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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> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <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">&nbsp;en&nbsp;</a> |
<a href="./fr/new_features_2_4.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</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
     version 2.0, see the <a href="new_features_2_2.html">2.2 new features</a>
     document.</p>
</div>
<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="#developer">Module Developer Changes</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>
    
    <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>
      <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
      level.</dd>
    </dl>
  </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>
    
    <dl>
      <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_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_lua.html">mod_lua</a></code></dt>
      <dd>Embeds the <a href="http://www.lua.org/">Lua</a> language into httpd, 
      for configuration and small business logic functions.</dd>

      <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_ratelimit.html">mod_ratelimit</a></code></dt>
      <dd>Provides Bandwidth Rate Limiting for Clients</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_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_reqtimeout.html">mod_reqtimeout</a></code></dt>
      <dd>Set timeout and minimum data rate for receiving requests</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_slotmem_shm.html">mod_slotmem_shm</a></code></dt>
      <dd>Provides a Slot-based shared memory provider (ala the scoreboard).</dd>

    </dl>
  </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>
    
    <dl>
      <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>
 
      <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>

      <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>

      <dt><code class="module"><a href="./mod/mod_cache.html">mod_cache</a></code></dt>

      <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>

    </dl>
  </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>
    
    <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><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>
    
    <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
          exposed in <var>ap_expr.h</var>.  This is adapted from the
          expression parser previously implemented in
          <code class="module"><a href="./mod/mod_include.html">mod_include</a></code>.</dd>

      <dt>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>, all
          provided by the <code class="module"><a href="./mod/mod_authz_core.html">mod_authz_core</a></code> module.</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
      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
    <a href="developer/new_api_2_4.html">detailed list of API changes</a>.</p>
  </div></div>
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<a href="./fr/new_features_2_4.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a></p>
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