Apache HTTP Server Original author(s) Robert McCool Developer(s) Apache Software Foundation Initial release 19951 Stable release 2.2.17 / October 19, 2010; 3 months ago (2010-10-19) Preview release 2.3.10-alpha / December 21, 2010; 48 days ago (2010-12-21) 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 Oracle iPlanet 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, AmigaOS, 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 2011[update] Apache served over 59.13% of all websites and over 66.62% of the million busiest.4 Contents 1 Features 2 Performance 3 License 4 See also 5 References 6 Further reading 7 External links // 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 several graphical user interfaces (GUIs). Performance This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2009) Although the main design goal of Apache is not to be the "fastest" web server, Apache does have performance comparable to other "high-performance" web servers. Instead of implementing a single architecture, Apache provides a variety of MultiProcessing Modules (MPMs) which allow Apache to run in a process-based, hybrid (process and thread) or event-hybrid mode, to better match the demands of each particular infrastructure. This implies that the choice of correct MPM and the correct configuration is important. Where compromises in performance need to be made, the design of Apache is to reduce latency and increase throughput, relative to simply handling more requests, thus ensuring consistent and reliable processing of requests within reasonable time-frames.

The Apache version considered by the Apache Foundation as providing high-performances is the multi-threaded version which mixes the use of several processes and several threads per process.5 While this architecture works faster than the previous multi-process based topology (because threads have a lower overhead than processes), it does not match the performances of the event-based architecture provided by other servers, especially when they process events with several worker threads. This difference can be easily explained by the overhead that one thread per connection brings (as opposed to a couple of worker threads per CPU, each processing many connection events). Each thread needs to maintain its own stack, environment, and switching from one thread to another is also an expensive task for CPUs. License Main article: Apache License The software license under which software from the Apache Software Foundation is distributed is a distinctive part of the Apache HTTP Server's history and presence in the open-source software community. The Apache License allows for the distribution of both open and closed source derivations of the source code.

The Free Software Foundation does not consider the Apache License to be compatible with version 2 of the GNU General Public License (GPL) in that software licensed under the Apache License cannot be integrated with software that is distributed under the GPL: This is a free software license but it is incompatible with the GPL. The Apache Software License is incompatible with the GPL because it has a specific requirement that is not in the GPL: it has certain patent termination cases that the GPL does not require. We don't think those patent termination cases are inherently a bad idea, but nonetheless they are incompatible with the GNU GPL.6 However, version 3 of the GPL includes a provision (Section 7e) which allows it to be compatible with licenses that have patent retaliation clauses, including the Apache License. The name Apache is a registered trademark and may only be used with the trademark holder's express permission.7 See also Free software portal List of Apache modules .htaccess ApacheBench POSSE project Stronghold (software) Solution stack LAMP

Overview & Discussions Internet Information Services Web accelerator which discusses host-based HTTP acceleration Proxy server which discusses client-side proxies Reverse proxy which discusses origin-side proxies Comparison of web servers Comparison of lightweight web servers Internet Cache Protocol Proxy-Servers lighttpd - open-source web server, optimized for speed-critical environments Nginx - lightweight, high-performance web server, reverse proxy and e-mail proxy (IMAP/POP3) Polipo - lightweight pipelining, multiplexing proxy server and daemon for a small number of users Pound reverse proxy Privoxy - privacy enhancing proxy Squid (software) - a proxy server and web cache daemon Varnish - a performance-focused open source reverse proxy Ziproxy - lightweight forwarding, non-caching, HTTP proxy for traffic optimization References ^ "About the Apache HTTP Server Project". Apache Software Foundation. http://httpd.apache.org/ABOUT_APACHE.html. Retrieved 2008-06-25.  ^ Netcraft Market Share for Top Servers Across All Domains August 1995 - November 2009 ^ "February 2009 Web Server Survey". Netcraft. http://news.netcraft.com/archives/2009/02/18/february_2009_web_server_survey.html. Retrieved 2009-03-29.  ^ "January 2011 Web Server Survey". Netcraft. January 12, 2011. http://news.netcraft.com/archives/2011/01/12/january-2011-web-server-survey-4.html. . ^ Apache MPM worker ^ Various Licenses and Comments about Them from GNU ^ "Apache License and Distribution FAQ". The Apache Software Foundation. 2007. http://www.apache.org/foundation/licence-FAQ.html#Marks.  Further reading Wikinomics: How Mass Collaboration Changes Everything (2006); Don Tapscott, Anthony D. Williams. External links Official website v · d · eApache Software Foundation Top level projects Abdera · ActiveMQ · Ant · Apache HTTP Server · APR · Buildr · Camel · Cassandra · Cayenne · Click · Cocoon · Continuum · CouchDB · CXF · Derby · Directory · Excalibur · Felix · Forrest · Geronimo · Gump · Hadoop · Harmony · HBase · Jackrabbit · James · Karaf · Lenya · Maven · mod_perl · MyFaces · ODE · OFBiz · OpenEJB · OpenJPA · POI · Pivot · Qpid · Roller · Shindig · Shiro · Sling · SpamAssassin · stdcxx · Struts · Subversion · Tapestry · Tomcat · Trafficserver · Tuscany · Velocity · Wicket · XMLBeans Jakarta Projects BCEL · BSF · Cactus · JMeter Commons Projects Daemon · Sanselan · Jelly Lucene Projects Lucene Java · Droids · Lucene.Net · Lucy · Mahout · Nutch · Open Relevance Project · PyLucene · Solr · Tika Hadoop Projects Avro · HDFS · Hive Other projects Buildr · Chainsaw · Xerces · Batik · FOP · Log4j · XAP · River · ServiceMix · Log4Net · Abdera · Ivy · Wink · MINA Incubator Projects ACE · Aries · Bluesky · Composer · Empire-db · Hama · JSPWiki · Thrift · UIMA · XAP · Wink · libcloud Apache Attic AxKit · Beehive · HiveMind · Slide · Shale · iBATIS License: Apache License · Website: http://apache.org/