Apache: The Definitive Guide, 3rd Edition

New Features in Apache v2

The procedure for configuring and compiling Apache has changed, as we will see later.

High-level decisions about the way Apache works internally can now be made at compile time by including one of a series of Multi Processing Modules (MPMs). This is done by attaching a flag to configure:

./configure <other flags> --with_mpm=<name of MPM>

Although MPMs are rather like ordinary modules, only one can be used at a time. Some of them are designed to adapt Apache to different operating systems; others offer a range of different optimizations for Unix.

It will be shown, along with the other compiled-in modules, by executing httpd -l. When we went to press, these were the possible MPMs under Unix:

prefork

Default. Most closely imitates behavior of v1.3. Currently the default for Unix and sites that require stability, though we hope that threading will become the default later on.

threaded

Suitable for sites that require the benefits brought by threading, particularly reduced memory footprint and improved interthread communications. But see “prefork” earlier in this list.

perchild

Allows different hosts to have different user IDs.

mpmt_pthread

Similar to prefork, but each child process has a specified number of threads. It is possible to specify a minimum and maximum number of idle threads.

Dexter

Multiprocess, multithreaded MPM that allows you to specify a static number of processes.

Perchild

Similar to Dexter, but you can define a seperate user and group for each child ...