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| |
| <modulesynopsis metafile="mpm_common.xml.meta"> |
| |
| <name>mpm_common</name> |
| <description>A collection of directives that are implemented by |
| more than one multi-processing module (MPM)</description> |
| <status>MPM</status> |
| |
| <directivesynopsis> |
| <name>CoreDumpDirectory</name> |
| <description>Directory where Apache HTTP Server attempts to |
| switch before dumping core</description> |
| <syntax>CoreDumpDirectory <var>directory</var></syntax> |
| <default>See usage for the default setting</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module></modulelist> |
| |
| <usage> |
| <p>This controls the directory to which Apache httpd attempts to |
| switch before dumping core. If your operating system is configured to |
| create core files in the working directory of the crashing process, |
| <directive>CoreDumpDirectory</directive> is necessary to change working |
| directory from the default <directive module="core">ServerRoot</directive> |
| directory, which should not be writable by the user the server runs as.</p> |
| |
| <p>If you want a core dump for debugging, you can use this directive to |
| place it in a different location. This directive has no effect if your |
| operating system is not configured to write core files to the working directory |
| of the crashing processes.</p> |
| |
| <note><title>Core Dumps on Linux</title> |
| <p>If Apache httpd starts as root and switches to another user, the |
| Linux kernel <em>disables</em> core dumps even if the directory is |
| writable for the process. Apache httpd (2.0.46 and later) reenables core dumps |
| on Linux 2.4 and beyond, but only if you explicitly configure a <directive |
| >CoreDumpDirectory</directive>.</p> |
| </note> |
| |
| <note> |
| <title>Core Dumps on BSD</title> |
| <p>To enable core-dumping of suid-executables on BSD-systems (such |
| as FreeBSD), set <code>kern.sugid_coredump</code> to 1. |
| </p> |
| </note> |
| |
| <note><title>Specific signals</title> |
| <p><directive>CoreDumpDirectory</directive> processing only occurs for |
| a select set of fatal signals: SIGFPE, SIGILL, SIGABORT, |
| SIGSEGV, and SIGBUS.</p> |
| <p>On some operating systems, SIGQUIT also results in a core dump but |
| does not go through <directive>CoreDumpDirectory</directive> or |
| <directive>EnableExceptionHook</directive> processing, so the core |
| location is dictated entirely by the operating system.</p> |
| </note> |
| |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>EnableExceptionHook</name> |
| <description>Enables a hook that runs exception handlers |
| after a crash</description> |
| <syntax>EnableExceptionHook On|Off</syntax> |
| <default>EnableExceptionHook Off</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist> |
| <module>event</module><module>worker</module> |
| <module>prefork</module></modulelist> |
| |
| <usage> |
| <p>For safety reasons this directive is only available if the server was |
| configured with the <code>--enable-exception-hook</code> option. It |
| enables a hook that allows external modules to plug in and do something |
| after a child crashed.</p> |
| |
| <p>There are already two modules, <code>mod_whatkilledus</code> and |
| <code>mod_backtrace</code> that make use of this hook. Please have a |
| look at Jeff Trawick's <a |
| href="https://emptyhammock.com/projects/httpd/diag/" |
| >EnableExceptionHook site</a> for more information about these.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>GracefulShutdownTimeout</name> |
| <description>Specify a timeout after which a gracefully shutdown server |
| will exit.</description> |
| <syntax>GracefulShutdownTimeout <var>seconds</var></syntax> |
| <default>GracefulShutdownTimeout 0</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module></modulelist> |
| <compatibility>Available in version 2.2 and later</compatibility> |
| |
| <usage> |
| <p>The <directive>GracefulShutdownTimeout</directive> specifies |
| how many seconds after receiving a "graceful-stop" signal, a |
| server should continue to run, handling the existing connections.</p> |
| |
| <p>Setting this value to zero means that the server will wait |
| indefinitely until all remaining requests have been fully served.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>PidFile</name> |
| <description>File where the server records the process ID |
| of the daemon</description> |
| <syntax>PidFile <var>filename</var></syntax> |
| <default>PidFile logs/httpd.pid</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module><module>mpm_winnt</module> |
| <module>mpmt_os2</module> |
| </modulelist> |
| |
| <usage> |
| <p>The <directive>PidFile</directive> directive sets the file to |
| which the server records the process id of the daemon. If the |
| filename is not absolute then it is assumed to be relative to the |
| <directive module="core">ServerRoot</directive>.</p> |
| |
| <example><title>Example</title> |
| <highlight language="config"> |
| PidFile /var/run/apache.pid |
| </highlight> |
| </example> |
| |
| <p>It is often useful to be able to send the server a signal, |
| so that it closes and then re-opens its <directive |
| module="core">ErrorLog</directive> and <directive |
| module="mod_log_config">TransferLog</directive>, and |
| re-reads its configuration files. This is done by sending a |
| SIGHUP (kill -1) signal to the process id listed in the |
| <directive>PidFile</directive>.</p> |
| |
| <p>The <directive>PidFile</directive> is subject to the same |
| warnings about log file placement and <a |
| href="../misc/security_tips.html#serverroot">security</a>.</p> |
| |
| <note><title>Note</title> |
| <p>As of Apache HTTP Server 2, we recommended that you only use the <program> |
| apachectl</program> script, or the init script that your OS provides, |
| for (re-)starting or stopping the server.</p> |
| </note> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>Listen</name> |
| <description>IP addresses and ports that the server |
| listens to</description> |
| <syntax>Listen [<var>IP-address</var>:]<var>portnumber</var> [<var>protocol</var>]</syntax> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module><module>mpm_winnt</module> |
| <module>mpm_netware</module><module>mpmt_os2</module> |
| </modulelist> |
| <compatibility>The <var>protocol</var> argument was added in 2.1.5</compatibility> |
| |
| <usage> |
| <p>The <directive>Listen</directive> directive instructs Apache httpd to |
| listen to only specific IP addresses or ports; by default it |
| responds to requests on all IP interfaces. <directive>Listen</directive> |
| is now a required directive. If it is not in the config file, the |
| server will fail to start. This is a change from previous versions |
| of Apache httpd.</p> |
| |
| <p>The <directive>Listen</directive> directive tells the server to |
| accept incoming requests on the specified port or address-and-port |
| combination. If only a port number is specified, the server listens to |
| the given port on all interfaces. If an IP address is given as well |
| as a port, the server will listen on the given port and |
| interface.</p> |
| |
| <p>Multiple <directive>Listen</directive> directives may be used to |
| specify a number of addresses and ports to listen to. The server will |
| respond to requests from any of the listed addresses and ports.</p> |
| |
| <p>For example, to make the server accept connections on both |
| port 80 and port 8000, use:</p> |
| |
| <highlight language="config"> |
| Listen 80 |
| Listen 8000 |
| </highlight> |
| |
| <p>To make the server accept connections on two specified |
| interfaces and port numbers, use </p> |
| |
| <highlight language="config"> |
| Listen 192.170.2.1:80 |
| Listen 192.170.2.5:8000 |
| </highlight> |
| |
| <p>IPv6 addresses must be surrounded in square brackets, as in the |
| following example:</p> |
| |
| <highlight language="config"> |
| Listen [2001:db8::a00:20ff:fea7:ccea]:80 |
| </highlight> |
| |
| <p>The optional <var>protocol</var> argument is not required for most |
| configurations. If not specified, <code>https</code> is the default for |
| port 443 and <code>http</code> the default for all other ports. The |
| protocol is used to determine which module should handle a request, and |
| to apply protocol specific optimizations with the |
| <directive module="core">AcceptFilter</directive> directive.</p> |
| |
| <p>You only need to set the protocol if you are running on non-standard |
| ports. For example, running an <code>https</code> site on port 8443:</p> |
| |
| <highlight language="config"> |
| Listen 192.170.2.1:8443 https |
| </highlight> |
| |
| <note><title>Error condition</title> |
| Multiple <directive>Listen</directive> directives for the same ip |
| address and port will result in an <code>Address already in use</code> |
| error message. |
| </note> |
| |
| </usage> |
| <seealso><a href="../dns-caveats.html">DNS Issues</a></seealso> |
| <seealso><a href="../bind.html">Setting which addresses and ports Apache HTTP Server |
| uses</a></seealso> |
| <seealso><a |
| href="http://wiki.apache.org/httpd/CouldNotBindToAddress">Further |
| discussion of the <code>Address already in use</code> error message, |
| including other causes.</a></seealso> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>ListenCoresBucketsRatio</name> |
| <description>Ratio between the number of CPU cores (online) and the number of |
| listeners' buckets</description> |
| <syntax>ListenCoresBucketsRatio <var>ratio</var></syntax> |
| <default>ListenCoresBucketsRatio 0 (disabled)</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module> |
| </modulelist> |
| <compatibility>Available in Apache HTTP Server 2.4.17, with a kernel supporting |
| the socket option <code>SO_REUSEPORT</code> and distributing new connections |
| evenly across listening processes' (or threads') sockets using it (eg. Linux |
| 3.9 and later, but not the current implementations of <code>SO_REUSEPORT</code> |
| in *BSDs.</compatibility> |
| |
| <usage> |
| <p>A <var>ratio</var> between the number of (online) CPU cores and the |
| number of listeners' buckets can be used to make Apache HTTP Server create |
| <code>num_cpu_cores / ratio</code> listening buckets, each containing its |
| own <directive>Listen</directive>-ing socket(s) on the same port(s), and |
| then make each child handle a single bucket (with round-robin distribution |
| of the buckets at children creation time).</p> |
| |
| <note><title>Meaning of "online" CPU core</title> |
| <p>On Linux (and also BSD) a CPU core can be turned on/off if |
| <a href="https://www.kernel.org/doc/Documentation/cpu-hotplug.txt">Hotplug</a> |
| is configured, therefore <directive>ListenCoresBucketsRatio</directive> needs to |
| take this parameter into account while calculating the number of buckets to create.</p> |
| </note> |
| |
| <p><directive>ListenCoresBucketsRatio</directive> can improve the |
| scalability when accepting new connections is/becomes the bottleneck. |
| On systems with a large number of CPU cores, enabling this feature has |
| been tested to show significant performances improvement and shorter |
| responses time.</p> |
| |
| <p>There must be at least twice the number of CPU cores than the |
| configured <var>ratio</var> for this to be active. The recommended |
| <var>ratio</var> is <code>8</code>, hence at least <code>16</code> |
| cores should be available at runtime when this value is used. |
| The right <var>ratio</var> to obtain maximum performance needs to be calculated |
| for each target system, testing multiple values and observing the variations in your |
| key performance metrics.</p> |
| |
| <p>This directive influences the calculation of the |
| <directive module="mpm_common">MinSpareThreads</directive> and |
| <directive module="mpm_common">MaxSpareThreads</directive> lower bound values. |
| The number of children processes needs to be a multiple of the number |
| of buckets to optimally accept connections.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>ListenBackLog</name> |
| <description>Maximum length of the queue of pending connections</description> |
| <syntax>ListenBacklog <var>backlog</var></syntax> |
| <default>ListenBacklog 511</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module><module>mpm_winnt</module> |
| <module>mpm_netware</module><module>mpmt_os2</module> |
| </modulelist> |
| |
| <usage> |
| <p>The maximum length of the queue of pending connections. |
| Generally no tuning is needed or desired, however on some |
| systems it is desirable to increase this when under a TCP SYN |
| flood attack. See the backlog parameter to the |
| <code>listen(2)</code> system call.</p> |
| |
| <p>This will often be limited to a smaller number by the |
| operating system. This varies from OS to OS. Also note that |
| many OSes do not use exactly what is specified as the backlog, |
| but use a number based on (but normally larger than) what is |
| set.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>MaxRequestWorkers</name> |
| <description>Maximum number of connections that will be processed |
| simultaneously</description> |
| <syntax>MaxRequestWorkers <var>number</var></syntax> |
| <default>See usage for details</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module> |
| </modulelist> |
| |
| <usage> |
| <p>The <directive>MaxRequestWorkers</directive> directive sets the limit |
| on the number of simultaneous requests that will be served. Any |
| connection attempts over the <directive>MaxRequestWorkers</directive> |
| limit will normally be queued, up to a number based on the |
| <directive module="mpm_common">ListenBacklog</directive> |
| directive. Once a child process is freed at the end of a different |
| request, the connection will then be serviced.</p> |
| |
| <p>For non-threaded servers (<em>i.e.</em>, <module>prefork</module>), |
| <directive>MaxRequestWorkers</directive> translates into the maximum |
| number of child processes that will be launched to serve requests. |
| The default value is <code>256</code>; to increase it, you must also raise |
| <directive module="mpm_common">ServerLimit</directive>.</p> |
| |
| <p>For threaded and hybrid servers (<em>e.g.</em> <module>event</module> |
| or <module>worker</module>) <directive>MaxRequestWorkers</directive> restricts |
| the total number of threads that will be available to serve clients. |
| For hybrid MPMs the default value is <code>16</code> (<directive |
| module="mpm_common">ServerLimit</directive>) multiplied by the value of |
| <code>25</code> (<directive module="mpm_common" |
| >ThreadsPerChild</directive>). Therefore, to increase <directive |
| >MaxRequestWorkers</directive> to a value that requires more than 16 processes, |
| you must also raise <directive module="mpm_common" |
| >ServerLimit</directive>.</p> |
| |
| <p><directive>MaxRequestWorkers</directive> was called |
| <directive>MaxClients</directive> before version 2.3.13. The old name is still |
| supported.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>MaxMemFree</name> |
| <description>Maximum amount of memory that the main allocator is allowed |
| to hold without calling <code>free()</code></description> |
| <syntax>MaxMemFree <var>KBytes</var></syntax> |
| <default>MaxMemFree 2048</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module><module>mpm_winnt</module> |
| <module>mpm_netware</module> |
| </modulelist> |
| |
| <usage> |
| <p>The <directive>MaxMemFree</directive> directive sets the |
| maximum number of free Kbytes that every allocator is allowed |
| to hold without calling <code>free()</code>. In threaded MPMs, every |
| thread has its own allocator. When set |
| to zero, the threshold will be set to unlimited.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>MaxConnectionsPerChild</name> |
| <description>Limit on the number of connections that an individual child server |
| will handle during its life</description> |
| <syntax>MaxConnectionsPerChild <var>number</var></syntax> |
| <default>MaxConnectionsPerChild 0</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module><module>mpm_winnt</module> |
| <module>mpm_netware</module><module>mpmt_os2</module> |
| </modulelist> |
| <compatibility>Available Apache HTTP Server 2.3.9 and later. The old name |
| <code>MaxRequestsPerChild</code> is still supported.</compatibility> |
| |
| <usage> |
| <p>The <directive>MaxConnectionsPerChild</directive> directive sets |
| the limit on the number of connections that an individual child |
| server process will handle. After |
| <directive>MaxConnectionsPerChild</directive> connections, the child |
| process will die. If <directive>MaxConnectionsPerChild</directive> is |
| <code>0</code>, then the process will never expire.</p> |
| |
| <p>Setting <directive>MaxConnectionsPerChild</directive> to a |
| non-zero value limits the amount of memory that process can consume |
| by (accidental) memory leakage.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>MaxSpareThreads</name> |
| <description>Maximum number of idle threads</description> |
| <syntax>MaxSpareThreads <var>number</var></syntax> |
| <default>See usage for details</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>mpm_netware</module><module>mpmt_os2</module> |
| </modulelist> |
| |
| <usage> |
| <p>Maximum number of idle threads. Different MPMs deal with this |
| directive differently.</p> |
| |
| <p>For <module>worker</module> and <module>event</module>, the default is |
| <code>MaxSpareThreads 250</code>. These MPMs deal with idle threads |
| on a server-wide basis. If there are too many idle threads in the |
| server then child processes are killed until the number of idle |
| threads is less than this number. Additional processes/threads |
| might be created if <directive module="mpm_common">ListenCoresBucketsRatio</directive> |
| is enabled.</p> |
| |
| <p>For <module>mpm_netware</module> the default is |
| <code>MaxSpareThreads 100</code>. Since this MPM runs a |
| single-process, the spare thread count is also server-wide.</p> |
| |
| <p><module>mpmt_os2</module> works |
| similar to <module>mpm_netware</module>. For |
| <module>mpmt_os2</module> the default value is <code>10</code>.</p> |
| |
| <note><title>Restrictions</title> |
| <p>The range of the <directive>MaxSpareThreads</directive> value |
| is restricted. Apache httpd will correct the given value automatically |
| according to the following rules:</p> |
| <ul> |
| <li><module>mpm_netware</module> wants the value to be greater than |
| <directive module="mpm_common">MinSpareThreads</directive>.</li> |
| |
| <li>For <module>worker</module> and <module>event</module>, the value |
| must be greater or equal to the sum of <directive module="mpm_common"> |
| MinSpareThreads</directive> and <directive module="mpm_common"> |
| ThreadsPerChild</directive>.</li> |
| </ul> |
| </note> |
| </usage> |
| <seealso><directive module="mpm_common">MinSpareThreads</directive></seealso> |
| <seealso><directive module="mpm_common">StartServers</directive></seealso> |
| <seealso><directive module="prefork">MaxSpareServers</directive></seealso> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>MinSpareThreads</name> |
| <description>Minimum number of idle threads available to handle request |
| spikes</description> |
| <syntax>MinSpareThreads <var>number</var></syntax> |
| <default>See usage for details</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>mpm_netware</module><module>mpmt_os2</module> |
| </modulelist> |
| |
| <usage> |
| <p>Minimum number of idle threads to handle request spikes. |
| Different MPMs deal with this directive differently.</p> |
| |
| <p><module>worker</module> and <module>event</module> use a default of |
| <code>MinSpareThreads 75</code> and deal with idle threads on a server-wide |
| basis. If there aren't enough idle threads in the server then child |
| processes are created until the number of idle threads is greater |
| than <var>number</var>. Additional processes/threads |
| might be created if <directive module="mpm_common">ListenCoresBucketsRatio</directive> |
| is enabled.</p> |
| |
| <p><module>mpm_netware</module> uses a default of |
| <code>MinSpareThreads 10</code> and, since it is a single-process |
| MPM, tracks this on a server-wide bases.</p> |
| |
| <p><module>mpmt_os2</module> works |
| similar to <module>mpm_netware</module>. For |
| <module>mpmt_os2</module> the default value is <code>5</code>.</p> |
| </usage> |
| <seealso><directive module="mpm_common">MaxSpareThreads</directive></seealso> |
| <seealso><directive module="mpm_common">StartServers</directive></seealso> |
| <seealso><directive module="prefork">MinSpareServers</directive></seealso> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>ScoreBoardFile</name> |
| <description>Location of the file used to store coordination data for |
| the child processes</description> |
| <syntax>ScoreBoardFile <var>file-path</var></syntax> |
| <default>ScoreBoardFile logs/apache_runtime_status</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module><module>mpm_winnt</module> |
| </modulelist> |
| |
| <usage> |
| <p>Apache HTTP Server uses a scoreboard to communicate between its parent |
| and child processes. Some architectures require a file to facilitate |
| this communication. If the file is left unspecified, Apache httpd first |
| attempts to create the scoreboard entirely in memory (using anonymous |
| shared memory) and, failing that, will attempt to create the file on |
| disk (using file-based shared memory). Specifying this directive causes |
| Apache httpd to always create the file on the disk.</p> |
| |
| <example><title>Example</title> |
| <highlight language="config"> |
| ScoreBoardFile /var/run/apache_runtime_status |
| </highlight> |
| </example> |
| |
| <p>File-based shared memory is useful for third-party applications |
| that require direct access to the scoreboard.</p> |
| |
| <p>If you use a <directive>ScoreBoardFile</directive> then |
| you may see improved speed by placing it on a RAM disk. But be |
| careful that you heed the same warnings about log file placement |
| and <a href="../misc/security_tips.html">security</a>.</p> |
| </usage> |
| <seealso><a href="../stopping.html">Stopping and Restarting |
| Apache HTTP Server</a></seealso> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>ReceiveBufferSize</name> |
| <description>TCP receive buffer size</description> |
| <syntax>ReceiveBufferSize <var>bytes</var></syntax> |
| <default>ReceiveBufferSize 0</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module><module>mpm_winnt</module> |
| <module>mpm_netware</module><module>mpmt_os2</module> |
| </modulelist> |
| |
| <usage> |
| <p>The server will set the TCP receive buffer size to the number of |
| bytes specified.</p> |
| |
| <p>If set to the value of <code>0</code>, the server will use the |
| OS default.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>SendBufferSize</name> |
| <description>TCP buffer size</description> |
| <syntax>SendBufferSize <var>bytes</var></syntax> |
| <default>SendBufferSize 0</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module><module>mpm_winnt</module> |
| <module>mpm_netware</module><module>mpmt_os2</module> |
| </modulelist> |
| |
| <usage> |
| <p>Sets the server's TCP send buffer size to the number of bytes |
| specified. It is often useful to set this past the OS's standard |
| default value on high speed, high latency connections |
| (<em>i.e.</em>, 100ms or so, such as transcontinental fast pipes).</p> |
| |
| <p>If set to the value of <code>0</code>, the server will use the |
| default value provided by your OS.</p> |
| |
| <p>Further configuration of your operating system may be required to elicit |
| better performance on high speed, high latency connections.</p> |
| |
| <note> <p> On some operating systems, changes in TCP behavior resulting |
| from a larger <directive>SendBufferSize</directive> may not be seen unless |
| <directive module="core">EnableSendfile</directive> is set to OFF. This |
| interaction applies only to static files.</p> </note> |
| |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>ServerLimit</name> |
| <description>Upper limit on configurable number of processes</description> |
| <syntax>ServerLimit <var>number</var></syntax> |
| <default>See usage for details</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module> |
| </modulelist> |
| |
| <usage> |
| <p>For the <module>prefork</module> MPM, this directive sets the |
| maximum configured value for <directive |
| module="mpm_common">MaxRequestWorkers</directive> for the lifetime of the |
| Apache httpd process. For the <module>worker</module> and <module>event |
| </module> MPMs, this directive in combination with <directive |
| module="mpm_common">ThreadLimit</directive> sets |
| the maximum configured value for <directive |
| module="mpm_common">MaxRequestWorkers</directive> for the lifetime of the |
| Apache httpd process. For the <module>event</module> MPM, this directive |
| also defines how many old server processes may keep running and finish processing |
| open connections. |
| Any attempts to change this directive during a restart will be ignored, but |
| <directive module="mpm_common">MaxRequestWorkers</directive> can be modified |
| during a restart.</p> |
| |
| <p>Special care must be taken when using this directive. If |
| <directive>ServerLimit</directive> is set to a value much higher |
| than necessary, extra, unused shared memory will be allocated. If |
| both <directive>ServerLimit</directive> and <directive |
| module="mpm_common">MaxRequestWorkers</directive> are set to values |
| higher than the system can handle, Apache httpd may not start or the |
| system may become unstable.</p> |
| |
| <p>With the <module>prefork</module> MPM, use this directive only |
| if you need to set <directive |
| module="mpm_common">MaxRequestWorkers</directive> higher than 256 (default). |
| Do not set the value of this directive any higher than what you |
| might want to set <directive |
| module="mpm_common">MaxRequestWorkers</directive> to.</p> |
| |
| <p>With <module>worker</module>, use this directive only if your |
| <directive module="mpm_common">MaxRequestWorkers |
| </directive> and <directive module="mpm_common">ThreadsPerChild</directive> |
| settings require more than 16 server processes (default). Do not set |
| the value of this directive any higher than the number of server |
| processes required by what you may want for <directive |
| module="mpm_common">MaxRequestWorkers </directive> and <directive |
| module="mpm_common">ThreadsPerChild</directive>.</p> |
| |
| <p>With <module>event</module>, increase this directive if the process |
| number defined by your <directive |
| module="mpm_common">MaxRequestWorkers</directive> and <directive |
| module="mpm_common">ThreadsPerChild</directive> settings, plus the |
| number of gracefully shutting down processes, is more than 16 server |
| processes (default).</p> |
| |
| <note><title>Note</title> |
| <p>There is a hard limit of <code>ServerLimit 20000</code> compiled |
| into the server (for the <module>prefork</module> MPM 200000). This is |
| intended to avoid nasty effects caused by typos. To increase it |
| even further past this limit, you will need to modify the value of |
| MAX_SERVER_LIMIT in the mpm source file and rebuild the server.</p> |
| </note> |
| </usage> |
| <seealso><a href="../stopping.html">Stopping and Restarting Apache HTTP Server</a></seealso> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>StartServers</name> |
| <description>Number of child server processes created at startup</description> |
| <syntax>StartServers <var>number</var></syntax> |
| <default>See usage for details</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>prefork</module><module>mpmt_os2</module> |
| </modulelist> |
| |
| <usage> |
| <p>The <directive>StartServers</directive> directive sets the |
| number of child server processes created on startup. As the number |
| of processes is dynamically controlled depending on the load, (see |
| <directive module="mpm_common">MinSpareThreads</directive>, |
| <directive module="mpm_common">MaxSpareThreads</directive>, |
| <directive module="prefork">MinSpareServers</directive>, <directive |
| module="prefork">MaxSpareServers</directive>) |
| there is usually little reason to adjust this parameter.</p> |
| |
| <p>The default value differs from MPM to MPM. <module>worker</module> and |
| <module>event</module> default to <code>StartServers 3</code>; <module> |
| prefork</module> defaults to <code>5</code>; <module>mpmt_os2</module> |
| defaults to <code>2</code>.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>StartThreads</name> |
| <description>Number of threads created on startup</description> |
| <syntax>StartThreads <var>number</var></syntax> |
| <default>See usage for details</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>mpm_netware</module></modulelist> |
| |
| <usage> |
| <p>Number of threads created on startup. As the |
| number of threads is dynamically controlled depending on the |
| load, (see |
| <directive module="mpm_common">MinSpareThreads</directive>, |
| <directive module="mpm_common">MaxSpareThreads</directive>, |
| <directive module="prefork">MinSpareServers</directive>, <directive |
| module="prefork">MaxSpareServers</directive>) |
| there is usually little reason to adjust this |
| parameter.</p> |
| |
| <p>For <module>mpm_netware</module> the default is |
| <code>StartThreads 50</code> and, since there is only a single |
| process, this is the total number of threads created at startup to |
| serve requests.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>ThreadLimit</name> |
| <description>Sets the upper limit on the configurable number of threads |
| per child process</description> |
| <syntax>ThreadLimit <var>number</var></syntax> |
| <default>See usage for details</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>mpm_winnt</module> |
| </modulelist> |
| |
| <usage> |
| <p>This directive sets the maximum configured value for <directive |
| module="mpm_common">ThreadsPerChild</directive> for the lifetime |
| of the Apache httpd process. Any attempts to change this directive |
| during a restart will be ignored, but <directive |
| module="mpm_common">ThreadsPerChild</directive> can be modified |
| during a restart up to the value of this directive.</p> |
| |
| <p>Special care must be taken when using this directive. If |
| <directive>ThreadLimit</directive> is set to a value much higher |
| than <directive module="mpm_common">ThreadsPerChild</directive>, |
| extra unused shared memory will be allocated. If both |
| <directive>ThreadLimit</directive> and <directive |
| module="mpm_common">ThreadsPerChild</directive> are set to values |
| higher than the system can handle, Apache httpd may not start or the |
| system may become unstable. Do not set the value of this directive |
| any higher than your greatest predicted setting of <directive |
| module="mpm_common">ThreadsPerChild</directive> for the |
| current run of Apache httpd.</p> |
| |
| <p>The default value for <directive>ThreadLimit</directive> is |
| <code>1920</code> when used with <module>mpm_winnt</module> and |
| <code>64</code> when used with the others.</p> |
| |
| <note><title>Note</title> |
| <p>There is a hard limit of <code>ThreadLimit 20000</code> (or |
| <code>ThreadLimit 100000</code> with <module>event</module>, |
| <code>ThreadLimit 15000</code> with <module>mpm_winnt</module>) |
| compiled into the server. This is intended to avoid nasty effects |
| caused by typos. To increase it even further past this limit, you |
| will need to modify the value of MAX_THREAD_LIMIT in the mpm |
| source file and rebuild the server.</p> |
| </note> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>ThreadsPerChild</name> |
| <description>Number of threads created by each child process</description> |
| <syntax>ThreadsPerChild <var>number</var></syntax> |
| <default>See usage for details</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>mpm_winnt</module> |
| </modulelist> |
| |
| <usage> |
| <p>This directive sets the number of threads created by each |
| child process. The child creates these threads at startup and |
| never creates more. If using an MPM like <module>mpm_winnt</module>, |
| where there is only one child process, this number should be high |
| enough to handle the entire load of the server. If using an MPM |
| like <module>worker</module>, where there are multiple child processes, |
| the <em>total</em> number of threads should be high enough to handle |
| the common load on the server.</p> |
| |
| <p>The default value for <directive>ThreadsPerChild</directive> is |
| <code>64</code> when used with <module>mpm_winnt</module> and |
| <code>25</code> when used with the others.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>ThreadStackSize</name> |
| <description>The size in bytes of the stack used by threads handling |
| client connections</description> |
| <syntax>ThreadStackSize <var>size</var></syntax> |
| <default>65536 on NetWare; varies on other operating systems</default> |
| <contextlist><context>server config</context></contextlist> |
| <modulelist><module>event</module><module>worker</module> |
| <module>mpm_winnt</module><module>mpm_netware</module> |
| <module>mpmt_os2</module> |
| </modulelist> |
| <compatibility>Available in Apache HTTP Server 2.1 and later</compatibility> |
| |
| <usage> |
| <p>The <directive>ThreadStackSize</directive> directive sets the |
| size of the stack (for autodata) of threads which handle client |
| connections and call modules to help process those connections. |
| In most cases the operating system default for stack size is |
| reasonable, but there are some conditions where it may need to be |
| adjusted:</p> |
| |
| <ul> |
| <li>On platforms with a relatively small default thread stack size |
| (e.g., HP-UX), Apache httpd may crash when using some third-party modules |
| which use a relatively large amount of autodata storage. Those |
| same modules may have worked fine on other platforms where the |
| default thread stack size is larger. This type of crash is |
| resolved by setting <directive>ThreadStackSize</directive> to a |
| value higher than the operating system default. This type of |
| adjustment is necessary only if the provider of the third-party |
| module specifies that it is required, or if diagnosis of an Apache httpd |
| crash indicates that the thread stack size was too small.</li> |
| |
| <li>On platforms where the default thread stack size is |
| significantly larger than necessary for the web server |
| configuration, a higher number of threads per child process |
| will be achievable if <directive>ThreadStackSize</directive> is |
| set to a value lower than the operating system default. This type |
| of adjustment should only be made in a test environment which allows |
| the full set of web server processing can be exercised, as there |
| may be infrequent requests which require more stack to process. |
| The minimum required stack size strongly depends on the modules |
| used, but any change in the web server configuration can invalidate |
| the current <directive>ThreadStackSize</directive> setting.</li> |
| |
| <li>On Linux, this directive can only be used to increase the default |
| stack size, as the underlying system call uses the value as a |
| <em>minimum</em> stack size. The (often large) soft limit for |
| <code>ulimit -s</code> (8MB if unlimited) is used as the default stack |
| size.</li> |
| </ul> |
| |
| <note>It is recommended to not reduce <directive>ThreadStackSize</directive> |
| unless a high number of threads per child process is needed. On some |
| platforms (including Linux), a setting of 128000 is already too low and |
| causes crashes with some common modules.</note> |
| </usage> |
| </directivesynopsis> |
| |
| </modulesynopsis> |