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   8 <title>mpm_common - Apache HTTP Server</title>
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  15 <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>
  16 <p class="apache">Apache HTTP Server Version 2.3</p>
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  20 <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 2.3</a> &gt; <a href="./">Modules</a></div>
  21 <div id="page-content">
  22 <div id="preamble"><h1>Apache MPM Common Directives</h1>
  23 <div class="toplang">
  24 <p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
  25 <a href="../en/mod/mpm_common.html" title="English">&nbsp;en&nbsp;</a> |
  26 <a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
  27 <a href="../tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
  28 </div>
  29 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>A collection of directives that are implemented by
  30 more than one multi-processing module (MPM)</td></tr>
  31 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>MPM</td></tr></table>
  32 </div>
  33 <div id="quickview"><h3 class="directives">Directives</h3>
  34 <ul id="toc">
  35 <li><img alt="" src="../images/down.gif" /> <a href="#coredumpdirectory">CoreDumpDirectory</a></li>
  36 <li><img alt="" src="../images/down.gif" /> <a href="#enableexceptionhook">EnableExceptionHook</a></li>
  37 <li><img alt="" src="../images/down.gif" /> <a href="#gracefulshutdowntimeout">GracefulShutdownTimeout</a></li>
  38 <li><img alt="" src="../images/down.gif" /> <a href="#listen">Listen</a></li>
  39 <li><img alt="" src="../images/down.gif" /> <a href="#listenbacklog">ListenBackLog</a></li>
  40 <li><img alt="" src="../images/down.gif" /> <a href="#maxclients">MaxClients</a></li>
  41 <li><img alt="" src="../images/down.gif" /> <a href="#maxconnectionsperchild">MaxConnectionsPerChild</a></li>
  42 <li><img alt="" src="../images/down.gif" /> <a href="#maxmemfree">MaxMemFree</a></li>
  43 <li><img alt="" src="../images/down.gif" /> <a href="#maxsparethreads">MaxSpareThreads</a></li>
  44 <li><img alt="" src="../images/down.gif" /> <a href="#minsparethreads">MinSpareThreads</a></li>
  45 <li><img alt="" src="../images/down.gif" /> <a href="#pidfile">PidFile</a></li>
  46 <li><img alt="" src="../images/down.gif" /> <a href="#receivebuffersize">ReceiveBufferSize</a></li>
  47 <li><img alt="" src="../images/down.gif" /> <a href="#scoreboardfile">ScoreBoardFile</a></li>
  48 <li><img alt="" src="../images/down.gif" /> <a href="#sendbuffersize">SendBufferSize</a></li>
  49 <li><img alt="" src="../images/down.gif" /> <a href="#serverlimit">ServerLimit</a></li>
  50 <li><img alt="" src="../images/down.gif" /> <a href="#startservers">StartServers</a></li>
  51 <li><img alt="" src="../images/down.gif" /> <a href="#startthreads">StartThreads</a></li>
  52 <li><img alt="" src="../images/down.gif" /> <a href="#threadlimit">ThreadLimit</a></li>
  53 <li><img alt="" src="../images/down.gif" /> <a href="#threadsperchild">ThreadsPerChild</a></li>
  54 <li><img alt="" src="../images/down.gif" /> <a href="#threadstacksize">ThreadStackSize</a></li>
  55 </ul>
  56 </div>
  57
  58 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  59 <div class="directive-section"><h2><a name="CoreDumpDirectory" id="CoreDumpDirectory">CoreDumpDirectory</a> <a name="coredumpdirectory" id="coredumpdirectory">Directive</a></h2>
  60 <table class="directive">
  61 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Directory where Apache HTTP Server attempts to
  62 switch before dumping core</td></tr>
  63 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CoreDumpDirectory <var>directory</var></code></td></tr>
  64 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for the default setting</code></td></tr>
  65 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
  66 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
  67 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><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>
  68 </table>
  69     <p>This controls the directory to which Apache httpd attempts to
  70     switch before dumping core. If your operating system is configured to
  71     create core files in the working directory of the crashing process,
  72     <code class="directive">CoreDumpDirectory</code> is necessary to change working
  73     directory from the default <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>
  74     directory, which should not be writable by the user the server runs as.</p>
  75
  76     <p>If you want a core dump for debugging, you can use this directive to
  77     place it in a different location. This directive has no effect if your
  78     operating system is not configured to write core files to the working directory
  79     of the crashing processes.</p>
  80
  81     <div class="note"><h3>Core Dumps on Linux</h3>
  82       <p>If Apache httpd starts as root and switches to another user, the
  83       Linux kernel <em>disables</em> core dumps even if the directory is
  84       writable for the process. Apache httpd (2.0.46 and later) reenables core dumps
  85       on Linux 2.4 and beyond, but only if you explicitly configure a <code class="directive">CoreDumpDirectory</code>.</p>
  86     </div>
  87
  88     <div class="note"><h3>Specific signals</h3>
  89       <p><code class="directive">CoreDumpDirectory</code> processing only occurs for
  90       a select set of fatal signals: SIGFPE, SIGILL, SIGABORT,
  91       SIGSEGV, and SIGBUS.</p>
  92       <p>On some operating systems, SIGQUIT also results in a core dump but
  93       does not go through <code class="directive">CoreDumpDirectory</code> or
  94       <code class="directive">EnableExceptionHook</code> processing, so the core
  95       location is dictated entirely by the operating system.</p>
  96     </div>
  97
  98
  99 </div>
 100 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 101 <div class="directive-section"><h2><a name="EnableExceptionHook" id="EnableExceptionHook">EnableExceptionHook</a> <a name="enableexceptionhook" id="enableexceptionhook">Directive</a></h2>
 102 <table class="directive">
 103 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables a hook that runs exception handlers
 104 after a crash</td></tr>
 105 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>EnableExceptionHook On|Off</code></td></tr>
 106 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>EnableExceptionHook Off</code></td></tr>
 107 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 108 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 109 <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></td></tr>
 110 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.0.49 and later</td></tr>
 111 </table>
 112     <p>For safety reasons this directive is only available if the server was
 113     configured with the <code>--enable-exception-hook</code> option. It
 114     enables a hook that allows external modules to plug in and do something
 115     after a child crashed.</p>
 116
 117     <p>There are already two modules, <code>mod_whatkilledus</code> and
 118     <code>mod_backtrace</code> that make use of this hook. Please have a
 119     look at Jeff Trawick's <a href="http://www.apache.org/~trawick/exception_hook.html">EnableExceptionHook site</a> for more information about these.</p>
 120
 121 </div>
 122 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 123 <div class="directive-section"><h2><a name="GracefulShutdownTimeout" id="GracefulShutdownTimeout">GracefulShutdownTimeout</a> <a name="gracefulshutdowntimeout" id="gracefulshutdowntimeout">Directive</a></h2>
 124 <table class="directive">
 125 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a timeout after which a gracefully shutdown server
 126 will exit.</td></tr>
 127 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>GracefulShutDownTimeout <var>seconds</var></code></td></tr>
 128 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>GracefulShutDownTimeout 0</code></td></tr>
 129 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 130 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 131 <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>
 132 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.2 and later</td></tr>
 133 </table>
 134     <p>The <code class="directive">GracefulShutdownTimeout</code> specifies
 135     how many seconds after receiving a "graceful-stop" signal, a
 136     server should continue to run, handling the existing connections.</p>
 137
 138     <p>Setting this value to zero means that the server will wait
 139     indefinitely until all remaining requests have been fully served.</p>
 140
 141 </div>
 142 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 143 <div class="directive-section"><h2><a name="Listen" id="Listen">Listen</a> <a name="listen" id="listen">Directive</a></h2>
 144 <table class="directive">
 145 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>IP addresses and ports that the server
 146 listens to</td></tr>
 147 <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>
 148 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 149 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 150 <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>
 151 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Required directive since Apache HTTP Server 2.0<br />
 152 The <var>protocol</var> argument was added in 2.1.5</td></tr>
 153 </table>
 154     <p>The <code class="directive">Listen</code> directive instructs Apache httpd to
 155     listen to only specific IP addresses or ports; by default it
 156     responds to requests on all IP interfaces. <code class="directive">Listen</code>
 157     is now a required directive. If it is not in the config file, the
 158     server will fail to start. This is a change from previous versions
 159     of Apache httpd.</p>
 160
 161     <p>The <code class="directive">Listen</code> directive tells the server to
 162     accept incoming requests on the specified port or address-and-port
 163     combination. If only a port number is specified, the server listens to
 164     the given port on all interfaces. If an IP address is given as well
 165     as a port, the server will listen on the given port and
 166     interface.</p>
 167
 168     <p>Multiple <code class="directive">Listen</code> directives may be used to
 169     specify a number of addresses and ports to listen to. The server will
 170     respond to requests from any of the listed addresses and ports.</p>
 171
 172     <p>For example, to make the server accept connections on both
 173     port 80 and port 8000, use:</p>
 174
 175     <div class="example"><p><code>
 176       Listen 80<br />
 177       Listen 8000
 178     </code></p></div>
 179
 180     <p>To make the server accept connections on two specified
 181     interfaces and port numbers, use </p>
 182
 183     <div class="example"><p><code>
 184       Listen 192.170.2.1:80<br />
 185       Listen 192.170.2.5:8000
 186     </code></p></div>
 187
 188     <p>IPv6 addresses must be surrounded in square brackets, as in the
 189     following example:</p>
 190
 191     <div class="example"><p><code>
 192       Listen [2001:db8::a00:20ff:fea7:ccea]:80
 193     </code></p></div>
 194
 195     <p>The optional <var>protocol</var> argument is not required for most
 196        configurations. If not specified, <code>https</code> is the default for
 197        port 443 and <code>http</code> the default for all other ports.  The
 198        protocol is used to determine which module should handle a request, and
 199        to apply protocol specific optimizations with the
 200        <code class="directive"><a href="../mod/core.html#acceptfilter">AcceptFilter</a></code> directive.</p>
 201
 202     <p>You only need to set the protocol if you are running on non-standard
 203        ports.  For example, running an <code>https</code> site on port 8443:</p>
 204
 205     <div class="example"><p><code>
 206       Listen 192.170.2.1:8443 https
 207     </code></p></div>
 208
 209     <div class="note"><h3>Error condition</h3>
 210       Multiple <code class="directive">Listen</code> directives for the same ip
 211       address and port will result in an <code>Address already in use</code>
 212       error message.
 213     </div>
 214
 215
 216 <h3>See also</h3>
 217 <ul>
 218 <li><a href="../dns-caveats.html">DNS Issues</a></li>
 219 <li><a href="../bind.html">Setting which addresses and ports Apache HTTP Server
 220     uses</a></li>
 221 <li><a href="http://wiki.apache.org/httpd/CouldNotBindToAddress">Further
 222 discussion of the <code>Address already in use</code> error message,
 223 including other causes.</a></li>
 224 </ul>
 225 </div>
 226 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 227 <div class="directive-section"><h2><a name="ListenBackLog" id="ListenBackLog">ListenBackLog</a> <a name="listenbacklog" id="listenbacklog">Directive</a></h2>
 228 <table class="directive">
 229 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum length of the queue of pending connections</td></tr>
 230 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ListenBacklog <var>backlog</var></code></td></tr>
 231 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ListenBacklog 511</code></td></tr>
 232 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 233 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 234 <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></td></tr>
 235 </table>
 236     <p>The maximum length of the queue of pending connections.
 237     Generally no tuning is needed or desired, however on some
 238     systems it is desirable to increase this when under a TCP SYN
 239     flood attack. See the backlog parameter to the
 240     <code>listen(2)</code> system call.</p>
 241
 242     <p>This will often be limited to a smaller number by the
 243     operating system. This varies from OS to OS. Also note that
 244     many OSes do not use exactly what is specified as the backlog,
 245     but use a number based on (but normally larger than) what is
 246     set.</p>
 247
 248 </div>
 249 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 250 <div class="directive-section"><h2><a name="MaxClients" id="MaxClients">MaxClients</a> <a name="maxclients" id="maxclients">Directive</a></h2>
 251 <table class="directive">
 252 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of connections that will be processed
 253 simultaneously</td></tr>
 254 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxClients <var>number</var></code></td></tr>
 255 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 256 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 257 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 258 <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></td></tr>
 259 </table>
 260     <p>The <code class="directive">MaxClients</code> directive sets the limit
 261     on the number of simultaneous requests that will be served.  Any
 262     connection attempts over the <code class="directive">MaxClients</code>
 263     limit will normally be queued, up to a number based on the
 264     <code class="directive"><a href="#listenbacklog">ListenBacklog</a></code>
 265     directive. Once a child process is freed at the end of a different
 266     request, the connection will then be serviced.</p>
 267
 268     <p>For non-threaded servers (<em>i.e.</em>, <code class="module"><a href="../mod/prefork.html">prefork</a></code>),
 269     <code class="directive">MaxClients</code> translates into the maximum
 270     number of child processes that will be launched to serve requests.
 271     The default value is <code>256</code>; to increase it, you must also raise
 272     <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p>
 273
 274     <p>For threaded and hybrid servers (<em>e.g.</em> <code class="module"><a href="../mod/event.html">event</a></code>
 275     or <code class="module"><a href="../mod/worker.html">worker</a></code>) <code class="directive">MaxClients</code> restricts
 276     the total number of threads that will be available to serve clients.
 277     For hybrid MPMs the default value is <code>16</code> (<code class="directive"><a href="#serverlimit">ServerLimit</a></code>) multiplied by the value of
 278     <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,
 279     you must also raise <code class="directive"><a href="#serverlimit">ServerLimit</a></code>.</p>
 280
 281 </div>
 282 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 283 <div class="directive-section"><h2><a name="MaxConnectionsPerChild" id="MaxConnectionsPerChild">MaxConnectionsPerChild</a> <a name="maxconnectionsperchild" id="maxconnectionsperchild">Directive</a></h2>
 284 <table class="directive">
 285 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Limit on the number of connections that an individual child server
 286 will handle during its life</td></tr>
 287 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxConnectionsPerChild <var>number</var></code></td></tr>
 288 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxConnectionsPerChild 0</code></td></tr>
 289 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 290 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 291 <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></td></tr>
 292 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available Apache HTTP Server 2.3.9 and later. The old name
 293 <code>MaxRequestsPerChild</code> is still supported.</td></tr>
 294 </table>
 295     <p>The <code class="directive">MaxConnectionsPerChild</code> directive sets
 296     the limit on the number of connections that an individual child
 297     server process will handle. After
 298     <code class="directive">MaxConnectionsPerChild</code> connections, the child
 299     process will die. If <code class="directive">MaxConnectionsPerChild</code> is
 300     <code>0</code>, then the process will never expire.</p>
 301
 302     <div class="note"><h3>Different default values</h3>
 303       <p>The default value for <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> and
 304       <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> is <code>0</code>.</p>
 305     </div>
 306
 307     <p>Setting <code class="directive">MaxConnectionsPerChild</code> to a
 308     non-zero value limits the amount of memory that process can consume
 309     by (accidental) memory leakage.</p>
 310
 311 </div>
 312 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 313 <div class="directive-section"><h2><a name="MaxMemFree" id="MaxMemFree">MaxMemFree</a> <a name="maxmemfree" id="maxmemfree">Directive</a></h2>
 314 <table class="directive">
 315 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum amount of memory that the main allocator is allowed
 316 to hold without calling <code>free()</code></td></tr>
 317 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxMemFree <var>KBytes</var></code></td></tr>
 318 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>MaxMemFree 0</code></td></tr>
 319 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 320 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 321 <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/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>
 322 </table>
 323     <p>The <code class="directive">MaxMemFree</code> directive sets the
 324     maximum number of free Kbytes that the main allocator is allowed
 325     to hold without calling <code>free()</code>. When not set, or when set
 326     to zero, the threshold will be set to unlimited.</p>
 327
 328 </div>
 329 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 330 <div class="directive-section"><h2><a name="MaxSpareThreads" id="MaxSpareThreads">MaxSpareThreads</a> <a name="maxsparethreads" id="maxsparethreads">Directive</a></h2>
 331 <table class="directive">
 332 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum number of idle threads</td></tr>
 333 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MaxSpareThreads <var>number</var></code></td></tr>
 334 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 335 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 336 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 337 <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/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 338 </table>
 339     <p>Maximum number of idle threads. Different MPMs deal with this
 340     directive differently.</p>
 341
 342     <p>For <code class="module"><a href="../mod/worker.html">worker</a></code>, the default is
 343     <code>MaxSpareThreads 250</code>. This MPM deals with idle threads
 344     on a server-wide basis. If there are too many idle threads in the
 345     server then child processes are killed until the number of idle
 346     threads is less than this number.</p>
 347
 348     <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
 349     <code>MaxSpareThreads 100</code>. Since this MPM runs a
 350     single-process, the spare thread count is also server-wide.</p>
 351
 352     <p><code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> works
 353     similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>. For
 354     <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>10</code>.</p>
 355
 356     <div class="note"><h3>Restrictions</h3>
 357       <p>The range of the <code class="directive">MaxSpareThreads</code> value
 358       is restricted. Apache httpd will correct the given value automatically
 359       according to the following rules:</p>
 360       <ul>
 361         <li><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> wants the value to be greater than
 362         <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>.</li>
 363
 364         <li>For <code class="module"><a href="../mod/worker.html">worker</a></code>, the value must be greater or equal
 365         to the sum of <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>
 366         and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>.</li>
 367       </ul>
 368     </div>
 369
 370 <h3>See also</h3>
 371 <ul>
 372 <li><code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code></li>
 373 <li><code class="directive"><a href="#startservers">StartServers</a></code></li>
 374 <li><code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code></li>
 375 </ul>
 376 </div>
 377 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 378 <div class="directive-section"><h2><a name="MinSpareThreads" id="MinSpareThreads">MinSpareThreads</a> <a name="minsparethreads" id="minsparethreads">Directive</a></h2>
 379 <table class="directive">
 380 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Minimum number of idle threads available to handle request
 381 spikes</td></tr>
 382 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MinSpareThreads <var>number</var></code></td></tr>
 383 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 384 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 385 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 386 <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/mpmt_os2.html">mpmt_os2</a></code>, <code class="module"><a href="../mod/worker.html">worker</a></code></td></tr>
 387 </table>
 388     <p>Minimum number of idle threads to handle request spikes.
 389     Different MPMs deal with this directive
 390     differently.</p>
 391
 392     <p><code class="module"><a href="../mod/worker.html">worker</a></code> uses a default of <code>MinSpareThreads
 393     75</code> and deals with idle threads on a server-wide basis. If
 394     there aren't enough idle threads in the server then child
 395     processes are created until the number of idle threads is greater
 396     than <var>number</var>.</p>
 397
 398     <p><code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> uses a default of
 399     <code>MinSpareThreads 10</code> and, since it is a single-process
 400     MPM, tracks this on a server-wide bases.</p>
 401
 402     <p><code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> works
 403     similar to <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code>.  For
 404     <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> the default value is <code>5</code>.</p>
 405
 406 <h3>See also</h3>
 407 <ul>
 408 <li><code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code></li>
 409 <li><code class="directive"><a href="#startservers">StartServers</a></code></li>
 410 <li><code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code></li>
 411 </ul>
 412 </div>
 413 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 414 <div class="directive-section"><h2><a name="PidFile" id="PidFile">PidFile</a> <a name="pidfile" id="pidfile">Directive</a></h2>
 415 <table class="directive">
 416 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>File where the server records the process ID
 417 of the daemon</td></tr>
 418 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>PidFile <var>filename</var></code></td></tr>
 419 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>PidFile logs/httpd.pid</code></td></tr>
 420 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 421 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 422 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><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>
 423 </table>
 424     <p>The <code class="directive">PidFile</code> directive sets the file to
 425     which the server records the process id of the daemon. If the
 426     filename is not absolute then it is assumed to be relative to the
 427     <code class="directive"><a href="../mod/core.html#serverroot">ServerRoot</a></code>.</p>
 428
 429     <div class="example"><h3>Example</h3><p><code>
 430       PidFile /var/run/apache.pid
 431     </code></p></div>
 432
 433     <p>It is often useful to be able to send the server a signal,
 434     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
 435     re-reads its configuration files. This is done by sending a
 436     SIGHUP (kill -1) signal to the process id listed in the
 437     <code class="directive">PidFile</code>.</p>
 438
 439     <p>The <code class="directive">PidFile</code> is subject to the same
 440     warnings about log file placement and <a href="../misc/security_tips.html#serverroot">security</a>.</p>
 441
 442     <div class="note"><h3>Note</h3>
 443       <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,
 444       for (re-)starting or stopping the server.</p>
 445     </div>
 446
 447 </div>
 448 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 449 <div class="directive-section"><h2><a name="ReceiveBufferSize" id="ReceiveBufferSize">ReceiveBufferSize</a> <a name="receivebuffersize" id="receivebuffersize">Directive</a></h2>
 450 <table class="directive">
 451 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP receive buffer size</td></tr>
 452 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ReceiveBufferSize <var>bytes</var></code></td></tr>
 453 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ReceiveBufferSize 0</code></td></tr>
 454 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 455 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 456 <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></td></tr>
 457 </table>
 458     <p>The server will set the TCP receive buffer size to the number of
 459     bytes specified.</p>
 460
 461     <p>If set to the value of <code>0</code>, the server will use the
 462     OS default.</p>
 463
 464 </div>
 465 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 466 <div class="directive-section"><h2><a name="ScoreBoardFile" id="ScoreBoardFile">ScoreBoardFile</a> <a name="scoreboardfile" id="scoreboardfile">Directive</a></h2>
 467 <table class="directive">
 468 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Location of the file used to store coordination data for
 469 the child processes</td></tr>
 470 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ScoreBoardFile <var>file-path</var></code></td></tr>
 471 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ScoreBoardFile logs/apache_status</code></td></tr>
 472 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 473 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 474 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><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>
 475 </table>
 476     <p>Apache HTTP Server uses a scoreboard to communicate between its parent
 477     and child processes.  Some architectures require a file to facilitate
 478     this communication. If the file is left unspecified, Apache httpd first
 479     attempts to create the scoreboard entirely in memory (using anonymous
 480     shared memory) and, failing that, will attempt to create the file on
 481     disk (using file-based shared memory). Specifying this directive causes
 482     Apache httpd to always create the file on the disk.</p>
 483
 484     <div class="example"><h3>Example</h3><p><code>
 485       ScoreBoardFile /var/run/apache_status
 486     </code></p></div>
 487
 488     <p>File-based shared memory is useful for third-party applications
 489     that require direct access to the scoreboard.</p>
 490
 491     <p>If you use a <code class="directive">ScoreBoardFile</code> then
 492     you may see improved speed by placing it on a RAM disk. But be
 493     careful that you heed the same warnings about log file placement
 494     and <a href="../misc/security_tips.html">security</a>.</p>
 495
 496 <h3>See also</h3>
 497 <ul>
 498 <li><a href="../stopping.html">Stopping and Restarting
 499 Apache HTTP Server</a></li>
 500 </ul>
 501 </div>
 502 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 503 <div class="directive-section"><h2><a name="SendBufferSize" id="SendBufferSize">SendBufferSize</a> <a name="sendbuffersize" id="sendbuffersize">Directive</a></h2>
 504 <table class="directive">
 505 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>TCP buffer size</td></tr>
 506 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>SendBufferSize <var>bytes</var></code></td></tr>
 507 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>SendBufferSize 0</code></td></tr>
 508 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 509 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 510 <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></td></tr>
 511 </table>
 512     <p>Sets the server's TCP send buffer size to the number of bytes
 513     specified. It is often useful to set this past the OS's standard
 514     default value on high speed, high latency conections
 515     (<em>i.e.</em>, 100ms or so, such as transcontinental fast pipes).</p>
 516
 517     <p>If set to the value of <code>0</code>, the server will use the
 518     default value provided by your OS.</p>
 519
 520 </div>
 521 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 522 <div class="directive-section"><h2><a name="ServerLimit" id="ServerLimit">ServerLimit</a> <a name="serverlimit" id="serverlimit">Directive</a></h2>
 523 <table class="directive">
 524 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Upper limit on configurable number of processes</td></tr>
 525 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ServerLimit <var>number</var></code></td></tr>
 526 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 527 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 528 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 529 <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></td></tr>
 530 </table>
 531     <p>For the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, this directive sets the
 532     maximum configured value for <code class="directive"><a href="#maxclients">MaxClients</a></code> for the lifetime of the
 533     Apache httpd process.  For the <code class="module"><a href="../mod/worker.html">worker</a></code> MPM, this directive
 534     in combination with <code class="directive"><a href="#threadlimit">ThreadLimit</a></code> sets
 535     the maximum configured value for <code class="directive"><a href="#maxclients">MaxClients</a></code> for the lifetime of the
 536     Apache httpd process.  Any attempts to change this directive during a
 537     restart will be ignored, but <code class="directive"><a href="#maxclients">MaxClients</a></code> can be modified during
 538     a restart.</p>
 539
 540     <p>Special care must be taken when using this directive.  If
 541     <code class="directive">ServerLimit</code> is set to a value much higher
 542     than necessary, extra, unused shared memory will be allocated.  If
 543     both <code class="directive">ServerLimit</code> and <code class="directive"><a href="#maxclients">MaxClients</a></code> are set to values
 544     higher than the system can handle, Apache httpd may not start or the
 545     system may become unstable.</p>
 546
 547     <p>With the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM, use this directive only
 548     if you need to set <code class="directive"><a href="#maxclients">MaxClients</a></code> higher than 256 (default).
 549     Do not set the value of this directive any higher than what you
 550     might want to set <code class="directive"><a href="#maxclients">MaxClients</a></code> to.</p>
 551
 552     <p>With <code class="module"><a href="../mod/worker.html">worker</a></code>, use this directive only
 553     if your <code class="directive"><a href="#maxclients">MaxClients</a></code> and
 554     <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>
 555     settings require more than 16 server processes (default). Do not set
 556     the value of this directive any higher than the number of server
 557     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>
 558
 559     <div class="note"><h3>Note</h3>
 560       <p>There is a hard limit of <code>ServerLimit 20000</code> compiled
 561       into the server (for the <code class="module"><a href="../mod/prefork.html">prefork</a></code> MPM 200000). This is
 562       intended to avoid nasty effects caused by typos. To increase it
 563       even further past this limit, you will need to modify the value of
 564       MAX_SERVER_LIMIT in the mpm source file and rebuild the server.</p>
 565     </div>
 566
 567 <h3>See also</h3>
 568 <ul>
 569 <li><a href="../stopping.html">Stopping and Restarting Apache HTTP Server</a></li>
 570 </ul>
 571 </div>
 572 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 573 <div class="directive-section"><h2><a name="StartServers" id="StartServers">StartServers</a> <a name="startservers" id="startservers">Directive</a></h2>
 574 <table class="directive">
 575 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of child server processes created at startup</td></tr>
 576 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartServers <var>number</var></code></td></tr>
 577 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 578 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 579 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 580 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><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>
 581 </table>
 582     <p>The <code class="directive">StartServers</code> directive sets the
 583     number of child server processes created on startup. As the number
 584     of processes is dynamically controlled depending on the load, (see
 585     <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>,
 586     <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code>,
 587     <code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code>, <code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code>)
 588     there is usually little reason to adjust this parameter.</p>
 589
 590     <p>The default value differs from MPM to MPM. <code class="module"><a href="../mod/worker.html">worker</a></code>
 591     defaults to <code>StartServers 3</code>; <code class="module"><a href="../mod/prefork.html">prefork</a></code>
 592     defaults to <code>5</code>; <code class="module"><a href="../mod/mpmt_os2.html">mpmt_os2</a></code> defaults to
 593     <code>2</code>.</p>
 594
 595 </div>
 596 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 597 <div class="directive-section"><h2><a name="StartThreads" id="StartThreads">StartThreads</a> <a name="startthreads" id="startthreads">Directive</a></h2>
 598 <table class="directive">
 599 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created on startup</td></tr>
 600 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>StartThreads <var>number</var></code></td></tr>
 601 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 602 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 603 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 604 <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>
 605 </table>
 606     <p>Number of threads created on startup. As the
 607     number of threads is dynamically controlled depending on the
 608     load, (see
 609     <code class="directive"><a href="#minsparethreads">MinSpareThreads</a></code>,
 610     <code class="directive"><a href="#maxsparethreads">MaxSpareThreads</a></code>,
 611     <code class="directive"><a href="../mod/prefork.html#minspareservers">MinSpareServers</a></code>, <code class="directive"><a href="../mod/prefork.html#maxspareservers">MaxSpareServers</a></code>)
 612     there is usually little reason to adjust this
 613     parameter.</p>
 614
 615     <p>For <code class="module"><a href="../mod/mpm_netware.html">mpm_netware</a></code> the default is
 616     <code>StartThreads 50</code> and, since there is only a single
 617     process, this is the total number of threads created at startup to
 618     serve requests.</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="ThreadLimit" id="ThreadLimit">ThreadLimit</a> <a name="threadlimit" id="threadlimit">Directive</a></h2>
 623 <table class="directive">
 624 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the upper limit on the configurable number of threads
 625 per child process</td></tr>
 626 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadLimit <var>number</var></code></td></tr>
 627 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 628 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 629 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 630 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><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>
 631 <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
 632 and later</td></tr>
 633 </table>
 634     <p>This directive sets the maximum configured value for <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the lifetime
 635     of the Apache httpd process.  Any attempts to change this directive
 636     during a restart will be ignored, but <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> can be modified
 637     during a restart up to the value of this directive.</p>
 638
 639     <p>Special care must be taken when using this directive.  If
 640     <code class="directive">ThreadLimit</code> is set to a value much higher
 641     than <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code>,
 642     extra unused shared memory will be allocated.  If both
 643     <code class="directive">ThreadLimit</code> and <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> are set to values
 644     higher than the system can handle, Apache httpd may not start or the
 645     system may become unstable. Do not set the value of this directive
 646     any higher than your greatest predicted setting of <code class="directive"><a href="#threadsperchild">ThreadsPerChild</a></code> for the
 647     current run of Apache httpd.</p>
 648
 649     <p>The default value for <code class="directive">ThreadLimit</code> is
 650     <code>1920</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
 651     <code>64</code> when used with the others.</p>
 652
 653     <div class="note"><h3>Note</h3>
 654       <p>There is a hard limit of <code>ThreadLimit 20000</code> (or
 655       <code>ThreadLimit 15000</code> with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>)
 656       compiled into the server. This is intended to avoid nasty effects
 657       caused by typos. To increase it even further past this limit, you
 658       will need to modify the value of MAX_THREAD_LIMIT in the mpm
 659       source file and rebuild the server.</p>
 660     </div>
 661
 662 </div>
 663 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 664 <div class="directive-section"><h2><a name="ThreadsPerChild" id="ThreadsPerChild">ThreadsPerChild</a> <a name="threadsperchild" id="threadsperchild">Directive</a></h2>
 665 <table class="directive">
 666 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Number of threads created by each child process</td></tr>
 667 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadsPerChild <var>number</var></code></td></tr>
 668 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>See usage for details</code></td></tr>
 669 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
 670 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>MPM</td></tr>
 671 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td><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>
 672 </table>
 673     <p>This directive sets the number of threads created by each
 674     child process. The child creates these threads at startup and
 675     never creates more. If using an MPM like <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code>,
 676     where there is only one child process, this number should be high
 677     enough to handle the entire load of the server. If using an MPM
 678     like <code class="module"><a href="../mod/worker.html">worker</a></code>, where there are multiple child processes,
 679     the <em>total</em> number of threads should be high enough to handle
 680     the common load on the server.</p>
 681
 682     <p>The default value for <code class="directive">ThreadsPerChild</code> is
 683     <code>64</code> when used with <code class="module"><a href="../mod/mpm_winnt.html">mpm_winnt</a></code> and
 684     <code>25</code> when used with the others.</p>
 685
 686 </div>
 687 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 688 <div class="directive-section"><h2><a name="ThreadStackSize" id="ThreadStackSize">ThreadStackSize</a> <a name="threadstacksize" id="threadstacksize">Directive</a></h2>
 689 <table class="directive">
 690 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The size in bytes of the stack used by threads handling
 691 client connections</td></tr>
 692 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ThreadStackSize <var>size</var></code></td></tr>
 693 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>65536 on NetWare; varies on other operating systems</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/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/worker.html">worker</a></code>, <code class="module"><a href="../mod/event.html">event</a></code></td></tr>
 697 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache HTTP Server 2.1 and later</td></tr>
 698 </table>
 699     <p>The <code class="directive">ThreadStackSize</code> directive sets the
 700     size of the stack (for autodata) of threads which handle client
 701     connections and call modules to help process those connections.
 702     In most cases the operating system default for stack size is
 703     reasonable, but there are some conditions where it may need to be
 704     adjusted:</p>
 705
 706     <ul>
 707       <li>On platforms with a relatively small default thread stack size
 708       (e.g., HP-UX), Apache httpd may crash when using some third-party modules
 709       which use a relatively large amount of autodata storage.  Those
 710       same modules may have worked fine on other platforms where the
 711       default thread stack size is larger.  This type of crash is
 712       resolved by setting <code class="directive">ThreadStackSize</code> to a
 713       value higher than the operating system default.  This type of
 714       adjustment is necessary only if the provider of the third-party
 715       module specifies that it is required, or if diagnosis of an Apache httpd
 716       crash indicates that the thread stack size was too small.</li>
 717
 718       <li>On platforms where the default thread stack size is
 719       significantly larger than necessary for the web server
 720       configuration, a higher number of threads per child process
 721       will be achievable if <code class="directive">ThreadStackSize</code> is
 722       set to a value lower than the operating system default.  This type
 723       of adjustment should only be made in a test environment which allows
 724       the full set of web server processing can be exercised, as there
 725       may be infrequent requests which require more stack to process.
 726       The minumum required stack size strongly depends on the modules
 727       used, but any change in the web server configuration can invalidate
 728       the current <code class="directive">ThreadStackSize</code> setting.</li>
 729     </ul>
 730
 731     <div class="note">It is recommended to not reduce <code class="directive">ThreadStackSize</code>
 732     unless a high number of threads per child process is needed. On some
 733     platforms (including Linux), a setting of 128000 is already too low and
 734     causes crashes with some common modules.</div>
 735
 736 </div>
 737 </div>
 738 <div class="bottomlang">
 739 <p><span>Available Languages: </span><a href="../de/mod/mpm_common.html" hreflang="de" rel="alternate" title="Deutsch">&nbsp;de&nbsp;</a> |
 740 <a href="../en/mod/mpm_common.html" title="English">&nbsp;en&nbsp;</a> |
 741 <a href="../ja/mod/mpm_common.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
 742 <a href="../tr/mod/mpm_common.html" hreflang="tr" rel="alternate" title="Türkçe">&nbsp;tr&nbsp;</a></p>
 743 </div><div id="footer">
 744 <p class="apache">Copyright 2010 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
 745 <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></div>
 746 </body></html>