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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:01:30 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:01:30 +0000 |
| commit | 6beeb1b708550be0d4a53b272283e17e5e35fe17 (patch) | |
| tree | 1ce8673d4aaa948e5554000101f46536a1e4cc29 /docs/manual/mod/mpm_common.html.en | |
| parent | Initial commit. (diff) | |
| download | apache2-upstream/2.4.57.tar.xz apache2-upstream/2.4.57.zip | |
Adding upstream version 2.4.57.upstream/2.4.57
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'docs/manual/mod/mpm_common.html.en')
| -rw-r--r-- | docs/manual/mod/mpm_common.html.en | 891 |
1 files changed, 891 insertions, 0 deletions
diff --git a/docs/manual/mod/mpm_common.html.en b/docs/manual/mod/mpm_common.html.en new file mode 100644 index 0000000..0c12f55 --- /dev/null +++ b/docs/manual/mod/mpm_common.html.en @@ -0,0 +1,891 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!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> +<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" /> +<!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>mpm_common - Apache HTTP Server Version 2.4</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.min.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/directives.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 2.4</p> +<img alt="" src="../images/feather.png" /></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 2.4</a> > <a href="./">Modules</a></div> +<div id="page-content"> +<div id="preamble"><h1>Apache MPM Common Directives</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | +<a href="../en/mod/mpm_common.html" title="English"> en </a> | +<a href="../fr/mod/mpm_common.html" hreflang="fr" rel="alternate" title="Français"> fr </a> | +<a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | +<a href="../tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p> +</div> +<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>A collection of directives that are implemented by +more than one multi-processing module (MPM)</td></tr> +<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr></table> +</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/down.gif" /> <a href="#coredumpdirectory">CoreDumpDirectory</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#enableexceptionhook">EnableExceptionHook</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#gracefulshutdowntimeout">GracefulShutdownTimeout</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#listen">Listen</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#listenbacklog">ListenBackLog</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#listencoresbucketsratio">ListenCoresBucketsRatio</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#maxconnectionsperchild">MaxConnectionsPerChild</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#maxmemfree">MaxMemFree</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#maxrequestworkers">MaxRequestWorkers</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#maxsparethreads">MaxSpareThreads</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#minsparethreads">MinSpareThreads</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#pidfile">PidFile</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#receivebuffersize">ReceiveBufferSize</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#scoreboardfile">ScoreBoardFile</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#sendbuffersize">SendBufferSize</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#serverlimit">ServerLimit</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#startservers">StartServers</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#startthreads">StartThreads</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#threadlimit">ThreadLimit</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#threadsperchild">ThreadsPerChild</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#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__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mpm_common">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mpm_common">Report a bug</a></li></ul><h3>See also</h3> +<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="directive-section"><h2><a name="CoreDumpDirectory" id="CoreDumpDirectory">CoreDumpDirectory</a> <a name="coredumpdirectory" id="coredumpdirectory">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory where Apache HTTP Server attempts to +switch before dumping core</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CoreDumpDirectory <var>directory</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for the default setting</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr> +</table> + <p>This controls the directory to which Apache httpd attempts to + switch before dumping core. If your operating system is configured to + create core files in the working directory of the crashing process, + <code class="directive">CoreDumpDirectory</code> is necessary to change working + directory from the default <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code> + directory, which should not be writable by the user the server runs as.</p> + + <p>If you want a core dump for debugging, you can use this directive to + place it in a different location. This directive has no effect if your + operating system is not configured to write core files to the working directory + of the crashing processes.</p> + + <div class="warning"> + <h3>Security note for Linux systems</h3> + + <p>Using this directive on Linux may allow other processes on + the system (if running with similar privileges, such as CGI + scripts) to attach to httpd children via the <code>ptrace</code> + system call. This may make weaken the protection from certain + security attacks. It is not recommended to use this directive + on production systems.</p> + </div> + + <div class="note"><h3>Core Dumps on Linux</h3> + <p>If Apache httpd starts as root and switches to another user, the + Linux kernel <em>disables</em> core dumps even if the directory is + writable for the process. Apache httpd (2.0.46 and later) reenables core dumps + on Linux 2.4 and beyond, but only if you explicitly configure a <code class="directive">CoreDumpDirectory</code>.</p> + </div> + + <div class="note"> + <h3>Core Dumps on BSD</h3> + <p>To enable core-dumping of suid-executables on BSD-systems (such + as FreeBSD), set <code>kern.sugid_coredump</code> to 1. + </p> + </div> + + <div class="note"><h3>Specific signals</h3> + <p><code class="directive">CoreDumpDirectory</code> processing only occurs for + a select set of fatal signals: SIGFPE, SIGILL, SIGABORT, + SIGSEGV, and SIGBUS.</p> + <p>On some operating systems, SIGQUIT also results in a core dump but + does not go through <code class="directive">CoreDumpDirectory</code> or + <code class="directive">EnableExceptionHook</code> processing, so the core + location is dictated entirely by the operating system.</p> + </div> + + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="EnableExceptionHook" id="EnableExceptionHook">EnableExceptionHook</a> <a name="enableexceptionhook" id="enableexceptionhook">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables a hook that runs exception handlers +after a crash</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableExceptionHook On|Off</code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableExceptionHook Off</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr> +</table> + <p>For safety reasons this directive is only available if the server was + configured with the <code>--enable-exception-hook</code> option. It + enables a hook that allows external modules to plug in and do something + after a child crashed.</p> + + <p>There are already two modules, <code>mod_whatkilledus</code> and + <code>mod_backtrace</code> that make use of this hook. Please have a + look at Jeff Trawick's <a href="https://emptyhammock.com/projects/httpd/diag/">EnableExceptionHook site</a> for more information about these.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="GracefulShutdownTimeout" id="GracefulShutdownTimeout">GracefulShutdownTimeout</a> <a name="gracefulshutdowntimeout" id="gracefulshutdowntimeout">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a timeout after which a gracefully shutdown server +will exit.</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>GracefulShutdownTimeout <var>seconds</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>GracefulShutdownTimeout 0</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr> +<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.2 and later</td></tr> +</table> + <p>The <code class="directive">GracefulShutdownTimeout</code> specifies + how many seconds after receiving a "graceful-stop" signal, a + server should continue to run, handling the existing connections.</p> + + <p>Setting this value to zero means that the server will wait + indefinitely until all remaining requests have been fully served.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="Listen" id="Listen">Listen</a> <a name="listen" id="listen">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>IP addresses and ports that the server +listens to</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Listen [<var>IP-address</var>:]<var>portnumber</var> [<var>protocol</var>]</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The <var>protocol</var> argument was added in 2.1.5</td></tr> +</table> + <p>The <code class="directive">Listen</code> directive instructs Apache httpd to + listen to only specific IP addresses or ports; by default it + responds to requests on all IP interfaces. <code class="directive">Listen</code> + is now a required directive. If it is not in the config file, the + server will fail to start. This is a change from previous versions + of Apache httpd.</p> + + <p>The <code class="directive">Listen</code> directive tells the server to + accept incoming requests on the specified port or address-and-port + combination. If only a port number is specified, the server listens to + the given port on all interfaces. If an IP address is given as well + as a port, the server will listen on the given port and + interface.</p> + + <p>Multiple <code class="directive">Listen</code> directives may be used to + specify a number of addresses and ports to listen to. The server will + respond to requests from any of the listed addresses and ports.</p> + + <p>For example, to make the server accept connections on both + port 80 and port 8000, use:</p> + + <pre class="prettyprint lang-config">Listen 80 +Listen 8000</pre> + + + <p>To make the server accept connections on two specified + interfaces and port numbers, use </p> + + <pre class="prettyprint lang-config">Listen 192.170.2.1:80 +Listen 192.170.2.5:8000</pre> + + + <p>IPv6 addresses must be surrounded in square brackets, as in the + following example:</p> + + <pre class="prettyprint lang-config">Listen [2001:db8::a00:20ff:fea7:ccea]:80</pre> + + + <p>The optional <var>protocol</var> argument is not required for most + configurations. If not specified, <code>https</code> is the default for + port 443 and <code>http</code> the default for all other ports. The + protocol is used to determine which module should handle a request, and + to apply protocol specific optimizations with the + <code class="directive"><a href="../mod/core.html#acceptfilter">AcceptFilter</a></code> directive.</p> + + <p>You only need to set the protocol if you are running on non-standard + ports. For example, running an <code>https</code> site on port 8443:</p> + + <pre class="prettyprint lang-config">Listen 192.170.2.1:8443 https</pre> + + + <div class="note"><h3>Error condition</h3> + Multiple <code class="directive">Listen</code> directives for the same ip + address and port will result in an <code>Address already in use</code> + error message. + </div> + + +<h3>See also</h3> +<ul> +<li><a href="../dns-caveats.html">DNS Issues</a></li> +<li><a href="../bind.html">Setting which addresses and ports Apache HTTP Server + uses</a></li> +<li><a href="http://wiki.apache.org/httpd/CouldNotBindToAddress">Further +discussion of the <code>Address already in use</code> error message, +including other causes.</a></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="ListenBackLog" id="ListenBackLog">ListenBackLog</a> <a name="listenbacklog" id="listenbacklog">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum length of the queue of pending connections</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ListenBackLog <var>backlog</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ListenBackLog 511</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +</table> + <p>The maximum length of the queue of pending connections. + Generally no tuning is needed or desired; however on some + systems, it is desirable to increase this when under a TCP SYN + flood attack. See the backlog parameter to the + <code>listen(2)</code> system call.</p> + + <p>This will often be limited to a smaller number by the + operating system. This varies from OS to OS. Also note that + many OSes do not use exactly what is specified as the backlog, + but use a number based on (but normally larger than) what is + set.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ListenCoresBucketsRatio" id="ListenCoresBucketsRatio">ListenCoresBucketsRatio</a> <a name="listencoresbucketsratio" id="listencoresbucketsratio">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Ratio between the number of CPU cores (online) and the number of +listeners' buckets</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ListenCoresBucketsRatio <var>ratio</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ListenCoresBucketsRatio 0 (disabled)</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr> +<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.4.17, with a kernel supporting +the socket option <code>SO_REUSEPORT</code> and distributing new connections +evenly across listening processes' (or threads') sockets using it (eg. Linux +3.9 and later, but not the current implementations of <code>SO_REUSEPORT</code> +in *BSDs.</td></tr> +</table> + <p>A <var>ratio</var> between the number of (online) CPU cores and the + number of listeners' buckets can be used to make Apache HTTP Server create + <code>num_cpu_cores / ratio</code> listening buckets, each containing its + own <code class="directive"><a href="#listen">Listen</a></code>-ing socket(s) on the same port(s), and + then make each child handle a single bucket (with round-robin distribution + of the buckets at children creation time).</p> + + <div class="note"><h3>Meaning of "online" CPU core</h3> + <p>On Linux (and also BSD) a CPU core can be turned on/off if + <a href="https://www.kernel.org/doc/Documentation/cpu-hotplug.txt">Hotplug</a> + is configured, therefore <code class="directive">ListenCoresBucketsRatio</code> needs to + take this parameter into account while calculating the number of buckets to create.</p> + </div> + + <p><code class="directive">ListenCoresBucketsRatio</code> can improve the + scalability when accepting new connections is/becomes the bottleneck. + On systems with a large number of CPU cores, enabling this feature has + been tested to show significant performances improvement and shorter + responses time.</p> + + <p>There must be at least twice the number of CPU cores than the + configured <var>ratio</var> for this to be active. The recommended + <var>ratio</var> is <code>8</code>, hence at least <code>16</code> + cores should be available at runtime when this value is used. + The right <var>ratio</var> to obtain maximum performance needs to be calculated + for each target system, testing multiple values and observing the variations in your + key performance metrics.</p> + + <p>This directive influences the calculation of the + <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code> and + <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code> lower bound values. + The number of children processes needs to be a multiple of the number + of buckets to optimally accept connections.</p> + + <div class="note"> + <h3>Multiple <code class="directive">Listen</code>ers or Apache HTTP servers on + the same IP address and port</h3> + <p>Setting the <code>SO_REUSEPORT</code> option on the listening socket(s) + consequently allows multiple processes (sharing the same <code>EUID</code>, + e.g. <code>root</code>) to bind to the the same IP address and port, + without the binding error raised by the system in the usual case.</p> + <p>This also means that multiple instances of Apache httpd configured on a + same <code>IP:port</code> and with a positive <code class="directive">ListenCoresBucketsRatio</code> + would start without an error too, and then run with incoming connections + evenly distributed across both instances (this is NOT a recommendation or + a sensible usage in any case, but just a notice that it would prevent such + possible issues to be detected).</p> + <p>Within the same instance, Apache httpd will check and fail to start if + multiple <code class="directive">Listen</code> directives on the exact same IP (or + hostname) and port are configured, thus avoiding the creation of some + duplicated buckets which would be useless and kill performances. However + it can't (and won't try harder to) catch all the possible overlapping cases + (like a hostname resolving to an IP used elsewhere).</p> + </div> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="MaxConnectionsPerChild" id="MaxConnectionsPerChild">MaxConnectionsPerChild</a> <a name="maxconnectionsperchild" id="maxconnectionsperchild">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit on the number of connections that an individual child server +will handle during its life</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxConnectionsPerChild <var>number</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxConnectionsPerChild 0</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available Apache HTTP Server 2.3.9 and later. The old name +<code>MaxRequestsPerChild</code> is still supported.</td></tr> +</table> + <p>The <code class="directive">MaxConnectionsPerChild</code> directive sets + the limit on the number of connections that an individual child + server process will handle. After + <code class="directive">MaxConnectionsPerChild</code> connections, the child + process will die. If <code class="directive">MaxConnectionsPerChild</code> is + <code>0</code>, then the process will never expire.</p> + + <p>Setting <code class="directive">MaxConnectionsPerChild</code> to a + non-zero value limits the amount of memory that a process can consume + by (accidental) memory leakage.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="MaxMemFree" id="MaxMemFree">MaxMemFree</a> <a name="maxmemfree" id="maxmemfree">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of memory that the main allocator is allowed +to hold without calling <code>free()</code></td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxMemFree <var>KBytes</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxMemFree 2048</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code></td></tr> +</table> + <p>The <code class="directive">MaxMemFree</code> directive sets the + maximum number of free Kbytes that every allocator is allowed + to hold without calling <code>free()</code>. In threaded MPMs, every + thread has its own allocator. When set + to zero, the threshold will be set to unlimited.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="MaxRequestWorkers" id="MaxRequestWorkers">MaxRequestWorkers</a> <a name="maxrequestworkers" id="maxrequestworkers">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of connections that will be processed +simultaneously</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxRequestWorkers <var>number</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr> +</table> + <p>The <code class="directive">MaxRequestWorkers</code> directive sets the limit + on the number of simultaneous requests that will be served. Any + connection attempts over the <code class="directive">MaxRequestWorkers</code> + limit will normally be queued, up to a number based on the + <code class="directive"><a href="#listenbacklog">ListenBacklog</a></code> + directive. Once a child process is freed at the end of a different + request, the connection will then be serviced.</p> + + <p>For non-threaded servers (<em>i.e.</em>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>), + <code class="directive">MaxRequestWorkers</code> translates into the maximum + number of child processes that will be launched to serve requests. + The default value is <code>256</code>; to increase it, you must also raise + <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p> + + <p>For threaded and hybrid servers (<em>e.g.</em> <code class="module"><a href="../mod/event.html">event</a></code> + or <code class="module"><a href="../mod/worker.html">worker</a></code>), <code class="directive">MaxRequestWorkers</code> restricts + the total number of threads that will be available to serve clients. + For hybrid MPMs, the default value is <code>16</code> (<code class="directive"><a href="#serverlimit">ServerLimit</a></code>) multiplied by the value of + <code>25</code> (<code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>). Therefore, to increase <code class="directive">MaxRequestWorkers</code> to a value that requires more than 16 processes, + you must also raise <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p> + + <p><code class="directive">MaxRequestWorkers</code> was called + <code class="directive">MaxClients</code> before version 2.3.13. The old name is still + supported.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="MaxSpareThreads" id="MaxSpareThreads">MaxSpareThreads</a> <a name="maxsparethreads" id="maxsparethreads">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle threads</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareThreads <var>number</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +</table> + <p>Maximum number of idle threads. Different MPMs deal with this + directive differently.</p> + + <p>For <code class="module"><a href="../mod/worker.html">worker</a></code> and <code class="module"><a href="../mod/event.html">event</a></code>, the default is + <code>MaxSpareThreads 250</code>. These MPMs deal with idle threads + on a server-wide basis. If there are too many idle threads in the + server, then child processes are killed until the number of idle + threads is less than this number. Additional processes/threads + might be created if <code class="directive"><a href="#listencoresbucketsratio">ListenCoresBucketsRatio</a></code> + is enabled.</p> + + <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is + <code>MaxSpareThreads 100</code>. Since this MPM runs a + single-process, the spare thread count is also server-wide.</p> + + <p><code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> works + similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. For + <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>10</code>.</p> + + <div class="note"><h3>Restrictions</h3> + <p>The range of the <code class="directive">MaxSpareThreads</code> value + is restricted. Apache httpd will correct the given value automatically + according to the following rules:</p> + <ul> + <li><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> wants the value to be greater than + <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>.</li> + + <li>For <code class="module"><a href="../mod/worker.html">worker</a></code> and <code class="module"><a href="../mod/event.html">event</a></code>, the value + must be greater or equal to the sum of <code class="directive"><a href="#minsparethreads"> + MinSpareThreads</a></code> and <code class="directive"><a href="#threadsperchild"> + ThreadsPerChild</a></code>.</li> + </ul> + </div> + +<h3>See also</h3> +<ul> +<li><code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code></li> +<li><code class="directive"><a href="#startservers">StartServers</a></code></li> +<li><code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code></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="MinSpareThreads" id="MinSpareThreads">MinSpareThreads</a> <a name="minsparethreads" id="minsparethreads">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle threads available to handle request +spikes</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareThreads <var>number</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +</table> + <p>Minimum number of idle threads to handle request spikes. + Different MPMs deal with this directive differently.</p> + + <p><code class="module"><a href="../mod/worker.html">worker</a></code> and <code class="module"><a href="../mod/event.html">event</a></code> use a default of + <code>MinSpareThreads 75</code> and deal with idle threads on a server-wide + basis. If there aren't enough idle threads in the server, then child + processes are created until the number of idle threads is greater + than <var>number</var>. Additional processes/threads + might be created if <code class="directive"><a href="#listencoresbucketsratio">ListenCoresBucketsRatio</a></code> + is enabled.</p> + + <p><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> uses a default of + <code>MinSpareThreads 10</code> and, since it is a single-process + MPM, tracks this on a server-wide basis.</p> + + <p><code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> works + similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. For + <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>5</code>.</p> + +<h3>See also</h3> +<ul> +<li><code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code></li> +<li><code class="directive"><a href="#startservers">StartServers</a></code></li> +<li><code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code></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="PidFile" id="PidFile">PidFile</a> <a name="pidfile" id="pidfile">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>File where the server records the process ID +of the daemon</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PidFile <var>filename</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>PidFile logs/httpd.pid</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +</table> + <p>The <code class="directive">PidFile</code> directive sets the file to + which the server records the process id of the daemon. If the + filename is not absolute, then it is assumed to be relative to the + <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p> + + <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">PidFile /var/run/apache.pid</pre> +</div> + + <p>It is often useful to be able to send the server a signal, + so that it closes and then re-opens its <code class="directive"><a href="../mod/core.html#errorlog">ErrorLog</a></code> and <code class="directive"><a href="../mod/mod_log_config.html#transferlog">TransferLog</a></code>, and + re-reads its configuration files. This is done by sending a + SIGHUP (kill -1) signal to the process id listed in the + <code class="directive">PidFile</code>.</p> + + <p>The <code class="directive">PidFile</code> is subject to the same + warnings about log file placement and <a href="../misc/security_tips.html#serverroot">security</a>.</p> + + <div class="note"><h3>Note</h3> + <p>As of Apache HTTP Server 2, we recommended that you only use the <code class="program"><a href="../programs/apachectl.html">apachectl</a></code> script, or the init script that your OS provides, + for (re-)starting or stopping the server.</p> + </div> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ReceiveBufferSize" id="ReceiveBufferSize">ReceiveBufferSize</a> <a name="receivebuffersize" id="receivebuffersize">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP receive buffer size</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ReceiveBufferSize <var>bytes</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ReceiveBufferSize 0</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +</table> + <p>The server will set the TCP receive buffer size to the number of + bytes specified.</p> + + <p>If set to the value of <code>0</code>, the server will use the + OS default.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ScoreBoardFile" id="ScoreBoardFile">ScoreBoardFile</a> <a name="scoreboardfile" id="scoreboardfile">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the file used to store coordination data for +the child processes</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ScoreBoardFile <var>file-path</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ScoreBoardFile logs/apache_runtime_status</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code></td></tr> +</table> + <p>Apache HTTP Server uses a scoreboard to communicate between its parent + and child processes. Some architectures require a file to facilitate + this communication. If the file is left unspecified, Apache httpd first + attempts to create the scoreboard entirely in memory (using anonymous + shared memory) and, failing that, will attempt to create the file on + disk (using file-based shared memory). Specifying this directive causes + Apache httpd to always create the file on the disk.</p> + + <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">ScoreBoardFile /var/run/apache_runtime_status</pre> +</div> + + <p>File-based shared memory is useful for third-party applications + that require direct access to the scoreboard.</p> + + <p>If you use a <code class="directive">ScoreBoardFile</code>, then + you may see improved speed by placing it on a RAM disk. But be + careful that you heed the same warnings about log file placement + and <a href="../misc/security_tips.html">security</a>.</p> + +<h3>See also</h3> +<ul> +<li><a href="../stopping.html">Stopping and Restarting +Apache HTTP Server</a></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="SendBufferSize" id="SendBufferSize">SendBufferSize</a> <a name="sendbuffersize" id="sendbuffersize">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP buffer size</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SendBufferSize <var>bytes</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SendBufferSize 0</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +</table> + <p>Sets the server's TCP send buffer size to the number of bytes + specified. It is often useful to set this past the OS's standard + default value on high speed, high latency connections + (<em>i.e.</em>, 100ms or so, such as transcontinental fast pipes).</p> + + <p>If set to the value of <code>0</code>, the server will use the + default value provided by your OS.</p> + + <p>Further configuration of your operating system may be required to elicit + better performance on high speed, high latency connections.</p> + + <div class="note"> <p> On some operating systems, changes in TCP behavior resulting + from a larger <code class="directive">SendBufferSize</code> may not be seen unless + <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code> is set to OFF. This + interaction applies only to static files.</p> </div> + + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ServerLimit" id="ServerLimit">ServerLimit</a> <a name="serverlimit" id="serverlimit">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Upper limit on configurable number of processes</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerLimit <var>number</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code></td></tr> +</table> + <p>For the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, this directive sets the + maximum configured value for <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> for the lifetime of the + Apache httpd process. For the <code class="module"><a href="../mod/worker.html">worker</a></code> and <code class="module"><a href="../mod/event.html">event + </a></code> MPMs, this directive in combination with <code class="directive"><a href="#threadlimit">ThreadLimit</a></code> sets + the maximum configured value for <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> for the lifetime of the + Apache httpd process. For the <code class="module"><a href="../mod/event.html">event</a></code> MPM, this directive + also defines how many old server processes may keep running and finish processing + open connections. + Any attempts to change this directive during a restart will be ignored, but + <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> can be modified + during a restart.</p> + + <p>Special care must be taken when using this directive. If + <code class="directive">ServerLimit</code> is set to a value much higher + than necessary, extra, unused shared memory will be allocated. If + both <code class="directive">ServerLimit</code> and <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> are set to values + higher than the system can handle, Apache httpd may not start or the + system may become unstable.</p> + + <p>With the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, use this directive only + if you need to set <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> higher than 256 (default). + Do not set the value of this directive any higher than what you + might want to set <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> to.</p> + + <p>With <code class="module"><a href="../mod/worker.html">worker</a></code>, use this directive only if your + <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers + </a></code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> + settings require more than 16 server processes (default). Do not set + the value of this directive any higher than the number of server + processes required by what you may want for <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers </a></code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>.</p> + + <p>With <code class="module"><a href="../mod/event.html">event</a></code>, increase this directive if the process + number defined by your <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> settings, plus the + number of gracefully shutting down processes, is more than 16 server + processes (default).</p> + + <div class="note"><h3>Note</h3> + <p>There is a hard limit of <code>ServerLimit 20000</code> compiled + into the server (for the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM 200000). This is + intended to avoid nasty effects caused by typos. To increase it + even further past this limit, you will need to modify the value of + MAX_SERVER_LIMIT in the mpm source file and rebuild the server.</p> + </div> + +<h3>See also</h3> +<ul> +<li><a href="../stopping.html">Stopping and Restarting Apache HTTP Server</a></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="StartServers" id="StartServers">StartServers</a> <a name="startservers" id="startservers">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of child server processes created at startup</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartServers <var>number</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +</table> + <p>The <code class="directive">StartServers</code> directive sets the + number of child server processes created on startup. As the number + of processes is dynamically controlled depending on the load, (see + <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>, + <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code>, + <code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code>, <code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code>) + there is usually little reason to adjust this parameter.</p> + + <p>The default value differs from MPM to MPM. <code class="module"><a href="../mod/worker.html">worker</a></code> and + <code class="module"><a href="../mod/event.html">event</a></code> default to <code>StartServers 3</code>; <code class="module"><a href="../mod/prefork.html"> + prefork</a></code> defaults to <code>5</code>; <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> + defaults to <code>2</code>.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="StartThreads" id="StartThreads">StartThreads</a> <a name="startthreads" id="startthreads">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created on startup</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartThreads <var>number</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code></td></tr> +</table> + <p>Number of threads created on startup. As the + number of threads is dynamically controlled depending on the + load, (see + <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>, + <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code>, + <code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code>, <code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code>) + there is usually little reason to adjust this + parameter.</p> + + <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is + <code>StartThreads 50</code> and, since there is only a single + process, this is the total number of threads created at startup to + serve requests.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ThreadLimit" id="ThreadLimit">ThreadLimit</a> <a name="threadlimit" id="threadlimit">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the upper limit on the configurable number of threads +per child process</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadLimit <var>number</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code></td></tr> +</table> + <p>This directive sets the maximum configured value for <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the lifetime + of the Apache httpd process. Any attempts to change this directive + during a restart will be ignored, but <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> can be modified + during a restart up to the value of this directive.</p> + + <p>Special care must be taken when using this directive. If + <code class="directive">ThreadLimit</code> is set to a value much higher + than <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>, + extra unused shared memory will be allocated. If both + <code class="directive">ThreadLimit</code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> are set to values + higher than the system can handle, Apache httpd may not start or the + system may become unstable. Do not set the value of this directive + any higher than your greatest predicted setting of <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the + current run of Apache httpd.</p> + + <p>The default value for <code class="directive">ThreadLimit</code> is + <code>1920</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and + <code>64</code> when used with the others.</p> + + <div class="note"><h3>Note</h3> + <p>There is a hard limit of <code>ThreadLimit 20000</code> (or + <code>ThreadLimit 100000</code> with <code class="module"><a href="../mod/event.html">event</a></code>, + <code>ThreadLimit 15000</code> with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>) + compiled into the server. This is intended to avoid nasty effects + caused by typos. To increase it even further past this limit, you + will need to modify the value of MAX_THREAD_LIMIT in the mpm + source file and rebuild the server.</p> + </div> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ThreadsPerChild" id="ThreadsPerChild">ThreadsPerChild</a> <a name="threadsperchild" id="threadsperchild">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created by each child process</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadsPerChild <var>number</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code></td></tr> +</table> + <p>This directive sets the number of threads created by each + child process. The child creates these threads at startup and + never creates more. If using an MPM like <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, + where there is only one child process, this number should be high + enough to handle the entire load of the server. If using an MPM + like <code class="module"><a href="../mod/worker.html">worker</a></code>, where there are multiple child processes, + the <em>total</em> number of threads should be high enough to handle + the common load on the server.</p> + + <p>The default value for <code class="directive">ThreadsPerChild</code> is + <code>64</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and + <code>25</code> when used with the others.</p> + + <p>The value of <code class="directive">ThreadsPerChild</code> can not exceed the + value of <code class="directive"><a href="#threadlimit">ThreadLimit</a></code>. If a + higher value is configured, it will be automatically reduced at start-up + and a warning will be logged. The relationship between these 2 directives + is explained in <code class="directive"><a href="#threadlimit">ThreadLimit</a></code>.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ThreadStackSize" id="ThreadStackSize">ThreadStackSize</a> <a name="threadstacksize" id="threadstacksize">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The size in bytes of the stack used by threads handling +client connections</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadStackSize <var>size</var></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>65536 on NetWare; varies on other operating systems</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><code class="module"><a href="../mod/event.html">event</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code>, <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code></td></tr> +<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.1 and later</td></tr> +</table> + <p>The <code class="directive">ThreadStackSize</code> directive sets the + size of the stack (for autodata) of threads which handle client + connections and call modules to help process those connections. + In most cases the operating system default for stack size is + reasonable, but there are some conditions where it may need to be + adjusted:</p> + + <ul> + <li>On platforms with a relatively small default thread stack size + (e.g., HP-UX), Apache httpd may crash when using some third-party modules + which use a relatively large amount of autodata storage. Those + same modules may have worked fine on other platforms where the + default thread stack size is larger. This type of crash is + resolved by setting <code class="directive">ThreadStackSize</code> to a + value higher than the operating system default. This type of + adjustment is necessary only if the provider of the third-party + module specifies that it is required, or if diagnosis of an Apache httpd + crash indicates that the thread stack size was too small.</li> + + <li>On platforms where the default thread stack size is + significantly larger than necessary for the web server + configuration, a higher number of threads per child process + will be achievable if <code class="directive">ThreadStackSize</code> is + set to a value lower than the operating system default. This type + of adjustment should only be made in a test environment which allows + the full set of web server processing to be exercised, as there + may be infrequent requests which require more stack to process. + The minimum required stack size strongly depends on the modules + used, but any change in the web server configuration can invalidate + the current <code class="directive">ThreadStackSize</code> setting.</li> + + <li>On Linux, this directive can only be used to increase the default + stack size, as the underlying system call uses the value as a + <em>minimum</em> stack size. The (often large) soft limit for + <code>ulimit -s</code> (8MB if unlimited) is used as the default stack + size.</li> + </ul> + + <div class="note">It is recommended to not reduce <code class="directive">ThreadStackSize</code> + unless a high number of threads per child process is needed. On some + platforms (including Linux), a setting of 128000 is already too low and + causes crashes with some common modules.</div> + +</div> +</div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | +<a href="../en/mod/mpm_common.html" title="English"> en </a> | +<a href="../fr/mod/mpm_common.html" hreflang="fr" rel="alternate" title="Français"> fr </a> | +<a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | +<a href="../tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </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. 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