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<title>Overview of new features in Apache HTTP Server 2.4 - Apache HTTP Server</title>
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<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="/faq/">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p>
<p class="apache">Apache HTTP Server Version 2.3</p>
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<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="./">Version 2.3</a></div><div id="page-content"><div id="preamble"><h1>Overview of new features in Apache HTTP Server 2.4</h1>
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<p><span>Available Languages: </span><a href="/en/new_features_2_4.html" title="English"> en </a> |
<a href="/fr/new_features_2_4.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a></p>
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<p>This document describes some of the major changes between the
2.2 and 2.4 versions of the Apache HTTP Server. For new features since
document.</p>
</div>
<div id="quickview"><ul id="toc"><li><img alt="" src="/images/down.gif" /> <a href="#core">Core Enhancements</a></li>
</ul></div>
<div class="section">
<h2><a name="core" id="core">Core Enhancements</a></h2>
<dl>
<dt>KeepAliveTimeout in milliseconds</dt>
<dd>It is now possible to specify <code class="directive"><a href="/mod/core.html#keepalivetimeout">KeepAliveTimeout</a></code> in milliseconds.
</dd>
<dt>Loadable MPMs</dt>
<dd>Multiple MPMs can now be built as loadable modules at compile time.
The MPM of choice can be configured at run time.</dd>
<dt>Per-module and per-directory LogLevel configuration</dt>
configured per module and per directory. New levels <code>trace1</code>
to <code>trace8</code> have been added above the <code>debug</code> log
level.</dd>
<dt>Event MPM</dt>
<dd>The Event MPM is no longer experimental but is now fully supported.</dd>
<dt>Asynchronous support</dt>
platforms.</dd>
<dt>Per-request configuration sections</dt>
<dd><<code class="directive"><a href="/mod/core.html#if">If</a></code>> sections can be used to
set the configuration based on per-request criteria</dd>
<dt>NameVirtualHost directive</dt>
<dd>No longer needed and is now deprecated.</dd>
</dl>
<div class="section">
<h2><a name="newmods" id="newmods">New Modules</a></h2>
<dl>
<dd>New module to restrict certain HTTP methods without interfering with
authentication or authorization.</dd>
<dd>Provides for buffering the input and output filter stacks</dd>
<dd>Convert response body into an RFC2397 data URL</dd>
for configuration and small business logic functions.</dd>
<dd>Provides dynamically configured mass reverse proxies for <code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code></dd>
<dd>FastCGI Protocol backend for <code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code></dd>
<dd>SCGI Protocol backend for <code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code></dd>
<dd>Provides Bandwidth Rate Limiting for Clients</dd>
<dd>Provides Reflection of a request body as a response via the output filter stack.</dd>
<dd>Replaces the apparent client remote IP address and hostname for the request
with the IP address list presented by a proxies or a load balancer via
the request headers.</dd>
<dd>Set timeout and minimum data rate for receiving requests</dd>
<dd>Provides Filters to handle and make available HTTP request bodies</dd>
<dd>Provides a Slot-based shared memory provider (ala the scoreboard).</dd>
<dd>Allows to add customizable debug logging at different phases of the
request processing.</dd>
<dd>Formerly a third-party module, this supports internationalisation
in libxml2-based (markup-aware) filter modules.</dd>
<dd>Formerly a third-party module, this supports fixing of HTML
links in a reverse proxy situation, where the backend generates
URLs that are not valid for the proxy's clients.</dd>
</dl>
<div class="section">
<h2><a name="module" id="module">Module Enhancements</a></h2>
<dl>
<dd><code class="module"><a href="/mod/mod_ssl.html">mod_ssl</a></code> can now be configured to use an
OCSP server to check the validation status of a client
certificate. The default responder is configurable, along with
the decision on whether to prefer the responder designated in
the client certificate itself.</dd>
<dd><code class="module"><a href="/mod/mod_ssl.html">mod_ssl</a></code> now also supports OCSP stapling, where the
server pro-actively obtains an OCSP verification of its certificate and
transmits that to the client during the handshake. </dd>
<dd><code class="module"><a href="/mod/mod_ssl.html">mod_ssl</a></code> can now be configured to share SSL Session
data between servers through memcached</dd>
<dd>The <code class="directive"><a href="/mod/mod_proxy.html#proxypass">ProxyPass</a></code> directive
is now most optimally configured within a
block, and offers a significant performance advantage over the traditional
two-parameter syntax when present in large numbers.</dd>
<dd>More runtime configuration changes for BalancerMembers via balancer-manager</dd>
<dd>Additional BalancerMembers can be added at runtime via balancer-manager</dd>
<dd>Runtime configuration of a subset of Balancer parameters</dd>
<dd>BalancerMembers can be set to 'Drain' so that they only respond to existing sticky
sessions, allowing them to be taken gracefully offline.</dd>
<dd>Balancer settings can be persistant after restarts.</dd>
<dd><code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> can now cache HEAD requests.</dd>
<dd>Where possible, <code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> directives can now be set
per directory, instead of per server.</dd>
<dd>The base URL of cached URLs can be customised, so that a cluster of
caches can share the same endpoint URL prefix.</dd>
<dd><code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> is now capable of serving stale cached
data when a backend is unavailable (error 5xx).</dd>
<dd><code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> can now insert HIT/MISS/REVALIDATE into
an X-Cache header.</dd>
<dd>Support for the 'onerror' attribute within an 'include' element,
allowing an error document to be served on error instead of the default
error string.</dd>
<dt><code class="module"><a href="/mod/mod_cgi.html">mod_cgi</a></code>, <code class="module"><a href="/mod/mod_include.html">mod_include</a></code>,
<dd>Translation of headers to environment variables is more strict than
before to mitigate some possible cross-site-scripting attacks via header
injection. Headers containing invalid characters (including underscores)
are now silently dropped. <a href="env.html">Environment Variables
in Apache</a> has some pointers on how to work around broken legacy
clients which require such headers. (This affects all modules which
use these environment variables.)</dd>
<dt><code class="module"><a href="/mod/mod_authz_core.html">mod_authz_core</a></code> Authorization Logic Containers</dt>
<dd>Advanced authorization logic may now be specified using the
and the related container directives, such as
<code class="directive"><a href="/mod/mod_authz_core.html#requireall"><RequireAll></a></code>.</dd>
<dd><code class="module"><a href="/mod/mod_info.html">mod_info</a></code> can now dump the pre-parsed configuration
to stdout during server startup.</dd>
<dd><code class="module"><a href="/mod/mod_rewrite.html">mod_rewrite</a></code> adds the <code>[QSD]</code>
(Query String Discard) and <code>[END]</code> flags for
simplify common rewriting scenarios.</dd>
</dl>
<div class="section">
<h2><a name="programs" id="programs">Program Enhancements</a></h2>
<dl>
<dt>fcgistarter</dt>
<dd>FastCGI deamon starter utility</dd>
<dt>htcacheclean</dt>
<dd>Current cached URLs can now be listed, with optional metadata
included.</dd>
<dd>Allow explicit deletion of individual cached URLs from the
cache.</dd>
<dd>File sizes can now be rounded up to the given block size, making
the size limits map more closely to the real size on disk.</dd>
<dd>Cache size can now be limited by the number of inodes, instead
of or in addition to being limited by the size of the files on
disk.</dd>
</dl>
<div class="section">
<h2><a name="developer" id="developer">Module Developer Changes</a></h2>
<dl>
<dt>Check Configuration Hook Added</dt>
<dd>A new hook, <code>check_config</code>, has been added which runs
between the <code>pre_config</code> and <code>open_logs</code>
hooks. It also runs before the <code>test_config</code> hook
when the <code>-t</code> option is passed to
<code class="program"><a href="/programs/httpd.html">httpd</a></code>. The <code>check_config</code> hook
allows modules to review interdependent configuration directive
values and adjust them while messages can still be logged to the
console. The user can thus be alerted to misconfiguration problems
before the core <code>open_logs</code> hook function redirects
console output to the error log.</dd>
<dt>Expression Parser Added</dt>
<dd>We now have a general-purpose expression parser, whose API is
expression parser previously implemented in
<dt>Authorization Logic Containers</dt>
<dd>Authorization modules now register as a provider, via
ap_register_auth_provider(), to support advanced authorization logic,
such as <code class="directive"><a href="/mod/mod_authz_core.html#requireall"><RequireAll></a></code>.</dd>
<dt>Small-Object Caching Interface</dt>
interface for caching small data objects, based on the previous
implementation of the <code class="module"><a href="/mod/mod_ssl.html">mod_ssl</a></code> session cache.
Providers using a shared-memory cyclic buffer, disk-based dbm
files, and a memcache distributed cache are currently
supported.</dd>
<dt>Cache Status Hook Added</dt>
<dd>The <code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> module now includes a new
<code>cache_status</code> hook, which is called when the caching
decision becomes known. A default implementation is provided
which adds an optional <code>X-Cache</code> and
<code>X-Cache-Detail</code> header to the response.</dd>
</dl>
<p>The developer documentation contains a
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