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<title>Overview of new features in Apache 2.2</title>

<summary>

<p>This document describes some of the major changes between the

2.0 and 2.2 versions of the Apache HTTP Server. For new features since

version 1.3, see the <a href="new_features_2_0.html">2.0 new features</a>

document.</p>

</summary>

<section id="core">

<title>Core Enhancements</title>

<dl>

<dt>Authn/Authz</dt>

<dd>The bundled authentication and authorization modules have

been refactored. The new <module>mod_authn_alias</module> module

can greatly simplify certain authentication configurations.

See <a href="#module">module name changes</a>, and

<a href="#developer">the developer changes</a> for more

information about how these changes affects users and module

writers.</dd>

<dt>Caching</dt>

<dd><module>mod_cache</module>, <module>mod_disk_cache</module>, and

<module>mod_mem_cache</module> have undergone a lot of changes, and

are now considered production-quality. <program>htcacheclean</program>

has been introduced to clean up <module>mod_disk_cache</module>

setups.</dd>

<dt>Configuration</dt>

<dd>The default configuration layout has been simplified and

modularised. Configuration snippets which can be used to

enable commonly-used features are now bundled with Apache, and

can be easily added to the main server config.</dd>

<dt>Graceful stop</dt>

<dd>The <module>prefork</module>, <module>worker</module> and

<module>event</module> MPMs now allow <program>httpd</program>

to be shutdown gracefully via the

<a href="stopping.html#gracefulstop"><code>graceful-stop</code></a>

signal. The <directive

module="mpm_common">GracefulShutdownTimeout</directive> directive

has been added to specify an optional timeout, after which

<program>httpd</program> will terminate regardless of the status

of any requests being served.</dd>

<dt>Proxying</dt>

<dd>The new <module>mod_proxy_balancer</module> module provides

load balancing services for <module>mod_proxy</module>.

The new <module>mod_proxy_ajp</module> module adds support for the

<code>Apache JServ Protocol version 1.3</code> used by

<a href="http://jakarta.apache.org/tomcat/">Apache Tomcat</a>.</dd>

<dt>Regular Expression Library Updated</dt>

<dd>Version 5.0 of the

<a href="http://www.pcre.org/">Perl Compatible Regular Expression

Library</a> (PCRE) is now included. <program>httpd</program> can be

configured to use a system installation of PCRE by passing the

<code>--with-pcre</code> flag to configure.</dd>

<dt>Smart Filtering</dt>

<dd><module>mod_filter</module> introduces dynamic configuration

to the output filter chain. It enables filters to be conditionally

inserted, based on any Request or Response header or environment

variable, and dispenses with the more problematic dependencies and

ordering problems in the 2.0 architecture.</dd>

<dt>Large File Support</dt>

<dd><program>httpd</program> is now built with support for files larger

than 2GB on modern 32-bit Unix systems. Support for handling

&gt;2GB request bodies has also been added.</dd>

<dt>Event MPM</dt>

<dd>The <module>event</module> MPM uses a separate thread to handle

Keep Alive requests and accepting connections. Keep Alive requests

have traditionally required httpd to dedicate a worker to handle it.

This dedicated worker could not be used again until the Keep Alive

timeout was reached.</dd>

<dt>SQL Database Support</dt>

<dd><module>mod_dbd</module>, together with the <code>apr_dbd</code>

framework, brings direct SQL support to modules that need it.

Supports connection pooling in threaded MPMs.</dd>

</dl>

</section>

<section id="module">

<title>Module Enhancements</title>

<dl>

<dt>Authn/Authz</dt>

<dd>Modules in the aaa directory have been renamed and offer

better support for digest authentication. For example,

<code>mod_auth</code> is now split into

<module>mod_auth_basic</module> and

<module>mod_authn_file</module>; <code>mod_auth_dbm</code> is now

called <module>mod_authn_dbm</module>; <code>mod_access</code> has

been renamed <module>mod_authz_host</module>. There is also a new

<module>mod_authn_alias</module> module for simplifying

certain authentication configurations.

</dd>

<dt><module>mod_authnz_ldap</module></dt>

<dd>This module is a port of the 2.0

<code>mod_auth_ldap</code> module to the 2.2 <code>Authn/Authz</code>

framework. New features include using LDAP attribute values and

complicated search filters in the

<directive module="mod_authz_core">Require</directive> directive.</dd>

<dt><module>mod_authz_owner</module></dt>

<dd>A new module that authorizes access to files based

on the owner of the file on the file system</dd>

<dt><module>mod_version</module></dt>

<dd>A new module that allows configuration blocks to be enabled based on the

version number of the running server.</dd>

<dt><module>mod_info</module></dt>

<dd>Added a new <code>?config</code> argument which will show

the configuration directives as parsed by Apache, including

their file name and line number. The module also

shows the order of all request hooks and additional

build information, similar to <code>httpd -V</code>.</dd>

<dt><module>mod_ssl</module></dt>

<!-- Need Info on SSLEngine Support? -->

<dd>Added a support for

<a href="http://www.ietf.org/rfc/rfc2817.txt">RFC 2817</a>, which

allows connections to upgrade from clear text to TLS encryption.</dd>

<dt><module>mod_imagemap</module></dt>

<dd><code>mod_imap</code> has been renamed to

<module>mod_imagemap</module> to avoid user confusion.</dd>

</dl>

</section>

<section id="programs">

<title>Program Enhancements</title>

<dl>

<dt><program>httpd</program></dt>

<dd>A new command line option <code>-M</code> has been added that

lists all modules that are loaded based on the current

configuration. Unlike the <code>-l</code> option, this list

includes DSOs loaded via <module>mod_so</module>.</dd>

<dt><program>httxt2dbm</program></dt>

<dd>A new program used to generate dbm files from text input,

for use in <directive module="mod_rewrite">RewriteMap</directive>

with the <code>dbm</code> map type.</dd>

</dl>

</section>

<section id="developer">

<title>Module Developer Changes</title>

<dl>

<dt><glossary>APR</glossary> 1.0 API</dt>

<dd>Apache 2.2 uses the APR 1.0 API. All deprecated functions and

symbols have been removed from <code>APR</code> and

<code>APR-Util</code>. For details, see the

<a href="http://apr.apache.org/">APR Website</a>.</dd>

<dt>Authn/Authz</dt>

<dd>The bundled authentication and authorization modules have

been renamed along the following lines:

<ul>

<li><code>mod_auth_*</code> -> Modules that implement an HTTP

authentication mechanism</li>

<li><code>mod_authn_*</code> -> Modules that provide a backend

authentication provider</li>

<li><code>mod_authz_*</code> -> Modules that implement

authorization (or access)</li>

<li><code>mod_authnz_*</code> -> Module that implements both

authentication &amp; authorization</li>

</ul>

There is a new authentication backend provider

scheme which greatly eases the construction of new authentication

backends.</dd>

<dt>Connection Error Logging</dt>

<dd>A new function, <code>ap_log_cerror</code> has been added to log

errors that occur with the client's connection. When logged,

the message includes the client IP address.</dd>

<dt>Test Configuration Hook Added</dt>

<dd>A new hook, <code>test_config</code> has been added to aid

modules that want to execute special code only when the user passes

<code>-t</code> to <program>httpd</program>.</dd>

<dt>Set Threaded MPM's Stacksize</dt>

<dd>A new directive, <directive module="mpm_common"

>ThreadStackSize</directive> has been added to

set the stack size on all threaded MPMs. This is required

for some third-party modules on platforms with small default

thread stack size.</dd>

<dt>Protocol handling for output filters</dt>

<dd>In the past, every filter has been responsible for ensuring

that it generates the correct response headers where it affects

them. Filters can now delegate common protocol management to

<module>mod_filter</module>, using the

<code>ap_register_output_filter_protocol</code> or

<code>ap_filter_protocol</code> calls.</dd>

<dt>Monitor hook added</dt>

<dd>Monitor hook enables modules to run regular/scheduled jobs

in the parent (root) process.</dd>

<dt>Regular expression API changes</dt>

<dd>The <code>pcreposix.h</code> header is no longer available;

it is replaced by the new <code>ap_regex.h</code> header. The

POSIX.2 <code>regex.h</code> implementation exposed by the old

header is now available under the <code>ap_</code> namespace

from <code>ap_regex.h</code>. Calls to <code>regcomp</code>,

<code>regexec</code> and so on can be replaced by calls to

<code>ap_regcomp</code>, <code>ap_regexec</code>.</dd>

<dt>DBD Framework (SQL Database API)</dt>

<dd><p>With Apache 1.x and 2.0, modules requiring an SQL backend

had to take responsibility for managing it themselves. Apart

from reinventing the wheel, this can be very inefficient, for

example when several modules each maintain their own connections.</p>

<p>Apache 2.1 and later provides the <code>ap_dbd</code> API for

managing database connections (including optimised strategies

for threaded and unthreaded MPMs), while APR 1.2 and later provides

the <code>apr_dbd</code> API for interacting with the database.</p>

<p>New modules SHOULD now use these APIs for all SQL database

operations. Existing applications SHOULD be upgraded to use it

where feasible, either transparently or as a recommended option

to their users.</p></dd>

</dl>

</section>

</manualpage>