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  18 <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>
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  23 <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/">Documentation</a> &gt; <a href="../">Version 2.5</a> &gt; <a href="./">Modules</a></div>
  24 <div id="page-content">
  25 <div id="preamble"><h1>Apache MPM Common Directives</h1>
  26 <div class="toplang">
  27 <p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
  28 <a href="../en/mod/mpm_common.html" title="English">&nbsp;en&nbsp;</a> |
  29 <a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
  30 <a href="../tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
  31 </div>
  32 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>A collection of directives that are implemented by
  33 more than one multi-processing module (MPM)</td></tr>
  34 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr></table>
  35 </div>
  36 <div id="quickview"><h3 class="directives">Directives</h3>
  37 <ul id="toc">
  38 <li><img alt="" src="../images/down.gif" /> <a href="#coredumpdirectory">CoreDumpDirectory</a></li>
  39 <li><img alt="" src="../images/down.gif" /> <a href="#enableexceptionhook">EnableExceptionHook</a></li>
  40 <li><img alt="" src="../images/down.gif" /> <a href="#gracefulshutdowntimeout">GracefulShutdownTimeout</a></li>
  41 <li><img alt="" src="../images/down.gif" /> <a href="#listen">Listen</a></li>
  42 <li><img alt="" src="../images/down.gif" /> <a href="#listenbacklog">ListenBackLog</a></li>
  43 <li><img alt="" src="../images/down.gif" /> <a href="#maxconnectionsperchild">MaxConnectionsPerChild</a></li>
  44 <li><img alt="" src="../images/down.gif" /> <a href="#maxmemfree">MaxMemFree</a></li>
  45 <li><img alt="" src="../images/down.gif" /> <a href="#maxrequestworkers">MaxRequestWorkers</a></li>
  46 <li><img alt="" src="../images/down.gif" /> <a href="#maxsparethreads">MaxSpareThreads</a></li>
  47 <li><img alt="" src="../images/down.gif" /> <a href="#minsparethreads">MinSpareThreads</a></li>
  48 <li><img alt="" src="../images/down.gif" /> <a href="#pidfile">PidFile</a></li>
  49 <li><img alt="" src="../images/down.gif" /> <a href="#receivebuffersize">ReceiveBufferSize</a></li>
  50 <li><img alt="" src="../images/down.gif" /> <a href="#scoreboardfile">ScoreBoardFile</a></li>
  51 <li><img alt="" src="../images/down.gif" /> <a href="#sendbuffersize">SendBufferSize</a></li>
  52 <li><img alt="" src="../images/down.gif" /> <a href="#serverlimit">ServerLimit</a></li>
  53 <li><img alt="" src="../images/down.gif" /> <a href="#startservers">StartServers</a></li>
  54 <li><img alt="" src="../images/down.gif" /> <a href="#startthreads">StartThreads</a></li>
  55 <li><img alt="" src="../images/down.gif" /> <a href="#threadlimit">ThreadLimit</a></li>
  56 <li><img alt="" src="../images/down.gif" /> <a href="#threadsperchild">ThreadsPerChild</a></li>
  57 <li><img alt="" src="../images/down.gif" /> <a href="#threadstacksize">ThreadStackSize</a></li>
  58 </ul>
  59 <ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
  60
  61 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  62 <div class="directive-section"><h2><a name="CoreDumpDirectory" id="CoreDumpDirectory">CoreDumpDirectory</a> <a name="coredumpdirectory" id="coredumpdirectory">Directive</a></h2>
  63 <table class="directive">
  64 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory where Apache HTTP Server attempts to
  65 switch before dumping core</td></tr>
  66 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CoreDumpDirectory <var>directory</var></code></td></tr>
  67 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for the default setting</code></td></tr>
  68 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
  69 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
  70 <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/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
  71 </table>
  72     <p>This controls the directory to which Apache httpd attempts to
  73     switch before dumping core. If your operating system is configured to
  74     create core files in the working directory of the crashing process,
  75     <code class="directive">CoreDumpDirectory</code> is necessary to change working
  76     directory from the default <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>
  77     directory, which should not be writable by the user the server runs as.</p>
  78
  79     <p>If you want a core dump for debugging, you can use this directive to
  80     place it in a different location. This directive has no effect if your
  81     operating system is not configured to write core files to the working directory
  82     of the crashing processes.</p>
  83
  84     <div class="note"><h3>Core Dumps on Linux</h3>
  85       <p>If Apache httpd starts as root and switches to another user, the
  86       Linux kernel <em>disables</em> core dumps even if the directory is
  87       writable for the process. Apache httpd (2.0.46 and later) reenables core dumps
  88       on Linux 2.4 and beyond, but only if you explicitly configure a <code class="directive">CoreDumpDirectory</code>.</p>
  89     </div>
  90
  91     <div class="note">
  92     <h3>Core Dumps on BSD</h3>
  93     <p>To enable core-dumping of suid-executables on BSD-systems (such
  94     as FreeBSD), set <code>kern.sugid_coredump</code> to 1.
  95     </p>
  96     </div>
  97
  98     <div class="note"><h3>Specific signals</h3>
  99       <p><code class="directive">CoreDumpDirectory</code> processing only occurs for
 100       a select set of fatal signals: SIGFPE, SIGILL, SIGABORT,
 101       SIGSEGV, and SIGBUS.</p>
 102       <p>On some operating systems, SIGQUIT also results in a core dump but
 103       does not go through <code class="directive">CoreDumpDirectory</code> or
 104       <code class="directive">EnableExceptionHook</code> processing, so the core
 105       location is dictated entirely by the operating system.</p>
 106     </div>
 107
 108
 109 </div>
 110 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 111 <div class="directive-section"><h2><a name="EnableExceptionHook" id="EnableExceptionHook">EnableExceptionHook</a> <a name="enableexceptionhook" id="enableexceptionhook">Directive</a></h2>
 112 <table class="directive">
 113 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables a hook that runs exception handlers
 114 after a crash</td></tr>
 115 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableExceptionHook On|Off</code></td></tr>
 116 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableExceptionHook Off</code></td></tr>
 117 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 118 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 119 <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/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 120 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.0.49 and later</td></tr>
 121 </table>
 122     <p>For safety reasons this directive is only available if the server was
 123     configured with the <code>--enable-exception-hook</code> option. It
 124     enables a hook that allows external modules to plug in and do something
 125     after a child crashed.</p>
 126
 127     <p>There are already two modules, <code>mod_whatkilledus</code> and
 128     <code>mod_backtrace</code> that make use of this hook. Please have a
 129     look at Jeff Trawick's <a href="http://www.apache.org/~trawick/exception_hook.html">EnableExceptionHook site</a> for more information about these.</p>
 130
 131 </div>
 132 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 133 <div class="directive-section"><h2><a name="GracefulShutdownTimeout" id="GracefulShutdownTimeout">GracefulShutdownTimeout</a> <a name="gracefulshutdowntimeout" id="gracefulshutdowntimeout">Directive</a></h2>
 134 <table class="directive">
 135 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a timeout after which a gracefully shutdown server
 136 will exit.</td></tr>
 137 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>GracefulShutDownTimeout <var>seconds</var></code></td></tr>
 138 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>GracefulShutDownTimeout 0</code></td></tr>
 139 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 140 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 141 <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>
 142 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.2 and later</td></tr>
 143 </table>
 144     <p>The <code class="directive">GracefulShutdownTimeout</code> specifies
 145     how many seconds after receiving a "graceful-stop" signal, a
 146     server should continue to run, handling the existing connections.</p>
 147
 148     <p>Setting this value to zero means that the server will wait
 149     indefinitely until all remaining requests have been fully served.</p>
 150
 151 </div>
 152 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 153 <div class="directive-section"><h2><a name="Listen" id="Listen">Listen</a> <a name="listen" id="listen">Directive</a></h2>
 154 <table class="directive">
 155 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>IP addresses and ports that the server
 156 listens to</td></tr>
 157 <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>
 158 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 159 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 160 <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>, <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/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>
 161 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Required directive since Apache HTTP Server 2.0<br />
 162 The <var>protocol</var> argument was added in 2.1.5</td></tr>
 163 </table>
 164     <p>The <code class="directive">Listen</code> directive instructs Apache httpd to
 165     listen to only specific IP addresses or ports; by default it
 166     responds to requests on all IP interfaces. <code class="directive">Listen</code>
 167     is now a required directive. If it is not in the config file, the
 168     server will fail to start. This is a change from previous versions
 169     of Apache httpd.</p>
 170
 171     <p>The <code class="directive">Listen</code> directive tells the server to
 172     accept incoming requests on the specified port or address-and-port
 173     combination. If only a port number is specified, the server listens to
 174     the given port on all interfaces. If an IP address is given as well
 175     as a port, the server will listen on the given port and
 176     interface.</p>
 177
 178     <p>Multiple <code class="directive">Listen</code> directives may be used to
 179     specify a number of addresses and ports to listen to. The server will
 180     respond to requests from any of the listed addresses and ports.</p>
 181
 182     <p>For example, to make the server accept connections on both
 183     port 80 and port 8000, use:</p>
 184
 185     <pre class="prettyprint lang-config">
 186 Listen 80
 187 Listen 8000
 188     </pre>
 189
 190
 191     <p>To make the server accept connections on two specified
 192     interfaces and port numbers, use </p>
 193
 194     <pre class="prettyprint lang-config">
 195 Listen 192.170.2.1:80
 196 Listen 192.170.2.5:8000
 197     </pre>
 198
 199
 200     <p>IPv6 addresses must be surrounded in square brackets, as in the
 201     following example:</p>
 202
 203     <pre class="prettyprint lang-config">
 204       Listen [2001:db8::a00:20ff:fea7:ccea]:80
 205     </pre>
 206
 207
 208     <p>The optional <var>protocol</var> argument is not required for most
 209        configurations. If not specified, <code>https</code> is the default for
 210        port 443 and <code>http</code> the default for all other ports.  The
 211        protocol is used to determine which module should handle a request, and
 212        to apply protocol specific optimizations with the
 213        <code class="directive"><a href="../mod/core.html#acceptfilter">AcceptFilter</a></code> directive.</p>
 214
 215     <p>You only need to set the protocol if you are running on non-standard
 216        ports.  For example, running an <code>https</code> site on port 8443:</p>
 217
 218     <pre class="prettyprint lang-config">
 219       Listen 192.170.2.1:8443 https
 220     </pre>
 221
 222
 223     <div class="note"><h3>Error condition</h3>
 224       Multiple <code class="directive">Listen</code> directives for the same ip
 225       address and port will result in an <code>Address already in use</code>
 226       error message.
 227     </div>
 228
 229
 230 <h3>See also</h3>
 231 <ul>
 232 <li><a href="../dns-caveats.html">DNS Issues</a></li>
 233 <li><a href="../bind.html">Setting which addresses and ports Apache HTTP Server
 234     uses</a></li>
 235 <li><a href="http://wiki.apache.org/httpd/CouldNotBindToAddress">Further
 236 discussion of the <code>Address already in use</code> error message,
 237 including other causes.</a></li>
 238 </ul>
 239 </div>
 240 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 241 <div class="directive-section"><h2><a name="ListenBackLog" id="ListenBackLog">ListenBackLog</a> <a name="listenbacklog" id="listenbacklog">Directive</a></h2>
 242 <table class="directive">
 243 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum length of the queue of pending connections</td></tr>
 244 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ListenBacklog <var>backlog</var></code></td></tr>
 245 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ListenBacklog 511</code></td></tr>
 246 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 247 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 248 <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/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/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 249 </table>
 250     <p>The maximum length of the queue of pending connections.
 251     Generally no tuning is needed or desired, however on some
 252     systems it is desirable to increase this when under a TCP SYN
 253     flood attack. See the backlog parameter to the
 254     <code>listen(2)</code> system call.</p>
 255
 256     <p>This will often be limited to a smaller number by the
 257     operating system. This varies from OS to OS. Also note that
 258     many OSes do not use exactly what is specified as the backlog,
 259     but use a number based on (but normally larger than) what is
 260     set.</p>
 261
 262 </div>
 263 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 264 <div class="directive-section"><h2><a name="MaxConnectionsPerChild" id="MaxConnectionsPerChild">MaxConnectionsPerChild</a> <a name="maxconnectionsperchild" id="maxconnectionsperchild">Directive</a></h2>
 265 <table class="directive">
 266 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit on the number of connections that an individual child server
 267 will handle during its life</td></tr>
 268 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxConnectionsPerChild <var>number</var></code></td></tr>
 269 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxConnectionsPerChild 0</code></td></tr>
 270 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 271 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 272 <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/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/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 273 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available Apache HTTP Server 2.3.9 and later. The old name
 274 <code>MaxRequestsPerChild</code> is still supported.</td></tr>
 275 </table>
 276     <p>The <code class="directive">MaxConnectionsPerChild</code> directive sets
 277     the limit on the number of connections that an individual child
 278     server process will handle. After
 279     <code class="directive">MaxConnectionsPerChild</code> connections, the child
 280     process will die. If <code class="directive">MaxConnectionsPerChild</code> is
 281     <code>0</code>, then the process will never expire.</p>
 282
 283     <p>Setting <code class="directive">MaxConnectionsPerChild</code> to a
 284     non-zero value limits the amount of memory that process can consume
 285     by (accidental) memory leakage.</p>
 286
 287 </div>
 288 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 289 <div class="directive-section"><h2><a name="MaxMemFree" id="MaxMemFree">MaxMemFree</a> <a name="maxmemfree" id="maxmemfree">Directive</a></h2>
 290 <table class="directive">
 291 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of memory that the main allocator is allowed
 292 to hold without calling <code>free()</code></td></tr>
 293 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxMemFree <var>KBytes</var></code></td></tr>
 294 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxMemFree 2048</code></td></tr>
 295 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 296 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 297 <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/mpm_netware.html">mpm_netware</a></code>, <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/mpm_winnt.html">mpm_winnt</a></code></td></tr>
 298 </table>
 299     <p>The <code class="directive">MaxMemFree</code> directive sets the
 300     maximum number of free Kbytes that every allocator is allowed
 301     to hold without calling <code>free()</code>. In threaded MPMs, every
 302     thread has its own allocator. When set
 303     to zero, the threshold will be set to unlimited.</p>
 304
 305 </div>
 306 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 307 <div class="directive-section"><h2><a name="MaxRequestWorkers" id="MaxRequestWorkers">MaxRequestWorkers</a> <a name="maxrequestworkers" id="maxrequestworkers">Directive</a></h2>
 308 <table class="directive">
 309 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of connections that will be processed
 310 simultaneously</td></tr>
 311 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxRequestWorkers <var>number</var></code></td></tr>
 312 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 313 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 314 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 315 <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/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 316 </table>
 317     <p>The <code class="directive">MaxRequestWorkers</code> directive sets the limit
 318     on the number of simultaneous requests that will be served.  Any
 319     connection attempts over the <code class="directive">MaxRequestWorkers</code>
 320     limit will normally be queued, up to a number based on the
 321     <code class="directive"><a href="#listenbacklog">ListenBacklog</a></code>
 322     directive. Once a child process is freed at the end of a different
 323     request, the connection will then be serviced.</p>
 324
 325     <p>For non-threaded servers (<em>i.e.</em>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>),
 326     <code class="directive">MaxRequestWorkers</code> translates into the maximum
 327     number of child processes that will be launched to serve requests.
 328     The default value is <code>256</code>; to increase it, you must also raise
 329     <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p>
 330
 331     <p>For threaded and hybrid servers (<em>e.g.</em> <code class="module"><a href="../mod/event.html">event</a></code>
 332     or <code class="module"><a href="../mod/worker.html">worker</a></code>) <code class="directive">MaxRequestWorkers</code> restricts
 333     the total number of threads that will be available to serve clients.
 334     For hybrid MPMs the default value is <code>16</code> (<code class="directive"><a href="#serverlimit">ServerLimit</a></code>) multiplied by the value of
 335     <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,
 336     you must also raise <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p>
 337
 338     <p><code class="directive">MaxRequestWorkers</code> was called
 339     <code class="directive">MaxClients</code> before version 2.3.13. The old name is still
 340     supported.</p>
 341
 342 </div>
 343 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 344 <div class="directive-section"><h2><a name="MaxSpareThreads" id="MaxSpareThreads">MaxSpareThreads</a> <a name="maxsparethreads" id="maxsparethreads">Directive</a></h2>
 345 <table class="directive">
 346 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle threads</td></tr>
 347 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareThreads <var>number</var></code></td></tr>
 348 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 349 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 350 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 351 <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/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/worker.html">worker</a></code></td></tr>
 352 </table>
 353     <p>Maximum number of idle threads. Different MPMs deal with this
 354     directive differently.</p>
 355
 356     <p>For <code class="module"><a href="../mod/worker.html">worker</a></code>, the default is
 357     <code>MaxSpareThreads 250</code>. This MPM deals with idle threads
 358     on a server-wide basis. If there are too many idle threads in the
 359     server then child processes are killed until the number of idle
 360     threads is less than this number.</p>
 361
 362     <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
 363     <code>MaxSpareThreads 100</code>. Since this MPM runs a
 364     single-process, the spare thread count is also server-wide.</p>
 365
 366     <p><code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> works
 367     similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. For
 368     <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>10</code>.</p>
 369
 370     <div class="note"><h3>Restrictions</h3>
 371       <p>The range of the <code class="directive">MaxSpareThreads</code> value
 372       is restricted. Apache httpd will correct the given value automatically
 373       according to the following rules:</p>
 374       <ul>
 375         <li><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> wants the value to be greater than
 376         <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>.</li>
 377
 378         <li>For <code class="module"><a href="../mod/worker.html">worker</a></code>, the value must be greater or equal
 379         to the sum of <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>
 380         and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>.</li>
 381       </ul>
 382     </div>
 383
 384 <h3>See also</h3>
 385 <ul>
 386 <li><code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code></li>
 387 <li><code class="directive"><a href="#startservers">StartServers</a></code></li>
 388 <li><code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code></li>
 389 </ul>
 390 </div>
 391 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 392 <div class="directive-section"><h2><a name="MinSpareThreads" id="MinSpareThreads">MinSpareThreads</a> <a name="minsparethreads" id="minsparethreads">Directive</a></h2>
 393 <table class="directive">
 394 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle threads available to handle request
 395 spikes</td></tr>
 396 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareThreads <var>number</var></code></td></tr>
 397 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 398 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 399 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 400 <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/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/worker.html">worker</a></code></td></tr>
 401 </table>
 402     <p>Minimum number of idle threads to handle request spikes.
 403     Different MPMs deal with this directive
 404     differently.</p>
 405
 406     <p><code class="module"><a href="../mod/worker.html">worker</a></code> uses a default of <code>MinSpareThreads
 407     75</code> and deals with idle threads on a server-wide basis. If
 408     there aren't enough idle threads in the server then child
 409     processes are created until the number of idle threads is greater
 410     than <var>number</var>.</p>
 411
 412     <p><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> uses a default of
 413     <code>MinSpareThreads 10</code> and, since it is a single-process
 414     MPM, tracks this on a server-wide bases.</p>
 415
 416     <p><code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> works
 417     similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>.  For
 418     <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>5</code>.</p>
 419
 420 <h3>See also</h3>
 421 <ul>
 422 <li><code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code></li>
 423 <li><code class="directive"><a href="#startservers">StartServers</a></code></li>
 424 <li><code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code></li>
 425 </ul>
 426 </div>
 427 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 428 <div class="directive-section"><h2><a name="PidFile" id="PidFile">PidFile</a> <a name="pidfile" id="pidfile">Directive</a></h2>
 429 <table class="directive">
 430 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>File where the server records the process ID
 431 of the daemon</td></tr>
 432 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PidFile <var>filename</var></code></td></tr>
 433 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>PidFile logs/httpd.pid</code></td></tr>
 434 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 435 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 436 <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/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/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 437 </table>
 438     <p>The <code class="directive">PidFile</code> directive sets the file to
 439     which the server records the process id of the daemon. If the
 440     filename is not absolute then it is assumed to be relative to the
 441     <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p>
 442
 443     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 444       PidFile /var/run/apache.pid
 445       </pre>
 446 </div>
 447
 448     <p>It is often useful to be able to send the server a signal,
 449     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
 450     re-reads its configuration files. This is done by sending a
 451     SIGHUP (kill -1) signal to the process id listed in the
 452     <code class="directive">PidFile</code>.</p>
 453
 454     <p>The <code class="directive">PidFile</code> is subject to the same
 455     warnings about log file placement and <a href="../misc/security_tips.html#serverroot">security</a>.</p>
 456
 457     <div class="note"><h3>Note</h3>
 458       <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,
 459       for (re-)starting or stopping the server.</p>
 460     </div>
 461
 462 </div>
 463 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 464 <div class="directive-section"><h2><a name="ReceiveBufferSize" id="ReceiveBufferSize">ReceiveBufferSize</a> <a name="receivebuffersize" id="receivebuffersize">Directive</a></h2>
 465 <table class="directive">
 466 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP receive buffer size</td></tr>
 467 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ReceiveBufferSize <var>bytes</var></code></td></tr>
 468 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ReceiveBufferSize 0</code></td></tr>
 469 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 470 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 471 <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/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/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 472 </table>
 473     <p>The server will set the TCP receive buffer size to the number of
 474     bytes specified.</p>
 475
 476     <p>If set to the value of <code>0</code>, the server will use the
 477     OS default.</p>
 478
 479 </div>
 480 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 481 <div class="directive-section"><h2><a name="ScoreBoardFile" id="ScoreBoardFile">ScoreBoardFile</a> <a name="scoreboardfile" id="scoreboardfile">Directive</a></h2>
 482 <table class="directive">
 483 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the file used to store coordination data for
 484 the child processes</td></tr>
 485 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ScoreBoardFile <var>file-path</var></code></td></tr>
 486 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ScoreBoardFile logs/apache_status</code></td></tr>
 487 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 488 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 489 <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/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 490 </table>
 491     <p>Apache HTTP Server uses a scoreboard to communicate between its parent
 492     and child processes.  Some architectures require a file to facilitate
 493     this communication. If the file is left unspecified, Apache httpd first
 494     attempts to create the scoreboard entirely in memory (using anonymous
 495     shared memory) and, failing that, will attempt to create the file on
 496     disk (using file-based shared memory). Specifying this directive causes
 497     Apache httpd to always create the file on the disk.</p>
 498
 499     <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">
 500       ScoreBoardFile /var/run/apache_status
 501       </pre>
 502 </div>
 503
 504     <p>File-based shared memory is useful for third-party applications
 505     that require direct access to the scoreboard.</p>
 506
 507     <p>If you use a <code class="directive">ScoreBoardFile</code> then
 508     you may see improved speed by placing it on a RAM disk. But be
 509     careful that you heed the same warnings about log file placement
 510     and <a href="../misc/security_tips.html">security</a>.</p>
 511
 512 <h3>See also</h3>
 513 <ul>
 514 <li><a href="../stopping.html">Stopping and Restarting
 515 Apache HTTP Server</a></li>
 516 </ul>
 517 </div>
 518 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 519 <div class="directive-section"><h2><a name="SendBufferSize" id="SendBufferSize">SendBufferSize</a> <a name="sendbuffersize" id="sendbuffersize">Directive</a></h2>
 520 <table class="directive">
 521 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP buffer size</td></tr>
 522 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SendBufferSize <var>bytes</var></code></td></tr>
 523 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SendBufferSize 0</code></td></tr>
 524 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 525 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 526 <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/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/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 527 </table>
 528     <p>Sets the server's TCP send buffer size to the number of bytes
 529     specified. It is often useful to set this past the OS's standard
 530     default value on high speed, high latency connections
 531     (<em>i.e.</em>, 100ms or so, such as transcontinental fast pipes).</p>
 532
 533     <p>If set to the value of <code>0</code>, the server will use the
 534     default value provided by your OS.</p>
 535
 536     <p>Further configuration of your operating system may be required to elicit
 537     better performance on high speed, high latency connections.</p>
 538
 539     <div class="note"> <p> On some operating systems, changes in TCP behavior resulting
 540     from a larger <code class="directive">SendBufferSize</code> may not be seen unless
 541     <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code> is set to OFF.  This
 542     interaction applies only to static files.</p> </div>
 543
 544
 545 </div>
 546 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 547 <div class="directive-section"><h2><a name="ServerLimit" id="ServerLimit">ServerLimit</a> <a name="serverlimit" id="serverlimit">Directive</a></h2>
 548 <table class="directive">
 549 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Upper limit on configurable number of processes</td></tr>
 550 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerLimit <var>number</var></code></td></tr>
 551 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 552 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 553 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 554 <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/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 555 </table>
 556     <p>For the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, this directive sets the
 557     maximum configured value for <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> for the lifetime of the
 558     Apache httpd process.  For the <code class="module"><a href="../mod/worker.html">worker</a></code> MPM, this directive
 559     in combination with <code class="directive"><a href="#threadlimit">ThreadLimit</a></code> sets
 560     the maximum configured value for <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> for the lifetime of the
 561     Apache httpd process.  Any attempts to change this directive during a
 562     restart will be ignored, but <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> can be modified during
 563     a restart.</p>
 564
 565     <p>Special care must be taken when using this directive.  If
 566     <code class="directive">ServerLimit</code> is set to a value much higher
 567     than necessary, extra, unused shared memory will be allocated.  If
 568     both <code class="directive">ServerLimit</code> and <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> are set to values
 569     higher than the system can handle, Apache httpd may not start or the
 570     system may become unstable.</p>
 571
 572     <p>With the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, use this directive only
 573     if you need to set <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> higher than 256 (default).
 574     Do not set the value of this directive any higher than what you
 575     might want to set <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> to.</p>
 576
 577     <p>With <code class="module"><a href="../mod/worker.html">worker</a></code>, use this directive only
 578     if your <code class="directive"><a href="#maxrequestworkers">MaxRequestWorkers</a></code> and
 579     <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>
 580     settings require more than 16 server processes (default). Do not set
 581     the value of this directive any higher than the number of server
 582     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>
 583
 584     <div class="note"><h3>Note</h3>
 585       <p>There is a hard limit of <code>ServerLimit 20000</code> compiled
 586       into the server (for the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM 200000). This is
 587       intended to avoid nasty effects caused by typos. To increase it
 588       even further past this limit, you will need to modify the value of
 589       MAX_SERVER_LIMIT in the mpm source file and rebuild the server.</p>
 590     </div>
 591
 592 <h3>See also</h3>
 593 <ul>
 594 <li><a href="../stopping.html">Stopping and Restarting Apache HTTP Server</a></li>
 595 </ul>
 596 </div>
 597 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 598 <div class="directive-section"><h2><a name="StartServers" id="StartServers">StartServers</a> <a name="startservers" id="startservers">Directive</a></h2>
 599 <table class="directive">
 600 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of child server processes created at startup</td></tr>
 601 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartServers <var>number</var></code></td></tr>
 602 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 603 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 604 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 605 <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/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 606 </table>
 607     <p>The <code class="directive">StartServers</code> directive sets the
 608     number of child server processes created on startup. As the number
 609     of processes is dynamically controlled depending on the load, (see
 610     <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>,
 611     <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code>,
 612     <code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code>, <code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code>)
 613     there is usually little reason to adjust this parameter.</p>
 614
 615     <p>The default value differs from MPM to MPM. <code class="module"><a href="../mod/worker.html">worker</a></code>
 616     defaults to <code>StartServers 3</code>; <code class="module"><a href="../mod/prefork.html">prefork</a></code>
 617     defaults to <code>5</code>; <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> defaults to
 618     <code>2</code>.</p>
 619
 620 </div>
 621 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 622 <div class="directive-section"><h2><a name="StartThreads" id="StartThreads">StartThreads</a> <a name="startthreads" id="startthreads">Directive</a></h2>
 623 <table class="directive">
 624 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created on startup</td></tr>
 625 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartThreads <var>number</var></code></td></tr>
 626 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 627 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 628 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 629 <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>
 630 </table>
 631     <p>Number of threads created on startup. As the
 632     number of threads is dynamically controlled depending on the
 633     load, (see
 634     <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>,
 635     <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code>,
 636     <code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code>, <code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code>)
 637     there is usually little reason to adjust this
 638     parameter.</p>
 639
 640     <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
 641     <code>StartThreads 50</code> and, since there is only a single
 642     process, this is the total number of threads created at startup to
 643     serve requests.</p>
 644
 645 </div>
 646 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 647 <div class="directive-section"><h2><a name="ThreadLimit" id="ThreadLimit">ThreadLimit</a> <a name="threadlimit" id="threadlimit">Directive</a></h2>
 648 <table class="directive">
 649 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the upper limit on the configurable number of threads
 650 per child process</td></tr>
 651 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadLimit <var>number</var></code></td></tr>
 652 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 653 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 654 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 655 <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/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 656 <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 HTTP Server 2.0.41
 657 and later</td></tr>
 658 </table>
 659     <p>This directive sets the maximum configured value for <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the lifetime
 660     of the Apache httpd process.  Any attempts to change this directive
 661     during a restart will be ignored, but <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> can be modified
 662     during a restart up to the value of this directive.</p>
 663
 664     <p>Special care must be taken when using this directive.  If
 665     <code class="directive">ThreadLimit</code> is set to a value much higher
 666     than <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>,
 667     extra unused shared memory will be allocated.  If both
 668     <code class="directive">ThreadLimit</code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> are set to values
 669     higher than the system can handle, Apache httpd may not start or the
 670     system may become unstable. Do not set the value of this directive
 671     any higher than your greatest predicted setting of <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the
 672     current run of Apache httpd.</p>
 673
 674     <p>The default value for <code class="directive">ThreadLimit</code> is
 675     <code>1920</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
 676     <code>64</code> when used with the others.</p>
 677
 678     <div class="note"><h3>Note</h3>
 679       <p>There is a hard limit of <code>ThreadLimit 20000</code> (or
 680       <code>ThreadLimit 15000</code> with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>)
 681       compiled into the server. This is intended to avoid nasty effects
 682       caused by typos. To increase it even further past this limit, you
 683       will need to modify the value of MAX_THREAD_LIMIT in the mpm
 684       source file and rebuild the server.</p>
 685     </div>
 686
 687 </div>
 688 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 689 <div class="directive-section"><h2><a name="ThreadsPerChild" id="ThreadsPerChild">ThreadsPerChild</a> <a name="threadsperchild" id="threadsperchild">Directive</a></h2>
 690 <table class="directive">
 691 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created by each child process</td></tr>
 692 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadsPerChild <var>number</var></code></td></tr>
 693 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 694 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 695 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 696 <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/mpm_winnt.html">mpm_winnt</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 697 </table>
 698     <p>This directive sets the number of threads created by each
 699     child process. The child creates these threads at startup and
 700     never creates more. If using an MPM like <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>,
 701     where there is only one child process, this number should be high
 702     enough to handle the entire load of the server. If using an MPM
 703     like <code class="module"><a href="../mod/worker.html">worker</a></code>, where there are multiple child processes,
 704     the <em>total</em> number of threads should be high enough to handle
 705     the common load on the server.</p>
 706
 707     <p>The default value for <code class="directive">ThreadsPerChild</code> is
 708     <code>64</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
 709     <code>25</code> when used with the others.</p>
 710
 711 </div>
 712 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 713 <div class="directive-section"><h2><a name="ThreadStackSize" id="ThreadStackSize">ThreadStackSize</a> <a name="threadstacksize" id="threadstacksize">Directive</a></h2>
 714 <table class="directive">
 715 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The size in bytes of the stack used by threads handling
 716 client connections</td></tr>
 717 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadStackSize <var>size</var></code></td></tr>
 718 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>65536 on NetWare; varies on other operating systems</code></td></tr>
 719 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 720 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 721 <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/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/mpm_winnt.html">mpm_winnt</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>
 722 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.1 and later</td></tr>
 723 </table>
 724     <p>The <code class="directive">ThreadStackSize</code> directive sets the
 725     size of the stack (for autodata) of threads which handle client
 726     connections and call modules to help process those connections.
 727     In most cases the operating system default for stack size is
 728     reasonable, but there are some conditions where it may need to be
 729     adjusted:</p>
 730
 731     <ul>
 732       <li>On platforms with a relatively small default thread stack size
 733       (e.g., HP-UX), Apache httpd may crash when using some third-party modules
 734       which use a relatively large amount of autodata storage.  Those
 735       same modules may have worked fine on other platforms where the
 736       default thread stack size is larger.  This type of crash is
 737       resolved by setting <code class="directive">ThreadStackSize</code> to a
 738       value higher than the operating system default.  This type of
 739       adjustment is necessary only if the provider of the third-party
 740       module specifies that it is required, or if diagnosis of an Apache httpd
 741       crash indicates that the thread stack size was too small.</li>
 742
 743       <li>On platforms where the default thread stack size is
 744       significantly larger than necessary for the web server
 745       configuration, a higher number of threads per child process
 746       will be achievable if <code class="directive">ThreadStackSize</code> is
 747       set to a value lower than the operating system default.  This type
 748       of adjustment should only be made in a test environment which allows
 749       the full set of web server processing can be exercised, as there
 750       may be infrequent requests which require more stack to process.
 751       The minimum required stack size strongly depends on the modules
 752       used, but any change in the web server configuration can invalidate
 753       the current <code class="directive">ThreadStackSize</code> setting.</li>
 754
 755       <li>On Linux, this directive can only be used to increase the default
 756       stack size, as the underlying system call uses the value as a
 757       <em>minimum</em> stack size.  The (often large) soft limit for
 758       <code>ulimit -s</code> (8MB if unlimited) is used as the default stack
 759       size.</li>
 760     </ul>
 761
 762     <div class="note">It is recommended to not reduce <code class="directive">ThreadStackSize</code>
 763     unless a high number of threads per child process is needed. On some
 764     platforms (including Linux), a setting of 128000 is already too low and
 765     causes crashes with some common modules.</div>
 766
 767 </div>
 768 </div>
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