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This module provides for loading of executable code and modules into the server at start-up or restart time.
Status: Base (Windows); Experimental (Unix)
Source File: mod_so.c
Module Identifier: so_module
Compatibility: Available in Apache 1.3 and later.
This is an experimental module. On selected operating systems it can be used to load modules into Apache 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), whilst on Windows this module loads DLL files. This module is only available in Apache 1.3 and up.
In previous releases, the functionality of this module was provided for Unix by mod_dld, and for Windows by mod_dll. On Windows, mod_dll was used in beta release 1.3b1 through 1.3b5. mod_so combines these two modules into a single module for all operating systems.
The Apache 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
for Windows does not have the Configure program of Apache
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
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
MODULE_VAR_EXPORT (defined in the Apache header files) to
your module's module record definition. For example, if your module
has:
module foo_module;
Replace the above with:
module MODULE_VAR_EXPORT 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 ApacheCore.lib export library that is created when the ApacheCore.dll shared library is compiled. You may also have to change the compiler settings to ensure that the Apache header files are correctly located.
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.
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 and absolute path or relative to ServerRoot.
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. Example (Unix, and for
Windows as of Apache 1.3.15):
LoadModule status_module modules/mod_status.so
Example (Windows prior to Apache 1.3.15, and some 3rd party modules):
LoadModule foo_module modules/ApacheModuleFoo.dll
Note that all modules bundled with the Apache Win32 binary distribution were renamed as of Apache version 1.3.15.
Win32 Apache modules are often distributed with the old style names, or even a name such as libfoo.dll. Whatever the name of the module, it must be the LoadModule directive requires the exact filename, no assumption is made about the filename extension.
