The Apache HTTP Server, commonly referred to as Apache , is web server software matchless with a view playing a pivotal role in the introductory development of the Set Extensive Web. In 2009 it became the ahead cobweb server software to pass beyond the 100 million website milestone. Apache was the first practicable different to the Netscape Communications Corporation web server (currently known as Oracle iPlanet Entanglement Server), and has since evolved to challenge other snare servers in terms of functionality and performance. Typically Apache is manufacture on a Unix-like operating system.
Apache is developed and maintained by way of an open community of developers under the protection of the Apache Software Foundation. The germaneness is readily obtainable representing a broad multiplicity 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 Commission, Apache is open-source software.
Since April 1996 Apache has been the most popular HTTP server software in use. As of May 2011 Apache was estimated to be accurate 63% of all websites and 66% of the million busiest.
Features

Apache supports a breed of features, tons implemented as compiled modules which proffer the pit functionality. These can choice from server-side programming phrasing stick up for to authentication schemes. Some common words interfaces buttress Perl, Python, Tcl, and PHP. Favoured authentication modules comprehend mod_access, mod_auth, mod_survive, and mod_auth_epitomize, the successor to mod_digest. A sample of other features comprise SSL and TLS stick (mod_ssl), a surrogate 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 reinforce (mod_comprehend and mod_ext_eliminate).
Stock compression methods on Apache allow for the exotic dimensions module, mod_gzip, implemented to ease with reduction of the size (authority) of entanglement pages served over with HTTP. ModSecurity is an available source intrusion detection and enjoining apparatus for web applications. Apache logs can be analyzed in the course a entanglement browser using sprung scripts such as AWStats/W3Perl or Visitors.
Essential hosting allows one Apache investiture to one's duty innumerable different actual websites. On benchmark, a specific machine with united Apache swearing-in could simultaneously be in the service of www.example.com, www.test.com, examine47.test-server.test.com, etc.
Apache features configurable error messages, DBMS-based authentication databases, and capacity negotiation. It is also supported next to disparate graphical drug interfaces (GUIs).
It supports password authentication and digital certificate authentication. Apache has a built in search machine and an HTML authorizing contraption and supports FTP.

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Although the main develop end of Apache is not to be the "fastest" spider's web server, Apache does take performance comparable to other "high-performance" trap servers. In lieu of of implementing a individual architecture, Apache provides a breed of MultiProcessing Modules (MPMs) which allow Apache to skip out in a process-based, composite (function and thread) or event-hybrid set-up, to think twice match the demands of each particular infrastructure. This implies that the choice of correct MPM and the mark configuration is important. Where compromises in doing lack to be made, the lay out of Apache is to reduce latency and increase throughput, relative to simply handling more requests, thus ensuring consistent and trusted processing of requests within tenable time-frames.
The Apache adaptation considered not later than the Apache Fundamental as providing high-performance is the multi-threaded style which mixes the utilize consume of several processes and individual threads per process.
While this architecture works faster than the too soon multi-process based topology (because threads suffer with a trim upper basic than processes), it does not copy the performances of the event-based architecture provided away other servers, unusually when they change events with respective worker threads.
This inequality can be easily explained on the skyward that a man filament per union brings (as opposed to a twosome of worker threads per CPU, each processing numberless connection events). Each sequence needs to contend its own stack, environs, and switching from one theme to another is also an expensive censure in compensation CPUs.