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<manualpage metafile="new_features_2_4.xml.meta">

<title>Overview of new features in Apache HTTP Server 2.4</title>

<summary>
  <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>
</summary>

  <section id="core">
    <title>Core Enhancements</title>
    <dl>
      <dt>KeepAliveTimeout in milliseconds</dt>

      <dd>It is now possible to specify <directive module="core"
      >KeepAliveTimeout</directive> in milliseconds.
      </dd>
 
      <dt>Simple MPM</dt>
      <dd>Cleanroom MPM implementation with advanced thread pool management</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 <directive module="core">LogLevel</directive> 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>
  </section>

  <section id="module">
    <title>Module Enhancements</title>
    <dl>
      <dt><module>mod_ssl</module></dt>

      <dd><module>mod_ssl</module> 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><module>mod_ssl</module> 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><module>mod_ssl</module> can now be configured to share SSL Session 
      data between servers through memcached</dd>
 
      <dt><module>mod_lua</module></dt>

      <dd>Embeds the <a href="http://www.lua.org/">Lua</a> language into httpd, 
      for configuration and small business logic functions.</dd>
 
      <dt><module>mod_proxy_fcgi</module></dt>

      <dd>FastCGI Protocol backend for <module>mod_proxy</module></dd>
    </dl>
  </section>

  <section id="programs">
    <title>Program Enhancements</title>
    <dl>
        <dt>fcgistarter</dt>
        <dd>FastCGI deamon starter utility</dd>
    </dl>
  </section>

  <section id="developer">
    <title>Module Developer Changes</title>
    <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
          <program>httpd</program>.  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
          <module>mod_include</module>.</dd>

      <dt>Authorization Logic Containers</dt>

      <dd>Advanced authorization logic may now be specified using the
          <directive module="mod_authz_core">Require</directive> directive
          and the related container directives, such as
          <directive module="mod_authz_core"
          type="section">RequireAll</directive>, all
          provided by the <module>mod_authz_core</module> 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 <module>mod_ssl</module> session cache.
      Providers using a shared-memory cyclic buffer, disk-based dbm
      files, and a memcache distributed cache are currently
      supported.</dd>

    </dl>
  </section>
</manualpage>
