Apache has more than twice the market share than its next competitor, Microsoft. This is not just because it is freeware and costs nothing. It is also open source,[3] which means that the source code can be examined by anyone so inclined. If there are errors in it, thousands of pairs of eyes scan it for mistakes. Because of this constant examination by outsiders, it is substantially more reliable[4] than any commercial software product that can only rely on the scrutiny of a closed list of employees. This is particularly important in the field of security, where apparently trivial mistakes can have horrible consequences.
Anyone is free to take the source code and change it to make Apache do something different. In particular, Apache is extensible through an established technology for writing new Modules (described in more detail in Chapter 20), which many people have used to introduce new features.
Apache suits sites of all sizes and types. You can run a single personal page on it or an enormous site serving millions of regular visitors. You can use it to serve static files over the Web or as a frontend to applications that generate customized responses for visitors. Some developers use Apache as a test-server on their desktops, writing and trying code in a local environment before publishing it to a wider audience. Apache can be an appropriate solution for practically any situation involving the HTTP protocol.
Apache is freeware . The intending user downloads the source code and compiles it (under Unix) or downloads the executable (for Windows) from http://www.apache.org or a suitable mirror site. Although it sounds difficult to download the source code and configure and compile it, it only takes about 20 minutes and is well worth the trouble. Many operating system vendors now bundle appropriate Apache binaries.
The result of Apache’s many advantages is clear. There are about 75 web-server software packages on the market. Their relative popularity is charted every month by Netcraft (http://www.netcraft.com). In July 2002, their June survey of active sites, shown in Table 1-1, had found that Apache ran nearly two-thirds of the sites they surveyed (continuing a trend that has been apparent for several years).
Table 1-1. Active sites counted by Netcraft survey, June 2002
|
Developer |
May 2002 |
Percent |
June 2002 |
Percent |
|---|---|---|---|---|
|
Apache |
10411000 |
65.11 |
10964734 |
64.42 |
|
Microsoft |
4121697 |
25.78 |
4243719 |
24.93 |
|
iPlanet |
247051 |
1.55 |
281681 |
1.66 |
|
Zeus |
214498 |
1.34 |
227857 |
1.34 |
[3] For more on the open source movement, see Open Sources: Voices from the Open Source Revolution (O’Reilly & Associates, 1999).
[4] Netcraft also surveys the uptime of various sites. At the time of writing, the longest running site was http://wwwprod1.telia.com, which had been up for 1,386 days.