRec::finfo
  • Apache2::Connection::local_addr
  • Apache2::Connection::remote_addr
  • Apache2::Util::ht_time
  • Apache2::Module::top_module
  • Apache2::Module::get_config
  • APR::URI::unparse

🚫 Use in CPAN Modules 🚫

The short answer: Do not use Apache2::compat in CPAN modules. periodt. 💅

The long answer:

Apache2::compat is useful during the mod_perl 1.0 code porting era. Though remember that it's implemented in pure Perl. In certain cases it overrides mod_perl 2.0 methods, because their API is very different and doesn't map 1:1 to mod_perl 1.0. So if anything, not under the user's control, loads Apache2::compat, the user's code is forced to use the potentially slower method. Which is quite bad. fr fr 😤

Some users may choose to keep using Apache2::compat in production and it may perform just fine. Other users will choose not to use that module, by porting their code to use the mod_perl 2.0 API. However it should be the users' choice whether to load this module or not — and not something enforced by CPAN modules. let the people decide!! 🗳️✨

If you port your CPAN modules to work with mod_perl 2.0, you should follow the porting Perl and XS module guidelines.

Users that are stuck with CPAN modules preloading Apache2::compat, can prevent this from happening by adding

  $INC{'Apache2/compat.pm'} = __FILE__;

at the very beginning of their startup.pl.

But this will most certainly break the module that needed this module. so like... knowingly chaotic. you've been warned 💀

🎀 API 🎀

You should be reading the mod_perl 1.0 API docs for usage of the methods and functions in this package, since what this module is doing is providing a backwards compatibility and it makes no sense to duplicate documentation. (no duplicating the homework, bestie — go read the source of truth 📚)

Another important document to read is: Migrating from mod_perl 1.0 to mod_perl 2.0 which covers all mod_perl 1.0 constants, functions and methods that have changed in mod_perl 2.0.

🦋 SEE ALSO 🦋

mod_perl 2.0 documentation.

mod_perl 2.0 and its core modules are copyrighted under The Apache Software License, Version 2.0.

👑 Authors 👑

The mod_perl development team and numerous contributors.

and that's the whole page, bestie 🫶 this was libapa...:compat(3pm) from perl v5.42.3, dated 2026-08-20 — mwah, go port your code, ily, bye 👋💖✨

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