What is it?
The Apache HTTP server - now 10 years old - is the product of an open source initiative dedicated to keeping the internet free from commercial control. It is a key part of the Lamp (Linux, Apache, MySQL, PHP/Perl/Python) platform.
Apache has been the most popular HTTP server on the internet since 1996. Although both Apache and Microsoft IIS are gaining numbers, their market shares are relatively constant, at just under 70% and just over 20% respectively.
In October this year Apache passed another milestone, with over 50 million sites recorded by the Netcraft survey, up from 40 million in February.
Where did it originate?
At the National Center for Supercomputing Applications (NCSA), University of Illinois, in 1995. It was put together out of patches for the old NCSA HTTP server, hence the name: "a patchy server". More recently it has been claimed the name was chosen out of respect for the strength and endurance of the Apache nation.
The Apache Software Foundation's philosophy is, "The tools of online publishing should be in the hands of everyone, and software companies should make their money providing value-added services such as specialised modules and support... To the extent that the protocols of the world wide web remain 'unowned' by a single company, the web will remain a level playing field for companies large and small."
The Apache Software Foundation is behind dozens of other open source projects, including the Tomcat Java servlet container, mod_perl, and the Struts Java application framework.
What is it for?
Apache is highly configurable and can be extended using compiled modules to provide support for many different server side programming languages, authentication schemes and other features. New modules can be written using the Apache module API.
What makes it special?
Other web servers have achieved better benchmarks, but the Apache team said, "We feel that it is better to have a mostly fast free server than an extremely fast server that costs thousands of dollars. Apache is run on sites that get millions of hits per day, and they have experienced no performance difficulties."
Apache has the reputation of being more secure than IIS, and of being fixed more quickly and effectively when it does go wrong.
How difficult is it to master?
It is getting easier, with a number of graphical user interfaces now available. A background in Unix/Linux/Solaris system admin, and Perl or PHP programming is helpful.
Where is it used?
Apache has been taken up across the board, from bloggers to trans-national corporations who could easily afford the most expensive of Apache's competitors.
What systems does it run on?
About 30 different operating systems, including most flavours of Unix, Linux and BSD, Windows, Mac OSX and Novell Netware. Apache is bundled with Linux distributions and hundreds of proprietary packages including the Oracle RDBMS, IBM's Websphere application server and Borland's Kylix and Delphi development suites.
What is coming up?
Major releases are rare, since development is not driven by licence revenue. Bug fixes are far more frequent. The Apache Software Foundation receives about 40 contributions a day from developers and users.