The Apache HTTP Server

Original author(s) Robert McCool
Developer(s) Apache Software Foundation
Initial release 1995[1]
Stable release 2.2.15 / March 6, 2010;
Preview release 2.3.5-alpha / January 28, 2010;
Written in C
Operating system Cross-platform
Available in English
Type Web server
License Apache License 2.0
Website: http://httpd.apache.org/

The Apache HTTP Server, commonly referred to as Apache (pronounced /əˈpætʃiː/), is web server software notable for playing a key role in the initial growth of the World Wide Web.[2] In 2009 it became the first web server software to surpass the 100 million web site milestone.[3]Apache was the first viable alternative to the Netscape Communications Corporation web server (currently known as Sun Java System Web Server), and has since evolved to rival other Unix-based web servers in terms of functionality and performance. The majority of web servers using Apache run a Unix-like operating system.[citation needed]
Apache is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation. The application is available for a wide variety of operating systems, including Unix, GNU, FreeBSD, Linux, Solaris, Novell NetWare, Mac OS X, Microsoft Windows, OS/2, TPF, and eComStation. Released under the Apache License, Apache is characterized as open source software.
Since April 1996 Apache has been the most popular HTTP server software in use. As of February 2010 Apache served over 54.46% of all websites and over 66% of the million busiest.[4]


History:

The first version of the Apache web server software was created by Robert McCool, who was heavily involved with the National Center for Supercomputing Applications web server, known simply as NCSA HTTPd. When McCool left NCSA in mid-1994, the development of httpd stalled, leaving a variety of patches for improvements circulating through e-mails. These patches were provided by a number of other developers besides McCool: Brian Behlendorf, Roy Fielding, Rob Hartill, David Robinson, Cliff Skolnick, Randy Terbush, Robert S. Thau, Andrew Wilson,Eric Hagberg, Frank Peters and Nicolas Pioch, and they thus helped to form the original "Apache Group".

There have been two explanations of the project's name. According to the Apache Foundation, the name was chosen out of respect for theNative American tribe of Apache (Indé), well-known for their endurance and their skills in warfare.[5] However, the original FAQ on the Apache Server project's website, from 1996 to 2001, claimed that "The result after combining [the NCSA httpd patches] was a patchy server.[6][7] The first explanation was supported at an Apache Conference[8] and in an interview in 2000 by Brian Behlendorf, who said that the name connoted "Take no prisoners. Be kind of aggressive and kick some ass".[9] Behlendorf then contradicted this in a 2007 interview, stating that "The Apache server isn't named in honor of Geronimo's tribe" but that so many revisions were sent in that "the group called it 'a patchy Web server'".[10] Both explanations are probably appropriate.[11]
Version 2 of the Apache server was a substantial re-write of much of the Apache 1.x code, with a strong focus on further modularization and the development of a portability layer, the Apache Portable Runtime. The Apache 2.x core has several major enhancements over Apache 1.x. These include UNIX threading, better support for non-Unix platforms (such as Microsoft Windows), a new Apache API, and IPv6 support.[12] The first alpha release of Apache 2 was in March 2000, with the first general availability release on April 6, 2002.[13]
Version 2.2 introduced a more flexible authorization API. It also features improved cache modules and proxy modules.[14]


Features:

Apache supports a variety of features, many implemented as compiled modules which extend the core functionality. These can range from server-side programming language support to authentication schemes. Some common language interfaces support Perl, Python, Tcl, and PHP. Popular authentication modules include mod_access, mod_auth, mod_digest, and mod_auth_digest, the successor to mod_digest. A sample of other features include SSL and TLS support (mod_ssl), a proxy module (mod_proxy), a URL rewriter (also known as a rewrite engine, implemented under mod_rewrite), custom log files (mod_log_config), and filtering support (mod_include and mod_ext_filter).
Popular compression methods on Apache include the external extension module, mod_gzip, implemented to help with reduction of the size (weight) of web pages served over HTTP. ModSecurity is an open source intrusion detection and prevention engine for web applications. Apache logs can be analyzed through a web browser using free scripts such as AWStats/W3Perl or Visitors.

Virtual hosting allows one Apache installation to serve many different actual websites. For example, one machine with one Apache installation could simultaneously serve www.example.com, www.test.com, test47.test-server.test.com, etc.
Apache features configurable error messages, DBMS-based authentication databases, and content negotiation. It is also supported by severalgraphical user interfaces (GUIs).