1docs::api::Apache2::comUpsaetr(3C)ontributed Perl Documednotcast:i:oanpi::Apache2::compat(3)
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NAME

6       Apache2::compat -- 1.0 backward compatibility functions deprecated in
7       2.0
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Synopsis

10         # either add at the very beginning of startup.pl
11         use Apache2::compat;
12         # or httpd.conf
13         PerlModule Apache2::compat
14
15         # override and restore compat functions colliding with mp2 API
16         Apache2::compat::override_mp2_api('Apache2::Connection::local_addr');
17         my ($local_port, $local_addr) = sockaddr_in($c->local_addr);
18         Apache2::compat::restore_mp2_api('Apache2::Connection::local_addr');
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Description

21       "Apache2::compat" provides mod_perl 1.0 compatibility layer and can be
22       used to smooth the transition process to mod_perl 2.0.
23
24       It includes functions that have changed their API or were removed in
25       mod_perl 2.0. If your code uses any of those functions, you should load
26       this module at the server startup, and everything should work as it did
27       in 1.0. If it doesn't please report the bug, but before you do that
28       please make sure that your code does work properly under mod_perl 1.0.
29
30       However, remember, that it's implemented in pure Perl and not C,
31       therefore its functionality is not optimized and it's the best to try
32       to port your code not to use deprecated functions and stop using the
33       compatibility layer.
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Compatibility Functions Colliding with mod_perl 2.0 API

36       Most of the functions provided by Apache2::compat don't interfere with
37       mod_perl 2.0 API. However there are several functions which have the
38       same name in the mod_perl 1.0 and mod_perl 2.0 API, accept the same
39       number of arguments, but either the arguments themselves aren't the
40       same or the return values are different. For example the mod_perl 1.0
41       code:
42
43         require Socket;
44         my $sockaddr_in = $c->local_addr;
45         my ($local_port, $local_addr) = Socket::sockaddr_in($sockaddr_in);
46
47       should be adjusted to be:
48
49         require Apache2::Connection;
50         require APR::SockAddr;
51         my $sockaddr = $c->local_addr;
52         my ($local_port, $local_addr) = ($sockaddr->port, $sockaddr->ip_get);
53
54       to work under mod_perl 2.0.
55
56       As you can see in mod_perl 1.0 API local_addr() was returning a
57       SOCKADDR_IN object (see the Socket perl manpage), in mod_perl 2.0 API
58       it returns an "APR::SockAddr" object, which is a totally different
59       beast. If Apache2::compat overrides the function "local_addr()" to be
60       back-compatible with mod_perl 1.0 API. Any code that relies on this
61       function to work as it should under mod_perl 2.0 will be broken.
62       Therefore the solution is not to override "local_addr()" by default.
63       Instead a special API is provided which overrides colliding functions
64       only when needed and which can be restored when no longer needed. So
65       for example if you have code from mod_perl 1.0:
66
67         my ($local_port, $local_addr) = Socket::sockaddr_in($c->local_addr);
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69       and you aren't ready to port it to to use the mp2 API:
70
71         my ($local_port, $local_addr) = ($c->local_addr->port,
72                                          $c->local_addr->ip_get);
73
74       you could do the following:
75
76         Apache2::compat::override_mp2_api('Apache2::Connection::local_addr');
77         my ($local_port, $local_addr) = Socket::sockaddr_in($c->local_addr);
78         Apache2::compat::restore_mp2_api('Apache2::Connection::local_addr');
79
80       Notice that you need to restore the API as soon as possible.
81
82       Both "override_mp2_api()" and "restore_mp2_api()" accept a list of
83       functions to operate on.
84
85   Available Overridable Functions
86       At the moment the following colliding functions are available for
87       overriding:
88
89       Apache2::RequestRec::notes
90       Apache2::RequestRec::filename
91       Apache2::RequestRec::finfo
92       Apache2::Connection::local_addr
93       Apache2::Connection::remote_addr
94       Apache2::Util::ht_time
95       Apache2::Module::top_module
96       Apache2::Module::get_config
97       APR::URI::unparse
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Use in CPAN Modules

100       The short answer: Do not use "Apache2::compat" in CPAN modules.
101
102       The long answer:
103
104       "Apache2::compat" is useful during the mod_perl 1.0 code porting.
105       Though remember that it's implemented in pure Perl. In certain cases it
106       overrides mod_perl 2.0 methods, because their API is very different and
107       doesn't map 1:1 to mod_perl 1.0. So if anything, not under user's
108       control, loads "Apache2::compat" user's code is forced to use the
109       potentially slower method. Which is quite bad.
110
111       Some users may choose to keep using "Apache2::compat" in production and
112       it may perform just fine. Other users will choose not to use that
113       module, by porting their code to use mod_perl 2.0 API. However it
114       should be users' choice whether to load this module or not and not to
115       be enforced by CPAN modules.
116
117       If you port your CPAN modules to work with mod_perl 2.0, you should
118       follow the porting Perl and XS module guidelines.
119
120       Users that are stuck with CPAN modules preloading "Apache2::compat",
121       can prevent this from happening by adding
122
123         $INC{'Apache2/compat.pm'} = __FILE__;
124
125       at the very beginning of their startup.pl. But this will most certainly
126       break the module that needed this module.
127

API

129       You should be reading the mod_perl 1.0 API docs for usage of the
130       methods and functions in this package, since what this module is doing
131       is providing a backwards compatibility and it makes no sense to
132       duplicate documentation.
133
134       Another important document to read is: Migrating from mod_perl 1.0 to
135       mod_perl 2.0 which covers all mod_perl 1.0 constants, functions and
136       methods that have changed in mod_perl 2.0.
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See Also

139       mod_perl 2.0 documentation.
140
142       mod_perl 2.0 and its core modules are copyrighted under The Apache
143       Software License, Version 2.0.
144

Authors

146       The mod_perl development team and numerous contributors.
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150perl v5.30.1                      2020-01-29     docs::api::Apache2::compat(3)
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