Commit b982734f authored by Joshua Slive's avatar Joshua Slive
Browse files

Using an mpm_common.html file for the common directives makes 

things considerably easier.  But, there is still lots of work to do.
Clearly, some of the directives are not implemented exactly the same.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87020 13f79535-47bb-0310-9956-ffa450edef68
parent 3755262d

docs/manual/mod/mpm_common.html

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">

<HTML>

<HEAD>

<TITLE>Apache MPM Common Directives</TITLE>

</HEAD>



<!-- Background white, links blue (unvisited), navy (visited), red (active) -->

<BODY

 BGCOLOR="#FFFFFF"

 TEXT="#000000"

 LINK="#0000FF"

 VLINK="#000080"

 ALINK="#FF0000"

>

<!--#include virtual="header.html" -->



<H1 ALIGN="CENTER">Multi-Processing Module Common Directives</H1>



<P>This file documents directives that are implemented by more

than one multi-processing module (MPM).

</P>



<H2>Directives</H2>

<UL>

<li><a href="#coredumpdirectory">CoreDumpDirectory</a></li>

<li><a href="#pidfile">PidFile</a></li>

<li><a href="#lockfile">LockFile</a></li>

<li><a href="#maxclients">MaxClients</a></li>

<li><a href="#maxrequestsperchild">MaxRequestsPerChild</a></li>

<li><a href="#maxsparethreads">MaxSpareThreads</a></li>

<li><a href="#minsparethreads">MinSpareThreads</a></li>

<li><a href="#scoreboardfile">ScoreBoardFile</a></li>

<li><a href="#startservers">StartServers</a></li>

<li><a href="#threadsperchild">ThreadsPerChild</a></li>

</UL>

<HR>



<H2><A NAME="coredumpdirectory">CoreDumpDirectory directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt CoreDumpDirectory} directive&gt; -->

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> CoreDumpDirectory <EM>directory</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> the same location as ServerRoot<BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> MPM<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread, prefork</p>



<p>This controls the directory to which Apache attempts to switch

before dumping core.  The default is in the <A

HREF="core.html#serverroot">ServerRoot</A> directory, however since

this should not be writable by the user the server runs as, core dumps

won't normally get written.  If you want a core dump for debugging,

you can use this directive to place it in a different location.<P><HR>



<H2><A NAME="pidfile">PidFile directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt PidFile} directive&gt; -->

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> PidFile <EM>filename</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>PidFile logs/httpd.pid</CODE><BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> MPM<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread, prefork</p>



<p>The PidFile directive sets the file to which the server records the

process id of the daemon. If the filename does not begin with a slash

(/) then it is assumed to be relative to the <A

HREF="core.html#serverroot">ServerRoot</A>.</p>



<p>It is often useful to be able to send the server a signal, so that

it closes and then reopens its <A

HREF="core.html#errorlog">ErrorLog</A> and TransferLog, and re-reads

its configuration files. This is done by sending a SIGHUP (kill -1)

signal to the process id listed in the PidFile.</p>



<p>The PidFile is subject to the same warnings about log file placement and

<A HREF="../misc/security_tips.html#serverroot">security</A>.</p>





<P><HR>





<H2><A NAME="lockfile">LockFile directive</A></H2>

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> LockFile <EM>filename</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>LockFile logs/accept.lock</CODE><BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> MPM<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread, prefork</p>



<p>The LockFile directive sets the path to the lockfile used when

Apache is compiled with either USE_FCNTL_SERIALIZED_ACCEPT or

USE_FLOCK_SERIALIZED_ACCEPT.  This directive should normally be

left at its default value.  The main reason for changing it is if

the <CODE>logs</CODE> directory is NFS mounted, since <STRONG>the lockfile

must be stored on a local disk</STRONG>.  The PID of the main

server process is automatically appended to the filename. <P>



<p><STRONG>SECURITY:</STRONG> It is best to avoid putting this file in a 

world writable directory such as <CODE>/var/tmp</CODE> because someone 

could create a denial of service attack and prevent the server from

starting by creating a lockfile with the same name as the one the 

server will try to create.</p>



<hr>



<H2><A NAME="maxclients">MaxClients directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt MaxClients} directive&gt; -->

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> MaxClients <EM>number</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>MaxClients 8</code> (with threads)

<code>MaxClients 256</code> (no threads)<BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> MPM<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread, prefork</p>



<P>The MaxClients directive sets the limit on the number of child

processes that will be created to serve requests.  When the server is

built without threading, no more than this number of clients can be

served simultaneously.  To configure more than 256 clients, you must

edit the <code>HARD_SERVER_LIMIT</code> entry in

<code>mpm_default.h</code> and recompile.



<P>Any connection attempts over the MaxClients limit will normally

be queued, up to a number based on the <A HREF="#listenbacklog">

ListenBacklog</A> directive.  Once a child process is freed at the

end of a different request, the connection will then be serviced.</p>



<p>When the server is compiled with threading, then the maximum number

of simultaneous requests that can be served is obtained from the value

of this directive multiplied by <a

href="#threadsperchild">ThreadsPerChild</a>.</p>



<HR>



<H2><A NAME="maxrequestsperchild">MaxRequestsPerChild directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt MaxRequestsPerChild} directive&gt; -->

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> MaxRequestsPerChild <EM>number</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>MaxRequestsPerChild 10000</CODE><BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> MPM<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread, prefork</p>



<p>The MaxRequestsPerChild directive sets the limit on the number of requests

that an individual child server process will handle. After MaxRequestsPerChild

requests, the child process will die. If MaxRequestsPerChild is 0, then

the process will never expire.<P>



Setting MaxRequestsPerChild to a non-zero limit has two beneficial effects:

<UL>

<LI>it limits the amount of memory that process can consume by (accidental)

memory leakage;

<LI> by giving processes a finite lifetime, it helps reduce the

number of processes when the server load reduces.

</UL>



<P><STRONG>NOTE:</STRONG> For <EM>KeepAlive</EM> requests, only the first

request is counted towards this limit. In effect, it changes the

behavior to limit the number of <EM>connections</EM> per child.



<P><HR>





<H2><A NAME="maxsparethreads">MaxSpareThreads directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt MaxSpareServers} directive&gt; -->

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> MaxSpareThreads <EM>number</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>MaxSpareThreads ??</CODE><BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> core<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread</p>



<P>Content needed here!</p>



<p>See also <A HREF="#minsparethreads">MinSpareThreads</A> and

<A HREF="#startservers">StartServers</A>.



<P><HR>



<H2><A NAME="minsparethreads">MinSpareThreads directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt MinSpareServers} directive&gt; -->

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> MinSpareServers <EM>number</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>MinSpareServers ???</CODE><BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> core<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread</p>



<p><strong>fix me</strong></p>



<p>The MinSpareServers directive sets the desired minimum number of <EM>idle</EM>

child server processes. An idle process is one which is not handling

a request. If there are fewer than MinSpareServers idle, then the parent

process creates new children at a maximum rate of 1 per second.<P>



Tuning of this parameter should only be necessary on very busy sites.

Setting this parameter to a large number is almost always a bad idea.<P>



This directive has no effect on Microsoft Windows.



<P>



See also <A HREF="#maxsparethreads">MaxSpareThreads</A> and

<A HREF="#startservers">StartServers</A>.<P><HR>





<H2><A NAME="scoreboardfile">ScoreBoardFile directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt ScoreBoardFile} directive&gt; -->

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> ScoreBoardFile <EM>filename</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>ScoreBoardFile logs/apache_status</CODE>

<BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> MPM<BR>

<A

 HREF="directive-dict.html#Compatibility"

 REL="Help"

>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread, prefork</p>



<p>The ScoreBoardFile directive is required on some architectures to place

a file that the server will use to communicate between its children and

the parent.  The easiest way to find out if your architecture requires

a scoreboard file is to run Apache and see if it creates the file named

by the directive.  If your architecture requires it then you must ensure

that this file is not used at the same time by more than one invocation

of Apache.</p>



<p>If you have to use a ScoreBoardFile 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>



<p><STRONG>See Also</STRONG>:

<A HREF="../stopping.html">Stopping and Restarting Apache</A></P>





<P><HR>



<H2><A NAME="startservers">StartServers directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt StartServers} directive&gt; -->

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> StartServers <EM>number</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>StartServers 5</CODE><BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> MPM<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread, prefork</p>



<p>The StartServers directive sets the number of child server processes created

on startup. As the number of processes is dynamically controlled depending

on the load, there is usually little reason to adjust this parameter.</P>



<P>See also <A HREF="#minsparethreads">MinSpareThreads</A> and

<A HREF="#maxsparethreads">MaxSpareThreads</A>.<P><HR>



<H2><A NAME="threadsperchild">ThreadsPerChild</A></H2>

<p><A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> ThreadsPerChild <EM>number</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>ThreadsPerChild 50</CODE><BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> Base<BR>

<A

 HREF="directive-dict.html#Module"

 REL="Help"

><STRONG>Module:</STRONG></A> mpmt_pthread</p>



<P>This directive sets the number of threads created by each child

process.</p>





<!--#include virtual="footer.html" -->

</BODY>

</HTML>

docs/manual/mod/mpmt_pthread.html

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docs/manual/mod/prefork.html

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">

<HTML>

<HEAD>

<TITLE>Apache MPM mpmt_pthread</TITLE>

</HEAD>



<!-- Background white, links blue (unvisited), navy (visited), red (active) -->

<BODY

 BGCOLOR="#FFFFFF"

 TEXT="#000000"

 LINK="#0000FF"

 VLINK="#000080"

 ALINK="#FF0000"

>

<!--#include virtual="header.html" -->



<H1 ALIGN="CENTER">Multi-Processing Module prefork</H1>

<P>

This Multi-Processing Module implements a pre-forking web server.

</P>



<P><A

HREF="module-dict.html#Status"

REL="Help"

><STRONG>Status:</STRONG></A> MPM

<BR>

<A

HREF="module-dict.html#SourceFile"

REL="Help"

><STRONG>Source File:</STRONG></A> prefork.c

<BR>

<A

HREF="module-dict.html#ModuleIdentifier"

REL="Help"

><STRONG>Module Identifier:</STRONG></A> mpm_prefork_module

</P>



<H2>Summary</H2>



<p>This Multi-Processing Module (MPM) implements a pre-forking

non-threaded web server which handles request in a manner

very similar to the default behavior of Apache 1.3 on Unix.</p>





<H2>Directives</H2>

<UL>

<li><a href="mpm_common.html#coredumpdirectory">CoreDumpDirectory</a></li>

<li><a href="mpm_common.html#pidfile">PidFile</a></li>

<li><a href="mpm_common.html#lockfile">LockFile</a></li>

<li><a href="mpm_common.html#maxclients">MaxClients</a></li>

<li><a href="mpm_common.html#maxrequestsperchild">MaxRequestsPerChild</a></li>

<li><a href="#maxsparethreads">MaxSpareServers</a></li>

<li><a href="#minsparethreads">MinSpareServers</a></li>

<li><a href="mpm_common.html#scoreboardfile">ScoreBoardFile</a></li>

<li><a href="mpm_common.html#startservers">StartServers</a></li>

</UL>



<hr>





<H2><A NAME="maxspareservers">MaxSpareServers directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt MaxSpareServers} directive&gt; -->

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> MaxSpareServers <EM>number</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>MaxSpareServers 10</CODE><BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> core<P>



The MaxSpareServers directive sets the desired maximum number of <EM>idle</EM>

child server processes. An idle process is one which is not handling

a request. If there are more than MaxSpareServers idle, then the parent

process will kill off the excess processes.<P>



Tuning of this parameter should only be necessary on very busy sites.

Setting this parameter to a large number is almost always a bad idea.<P>



<P>



See also <A HREF="#minspareservers">MinSpareServers</A> and

<A HREF="mpm_common.html#startservers">StartServers</A>.<P><HR>



<H2><A NAME="minspareservers">MinSpareServers directive</A></H2>

<!--%plaintext &lt;?INDEX {\tt MinSpareServers} directive&gt; -->

<A

 HREF="directive-dict.html#Syntax"

 REL="Help"

><STRONG>Syntax:</STRONG></A> MinSpareServers <EM>number</EM><BR>

<A

 HREF="directive-dict.html#Default"

 REL="Help"

><STRONG>Default:</STRONG></A> <CODE>MinSpareServers 5</CODE><BR>

<A

 HREF="directive-dict.html#Context"

 REL="Help"

><STRONG>Context:</STRONG></A> server config<BR>

<A

 HREF="directive-dict.html#Status"

 REL="Help"

><STRONG>Status:</STRONG></A> core<P>



The MinSpareServers directive sets the desired minimum number of <EM>idle</EM>

child server processes. An idle process is one which is not handling

a request. If there are fewer than MinSpareServers idle, then the parent

process creates new children at a maximum rate of 1 per second.<P>



Tuning of this parameter should only be necessary on very busy sites.

Setting this parameter to a large number is almost always a bad idea.<P>



This directive has no effect on Microsoft Windows.



<P>



See also <A HREF="#maxspareservers">MaxSpareServers</A> and

<A HREF="mpm_common.html#startservers">StartServers</A>.<P><HR>





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</BODY>

</HTML>