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| <!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd"> |
| <?xml-stylesheet type="text/xsl" href="../style/manual.xsl"?> |
| <modulesynopsis> |
| |
| <name>perchild</name> |
| <description>Multi-Processing Module allowing for daemon processes |
| serving requests to be assigned a variety of different |
| userids</description> |
| <status>MPM</status> |
| <sourcefile>perchild.c</sourcefile> |
| <identifier>mpm_perchild_module</identifier> |
| |
| <summary> |
| <note type="warning"> |
| This MPM does not currently work on most platforms. Work is ongoing to |
| make it functional. |
| </note> |
| |
| <p>This Multi-Processing Module (MPM) implements a hybrid |
| multi-process, multi-threaded web server. A fixed number of |
| processes create threads to handle requests. Fluctuations in |
| load are handled by increasing or decreasing the number of |
| threads in each process.</p> |
| |
| <p>A single control process launches the number of child processes |
| indicated by the <directive |
| module="mpm_common">NumServers</directive> directive at server |
| startup. Each child process creates threads as specified in the |
| <code>StartThreads</code> 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 new |
| threads to be created. For each child process, Apache assesses |
| the number of idle threads and creates or destroys threads to |
| keep this number within the boundaries specified by |
| <code>MinSpareThreads</code> and <code>MaxSpareThreads</code>. |
| 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 number of server processes |
| that will be created (<code>NumServers</code>) by the maximum |
| number of threads created in each process |
| (<code>MaxThreadsPerChild</code>).</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 |
| <code>User</code> and <code>Group</code> 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><code>MaxRequestsPerChild</code> controls how frequently the |
| server recycles processes by killing old ones and launching new |
| ones.</p> |
| |
| <p>See also: <a href="../bind.html">Setting which addresses and |
| ports Apache uses</a>.</p> |
| |
| <p>In addition it adds the extra ability to specify that |
| specific processes should serve requests under different |
| userids. These processes can then be associated with specific |
| virtual hosts.</p> |
| <!-- XXX: This desperately needs more explanation. --> |
| </summary> |
| |
| <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>MaxRequestsPerChild</name> |
| </directivesynopsis> |
| <directivesynopsis location="mpm_common"> |
| <name>MaxSpareThreads</name> |
| </directivesynopsis> |
| <directivesynopsis location="mpm_common"> |
| <name>MaxThreadsPerChild</name> |
| </directivesynopsis> |
| <directivesynopsis location="mpm_common"> |
| <name>MinSpareThreads</name> |
| </directivesynopsis> |
| <directivesynopsis location="mpm_common"> |
| <name>NumServers</name> |
| </directivesynopsis> |
| <directivesynopsis location="mpm_common"> |
| <name>ScoreBoardFile</name> |
| </directivesynopsis> |
| <directivesynopsis location="mpm_common"> |
| <name>SendBufferSize</name> |
| </directivesynopsis> |
| <directivesynopsis location="mpm_common"> |
| <name>StartThreads</name> |
| </directivesynopsis> |
| <directivesynopsis location="mpm_common"> |
| <name>User</name> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>AssignUserId</name> |
| <syntax>AssignUserID <em>user_id</em> <em>group_id</em></syntax> |
| <contextlist><context>virtual host</context></contextlist> |
| |
| <usage> |
| <p>Tie a virtual host to a specific child process. Requests addressed to |
| the virtual host where this directive appears will be served by the process |
| running with the specified user and group id.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>ChildPerUserId</name> |
| <syntax>ChildPerUserID <em>user_id</em> |
| <em>group_id</em> <em>child_id</em></syntax> |
| <contextlist><context>server config</context></contextlist> |
| |
| <usage> |
| <p>Specify a user id and group id for a specific child process. The number of |
| children if set by the <a href="mpm_common.html#numservers">NumServers</a> |
| directive. For example, the default value for <a |
| href="mpm_common.html#numservers">NumServers</a> is 5 and that means |
| children ids 1,2,3,4 and 5 are available for assigment. If a child does not |
| have an associated ChildPerUserID, it inherits the <a |
| href="mpm_common.html#user">User</a> and <a |
| href="mpm_common.html#group">Group</a> settings from the main server </p> |
| </usage> |
| </directivesynopsis> |
| |
| </modulesynopsis> |
| |