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<div id="preamble"><h1>Apache MPM winnt</h1>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Multi-Processing Module optimized for Windows NT.</td></tr>
<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>mpm_winnt_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mpm_winnt.c</td></tr></table>
<h3>Summary</h3>

    <p>This Multi-Processing Module (MPM) is the default for the
    Windows NT operating systems. It uses a single control process
    which launches a single child process which in turn creates
    threads to handle requests</p>

    <p>Capacity is configured using the 
    <code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code> directive,
    which sets the maximum number of concurrent client connections.</p>

    <p>By default, this MPM uses advanced Windows APIs for accepting
    new client connections.  In some configurations, third-party products
    may interfere with this implementation, with the following messages
    written to the web server log:</p>

    <div class="example"><p><code>
        Child: Encountered too many AcceptEx faults accepting client connections.<br />
        winnt_mpm: falling back to 'AcceptFilter none'.
    </code></p></div>

    <p>The MPM falls back to a safer implementation, but some client requests
    were not processed correctly.  In order to avoid this error, use
    <code class="directive"><a href="../mod/core.html#acceptfilter">AcceptFilter</a></code> with accept filter 
    <code>none</code>.</p>

    <pre class="prettyprint lang-config">AcceptFilter http none
AcceptFilter https none</pre>

    
    <p><em>In Apache httpd 2.0 and 2.2,
    <code class="directive">Win32DisableAcceptEx</code> was used for this purpose.</em></p>

    <p>The WinNT MPM differs from the Unix MPMs such as worker and event
    in several areas:</p>

    <ul>
      <li>When a child process is exiting due to shutdown, restart, or
      <code class="directive"><a href="../mod/mpm_common.html#maxconnectionsperchild">MaxConnectionsPerChild</a></code>,
      active requests in the exiting process have
      <code class="directive"><a href="../mod/core.html#timeout">TimeOut</a></code> seconds to finish before
      processing is aborted.  Alternate types of restart and shutdown are not
      implemented.</li>

      <li>New child processes read the configuration files instead of
      inheriting the configuration from the parent.  The behavior will
      be the same as on Unix if the child process is created at startup
      or restart, but if a child process is created because the prior
      one crashed or reached 
      <code class="directive"><a href="../mod/mpm_common.html#maxconnectionsperchild">MaxConnectionsPerChild</a></code>,
      any pending changes to the configuration will become active in the
      child at that point, and the parent and child will be using a
      different configuration.  If planned configuration changes have been
      partially implemented and the current configuration cannot be
      parsed, the replacement child process cannot start up and the server 
      will halt.  Because of this behavior, configuration files should not
      be changed until the time of a server restart.</li>

      <li>The <code>monitor</code> and <code>fatal_exception</code> hooks
      are not currently implemented.</li>

      <li><code class="directive">AcceptFilter</code> is implemented in the MPM
      and has a different type of control over handling of new connections.
      (Refer to the <code class="directive"><a href="../mod/core.html#acceptfilter">AcceptFilter</a></code>
      documentation for details.)</li>
    </ul>

</div>
<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/right.gif" /> <a href="core.html#acceptfilter">AcceptFilter</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listen">Listen</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#listenbacklog">ListenBacklog</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxconnectionsperchild">MaxConnectionsPerChild</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxmemfree">MaxMemFree</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#pidfile">PidFile</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#receivebuffersize">ReceiveBufferSize</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#sendbuffersize">SendBufferSize</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#threadlimit">ThreadLimit</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#threadsperchild">ThreadsPerChild</a></li>
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#threadstacksize">ThreadStackSize</a></li>
</ul>
<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&amp;list_id=144532&amp;product=Apache%20httpd-2&amp;query_format=specific&amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;component=mpm_winnt">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mpm_winnt">Report a bug</a></li></ul><h3>See also</h3>
<ul class="seealso">
<li><a href="../platform/windows.html">Using Apache HTTP Server on Microsoft Windows</a></li>
<li><a href="#comments_section">Comments</a></li></ul></div>

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