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15a44745412679c30a6d022733925af70a38b715David Lawrence<title>mpm_common - Apache HTTP Server</title>
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a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="/faq/">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p>
3d60fe9bafbf633e3a7811c11227baebb17878a4Brian Wellington<p class="apache">Apache HTTP Server Version 2.1</p>
9c3531d72aeaad6c5f01efe6a1c82023e1379e4dDavid Lawrence<img alt="" src="/images/feather.gif" /></div>
f41f183f628a148860a6d1f0070208cddd45b0c6Bob Halley<div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="/images/left.gif" /></a></div>
f41f183f628a148860a6d1f0070208cddd45b0c6Bob Halley<div id="path">
f41f183f628a148860a6d1f0070208cddd45b0c6Bob Halley<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs-project/">Documentation</a> &gt; <a href="../">Version 2.1</a> &gt; <a href="./">Modules</a></div>
f41f183f628a148860a6d1f0070208cddd45b0c6Bob Halley<div id="page-content">
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<div id="preamble"><h1>Apache MPM Common Directives</h1>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<div class="toplang">
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley<p><span>Available Languages: </span><a href="/de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley<a href="/en/mod/mpm_common.html" title="English">&nbsp;en&nbsp;</a> |
51917258dbb23cfe6069ae1cf2b7fc5aefc1e0c2Bob Halley<a href="/ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a></p>
51917258dbb23cfe6069ae1cf2b7fc5aefc1e0c2Bob Halley</div>
51917258dbb23cfe6069ae1cf2b7fc5aefc1e0c2Bob Halley<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>A collection of directives that are implemented by
6d5dcd0dc9bdbd679282b1ffc47987d24c3a1346Bob Halleymore than one multi-processing module (MPM)</td></tr>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr></table>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley</div>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<div id="quickview"><h3 class="directives">Directives</h3>
c45abd11bb68005d8a5c56c14b16f4184c3e057dMichael Graff<ul id="toc">
c45abd11bb68005d8a5c56c14b16f4184c3e057dMichael Graff<li><img alt="" src="/images/down.gif" /> <a href="#acceptmutex">AcceptMutex</a></li>
ab3f2d77bddef25a0af62d89894cb4964ee4f1d8Andreas Gustafsson<li><img alt="" src="/images/down.gif" /> <a href="#coredumpdirectory">CoreDumpDirectory</a></li>
ab3f2d77bddef25a0af62d89894cb4964ee4f1d8Andreas Gustafsson<li><img alt="" src="/images/down.gif" /> <a href="#enableexceptionhook">EnableExceptionHook</a></li>
ab3f2d77bddef25a0af62d89894cb4964ee4f1d8Andreas Gustafsson<li><img alt="" src="/images/down.gif" /> <a href="#gracefulshutdowntimeout">GracefulShutdownTimeout</a></li>
ab3f2d77bddef25a0af62d89894cb4964ee4f1d8Andreas Gustafsson<li><img alt="" src="/images/down.gif" /> <a href="#group">Group</a></li>
ab3f2d77bddef25a0af62d89894cb4964ee4f1d8Andreas Gustafsson<li><img alt="" src="/images/down.gif" /> <a href="#listen">Listen</a></li>
a685d9c3b608eb768d237f20e8e8b1c5d3902146David Lawrence<li><img alt="" src="/images/down.gif" /> <a href="#listenbacklog">ListenBackLog</a></li>
feb08cecf318bba330437cfcb725f48d999804d8James Brister<li><img alt="" src="/images/down.gif" /> <a href="#lockfile">LockFile</a></li>
c6d0fc864de5153699688ffd28ef8a286b986354James Brister<li><img alt="" src="/images/down.gif" /> <a href="#maxclients">MaxClients</a></li>
feb08cecf318bba330437cfcb725f48d999804d8James Brister<li><img alt="" src="/images/down.gif" /> <a href="#maxmemfree">MaxMemFree</a></li>
feb08cecf318bba330437cfcb725f48d999804d8James Brister<li><img alt="" src="/images/down.gif" /> <a href="#maxrequestsperchild">MaxRequestsPerChild</a></li>
feb08cecf318bba330437cfcb725f48d999804d8James Brister<li><img alt="" src="/images/down.gif" /> <a href="#maxsparethreads">MaxSpareThreads</a></li>
9d794b52031144006ffb987ac8533a95c677c378Brian Wellington<li><img alt="" src="/images/down.gif" /> <a href="#minsparethreads">MinSpareThreads</a></li>
e49d50b4436d760c040dca81c8426ee806996d6bDavid Lawrence<li><img alt="" src="/images/down.gif" /> <a href="#pidfile">PidFile</a></li>
e49d50b4436d760c040dca81c8426ee806996d6bDavid Lawrence<li><img alt="" src="/images/down.gif" /> <a href="#receivebuffersize">ReceiveBufferSize</a></li>
e323a667e0324e6ac67a10c6fdd82a6a57097dc8James Brister<li><img alt="" src="/images/down.gif" /> <a href="#scoreboardfile">ScoreBoardFile</a></li>
feb08cecf318bba330437cfcb725f48d999804d8James Brister<li><img alt="" src="/images/down.gif" /> <a href="#sendbuffersize">SendBufferSize</a></li>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington<li><img alt="" src="/images/down.gif" /> <a href="#serverlimit">ServerLimit</a></li>
698de4d4c0463cf0eb1cfd71e13387ee2cf8d7a5Brian Wellington<li><img alt="" src="/images/down.gif" /> <a href="#startservers">StartServers</a></li>
698de4d4c0463cf0eb1cfd71e13387ee2cf8d7a5Brian Wellington<li><img alt="" src="/images/down.gif" /> <a href="#startthreads">StartThreads</a></li>
d7483d67f7aa8f80d5f880aa4650f2bdb90d6623Brian Wellington<li><img alt="" src="/images/down.gif" /> <a href="#threadlimit">ThreadLimit</a></li>
5d0cca62ee6551a2af73e72ee53c05436b43520bBrian Wellington<li><img alt="" src="/images/down.gif" /> <a href="#threadsperchild">ThreadsPerChild</a></li>
3d60fe9bafbf633e3a7811c11227baebb17878a4Brian Wellington<li><img alt="" src="/images/down.gif" /> <a href="#threadstacksize">ThreadStackSize</a></li>
3d60fe9bafbf633e3a7811c11227baebb17878a4Brian Wellington<li><img alt="" src="/images/down.gif" /> <a href="#user">User</a></li>
65c4736d9c0ebc6d9b1d991593b55566909da9cdBrian Wellington</ul>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington</div>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington<div class="directive-section"><h2><a name="AcceptMutex" id="AcceptMutex">AcceptMutex</a> <a name="acceptmutex" id="acceptmutex">Directive</a></h2>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington<table class="directive">
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Method that Apache uses to serialize multiple children
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellingtonaccepting requests on network sockets</td></tr>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AcceptMutex Default|<var>method</var></code></td></tr>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>AcceptMutex Default</code></td></tr>
15f7ee3c0b027d9a6a3e25e548215236326b3b04Brian Wellington<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
65c4736d9c0ebc6d9b1d991593b55566909da9cdBrian Wellington<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
65c4736d9c0ebc6d9b1d991593b55566909da9cdBrian Wellington<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
75e4800964642475632766068e8d99de3ea3e8f0Brian Wellington</table>
75e4800964642475632766068e8d99de3ea3e8f0Brian Wellington <p>The <code class="directive">AcceptMutex</code> directives sets the
75e4800964642475632766068e8d99de3ea3e8f0Brian Wellington method that Apache uses to serialize multiple children accepting
65c4736d9c0ebc6d9b1d991593b55566909da9cdBrian Wellington requests on network sockets. Prior to Apache 2.0, the method was
65c4736d9c0ebc6d9b1d991593b55566909da9cdBrian Wellington selectable only at compile time. The optimal method to use is
65c4736d9c0ebc6d9b1d991593b55566909da9cdBrian Wellington highly architecture and platform dependent. For further details,
75e4800964642475632766068e8d99de3ea3e8f0Brian Wellington see the <a href="/misc/perf-tuning.html">performance tuning</a>
75e4800964642475632766068e8d99de3ea3e8f0Brian Wellington documentation.</p>
65c4736d9c0ebc6d9b1d991593b55566909da9cdBrian Wellington
65c4736d9c0ebc6d9b1d991593b55566909da9cdBrian Wellington <p>If this directive is set to <code>Default</code>, then the
15f7ee3c0b027d9a6a3e25e548215236326b3b04Brian Wellington compile-time selected default will be used. Other possible
15f7ee3c0b027d9a6a3e25e548215236326b3b04Brian Wellington methods are listed below. Note that not all methods are
15f7ee3c0b027d9a6a3e25e548215236326b3b04Brian Wellington available on all platforms. If a method is specified which is
d01c654984fd4f1a20cb4905548076afeba1c8c1Brian Wellington not available, a message will be written to the error log
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington listing the available methods.</p>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington <dl>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington <dt><code>flock</code></dt>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington <dd>uses the <code>flock(2)</code> system call to lock the
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington file defined by the <code class="directive"><a href="#lockfile">LockFile</a></code> directive.</dd>
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington
ec90f1a1d6a4dc7af1fbe166fbb2bd69fb0ca53bDavid Lawrence <dt><code>fcntl</code></dt>
5af0b591fdbd8634e245ace452767d2fc328c05aBrian Wellington <dd>uses the <code>fcntl(2)</code> system call to lock the
d8e93e7f902b73108952891ced5b02e743c71f99Brian Wellington file defined by the <code class="directive"><a href="#lockfile">LockFile</a></code> directive.</dd>
65c4736d9c0ebc6d9b1d991593b55566909da9cdBrian Wellington
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence <dt><code>posixsem</code></dt>
850d70818503ca1b0f98c9c70b16b51e789fd705Andreas Gustafsson <dd>uses POSIX compatible semaphores to implement the mutex.</dd>
6017f424ee3c02d7f22132c77576ea38542fa949Andreas Gustafsson
911ed0d3bee586b3bec42cb6c376d5cc6c0e1e24Brian Wellington <dt><code>pthread</code></dt>
911ed0d3bee586b3bec42cb6c376d5cc6c0e1e24Brian Wellington <dd>uses POSIX mutexes as implemented by the POSIX Threads
911ed0d3bee586b3bec42cb6c376d5cc6c0e1e24Brian Wellington (PThreads) specification.</dd>
911ed0d3bee586b3bec42cb6c376d5cc6c0e1e24Brian Wellington
ab3f2d77bddef25a0af62d89894cb4964ee4f1d8Andreas Gustafsson <dt><code>sysvsem</code></dt>
3cd88f71b01833d5c2474638854dfa5c4244a22aBrian Wellington <dd>uses SySV-style semaphores to implement the mutex.</dd>
3cd88f71b01833d5c2474638854dfa5c4244a22aBrian Wellington </dl>
3cd88f71b01833d5c2474638854dfa5c4244a22aBrian Wellington
ce1f5b8d0ae5936fd187c1f414ff12a7e3b0aa37Andreas Gustafsson <p>If you want to find out the compile time chosen default
850d70818503ca1b0f98c9c70b16b51e789fd705Andreas Gustafsson for your system, you may set your <code class="directive"><a href="/mod/core.html#loglevel">LogLevel</a></code> to <code>debug</code>. Then the default <code class="directive">AcceptMutex</code> will be written into the <code class="directive"><a href="/mod/core.html#errorlog">ErrorLog</a></code>.</p>
18d110413cf6416eb339c169b99159d09f690da1Brian Wellington
ab3f2d77bddef25a0af62d89894cb4964ee4f1d8Andreas Gustafsson <div class="warning"><h3>Warning</h3>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley <p>On most systems, when the <code>pthread</code> option
fc80027fb54b501cdd88461bf879d078259e0226David Lawrence is selected, if a child process terminates abnormally
850d70818503ca1b0f98c9c70b16b51e789fd705Andreas Gustafsson while holding the <code>AcceptCntl</code> mutex the
6017f424ee3c02d7f22132c77576ea38542fa949Andreas Gustafsson server will stop responding to requests. When this
911ed0d3bee586b3bec42cb6c376d5cc6c0e1e24Brian Wellington occurs, the server will require a manual restart to
911ed0d3bee586b3bec42cb6c376d5cc6c0e1e24Brian Wellington recover.</p>
911ed0d3bee586b3bec42cb6c376d5cc6c0e1e24Brian Wellington <p>Solaris is a notable exception as it provides a
911ed0d3bee586b3bec42cb6c376d5cc6c0e1e24Brian Wellington mechanism, used by Apache, which usually allows the
ab3f2d77bddef25a0af62d89894cb4964ee4f1d8Andreas Gustafsson mutex to be recovered after a child process terminates
3cd88f71b01833d5c2474638854dfa5c4244a22aBrian Wellington abnormally while holding a mutex.</p>
3cd88f71b01833d5c2474638854dfa5c4244a22aBrian Wellington <p>If your system implements the
3cd88f71b01833d5c2474638854dfa5c4244a22aBrian Wellington <code>pthread_mutexattr_setrobust_np()</code> function,
ce1f5b8d0ae5936fd187c1f414ff12a7e3b0aa37Andreas Gustafsson you may be able to use the <code>pthread</code> option safely.</p>
850d70818503ca1b0f98c9c70b16b51e789fd705Andreas Gustafsson </div>
18d110413cf6416eb339c169b99159d09f690da1Brian Wellington
4fd3e3482c7e4ce01e2cf28f13e0152c8e50d746Mark Andrews</div>
feb08cecf318bba330437cfcb725f48d999804d8James Brister<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
4fd3e3482c7e4ce01e2cf28f13e0152c8e50d746Mark Andrews<div class="directive-section"><h2><a name="CoreDumpDirectory" id="CoreDumpDirectory">CoreDumpDirectory</a> <a name="coredumpdirectory" id="coredumpdirectory">Directive</a></h2>
4fd3e3482c7e4ce01e2cf28f13e0152c8e50d746Mark Andrews<table class="directive">
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory where Apache attempts to
d2b5fe92a4755ce67f2dd6050955782b4fd6b3f3Mark Andrewsswitch before dumping core</td></tr>
d2b5fe92a4755ce67f2dd6050955782b4fd6b3f3Mark Andrews<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CoreDumpDirectory <var>directory</var></code></td></tr>
d2b5fe92a4755ce67f2dd6050955782b4fd6b3f3Mark Andrews<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for the default setting</code></td></tr>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley</table>
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley <p>This controls the directory to which Apache attempts to
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley switch before dumping core. The default is in the
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley <code class="directive"><a href="/mod/core.html#serverroot">ServerRoot</a></code> directory, however
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley since this should not be writable by the user the server runs
139154bd9894495042f4e748f554e9c8b98b7598Bob Halley as, core dumps won't normally get written. If you want a core
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley dump for debugging, you can use this directive to place it in a
193738b819e3c699f9edd18864a6810fcfcec855Andreas Gustafsson different location.</p>
fd35453765c6494d077edca44f4d998af5fd4cfaDavid Lawrence
fd35453765c6494d077edca44f4d998af5fd4cfaDavid Lawrence <div class="note"><h3>Core Dumps on Linux</h3>
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley <p>If Apache starts as root and switches to another user, the
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley Linux kernel <em>disables</em> core dumps even if the directory is
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley writable for the process. Apache (2.0.46 and later) reenables core dumps
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley on Linux 2.4 and beyond, but only if you explicitly configure a <code class="directive">CoreDumpDirectory</code>.</p>
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley </div>
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley</div>
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<div class="directive-section"><h2><a name="EnableExceptionHook" id="EnableExceptionHook">EnableExceptionHook</a> <a name="enableexceptionhook" id="enableexceptionhook">Directive</a></h2>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<table class="directive">
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables a hook that runs exception handlers
922e6a3c2ac4ef900dd9dc99f0cc137f18372583Andreas Gustafssonafter a crash</td></tr>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableExceptionHook On|Off</code></td></tr>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableExceptionHook Off</code></td></tr>
a2f3208f7f754cbc5156a1d798ae06d8f3546be2Bob Halley<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
a5d43b72413db3edd6b36a58f9bdf2cf6ff692f2Bob Halley<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
4880900113e4d0f17884f3fbdbf4c302e3f9ea91Bob Halley<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
fd35453765c6494d077edca44f4d998af5fd4cfaDavid Lawrence<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.0.49 and later</td></tr>
c8a42d6d81ff2fd9ad7fac94d4b85323554493c0Bob Halley</table>
4fd3e3482c7e4ce01e2cf28f13e0152c8e50d746Mark Andrews <p>For safety reasons this directive is only available if the server was
5d51e67c3b4f35c1be742574aacc1d88fe6ed444Mark Andrews configured with the <code>--enable-exception-hook</code> option. It
6ef838d427c1ea858d2f09194a369134babf8b98Mark Andrews enables a hook that allows external modules to plug in and do something
6ef838d427c1ea858d2f09194a369134babf8b98Mark Andrews after a child crashed.</p>
6ef838d427c1ea858d2f09194a369134babf8b98Mark Andrews
6ef838d427c1ea858d2f09194a369134babf8b98Mark Andrews <p>There are already two modules, <code>mod_whatkilledus</code> and
6d831cd0baf7dd2c133f7f9cbf295f3d80cf63a7David Lawrence <code>mod_backtrace</code> that make use of this hook. Please have a
6d831cd0baf7dd2c133f7f9cbf295f3d80cf63a7David Lawrence look at Jeff Trawick's <a href="http://www.apache.org/~trawick/exception_hook.html">EnableExceptionHook site</a> for more information about these.</p>
dac2799ea19735503a4d27f517d821aea210e594Andreas Gustafsson
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley</div>
5d51e67c3b4f35c1be742574aacc1d88fe6ed444Mark Andrews<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
6d7585b3e948dd31bf78321d83ac0e024f44a71bMark Andrews<div class="directive-section"><h2><a name="GracefulShutdownTimeout" id="GracefulShutdownTimeout">GracefulShutdownTimeout</a> <a name="gracefulshutdowntimeout" id="gracefulshutdowntimeout">Directive</a></h2>
6d5dcd0dc9bdbd679282b1ffc47987d24c3a1346Bob Halley<table class="directive">
6d7585b3e948dd31bf78321d83ac0e024f44a71bMark Andrews<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a timeout after which a gracefully shutdown server
6d7585b3e948dd31bf78321d83ac0e024f44a71bMark Andrewswill exit.</td></tr>
6d5dcd0dc9bdbd679282b1ffc47987d24c3a1346Bob Halley<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>GracefulShutDownTimeout <var>seconds</var></code></td></tr>
6d7585b3e948dd31bf78321d83ac0e024f44a71bMark Andrews<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>GracefulShutDownTimeout 0</code></td></tr>
1471a520e59ac12b413afa8d8b3158a87af97aa6Bob Halley<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
1471a520e59ac12b413afa8d8b3158a87af97aa6Bob Halley<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
1471a520e59ac12b413afa8d8b3158a87af97aa6Bob Halley<tr><th><a href="directive-dict.html#Module">Module:</a></th><td><code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code>, <code class="module"><a href="/mod/event.html">event</a></code></td></tr>
94a3bcd132e515b4baa0884ba9dd0f361d2e17bcMark Andrews<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.2 and later</td></tr>
1471a520e59ac12b413afa8d8b3158a87af97aa6Bob Halley</table>
1471a520e59ac12b413afa8d8b3158a87af97aa6Bob Halley <p>The <code class="directive">GracefulShutdownTimeout</code> specifies
4fd3e3482c7e4ce01e2cf28f13e0152c8e50d746Mark Andrews how many seconds after receiving a "graceful-stop" signal, a
5d51e67c3b4f35c1be742574aacc1d88fe6ed444Mark Andrews server should continue to run, handling the existing connections.</p>
6d5dcd0dc9bdbd679282b1ffc47987d24c3a1346Bob Halley
5d51e67c3b4f35c1be742574aacc1d88fe6ed444Mark Andrews <p>Setting this value to zero means that the server will wait
5d51e67c3b4f35c1be742574aacc1d88fe6ed444Mark Andrews indefinitely until all remaining requests have been fully served.</p>
139154bd9894495042f4e748f554e9c8b98b7598Bob Halley
bb556a9bf3a15c7160fa4f1b71773ce12b1bedf6Bob Halley</div>
64e41159a919b0711321fe688ca5da4f4d1b7d80Bob Halley<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div>
1471a520e59ac12b413afa8d8b3158a87af97aa6Bob Halley<div class="directive-section"><h2><a name="Group" id="Group">Group</a> <a name="group" id="group">Directive</a></h2>
1471a520e59ac12b413afa8d8b3158a87af97aa6Bob Halley<table class="directive">
1471a520e59ac12b413afa8d8b3158a87af97aa6Bob Halley<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Group under which the server will answer
fe37278859bce157001cca14cdfa3a761b0d5012Mark Andrewsrequests</td></tr>
1471a520e59ac12b413afa8d8b3158a87af97aa6Bob Halley<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Group <var>unix-group</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Group #-1</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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only valid in global server config since Apache
2.0</td></tr>
</table>
<p>The <code class="directive">Group</code> directive sets the group under
which the server will answer requests. In order to use this
directive, the server must be run initially as <code>root</code>. If
you start the server as a non-root user, it will fail to change to the
specified group, and will instead continue to run as the group of the
original user. <var>Unix-group</var> is one of:</p>
<dl>
<dt>A group name</dt>
<dd>Refers to the given group by name.</dd>
<dt><code>#</code> followed by a group number.</dt>
<dd>Refers to a group by its number.</dd>
</dl>
<div class="example"><h3>Example</h3><p><code>
Group www-group
</code></p></div>
<p>It is recommended that you set up a new group specifically for
running the server. Some admins use user <code>nobody</code>,
but this is not always possible or desirable.</p>
<div class="warning"><h3>Security</h3>
<p>Don't set <code class="directive">Group</code> (or <code class="directive"><a href="#user">User</a></code>) to <code>root</code> unless
you know exactly what you are doing, and what the dangers are.</p>
</div>
<p>Special note: Use of this directive in <code class="directive"><a href="/mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code> is no longer supported. To
configure your server for <code class="program"><a href="/programs/suexec.html">suexec</a></code> use
<code class="directive"><a href="/mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code>.</p>
<div class="note"><h3>Note</h3>
<p>Although the <code class="directive">Group</code> directive is present
in the <code class="module"><a href="/mod/beos.html">beos</a></code> and <code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code> MPMs,
it is actually a no-op there and only exists for compatibility
reasons.</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="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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</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>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code>, <code class="module"><a href="/mod/event.html">event</a></code></td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Required directive since Apache 2.0<br />
The <var>protocol</var> argument was added in 2.1.5</td></tr>
</table>
<p>The <code class="directive">Listen</code> directive instructs Apache 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.</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>
<div class="example"><p><code>
Listen 80<br />
Listen 8000
</code></p></div>
<p>To make the server accept connections on two specified
interfaces and port numbers, use </p>
<div class="example"><p><code>
Listen 192.170.2.1:80<br />
Listen 192.170.2.5:8000
</code></p></div>
<p>IPv6 addresses must be surrounded in square brackets, as in the
following example:</p>
<div class="example"><p><code>
Listen [fe80::a00:20ff:fea7:ccea]:80
</code></p></div>
<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 443:</p>
<div class="example"><p><code>
Listen 192.170.2.1:8443 https
</code></p></div>
<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
uses</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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</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>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</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="LockFile" id="LockFile">LockFile</a> <a name="lockfile" id="lockfile">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the accept serialization lock file</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LockFile <var>filename</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>LockFile logs/accept.lock</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/leader.html">leader</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
</table>
<p>The <code class="directive">LockFile</code> directive sets the path to
the lockfile used when Apache is used with an <code class="directive"><a href="#acceptmutex">AcceptMutex</a></code> value of either
<code>fcntl</code> or <code>flock</code>. This directive should
normally be left at its default value. The main reason for changing
it is if the <code>logs</code> directory is NFS mounted, since
<strong>the lockfile must be stored on a local disk</strong>. The PID
of the main server process is automatically appended to the
filename.</p>
<div class="warning"><h3>Security</h3>
<p>It is best to <em>avoid</em> putting this file in a world writable
directory such as <code>/var/tmp</code> because someone could create
a denial of service attack and prevent the server from starting by
creating a lockfile with the same name as the one the server will try
to create.</p>
</div>
<h3>See also</h3>
<ul>
<li><code class="directive"><a href="#acceptmutex">AcceptMutex</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="MaxClients" id="MaxClients">MaxClients</a> <a name="maxclients" id="maxclients">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of child processes that will be created
to serve requests</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxClients <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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
</table>
<p>The <code class="directive">MaxClients</code> directive sets the limit
on the number of simultaneous requests that will be served. Any
connection attempts over the <code class="directive">MaxClients</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">MaxClients</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/beos.html">beos</a></code>
or <code class="module"><a href="/mod/worker.html">worker</a></code>) <code class="directive">MaxClients</code> restricts
the total number of threads that will be available to serve clients.
The default value for <code class="module"><a href="/mod/beos.html">beos</a></code> is <code>50</code>. 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">MaxClients</code> to a value that requires more than 16 processes,
you must also raise <code class="directive"><a href="#serverlimit">ServerLimit</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="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 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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</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>The <code class="directive">MaxMemFree</code> directive sets the
maximum number of free Kbytes that the main allocator is allowed
to hold without calling <code>free()</code>. When not set, or 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="MaxRequestsPerChild" id="MaxRequestsPerChild">MaxRequestsPerChild</a> <a name="maxrequestsperchild" id="maxrequestsperchild">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit on the number of requests 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>MaxRequestsPerChild <var>number</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxRequestsPerChild 10000</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/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</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>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
</table>
<p>The <code class="directive">MaxRequestsPerChild</code> directive sets
the limit on the number of requests that an individual child
server process will handle. After
<code class="directive">MaxRequestsPerChild</code> requests, the child
process will die. If <code class="directive">MaxRequestsPerChild</code> is
<code>0</code>, then the process will never expire.</p>
<div class="note"><h3>Different default values</h3>
<p>The default value for <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code> and
<code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code> is <code>0</code>.</p>
</div>
<p>Setting <code class="directive">MaxRequestsPerChild</code> to a
non-zero limit has two beneficial effects:</p>
<ul>
<li>it limits the amount of memory that process can consume
by (accidental) memory leakage;</li>
<li>by giving processes a finite lifetime, it helps reduce
the number of processes when the server load reduces.</li>
</ul>
<div class="note"><h3>Note</h3>
<p>For <code class="directive"><a href="/mod/core.html#keepalive">KeepAlive</a></code> requests, only
the first request is counted towards this limit. In effect, it
changes the behavior to limit the number of <em>connections</em> per
child.</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="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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</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>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</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/perchild.html">perchild</a></code> the default is
<code>MaxSpareThreads 10</code>. This MPM monitors the number of
idle threads on a per-child basis. If there are too many idle
threads in that child, the server will begin to kill threads
within that child.</p>
<p>For <code class="module"><a href="/mod/worker.html">worker</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code> and <code class="module"><a href="/mod/threadpool.html">threadpool</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.</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/beos.html">beos</a></code> and <code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code> work
similar to <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code>. The default for
<code class="module"><a href="/mod/beos.html">beos</a></code> is <code>MaxSpareThreads 50</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 will correct the given value automatically
according to the following rules:</p>
<ul>
<li><code class="module"><a href="/mod/perchild.html">perchild</a></code> requires <code class="directive">MaxSpareThreads</code> to be less or equal than <code class="directive"><a href="#threadlimit">ThreadLimit</a></code>.</li>
<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/leader.html">leader</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code> and
<code class="module"><a href="/mod/worker.html">worker</a></code> the value must be greater or equal than
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>
</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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</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>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</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/perchild.html">perchild</a></code> uses a default of
<code>MinSpareThreads 5</code> and monitors the number of idle
threads on a per-child basis. If there aren't enough idle threads
in that child, the server will begin to create new threads within
that child. Thus, if you set <code class="directive"><a href="/mod/perchild.html#numservers">NumServers</a></code> to <code>10</code> and a <code class="directive">MinSpareThreads</code> value of <code>5</code>, you'll have
at least 50 idle threads on your system.</p>
<p><code class="module"><a href="/mod/worker.html">worker</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code> and
<code class="module"><a href="/mod/threadpool.html">threadpool</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 number.</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 bases.</p>
<p><code class="module"><a href="/mod/beos.html">beos</a></code> and <code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code> work
similar to <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code>. The default for
<code class="module"><a href="/mod/beos.html">beos</a></code> is <code>MinSpareThreads 1</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>
</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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</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>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</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><p><code>
PidFile /var/run/apache.pid
</code></p></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 2 it is recommended to use only the <code class="program"><a href="/programs/apachectl.html">apachectl</a></code> script 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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</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>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</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_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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
</table>
<p>Apache 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 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 to always create the file on the disk.</p>
<div class="example"><h3>Example</h3><p><code>
ScoreBoardFile /var/run/apache_status
</code></p></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</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/beos.html">beos</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</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>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
</table>
<p>The server will set the TCP send buffer size to the number of bytes
specified. Very useful to increase past standard OS defaults on
high speed high latency (<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
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="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/leader.html">leader</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</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="#maxclients">MaxClients</a></code> for the lifetime of the
Apache process. For the <code class="module"><a href="/mod/worker.html">worker</a></code> MPM, 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="#maxclients">MaxClients</a></code> for the lifetime of the
Apache process. Any attempts to change this directive during a
restart will be ignored, but <code class="directive"><a href="#maxclients">MaxClients</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="#maxclients">MaxClients</a></code> are set to values
higher than the system can handle, Apache 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="#maxclients">MaxClients</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="#maxclients">MaxClients</a></code> to.</p>
<p>With <code class="module"><a href="/mod/worker.html">worker</a></code>, <code class="module"><a href="/mod/leader.html">leader</a></code> and
<code class="module"><a href="/mod/threadpool.html">threadpool</a></code> use this directive only
if your <code class="directive"><a href="#maxclients">MaxClients</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="#maxclients ">MaxClients </a></code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>.</p>
<p>With the <code class="module"><a href="/mod/perchild.html">perchild</a></code> MPM, use this directive only
if you need to set <code class="directive"><a href="/mod/perchild.html#numservers">NumServers</a></code> higher than 8 (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.</p>
</div>
<h3>See also</h3>
<ul>
<li><a href="/stopping.html">Stopping and Restarting Apache</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/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</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,
there is usually little reason to adjust this parameter.</p>
<p>The default value differs from MPM to MPM. For
<code class="module"><a href="/mod/leader.html">leader</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code> and
<code class="module"><a href="/mod/worker.html">worker</a></code> the default is <code>StartServers 3</code>.
For <code class="module"><a href="/mod/prefork.html">prefork</a></code> defaults to <code>5</code> and for
<code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code> 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/beos.html">beos</a></code>, <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code></td></tr>
</table>
<p>Number of threads created on startup. As the
number of threads is dynamically controlled depending on the
load, there is usually little reason to adjust this
parameter.</p>
<p>For <code class="module"><a href="/mod/perchild.html">perchild</a></code> the default is <code>StartThreads
5</code> and this directive tracks the number of threads per
process at startup.</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>
<p>For <code class="module"><a href="/mod/beos.html">beos</a></code> the default is <code>StartThreads
10</code>. It also reflects 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/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available for <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code> in Apache 2.0.41
and later</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 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 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.</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 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.</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/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</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>
</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/leader.html">leader</a></code>, <code class="module"><a href="/mod/mpm_netware.html">mpm_netware</a></code>, <code class="module"><a href="/mod/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 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 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
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 can be exercised, as there
may be infrequent requests which require more stack to process.
A change in the web server configuration can invalidate the
current <code class="directive">ThreadStackSize</code> setting.</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="User" id="User">User</a> <a name="user" id="user">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The userid under which the server will answer
requests</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>User <var>unix-userid</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>User #-1</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/leader.html">leader</a></code>, <code class="module"><a href="/mod/perchild.html">perchild</a></code>, <code class="module"><a href="/mod/prefork.html">prefork</a></code>, <code class="module"><a href="/mod/threadpool.html">threadpool</a></code>, <code class="module"><a href="/mod/worker.html">worker</a></code></td></tr>
<tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Only valid in global server config since Apache
2.0</td></tr>
</table>
<p>The <code class="directive">User</code> directive sets the user ID as
which the server will answer requests. In order to use this
directive, the server must be run initially as <code>root</code>.
If you start the server as a non-root user, it will fail to change
to the lesser privileged user, and will instead continue to run as
that original user. If you do start the server as <code>root</code>,
then it is normal for the parent process to remain running as root.
<var>Unix-userid</var> is one of:</p>
<dl>
<dt>A username</dt>
<dd>Refers to the given user by name.</dd>
<dt># followed by a user number.</dt>
<dd>Refers to a user by its number.</dd>
</dl>
<p>The user should have no privileges that result in it being
able to access files that are not intended to be visible to the
outside world, and similarly, the user should not be able to
execute code that is not meant for HTTP requests. It is
recommended that you set up a new user and group specifically for
running the server. Some admins use user <code>nobody</code>, but
this is not always desirable, since the <code>nobody</code> user
can have other uses on the system.</p>
<div class="warning"><h3>Security</h3>
<p>Don't set <code class="directive">User</code> (or <code class="directive"><a href="#group">Group</a></code>) to <code>root</code> unless
you know exactly what you are doing, and what the dangers are.</p>
</div>
<p>With the <code class="module"><a href="/mod/perchild.html">perchild</a></code> MPM, which is intended to
server virtual hosts run under different user IDs, the
<code class="directive">User</code> directive defines the user ID for the
main server and the fallback for <code class="directive"><a href="/mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code> sections without an
<code class="directive"><a href="/mod/perchild.html#assignuserid">AssignUserID</a></code> directive.</p>
<p>Special note: Use of this directive in <code class="directive"><a href="/mod/core.html#virtualhost">&lt;VirtualHost&gt;</a></code> is no longer supported. To
configure your server for <code class="program"><a href="/programs/suexec.html">suexec</a></code> use
<code class="directive"><a href="/mod/mod_suexec.html#suexecusergroup">SuexecUserGroup</a></code>.</p>
<div class="note"><h3>Note</h3>
<p>Although the <code class="directive">User</code> directive is present
in the <code class="module"><a href="/mod/beos.html">beos</a></code> and <code class="module"><a href="/mod/mpmt_os2.html">mpmt_os2</a></code> MPMs,
it is actually a no-op there and only exists for compatibility
reasons.</p>
</div>
</div>
</div>
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