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<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE manualpage SYSTEM "./style/manualpage.dtd">
<?xml-stylesheet type="text/xsl" href="./style/manual.en.xsl"?>
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<manualpage metafile="new_features_2_2.xml.meta">
<title>Overview of new features in Apache HTTP Server 2.2</title>
<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>
<section id="core">
<title>Core Enhancements</title>
<dd>The bundled authentication and authorization modules have
been refactored. The new mod_authn_alias(already removed from 2.3/2.4)
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
<dd><module>mod_cache</module>, <module>mod_cache_disk</module>, and
mod_mem_cache(already removed from 2.3/2.4) have undergone a lot of changes, and
are now considered production-quality. <program>htcacheclean</program>
has been introduced to clean up <module>mod_cache_disk</module>
<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>
<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="">Apache Tomcat</a>.</dd>
<dt>Regular Expression Library Updated</dt>
<dd>Version 5.0 of the
<a href="">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>
<section id="module">
<title>Module Enhancements</title>
<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
mod_authn_alias(already removed from 2.3/2.4) module for simplifying
certain authentication configurations.
<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>
<dd>A new module that authorizes access to files based
on the owner of the file on the file system</dd>
<dd>A new module that allows configuration blocks to be enabled based on the
version number of the running server.</dd>
<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>
<!-- Need Info on SSLEngine Support? -->
<dd>Added a support for
<a href="">RFC 2817</a>, which
allows connections to upgrade from clear text to TLS encryption.</dd>
<dd><code>mod_imap</code> has been renamed to
<module>mod_imagemap</module> to avoid user confusion.</dd>
<section id="programs">
<title>Program Enhancements</title>
<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>
<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>
<section id="developer">
<title>Module Developer Changes</title>
<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="">APR Website</a>.</dd>
<dd>The bundled authentication and authorization modules have
been renamed along the following lines:
<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>
There is a new authentication backend provider
scheme which greatly eases the construction of new authentication
<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>
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