mirror of
https://github.com/apache/httpd.git
synced 2025-10-31 19:10:37 +03:00
4d09db3b6d
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1514216 13f79535-47bb-0310-9956-ffa450edef68
229 lines
15 KiB
XML
229 lines
15 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
|
||
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
|
||
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
|
||
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
|
||
This file is generated from xml source: DO NOT EDIT
|
||
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
|
||
-->
|
||
<title>event - Apache HTTP Server</title>
|
||
<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
|
||
<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
|
||
<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" />
|
||
<script src="../style/scripts/prettify.js" type="text/javascript">
|
||
</script>
|
||
|
||
<link href="../images/favicon.ico" rel="shortcut icon" /></head>
|
||
<body>
|
||
<div id="page-header">
|
||
<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
|
||
<p class="apache">Apache HTTP Server Version 2.5</p>
|
||
<img alt="" src="../images/feather.gif" /></div>
|
||
<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
|
||
<div id="path">
|
||
<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 2.5</a> > <a href="./">Modules</a></div>
|
||
<div id="page-content">
|
||
<div id="preamble"><h1>Apache MPM event</h1>
|
||
<div class="toplang">
|
||
<p><span>Available Languages: </span><a href="../en/mod/event.html" title="English"> en </a> |
|
||
<a href="../fr/mod/event.html" hreflang="fr" rel="alternate" title="Fran<61>ais"> fr </a></p>
|
||
</div>
|
||
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>A variant of the <code class="module"><a href="../mod/worker.html">worker</a></code> MPM with the goal
|
||
of consuming threads only for connections with active processing</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<EFBFBD>Identifier:</a></th><td>mpm_event_module</td></tr>
|
||
<tr><th><a href="module-dict.html#SourceFile">Source<EFBFBD>File:</a></th><td>event.c</td></tr></table>
|
||
<h3>Summary</h3>
|
||
|
||
<p>The <code class="module"><a href="../mod/event.html">event</a></code> Multi-Processing Module (MPM) is
|
||
designed to allow more requests to be served simultaneously by
|
||
passing off some processing work to supporting threads, freeing up
|
||
the main threads to work on new requests. It is based on the
|
||
<code class="module"><a href="../mod/worker.html">worker</a></code> MPM, which implements a hybrid
|
||
multi-process multi-threaded server. Run-time configuration
|
||
directives are identical to those provided by
|
||
<code class="module"><a href="../mod/worker.html">worker</a></code>.</p>
|
||
|
||
<p>To use the <code class="module"><a href="../mod/event.html">event</a></code> MPM, add
|
||
<code>--with-mpm=event</code> to the <code class="program"><a href="../programs/configure.html">configure</a></code>
|
||
script's arguments when building the <code class="program"><a href="../programs/httpd.html">httpd</a></code>.</p>
|
||
|
||
</div>
|
||
<div id="quickview"><h3 class="directives">Directives</h3>
|
||
<ul id="toc">
|
||
<li><img alt="" src="../images/down.gif" /> <a href="#asyncrequestworkerfactor">AsyncRequestWorkerFactor</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#enableexceptionhook">EnableExceptionHook</a></li>
|
||
<li><img alt="" src="../images/right.gif" /> <a href="mod_unixd.html#group">Group</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#maxrequestworkers">MaxRequestWorkers</a></li>
|
||
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#maxsparethreads">MaxSpareThreads</a></li>
|
||
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#minsparethreads">MinSpareThreads</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#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#serverlimit">ServerLimit</a></li>
|
||
<li><img alt="" src="../images/right.gif" /> <a href="mpm_common.html#startservers">StartServers</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>
|
||
<li><img alt="" src="../images/right.gif" /> <a href="mod_unixd.html#user">User</a></li>
|
||
</ul>
|
||
<h3>Topics</h3>
|
||
<ul id="topics">
|
||
<li><img alt="" src="../images/down.gif" /> <a href="#how-it-works">How it Works</a></li>
|
||
<li><img alt="" src="../images/down.gif" /> <a href="#requirements">Requirements</a></li>
|
||
</ul><h3>See also</h3>
|
||
<ul class="seealso">
|
||
<li><a href="worker.html">The worker MPM</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="how-it-works" id="how-it-works">How it Works</a></h2>
|
||
<p>This MPM tries to fix the 'keep alive problem' in HTTP. After a client
|
||
completes the first request, the client can keep the connection
|
||
open, and send further requests using the same socket. This can
|
||
save significant overhead in creating TCP connections. However,
|
||
Apache HTTP Server traditionally keeps an entire child process/thread waiting
|
||
for data from the client, which brings its own disadvantages. To
|
||
solve this problem, this MPM uses a dedicated thread to handle both
|
||
the Listening sockets, all sockets that are in a Keep Alive state,
|
||
and sockets where the handler and protocol filters have done their work
|
||
and the only remaining thing to do is send the data to the client. The
|
||
status page of <code class="module"><a href="../mod/mod_status.html">mod_status</a></code> shows how many connections are
|
||
in the mentioned states.</p>
|
||
|
||
<p>The improved connection handling may not work for certain connection
|
||
filters that have declared themselves as incompatible with event. In these
|
||
cases, this MPM will fall back to the behaviour of the
|
||
<code class="module"><a href="../mod/worker.html">worker</a></code> MPM and reserve one worker thread per connection.
|
||
All modules shipped with the server are compatible with the event MPM.</p>
|
||
|
||
<p>A similar restriction is currently present for requests involving an
|
||
output filter that needs to read and/or modify the whole response body,
|
||
like for example mod_ssl, mod_deflate, or mod_include. If the
|
||
connection to the client blocks while the filter is processing the
|
||
data, and the amount of data produced by the filter is too big to be
|
||
buffered in memory, the thread used for the request is not freed while
|
||
httpd waits until the pending data is sent to the client.</p>
|
||
|
||
<p>The MPM assumes that the underlying <code>apr_pollset</code>
|
||
implementation is reasonably threadsafe. This enables the MPM to
|
||
avoid excessive high level locking, or having to wake up the listener
|
||
thread in order to send it a keep-alive socket. This is currently
|
||
only compatible with KQueue and EPoll.</p>
|
||
|
||
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="section">
|
||
<h2><a name="requirements" id="requirements">Requirements</a></h2>
|
||
<p>This MPM depends on <a class="glossarylink" href="../glossary.html#apr" title="see glossary">APR</a>'s atomic
|
||
compare-and-swap operations for thread synchronization. If you are
|
||
compiling for an x86 target and you don't need to support 386s, or
|
||
you are compiling for a SPARC and you don't need to run on
|
||
pre-UltraSPARC chips, add
|
||
<code>--enable-nonportable-atomics=yes</code> to the
|
||
<code class="program"><a href="../programs/configure.html">configure</a></code> script's arguments. This will cause
|
||
APR to implement atomic operations using efficient opcodes not
|
||
available in older CPUs.</p>
|
||
|
||
<p>This MPM does not perform well on older platforms which lack good
|
||
threading, but the requirement for EPoll or KQueue makes this
|
||
moot.</p>
|
||
|
||
<ul>
|
||
|
||
<li>To use this MPM on FreeBSD, FreeBSD 5.3 or higher is recommended.
|
||
However, it is possible to run this MPM on FreeBSD 5.2.1, if you
|
||
use <code>libkse</code> (see <code>man libmap.conf</code>).</li>
|
||
|
||
<li>For NetBSD, at least version 2.0 is recommended.</li>
|
||
|
||
<li>For Linux, a 2.6 kernel is recommended. It is also necessary to
|
||
ensure that your version of <code>glibc</code> has been compiled
|
||
with support for EPoll.</li>
|
||
|
||
</ul>
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="AsyncRequestWorkerFactor" id="AsyncRequestWorkerFactor">AsyncRequestWorkerFactor</a> <a name="asyncrequestworkerfactor" id="asyncrequestworkerfactor">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit concurrent connections per process</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AsyncRequestWorkerFactor <var>factor</var></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>2</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>event</td></tr>
|
||
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.3.13 and later</td></tr>
|
||
</table>
|
||
<p>The event MPM handles some connections in an asynchronous way, where
|
||
request worker threads are only allocated for short periods of time as
|
||
needed, and other connections with one request worker thread reserved per
|
||
connection. This can lead to situations where all workers are tied up and
|
||
no worker thread is available to handle new work on established async
|
||
connections.</p>
|
||
|
||
<p>To mitigate this problem, the event MPM does two things: Firstly, it
|
||
limits the number of connections accepted per process, depending on the
|
||
number of idle request workers. Secondly, if all workers are busy, it will
|
||
close connections in keep-alive state even if the keep-alive timeout has
|
||
not expired. This allows the respective clients to reconnect to a
|
||
different process which may still have worker threads available.</p>
|
||
|
||
<p>This directive can be used to fine-tune the per-process connection
|
||
limit. A process will only accept new connections if the current number of
|
||
connections (not counting connections in the "closing" state) is lower
|
||
than:</p>
|
||
|
||
<p class="indent"><strong>
|
||
<code class="directive"><a href="../mod/mpm_common.html#threadsperchild">ThreadsPerChild</a></code> +
|
||
(<code class="directive">AsyncRequestWorkerFactor</code> *
|
||
<var>number of idle workers</var>)
|
||
</strong></p>
|
||
|
||
<p>This means the absolute maximum numbers of concurrent connections is:</p>
|
||
|
||
<p class="indent"><strong>
|
||
(<code class="directive">AsyncRequestWorkerFactor</code> + 1) *
|
||
<code class="directive"><a href="../mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code>
|
||
</strong></p>
|
||
|
||
<p><code class="directive"><a href="../mod/mpm_common.html#maxrequestworkers">MaxRequestWorkers</a></code> was called
|
||
<code class="directive">MaxClients</code> prior to version 2.3.13. The above value
|
||
shows that the old name did not accurately describe its meaning for the event MPM.</p>
|
||
|
||
<p><code class="directive">AsyncRequestWorkerFactor</code> can take non-integer
|
||
arguments, e.g "1.5".</p>
|
||
|
||
|
||
</div>
|
||
</div>
|
||
<div class="bottomlang">
|
||
<p><span>Available Languages: </span><a href="../en/mod/event.html" title="English"> en </a> |
|
||
<a href="../fr/mod/event.html" hreflang="fr" rel="alternate" title="Fran<61>ais"> fr </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&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="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
|
||
<script type="text/javascript"><!--//--><![CDATA[//><!--
|
||
var comments_shortname = 'httpd';
|
||
var comments_identifier = 'http://httpd.apache.org/docs/trunk/mod/event.html';
|
||
(function(w, d) {
|
||
if (w.location.hostname.toLowerCase() == "httpd.apache.org") {
|
||
d.write('<div id="comments_thread"><\/div>');
|
||
var s = d.createElement('script');
|
||
s.type = 'text/javascript';
|
||
s.async = true;
|
||
s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier;
|
||
(d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s);
|
||
}
|
||
else {
|
||
d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>');
|
||
}
|
||
})(window, document);
|
||
//--><!]]></script></div><div id="footer">
|
||
<p class="apache">Copyright 2013 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
|
||
<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div><script type="text/javascript"><!--//--><![CDATA[//><!--
|
||
if (typeof(prettyPrint) !== 'undefined') {
|
||
prettyPrint();
|
||
}
|
||
//--><!]]></script>
|
||
</body></html> |