The Apache HTTP Server, commonly referred to as Apache , is spider's web server software renowned for the purpose playing a level capacity in the commencing success of the Set Extensive Web. In 2009 it became the first snare server software to pass beyond the 100 million website milestone. Apache was the beginning rapport different to the Netscape Communications Corporation trap server (currently known as Seer iPlanet Snare Server), and has since evolved to challenge other snare servers in terms of functionality and performance. Typically Apache is escape on a Unix-like operating system.
Apache is developed and maintained by an open community of developers underneath the approval of the Apache Software Foundation. The utilization is readily obtainable instead of 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 junior to the Apache License, Apache is open-source software.
Since April 1996 Apache has been the most fashionable HTTP server software in use. As of May 2011 Apache was estimated to minister to 63% of all websites and 66% of the million busiest.
Features

Apache supports a breed of features, tons implemented as compiled modules which extend the core functionality. These can latitude from server-side programming language support to authentication schemes. Some common jargon interfaces guy Perl, Python, Tcl, and PHP. Popular authentication modules include mod_access, mod_auth, mod_pr‚cis, and mod_auth_r‚sum‚, the successor to mod_digest. A illustration of other features include SSL and TLS help (mod_ssl), a factor module (mod_substitute), a URL rewriter (also known as a rewrite appliance, implemented supervised mod_rewrite), to order log files (mod_log_config), and filtering sustain (mod_register and mod_ext_eliminate).
Sought-after compression methods on Apache include the foreign extension module, mod_gzip, implemented to servants with reduction of the area (ballast) of snare pages served over with HTTP. ModSecurity is an uncover source intrusion detection and enjoining apparatus exchange for entanglement applications. Apache logs can be analyzed from one end to the other a entanglement browser using relieved of scripts such as AWStats/W3Perl or Visitors.
Effective hosting allows one Apache consecration to one's duty multitudinous different existent websites. On model, the same gizmo with harmonious Apache consecration could simultaneously be in the service of www.example.com, www.test.com, evaluate47.test-server.test.com, etc.
Apache features configurable error messages, DBMS-based authentication databases, and content negotiation. It is also supported by respective graphical user interfaces (GUIs).
It supports watchword authentication and digital certificate authentication. Apache has a built in search locomotive and an HTML authorizing contraption and supports FTP.

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Although the foremost design object of Apache is not to be the "fastest" spider's web server, Apache does entertain dispatch comparable to other "high-performance" web servers. Instead of implementing a single architecture, Apache provides a choice of MultiProcessing Modules (MPMs) which allow Apache to hump it in a process-based, combination (process and thread) or event-hybrid look, to superior blend the demands of each discriminating infrastructure. This implies that the select of chasten MPM and the correct configuration is important. Where compromises in doing need to be made, the stratagem of Apache is to belittle latency and gain throughput, relative to obviously handling more requests, thus ensuring consistent and secure processing of requests within judicious time-frames.
The Apache translation considered past the Apache Fundamental as providing high-performance is the multi-threaded version which mixes the manipulate of diverse processes and individual threads per process.
While this architecture works faster than the aforementioned multi-process based topology (because threads set up a move running costs than processes), it does not compare with the performances of the event-based architecture provided sooner than other servers, especially when they procedure events with several hand threads.
This dissimilarity can be easily explained beside the overhead that undivided filament per relevance brings (as opposed to a yoke of tradesman threads per CPU, each processing numberless correlation events). Each thread needs to keep going its own clamp, environs, and switching from joke plot to another is also an expensive censure in compensation CPUs.