docs::a...:compat(3)

💖 NAME 💖

okay so this is the docs::a...:compat(3) page, and the name line is literally Apache2::compat -- 1.0 backward compatibility functions deprecated in 2.0. bestie, that’s the whole vibe: old mod_perl 1.0 stuff trying to survive in a 2.0 world 💅

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✨ Synopsis ✨

use it at server startup, either in startup.pl or httpd.conf:

# 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');

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🫶 Description 🫶

Apache2::compat gives you a mod_perl 1.0 compatibility layer, and it’s here to smooth the transition process to mod_perl 2.0. lowkey iconic of it.

It includes functions that changed their API or were removed in mod_perl 2.0. If your code uses any of those functions, you should load this module at the server startup, and everything should work as it did in 1.0. If it doesn’t, please report the bug — but before you do that, please make sure your code does work properly under mod_perl 1.0. fr fr, check that first 🙈

warning bestie: remember that it’s implemented in pure Perl and not C, so its functionality is not optimized. the best move is to try to port your code not to use deprecated functions and stop using the compatibility layer. periodt.

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💅 Compatibility Functions Colliding with mod_perl 2.0 API 💅

Most of the functions provided by Apache2::compat don’t interfere with mod_perl 2.0 API. but bestie, there are several functions which have the same name in the mod_perl 1.0 and mod_perl 2.0 API, accept the same number of arguments, but either the arguments themselves aren’t the same or the return values are different. it’s giving “same name, different beast” 😭

For example, the 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 mod_perl 1.0 API local_addr() was returning a SOCKADDR_IN object (see the Socket perl manpage), and in 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 mod_perl 1.0 API, any code that relies on this function to work as it should under mod_perl 2.0 will be broken. 💀

Therefore the solution is not to override local_addr() by default. Instead a special API is provided which overrides colliding functions only when needed and which can be restored when no longer needed. 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 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: you need to restore the API as soon as possible. don’t leave it overridden just vibing there 🫶

Both override_mp2_api() and restore_mp2_api() accept a list of functions to operate on.

🎀 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

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🌈 Use in CPAN Modules 🌈

The short answer: Do not use Apache2::compat in CPAN modules. no cap.

The long answer:

Apache2::compat is useful during the mod_perl 1.0 code porting. 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 user’s control, loads Apache2::compat user’s code is forced to use the potentially slower method. which is quite bad 😭

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 mod_perl 2.0 API. However it should be users’ choice whether to load this module or not and not to be enforced by CPAN modules. main character energy only for the actual user, tyvm 👑

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 yeah… proceed with caution bestie 🫠

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⭐ 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. iykyk 📚

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.

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🦋 See Also 🦋

mod_perl 2.0 documentation.

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👑 Copyright 👑

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

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🌸 Authors 🌸

The mod_perl development team and numerous contributors.

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💌 that’s the whole page, bestie 💌 — from perl v5.42.3, dated 2023-10-21, page docs::a...:compat(3). mwah 💋✨