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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="apache">Apache HTTP Server Version 2.5</p>
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<a href="">Apache</a> &gt; <a href="">HTTP Server</a> &gt; <a href="">Documentation</a> &gt; <a href="./">Version 2.5</a></div><div id="page-content"><div id="preamble"><h1>Overview of new features in Apache HTTP Server 2.4</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="./en/new_features_2_4.html" title="English">&nbsp;en&nbsp;</a> |
<a href="./fr/new_features_2_4.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
<a href="./tr/new_features_2_4.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
<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
version 2.0, see the <a href="new_features_2_2.html">2.2 new features</a>
<div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#core">Core Enhancements</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#newmods">New Modules</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#module">Module Enhancements</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#programs">Program Enhancements</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#documentation">Documentation</a></li>
<li><img alt="" src="./images/down.gif" /> <a href="#developer">Module Developer Changes</a></li>
</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="core" id="core">Core Enhancements</a></h2>
<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>Event MPM</dt>
<dd>The Event MPM is no longer experimental but is now fully supported.</dd>
<dt>Asynchronous support</dt>
<dd>Better support for asynchronous read/write for supporting MPMs and
<dt>Per-module and per-directory LogLevel configuration</dt>
<dd>The <code class="directive"><a href="./mod/core.html#loglevel">LogLevel</a></code> can now be
configured per module and per directory. New levels <code>trace1</code>
to <code>trace8</code> have been added above the <code>debug</code> log
<dt>Per-request configuration sections</dt>
<dd><code class="directive"><a href="./mod/core.html#if">&lt;If&gt;</a></code>,
<code class="directive"><a href="./mod/core.html#elseif">&lt;ElseIf&gt;</a></code>,
and <code class="directive"><a href="./mod/core.html#else">&lt;Else&gt;</a></code>
sections can be used to set the configuration based on per-request
<dt>General-purpose expression parser</dt>
<dd>A new expression parser allows to specify
<a href="expr.html">complex conditions</a> using a common syntax
in directives like
<code class="directive"><a href="./mod/mod_setenvif.html#setenvifexpr">SetEnvIfExpr</a></code>,
<code class="directive"><a href="./mod/mod_rewrite.html#rewritecond">RewriteCond</a></code>,
<code class="directive"><a href="./mod/mod_headers.html#header">Header</a></code>,
<code class="directive"><a href="./mod/core.html#if">&lt;If&gt;</a></code>,
and others.
<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.
<dt>NameVirtualHost directive</dt>
<dd>No longer needed and is now deprecated.</dd>
<dt>Override Configuration</dt>
<dd>The new <code class="directive"><a href="./mod/core.html#allowoverridelist">AllowOverrideList</a></code>
directive allows more fine grained control which directives are
allowed in <code>.htaccess</code> files. </dd>
<dt>Config file variables</dt>
<dd>It is now possible to <code class="directive"><a href="./mod/core.html#define">Define</a></code>
variables in the configuration, allowing a clearer representation
if the same value is used at many places in the configuration.
<dt>Reduced memory usage</dt>
<dd>Despite many new features, 2.4.x tends to use less memory than
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="newmods" id="newmods">New Modules</a></h2>
<dt><code class="module"><a href="./mod/mod_proxy_fcgi.html">mod_proxy_fcgi</a></code></dt>
<dd>FastCGI Protocol backend for <code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code></dd>
<dt><code class="module"><a href="./mod/mod_proxy_scgi.html">mod_proxy_scgi</a></code></dt>
<dd>SCGI Protocol backend for <code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code></dd>
<dt><code class="module"><a href="./mod/mod_proxy_express.html">mod_proxy_express</a></code></dt>
<dd>Provides dynamically configured mass reverse proxies for
<code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code></dd>
<dt><code class="module"><a href="./mod/mod_remoteip.html">mod_remoteip</a></code></dt>
<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>
<dt><code class="module"><a href="./mod/mod_heartmonitor.html">mod_heartmonitor</a></code>,
<code class="module"><a href="./mod/mod_lbmethod_heartbeat.html">mod_lbmethod_heartbeat</a></code></dt>
<dd>Allow <code class="module"><a href="./mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code> to base loadbalancing decisions
on the number of active connections on the backend servers.</dd>
<dt><code class="module"><a href="./mod/mod_proxy_html.html">mod_proxy_html</a></code></dt>
<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>
<dt><code class="module"><a href="./mod/mod_sed.html">mod_sed</a></code></dt>
<dd>An advanced replacement of <code class="module"><a href="./mod/mod_substitute.html">mod_substitute</a></code>, allows
to edit the response body with the full power of sed.</dd>
<dt><code class="module"><a href="./mod/mod_auth_form.html">mod_auth_form</a></code></dt>
<dd>Allows to do form-based authentication.</dd>
<dt><code class="module"><a href="./mod/mod_session.html">mod_session</a></code></dt>
<dd>Allows to keep session state for clients, using cookie or
database storage.</dd>
<dt><code class="module"><a href="./mod/mod_allowmethods.html">mod_allowmethods</a></code></dt>
<dd>New module to restrict certain HTTP methods without interfering with
authentication or authorization.</dd>
<dt><code class="module"><a href="./mod/mod_lua.html">mod_lua</a></code></dt>
<dd>Embeds the <a href="">Lua</a> language into httpd,
for configuration and small business logic functions. (Experimental)</dd>
<dt><code class="module"><a href="./mod/mod_log_debug.html">mod_log_debug</a></code></dt>
<dd>Allows to add customizable debug logging at different phases of the
request processing.</dd>
<dt><code class="module"><a href="./mod/mod_buffer.html">mod_buffer</a></code></dt>
<dd>Provides for buffering the input and output filter stacks</dd>
<dt><code class="module"><a href="./mod/mod_data.html">mod_data</a></code></dt>
<dd>Convert response body into an RFC2397 data URL</dd>
<dt><code class="module"><a href="./mod/mod_ratelimit.html">mod_ratelimit</a></code></dt>
<dd>Provides Bandwidth Rate Limiting for Clients</dd>
<dt><code class="module"><a href="./mod/mod_request.html">mod_request</a></code></dt>
<dd>Provides Filters to handle and make available HTTP request bodies</dd>
<dt><code class="module"><a href="./mod/mod_reflector.html">mod_reflector</a></code></dt>
<dd>Provides Reflection of a request body as a response via the output filter stack.</dd>
<dt><code class="module"><a href="./mod/mod_slotmem_shm.html">mod_slotmem_shm</a></code></dt>
<dd>Provides a Slot-based shared memory provider (ala the scoreboard).</dd>
<dt><code class="module"><a href="./mod/mod_xml2enc.html">mod_xml2enc</a></code></dt>
<dd>Formerly a third-party module, this supports internationalisation
in libxml2-based (markup-aware) filter modules.</dd>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="module" id="module">Module Enhancements</a></h2>
<dt><code class="module"><a href="./mod/mod_ssl.html">mod_ssl</a></code></dt>
<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>EC keys are now supported in addition to RSA and DSA.</dd>
<dt><code class="module"><a href="./mod/mod_proxy.html">mod_proxy</a></code></dt>
<dd>The <code class="directive"><a href="./mod/mod_proxy.html#proxypass">ProxyPass</a></code> directive
is now most optimally configured within a
<code class="directive"><a href="./mod/core.html#location">Location</a></code> or
<code class="directive"><a href="./mod/core.html#locationmatch">LocationMatch</a></code>
block, and offers a significant performance advantage over the traditional
two-parameter syntax when present in large numbers.</dd>
<dd>The source address used for proxy requests is now configurable.</dd>
<dt><code class="module"><a href="./mod/mod_proxy_balancer.html">mod_proxy_balancer</a></code></dt>
<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 persistent after restarts.</dd>
<dt><code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code></dt>
<dd>The <code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code> CACHE filter can be optionally inserted
at a given point in the filter chain to provide fine control over caching.
<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>
<dt><code class="module"><a href="./mod/mod_include.html">mod_include</a></code></dt>
<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>,
<code class="module"><a href="./mod/mod_isapi.html">mod_isapi</a></code>, ...</dt>
<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
<code class="directive"><a href="./mod/mod_authz_core.html#require">Require</a></code> directive
and the related container directives, such as
<code class="directive"><a href="./mod/mod_authz_core.html#requireall">&lt;RequireAll&gt;</a></code>.</dd>
<dt><code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code></dt>
<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
<code class="directive"><a href="./mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> to
simplify common rewriting scenarios.</dd>
<dd>Adds the possibility to use complex boolean expressions in <code class="directive"><a href="./mod/mod_rewrite.html#rewritecond">RewriteCond</a></code>.</dd>
<dd>Allows to use SQL queries as <code class="directive"><a href="./mod/mod_rewrite.html#rewritemap">RewriteMap</a></code> functions.</dd>
<dt><code class="module"><a href="./mod/mod_ldap.html">mod_ldap</a></code>, <code class="module"><a href="./mod/mod_authnz_ldap.html">mod_authnz_ldap</a></code></dt>
<dd><code class="module"><a href="./mod/mod_authnz_ldap.html">mod_authnz_ldap</a></code> adds support for nested groups.</dd>
<dd><code class="module"><a href="./mod/mod_ldap.html">mod_ldap</a></code> adds
<code class="directive"><a href="./mod/mod_ldap.html#ldapconnectionpoolttl">LDAPConnectionPoolTTL</a></code>,
<code class="directive"><a href="./mod/mod_ldap.html#ldaptimeout">LDAPTimeout</a></code>, and
other improvements in the handling of timeouts.
This is especially useful for setups where a
stateful firewall drops idle connections to the LDAP server.</dd>
<dd><code class="module"><a href="./mod/mod_ldap.html">mod_ldap</a></code> adds
<code class="directive"><a href="./mod/mod_ldap.html#ldaplibrarydebug">LDAPLibraryDebug</a></code> to log
debug information provided by the used LDAP toolkit.</dd>
<dt><code class="module"><a href="./mod/mod_info.html">mod_info</a></code></dt>
<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>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="programs" id="programs">Program Enhancements</a></h2>
<dd>New FastCGI deamon starter utility</dd>
<dd>Current cached URLs can now be listed, with optional metadata
<dd>Allow explicit deletion of individual cached URLs from the
<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
<dd>May now create a link to the current log file.</dd>
<dd>May now invoke a custom post-rotate script.</dd>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="documentation" id="documentation">Documentation</a></h2>
<dd>The <code class="module"><a href="./mod/mod_rewrite.html">mod_rewrite</a></code> documentation has been
rearranged and almost completely rewritten, with a focus on
examples and common usage, as well as on showing you when other
solutions are more appropriate. The <a href="rewrite/">Rewrite
Guide</a> is now a top-level section with much more detail and
better organization.</dd>
<dd>The <code class="module"><a href="./mod/mod_ssl.html">mod_ssl</a></code> documentation has been greatly
enhanced, with more examples at the getting started level, in
addition to the previous focus on technical details.</dd>
<dt>Caching Guide</dt>
<dd>The <a href="caching.html">Caching Guide</a> has been rewritten
to properly distinguish between the RFC2616 HTTP/1.1 caching
features provided by <code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code>, and the generic
key/value caching provided by the <a href="socache.html">socache</a>
interface, as well as to cover specialised caching provided by
mechanisms such as <code class="module"><a href="./mod/mod_file_cache.html">mod_file_cache</a></code>.</dd>
</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div>
<div class="section">
<h2><a name="developer" id="developer">Module Developer Changes</a></h2>
<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
exposed in <var>ap_expr.h</var>. This is adapted from the
expression parser previously implemented in
<code class="module"><a href="./mod/mod_ssl.html">mod_ssl</a></code>.</dd>
<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">&lt;RequireAll&gt;</a></code>.</dd>
<dt>Small-Object Caching Interface</dt>
<dd>The <var>ap_socache.h</var> header exposes a provider-based
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
<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>
<p>The developer documentation contains a
<a href="developer/new_api_2_4.html">detailed list of API changes</a>.</p>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="./en/new_features_2_4.html" title="English">&nbsp;en&nbsp;</a> |
<a href="./fr/new_features_2_4.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
<a href="./tr/new_features_2_4.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
</div><div class="top"><a href="#page-header"><img src="./images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&amp;A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="">mailing lists</a>.</div>
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