Apache HTTP Server Version 2.4
Apache HTTP Server Version 2.4
| Description: | Loading of executable code and modules into the server at start-up or restart time |
|---|---|
| Status: | Extension |
| ModuleIdentifier: | so_module |
| SourceFile: | mod_so.c |
| Compatibility: | This is a Base module (always included) on Windows |
On selected operating systems this module can be used to load modules into Apache HTTP Server at runtime via the Dynamic Shared Object (DSO) mechanism, rather than requiring a recompilation.
On Unix, the loaded code typically comes from shared object
files (usually with .so extension), on Windows
this may either be the .so or .dll
extension.
Modules built for one major version of the Apache HTTP Server will generally not work on another. (e.g. 1.3 vs. 2.0, or 2.0 vs. 2.2) There are usually API changes between one major version and another that require that modules be modified to work with the new version.
On Windows, where loadable files typically have a file extension
of .dll, Apache httpd modules are called
mod_whatever.so, just as they are on other platforms.
However, you may encounter third-party modules, such as PHP for
example, that continue to use the .dll convention.
While mod_so still loads modules with
ApacheModuleFoo.dll names, the new naming convention is
preferred; if you are converting your loadable module for 2.0,
please fix the name to this 2.0 convention.
The Apache httpd module API is unchanged between the Unix and Windows versions. Many modules will run on Windows with no or little change from Unix, although others rely on aspects of the Unix architecture which are not present in Windows, and will not work.
When a module does work, it can be added to the server in
one of two ways. As with Unix, it can be compiled into the
server. Because Apache httpd for Windows does not have the
Configure program of Apache httpd for Unix, the module's
source file must be added to the ApacheCore project file, and
its symbols must be added to the
os\win32\modules.c file.
The second way is to compile the module as a DLL, a shared
library that can be loaded into the server at runtime, using
the LoadModule
directive. These module DLLs can be distributed and run on any
Apache httpd for Windows installation, without recompilation of the
server.
To create a module DLL, a small change is necessary to the
module's source file: The module record must be exported from
the DLL (which will be created later; see below). To do this,
add the AP_MODULE_DECLARE_DATA (defined in the
Apache httpd header files) to your module's module record definition.
For example, if your module has:
module foo_module;
Replace the above with:
module AP_MODULE_DECLARE_DATA foo_module;
Note that this will only be activated on Windows, so the
module can continue to be used, unchanged, with Unix if needed.
Also, if you are familiar with .DEF files, you can
export the module record with that method instead.
Now, create a DLL containing your module. You will need to link this against the libhttpd.lib export library that is created when the libhttpd.dll shared library is compiled. You may also have to change the compiler settings to ensure that the Apache httpd header files are correctly located. You can find this library in your server root's modules directory. It is best to grab an existing module .dsp file from the tree to assure the build environment is configured correctly, or alternately compare the compiler and link options to your .dsp.
This should create a DLL version of your module. Now simply
place it in the modules directory of your server
root, and use the LoadModule
directive to load it.
| Description: | Link in the named object file or library |
|---|---|
| Syntax: | LoadFile filename [filename] ... |
| Context: | server config, virtual host |
| Status: | Extension |
| Module: | mod_so |
The LoadFile directive links in the named object files or
libraries when the server is started or restarted; this is used
to load additional code which may be required for some module
to work. Filename is either an absolute path or
relative to ServerRoot.
For example:
LoadFile "libexec/libxmlparse.so"
| Description: | Links in the object file or library, and adds to the list of active modules |
|---|---|
| Syntax: | LoadModule module filename |
| Context: | server config, virtual host |
| Status: | Extension |
| Module: | mod_so |
The LoadModule directive links in the object file or library
filename and adds the module structure named
module to the list of active modules. Module
is the name of the external variable of type
module in the file, and is listed as the Module Identifier
in the module documentation.
For example:
LoadModule status_module "modules/mod_status.so"
loads the named module from the modules subdirectory of the ServerRoot.
