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<modulesynopsis>

<name>worker</name>

<description>Multi-Processing Module implementing a hybrid

multi-threaded multi-process web server</description>

<status>MPM</status>

<sourcefile>worker.c</sourcefile>

<identifier>mpm_worker_module</identifier>

<summary>

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

multi-process multi-threaded server. By using threads to serve

requests, it is able to serve a large number of requests with

less system resources than a process-based server. Yet it

retains much of the stability of a process-based server by

keeping multiple processes available, each with many threads.</p>

<p>The most important directives used to control this MPM are

<directive module="mpm_common">ThreadsPerChild</directive> and

<directive module="mpm_common">MaxClients</directive>. By multiplying

together the value of these directives you define the total number

of simultaneous connections that the server can handle.</p>

</summary>

<seealso><a href="/bind.html">Setting which addresses and

ports Apache uses</a></seealso>

<section><title>How it Works</title>

<p>Each process has a fixed

number of threads. The server adjusts to handle load by

increasing or decreasing the number of processes.</p>

<p>A single control process is responsible for launching child

processes. Each child process creates a fixed number of threads as

specified in the <directive

module="mpm_common">ThreadsPerChild</directive> directive. The

individual threads then listen for connections and serve them when

they arrive.</p>

<p>Apache always tries to maintain a pool of <em>spare</em> or

idle server threads, which stand ready to serve incoming

requests. In this way, clients do not need to wait for a new

threads or processes to be created before their requests can be

served. Apache assesses the total number of idle threads in all

processes, and forks or kills processes to keep this number within

the boundaries specified by <directive

module="mpm_common">MinSpareThreads</directive> and <directive

module="mpm_common">MaxSpareThreads</directive>. Since this

process is very self-regulating, it is rarely necessary to modify

these directives from their default values. The maximum number of

clients that may be served simultaneously is determined by

multiplying the maximum number of server processes that will be

created (<directive module="mpm_common">MaxClients</directive>) by

the number of threads created in each process (<directive

module="mpm_common">ThreadsPerChild</directive>).</p>

<p>While the parent process is usually started as root under Unix

in order to bind to port 80, the child processes and threads are

launched by Apache as a less-privileged user. The <directive

module="mpm_common">User</directive> and <directive

module="mpm_common">Group</directive> directives are used to set

the privileges of the Apache child processes. The child processes

must be able to read all the content that will be served, but

should have as few privileges beyond that as possible. In

addition, unless <a href="/suexec.html">suexec</a> is used,

these directives also set the privileges which will be inherited

by CGI scripts.</p>

<p><directive module="mpm_common">MaxRequestsPerChild</directive>

controls how frequently the server recycles processes by killing

old ones and launching new ones.</p>

</section>

<directivesynopsis location="mpm_common"><name>CoreDumpDirectory</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>Group</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>PidFile</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>Listen</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>ListenBacklog</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>LockFile</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>MaxClients</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>MaxRequestsPerChild</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>MaxSpareThreads</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>MinSpareThreads</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>ScoreBoardFile</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>SendBufferSize</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>ServerLimit</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>StartServers</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>ThreadLimit</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>ThreadsPerChild</name>

</directivesynopsis>

<directivesynopsis location="mpm_common"><name>User</name>

</directivesynopsis>

</modulesynopsis>