<summary>
<p>The Apache HTTP Server is a modular program where the
administrator can choose the functionality to include in the
- server by selecting a set of modules. The modules can be
- statically compiled into the <program>httpd</program> binary when the
- server is built. Alternatively, modules can be compiled as
- Dynamic Shared Objects (DSOs) that exist separately from the
- main <program>httpd</program> binary file. DSO modules may be
- compiled at the time the server is built, or they may be
- compiled and added at a later time using the Apache Extension
- Tool (<program>apxs</program>).</p>
+ server by selecting a set of modules.
+ Modules will be compiled as Dynamic Shared Objects (DSOs)
+ that exist separately from the main <program>httpd</program>
+ binary file. DSO modules may be compiled at the time the server
+ is built, or they may be compiled and added at a later time
+ using the Apache Extension Tool (<program>apxs</program>).</p>
+ <p>Alternatively, the modules can be statically compiled into
+ the <program>httpd</program> binary when the server is built.</p>
<p>This document describes how to use DSO modules as well as
the theory behind their use.</p>
on a module named <module>mod_so</module> which must be statically
compiled into the Apache httpd core. It is the only module besides
<module>core</module> which cannot be put into a DSO
- itself. Practically all other distributed Apache httpd modules can then
- be placed into a DSO by individually enabling the DSO build for
- them via <program>configure</program>'s
- <code>--enable-mods-shared</code> option as discussed
- in the <a href="install.html">install documentation</a>. After a
- module is compiled into a DSO named <code>mod_foo.so</code> you
- can use <module>mod_so</module>'s <directive
- module="mod_so">LoadModule</directive> command in your
+ itself. Practically all other distributed Apache httpd modules will then
+ be placed into a DSO. After a module is compiled into a DSO named
+ <code>mod_foo.so</code> you can use <module>mod_so</module>'s <directive
+ module="mod_so">LoadModule</directive> directive in your
<code>httpd.conf</code> file to load this module at server startup
or restart.</p>
+ <p>The DSO builds for individual modules can be disabled via
+ <program>configure</program>'s <code>--enable-mods-static</code>
+ option as discussed in the <a href="install.html">install
+ documentation</a>.</p>
<p>To simplify this creation of DSO files for Apache httpd modules
(especially for third-party modules) a support program
<code>mod_foo.so</code>:</p>
<example>
-$ ./configure --prefix=/path/to/install --enable-foo --enable-mods-shared=foo<br />
+$ ./configure --prefix=/path/to/install --enable-foo<br />
$ make install
</example>
</li>
<li>
- <p>Configure Apache HTTP Server for <em>later installation</em> of shared
- modules:</p>
+ <p>Configure Apache HTTP Server with all modules enabled. Only a basic
+ set will be loaded during server startup. You can change the set of loaded
+ modules by activating or deactivating the <directive
+ module="mod_so">LoadModule</directive> directives in
+ <code>httpd.conf</code>.</p>
<example>
-$ ./configure --enable-so<br />
+$ ./configure --enable-mods-shared=all<br />
$ make install
</example>
</li>
<li>
- <p>Configure Apache HTTP Server with all modules enabled, and loaded
- as shared objects. You can then remove individual ones by
- commenting out the <directive
- module="mod_so">LoadModule</directive> directives in
- <code>httpd.conf</code>.</p>
+ <p>Some modules are only useful for developers and will not be build.
+ when using the module set <em>all</em>. To build all available modules
+ including developer modules use <em>reallyall</em>. In addition the
+ <directive module="mod_so">LoadModule</directive> directives for all
+ built modules can be activated via the configure option
+ <code>--enable-load-all-modules</code>.</p>
<example>
-$ ./configure --enable-modules=most --enable-mods-shared=all<br />
+$ ./configure --enable-mods-shared=reallyall --enable-load-all-modules<br />
$ make install
</example>
-
- <p>The <code>most</code> argument to
- <code>--enable-modules</code> indicates that all modules
- which are not experimental or example modules will be built.</p>
</li>
<li>
Build and install a <em>third-party</em> Apache httpd module, say
<code>mod_foo.c</code>, into its own DSO
<code>mod_foo.so</code> <em>outside of</em> the Apache httpd
- source tree using <program>apxs</program>:
+ source tree using <program>apxs</program>:
<example>
$ cd /path/to/3rdparty<br />
<section id="background"><title>Background</title>
- <p>On modern Unix derivatives there exists a nifty mechanism
- usually called dynamic linking/loading of <em>Dynamic Shared
+ <p>On modern Unix derivatives there exists a mechanism
+ called dynamic linking/loading of <em>Dynamic Shared
Objects</em> (DSO) which provides a way to build a piece of
program code in a special format for loading it at run-time
into the address space of an executable program.</p>
- <p>This loading can usually be done in two ways: Automatically
+ <p>This loading can usually be done in two ways: automatically
by a system program called <code>ld.so</code> when an
executable program is started or manually from within the
executing program via a programmatic system interface to the
<p>The shared library approach is the typical one, because it
is what the DSO mechanism was designed for, hence it is used
for nearly all types of libraries the operating system
- provides. On the other hand using shared objects for extending
- a program is not used by a lot of programs.</p>
+ provides.</p>
</section>
<ul>
<li>The server package is more flexible at run-time because
- the actual server process can be assembled at run-time via
+ the server process can be assembled at run-time via
<directive module="mod_so">LoadModule</directive>
- <code>httpd.conf</code> configuration commands instead of
- <program>configure</program> options at build-time. For instance
+ <code>httpd.conf</code> configuration directives instead of
+ <program>configure</program> options at build-time. For instance,
this way one is able to run different server instances
- (standard & SSL version, minimalistic & powered up
- version [mod_perl, PHP3], <em>etc.</em>) with only one Apache httpd
+ (standard & SSL version, minimalistic & dynamic
+ version [mod_perl, mod_php], <em>etc.</em>) with only one Apache httpd
installation.</li>
<li>The server package can be easily extended with
- third-party modules even after installation. This is at least
- a great benefit for vendor package maintainers who can create
- a Apache httpd core package and additional packages containing
- extensions like PHP, mod_perl, mod_security,
- <em>etc.</em></li>
+ third-party modules even after installation. This is
+ a great benefit for vendor package maintainers, who can create
+ an Apache httpd core package and additional packages containing
+ extensions like PHP, mod_perl, mod_security, <em>etc.</em></li>
- <li>Easier Apache httpd module prototyping because with the
+ <li>Easier Apache httpd module prototyping, because with the
DSO/<program>apxs</program> pair you can both work outside the
Apache httpd source tree and only need an <code>apxs -i</code>
command followed by an <code>apachectl restart</code> to
<p>DSO has the following disadvantages:</p>
<ul>
- <li>The DSO mechanism cannot be used on every platform
- because not all operating systems support dynamic loading of
- code into the address space of a program.</li>
-
<li>The server is approximately 20% slower at startup time
because of the symbol resolving overhead the Unix loader now
has to do.</li>
<li>The server is approximately 5% slower at execution time
- under some platforms because position independent code (PIC)
+ under some platforms, because position independent code (PIC)
sometimes needs complicated assembler tricks for relative
- addressing which are not necessarily as fast as absolute
+ addressing, which are not necessarily as fast as absolute
addressing.</li>
<li>Because DSO modules cannot be linked against other
projects / apache / blobdiff