Apache HTTP Server是以强大、灵活为方向设计的多平台万维网服务器。 在不同平台、环境中通常需要不同的功能和特性，或通过不同的方式高效地 实现某一功能。得益于Apache httpd模块化的设计思路，它可以适应多种环境。 这种设计允许网络管理员通过在编译、运行时选择加载什么模块来决定服务器的功能。 The Apache HTTP Server is designed to be a powerful and flexible web server that can work on a very wide variety of platforms in a range of different environments. Different platforms and different environments often require different features, or may have different ways of implementing the same feature most efficiently. Apache httpd has always accommodated a wide variety of environments through its modular design. This design allows the webmaster to choose which features will be included in the server by selecting which modules to load either at compile-time or at run-time.

Apache HTTP Server的2.0版本将模块化设计思路拓展到了网络服务器的 基本功能中。它提供了一系列可以用于绑定端口、接受并调度子进程处理请求的 多进程处理模块（MPMs）。 Apache HTTP Server 2.0 extends this modular design to the most basic functions of a web server. The server ships with a selection of Multi-Processing Modules (MPMs) which are responsible for binding to network ports on the machine, accepting requests, and dispatching children to handle the requests.

如此程度的模块化设计，可以为我们的网络服务器带来如下两个重要好处。 Extending the modular design to this level of the server allows two important benefits:

• Apache httpd能更妥善、高效地在多种操作系统中工作。尤其是在Windows版 的Apache HTTP Server中，mpm_winnt可以通过原生网络 功能取代先前1.3版本的POSIX层。该优势也延伸到了其他已实现对应多进程处理 模块的操作系统中。 Apache httpd can more cleanly and efficiently support a wide variety of operating systems. In particular, the Windows version of the server is now much more efficient, since mpm_winnt can use native networking features in place of the POSIX layer used in Apache httpd 1.3. This benefit also extends to other operating systems that implement specialized MPMs.
• Apache HTTP server可以更好的为特定站点的需要进行定制。例如， 有高可扩缩性需求的站点可以使用worker或event 这样线程化的多进程处理模块，而对于有高可靠性或兼容性需求的站点， 则可以选择使用prefork。 The server can be better customized for the needs of the particular site. For example, sites that need a great deal of scalability can choose to use a threaded MPM like worker or event, while sites requiring stability or compatibility with older software can use a prefork.

你可能会觉得多进程处理模块很像其他Apache httpd模块。确实如此，不过不同的是， 在运行期间内，服务器只能载入一个多进程处理模块。如需查看全部可用的多进程处理模块， 请见模块索引。 At the user level, MPMs appear much like other Apache httpd modules. The main difference is that one and only one MPM must be loaded into the server at any time. The list of available MPMs appears on the module index page.

下方表单列出了不同系统默认使用的多进程处理模块，该多进程处理模块将在你未在编译时 指定启用哪个多进程处理模块的情况下默认启用。 The following table lists the default MPMs for various operating systems. This will be the MPM selected if you do not make another choice at compile-time.

对于Unix而言，多进程处理模块的选择取决于两个问题： In the case of Unix, the decision as to which MPM is installed is based on two questions:

1.系统是否支持线程？ 1. Does the system support threads?

2.系统是否支持线程安全的轮询，特别是kqueue和epoll功能？ 2. Does the system support thread-safe polling (Specifically, the kqueue and epoll functions)?

如果这两个问题的答案都是“是”，那么默认的多进程处理模块就是event。 If the answer to both questions is 'yes', the default MPM is event.

如果问题1的答案是“是”，问题二的答案是“否”，那么默认的多进程处理模块是worker。 If The answer to #1 is 'yes', but the answer to #2 is 'no', the default will be worker.

如果两个问题的答案都是“否”，那么默认的多进程处理模块是prework。 If the answer to both questions is 'no', then the default MPM will be prefork.

一般来说，现代操作系统都支持这两个功能，在现代操作系统中安装的Apache HTTP Server 的默认多进程处理模块通常是event。 In practical terms, this means that the default will almost always be event, as all modern operating systems support these two features.

多进程处理模块可以在各平台上作为静态模块构建，并链接到服务器中。 这样构建的服务器，如果需要修改多进程处理模块，就还需要重新构建一遍服务器。 MPMs can be built as static modules on all platforms. A single MPM is chosen at build time and linked into the server. The server must be rebuilt in order to change the MPM.

你可以使用configur脚本的--with-mpm=NAME 选项，指定你想使用的多进程处理模块。NAME是你想要的多进程处理模块的名称。 To override the default MPM choice, use the --with-mpm=NAME option of the configure script. NAME is the name of the desired MPM.

服务器编译完成后，可以使用./httpd -l来确定所选的多进程处理模块。 该命令会列出包括多进程处理模块在内的，编译入服务器内的全部模块列表。 Once the server has been compiled, it is possible to determine which MPM was chosen by using ./httpd -l. This command will list every module that is compiled into the server, including the MPM.

在Unix等平台中，多进程处理模块可以构建为DSO模块，并可以以和其他DSO模块相同 的方式动态加载进服务器中。同时，多进程处理模块构建为DSO模块还可以让你通过 更新LoadModule来修改使用的多进程 处理模块，而无需重新构建服务器。 On Unix and similar platforms, MPMs can be built as DSO modules and dynamically loaded into the server in the same manner as other DSO modules. Building MPMs as DSO modules allows the MPM to be changed by updating the LoadModule directive for the MPM instead of by rebuilding the server.

如LoadModule中加载了 多个多进程处理模块，服务器将不能启动，并返回如下错误信息。 Attempting to LoadModule more than one MPM will result in a startup failure with the following error.

此功能可通过configure脚本的--enable-mpms-shared 选项启用。你可以通过传入参数all来安装适用于该平台的全部 多进程处理模块。或者，你可以传入一个带有你所想安装多进程处理模块的列表来设置所要安装的 多进程处理模块。 This feature is enabled using the --enable-mpms-shared option of the configure script. With argument all, all possible MPMs for the platform will be installed. Alternately, a list of MPMs can be specified as the argument.

无论是自动选择，还是通过configure脚本的--with-mpm 选项安装的默认多进程处理模块，都会加载到生成的服务器配置文件中，你可以通过编辑 LoadModule来选择不同的多进程处理模块。 The default MPM, either selected automatically or specified with the --with-mpm option of the configure script, will be loaded in the generated server configuration file. Edit the LoadModule directive to select a different MPM.