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<title>API Changes in Apache HTTP Server 2.4 since 2.2</title>

<summary>

<p>This document describes changes to the Apache HTTPD API from

version 2.2 to 2.4, that may be of interest to module/application

developers and core hacks. At the time of writing, the 2.4 API

is not finalised, and this document may serve to highlight

points that call for further review.</p>

<p>API changes fall into two categories: APIs that are altogether new,

and existing APIs that are expanded or changed. The latter are

further divided into those where all changes are back-compatible

(so existing modules can ignore them), and those that might

require attention by maintainers. As with the transition from

HTTPD 2.0 to 2.2, existing modules and applications will require

recompiling and may call for some attention, but most should not

require any substantial updating (although some may be able to

take advantage of API changes to offer significant improvements).</p>

<p>For the purpose of this document, the API is split according

to the public header files. These headers are themselves the

reference documentation, and can be used to generate a browsable

HTML reference with <code>make docs</code>.</p>

</summary>

<section id="ap_expr">

<title>ap_expr (NEW!)</title>

<p>Introduces a new API to parse and evaluate boolean and algebraic

expressions, including provision for a standard syntax and

customised variants.</p>

</section>

<section id="ap_listen">

<title>ap_listen (changed; back-compatible)</title>

<p>Introduces new API to enable apache child processes to serve different purposes.</p>

</section>

<section id="ap_mpm">

<title>ap_mpm (changed)</title>

<p><code>ap_mpm_run</code> is replaced by a new <code>mpm</code> hook.

Also <code>ap_graceful_stop_signalled</code> is lost, and

<code>ap_mpm_register_timed_callback</code> is new.</p>

</section>

<section id="ap_slotmem">

<title>ap_slotmem (NEW!)</title>

<p>Introduces an API for modules to allocate and manage memory slots

(normally) for shared memory.</p>

</section>

<section id="ap_socache">

<title>ap_socache (NEW!)</title>

<p>API to manage a shared object cache.</p>

</section>

<section id="heartbeat">

<title>heartbeat (NEW!)</title>

<p>common structures for heartbeat modules (should this be public API?)</p>

</section>

<section id="http_config">

<title>http_config (changed)</title>

<ul>

<li>Introduces per-module, per-directory loglevels, including macro wrappers.</li>

<li>New AP_DECLARE_MODULE macro to declare all modules.</li>

<li>New APLOG_USE_MODULE macro necessary for per-module loglevels in

multi-file modules.</li>

<li>New API to retain data across module unload/load</li>

<li>New check_config hook</li>

<li>New ap_process_fnmatch_configs() to process wildcards</li>

</ul>

</section>

<section id="http_core">

<title>http_core (changed)</title>

<ul>

<li>REMOVED ap_default_type, ap_requires, all 2.2 authnz API</li>

<li>Introduces Optional Functions for logio and authnz</li>

<li>New function ap_get_server_name_for_url to support ipv6 literals.</li>

</ul>

</section>

<section id="httpd">

<title>httpd (changed)</title>

<ul>

<li>Introduce per-directory, per-module loglevel</li>

<li>New loglevels APLOG_TRACEn</li>

<li>Support for mod_request kept_body</li>

<li>Support buffering filter data for async requests</li>

<li>New CONN_STATE values</li>

<li>Function changes: ap_escape_html updated; ap_unescape_all, ap_escape_path_segment_buffer</li>

</ul>

</section>

<section id="http_log">

<title>http_log (changed)</title>

<ul>

<li>Introduce per-directory, per-module loglevel</li>

<li>New loglevels APLOG_TRACEn</li>

<li>ap_log_*error become macro wrappers (fully back-compatible if

APLOG_MARK macro is used)</li>

<li>piped logging revamped</li>

<li>module_index added to error_log hook</li>

<li>new function: ap_log_command_line</li>

</ul>

</section>

<section id="http_request">

<title>http_request (changed)</title>

<ul>

<li>New auth_internal API and auth_provider API</li>

<li>New EOR bucket type</li>

<li>New function ap_process_async_request</li>

<li>New flags AP_AUTH_INTERNAL_PER_CONF and AP_AUTH_INTERNAL_PER_URI</li>

<li>New functions ap_hook_check_access, ap_hook_check_authn, ap_hook_check_authz which accept AP_AUTH_INTERNAL_PER_* flags</li>

<li>DEPRECATED direct use of ap_hook_access_checker, ap_hook_check_user_id, ap_hook_auth_checker</li>

<li>The auth_checker hook may be called with r-&gt;user == NULL</li>

</ul>

<p>When possible, registering all access control hooks (including

authentication and authorization hooks) using AP_AUTH_INTERNAL_PER_CONF

is recommended. If all modules' access control hooks are registered

with this flag, then whenever the server handles an internal

sub-request that matches the same set of access control configuration

directives as the initial request (which is the common case), it can

avoid invoking the access control hooks another time.</p>

<p>If your module requires the old behavior and must perform access

control checks on every sub-request with a different URI from the

initial request, even if that URI matches the same set of access

control configuration directives, then use AP_AUTH_INTERNAL_PER_URI.</p>

</section>

<section id="mod_auth">

<title>mod_auth (NEW!)</title>

<p>Introduces the new provider framework for authn and authz</p>

</section>

<section id="mod_core">

<title>mod_core (NEW!)</title>

<p>This introduces low-level APIs to send arbitrary headers,

and exposes functions to handle HTTP OPTIONS and TRACE.</p>

</section>

<section id="mod_request">

<title>mod_request (NEW!)</title>

<p>The API for <module>mod_request</module>, to make input data

available to multiple application/handler modules where required,

and to parse HTML form data.</p>

</section>

<section id="mpm_common">

<title>mpm_common (changed)</title>

<ul>

<li>REMOVES: accept, lockfile, lock_mech, set_scoreboard (locking uses the new ap_mutex API)</li>

<li>NEW API to drop privileges (delegates this platform-dependent

function to modules)</li>

<li>NEW Hooks: mpm_query, mpm_note_child_killed, timed_callback, get_name, and function ap_mpm_note_child_killed</li>

</ul>

</section>

<section id="scoreboard">

<title>scoreboard (changed)</title>

<p>ap_get_scoreboard_worker is gratuitously made non-back-compatible

as an alternative version is introduced. Additional proxy_balancer

support. Child status stuff revamped.</p>

</section>

<section id="util_cookies">

<title>util_cookies (NEW!)</title>

<p>Introduces a new API for managing HTTP Cookies.</p>

</section>

<section id="util_ldap">

<title>util_ldap (changed)</title>

<p>I have yet to get a handle on this update.</p>

</section>

<section id="util_mutex">

<title>util_mutex (NEW!)</title>

<p>A wrapper for APR proc and global mutexes in httpd.</p>

</section>

<section id="util_script">

<title>util_script (changed)</title>

<p>NEW: ap_args_to_table</p>

</section>

<section id="util_time">

<title>util_time (changed)</title>

<p>NEW: ap_recent_ctime_ex</p>

</section>

</manualpage>