From 5dff2d61cc1c27747ee398e04d8e02843aabb1f8 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Tue, 7 May 2024 04:04:06 +0200 Subject: Adding upstream version 2.4.38. Signed-off-by: Daniel Baumann --- docs/manual/mod/prefork.html.en | 218 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 218 insertions(+) create mode 100644 docs/manual/mod/prefork.html.en (limited to 'docs/manual/mod/prefork.html.en') diff --git a/docs/manual/mod/prefork.html.en b/docs/manual/mod/prefork.html.en new file mode 100644 index 0000000..0780b75 --- /dev/null +++ b/docs/manual/mod/prefork.html.en @@ -0,0 +1,218 @@ + + + + + +prefork - Apache HTTP Server Version 2.4 + + + + + + + +
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Modules | Directives | FAQ | Glossary | Sitemap

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Apache HTTP Server Version 2.4

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Apache MPM prefork

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Available Languages:  de  | + en  | + fr  | + ja  | + tr 

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Description:Implements a non-threaded, pre-forking web server
Status:MPM
Module Identifier:mpm_prefork_module
Source File:prefork.c
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Summary

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This Multi-Processing Module (MPM) implements a non-threaded, + pre-forking web server. Each server process may answer incoming + requests, and a parent process manages the size of the server pool. + It is appropriate for sites that need to avoid + threading for compatibility with non-thread-safe libraries. It + is also the best MPM for isolating each request, so that a problem + with a single request will not affect any other.

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This MPM is very self-regulating, so it is rarely necessary to + adjust its configuration directives. Most important is that + MaxRequestWorkers be big enough + to handle as many simultaneous requests as you expect to receive, but + small enough to assure that there is enough physical RAM for all + processes.

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How it Works

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A single control process is responsible for launching child + processes which listen for connections and serve them when they + arrive. Apache httpd always tries to maintain several spare + or idle server processes, which stand ready to serve incoming + requests. In this way, clients do not need to wait for a new + child processes to be forked before their requests can be + served.

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The StartServers, + MinSpareServers, + MaxSpareServers, and + MaxRequestWorkers regulate how + the parent process creates children to serve requests. In general, + Apache httpd is very self-regulating, so most sites do not need to + adjust these directives from their default values. Sites which + need to serve more than 256 simultaneous requests may need to + increase MaxRequestWorkers, + while sites with limited memory may need to decrease MaxRequestWorkers to keep the server from + thrashing (swapping memory to disk and back). More information + about tuning process creation is provided in the performance hints + documentation.

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While the parent process is usually started as root + under Unix in order to bind to port 80, the child processes are + launched by Apache httpd as a less-privileged user. The User and Group directives are used to set + the privileges of the Apache httpd 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.

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MaxConnectionsPerChild + controls how frequently the server recycles processes by killing + old ones and launching new ones.

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This MPM uses the mpm-accept mutex to serialize + access to incoming connections when subject to the thundering herd + problem (generally, when there are multiple listening sockets). + The implementation aspects of this mutex can be configured with the + Mutex directive. The performance hints + documentation has additional information about this mutex.

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MaxSpareServers Directive

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Description:Maximum number of idle child server processes
Syntax:MaxSpareServers number
Default:MaxSpareServers 10
Context:server config
Status:MPM
Module:prefork
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The MaxSpareServers directive sets the + desired maximum number of idle 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.

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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. If you are trying to set the value equal to or lower than + MinSpareServers, Apache HTTP Server + will automatically adjust it to MinSpareServers + 1.

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See also

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MinSpareServers Directive

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Description:Minimum number of idle child server processes
Syntax:MinSpareServers number
Default:MinSpareServers 5
Context:server config
Status:MPM
Module:prefork
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The MinSpareServers directive sets the + desired minimum number of idle 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: It will spawn one, wait a second, then spawn + two, wait a second, then spawn four, and it will + continue exponentially until it is spawning 32 children per second. It will + stop whenever it satisfies the MinSpareServers + setting.

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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.

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See also

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Available Languages:  de  | + en  | + fr  | + ja  | + tr 

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Comments

Notice:
This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our mailing lists.
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