Apache HTTP Server Version 2.0
Apache HTTP Server Version 2.0
| Description: | Multi-Processing Module allowing for daemon processes serving requests to be assigned a variety of different userids |
|---|---|
| Status: | MPM |
| Module Identifier: | mpm_perchild_module |
| Source File: | perchild.c |
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.
A single control process launches the number of child processes
indicated by the NumServers directive at server
startup. Each child process creates threads as specified in the
StartThreads directive.
The individual threads then
listen for connections and serve them when they arrive.
Apache always tries to maintain a pool of spare 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
MinSpareThreads
and MaxSpareThreads.
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 (NumServers) by the maximum
number of threads created in each process
(MaxThreadsPerChild).
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
User and Group 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 suexec is used, these directives also
set the privileges which will be inherited by CGI scripts.
MaxRequestsPerChild
controls how frequently the
server recycles processes by killing old ones and launching new
ones.
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.
AssignUserId ChildPerUserId
CoreDumpDirectory Group Listen ListenBacklog LockFile MaxRequestsPerChild MaxSpareThreads MaxThreadsPerChild MinSpareThreads NumServers PidFile ScoreBoardFile SendBufferSize StartThreads User
| Description: | |
|---|---|
| Syntax: | AssignUserID user_id group_id |
| Context: | virtual host |
| Status: | MPM |
| Module: | perchild |
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.
| Description: | |
|---|---|
| Syntax: | ChildPerUserID user_id
group_id num_children |
| Context: | server config |
| Status: | MPM |
| Module: | perchild |
Specify a user id and group id for a number of child processes. The third
argument, num_children, is the number of child processes to start with the
specified user and group. It does not represent a specific
child number. If the total number of child processes, found by totaling all of
the third arguments to all ChildPerUserId directives in the config file, is
less than NumServers, then all
remaining children will inherit the User and Group settings from the main server