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Apache HTTP Server
Apache HTTP Server
By LinuxHPC.org and Cluster Resources
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Apache HTTP Server is a free software/open source web server for Unix-like systems, Microsoft Windows, Novell NetWare and other platforms. Apache is notable for playing a key role in the initial growth of the World Wide Web, and continues to be the most popular web server in use, serving as the de facto reference platform against which other web servers are designed and judged.
Apache features configurable error messages, DBMS-based authentication databases, and content negotiation. It is also supported by several graphical user interfaces (GUIs) which permit easier, more intuitive configuration of the server.
Status
Apache is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation.
License
The License under which software from the Apache Foundation is distributed is a distinctive part of the Apache HTTP Server's history and presence in the open source software environment. The Apache License allows for the distribution of both open- and closed-source derivations of the source code.
Furthermore, it is perhaps surprising that the Free Software Foundation does not consider the Apache License to be "compatible" with version 2.0 of the GNU General Public License (GPL), meaning that software licensed under the Apache License cannot be integrated with software that is distributed under the GPL. Here is what the FSF says about the Apache License:
“This is a free software licenses but 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.)”
The current draft of 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.
Usage
Apache is primarily used to serve static and dynamic content on the World Wide Web. Many web applications are designed expecting the environment and features that Apache provides.
Apache is the web server component of the popular LAMP web server application stack, alongside Linux, MySQL, and the PHP/Perl/Python programming languages.
Apache is redistributed as part of various proprietary packages, such as the Oracle database or the IBM WebSphere application server. Mac OS X integrates Apache as its built-in web server. It is also supported in some way by Borland in the Kylix and Delphi development tools. Apache is included with Novell Netware 6.5, where it is the default web server.
Apache is used for many other tasks where content needs to be made available in a secure and reliable way. One example is sharing files from a personal computer over the Internet. A user who has Apache installed on their desktop can put arbitrary files in the Apache's document root which can then be shared.
Programmers developing web applications often use a locally installed version of Apache in order to preview and test code as it is being developed.
Benefits/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, and mod_digest. A sample of other features include SSL and TLS support (mod_ssl), a proxy module, a useful 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). Apache logs can be analyzed through a web browser using free scripts such as AWStats or Visitors.
Apache 2
Version 2 of the Apache server was a substantial re-write of much of the code, with a strong focus on further modularisation and the development of a portability layer; the APR. 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 Windows), a new Apache API, and IPv6 support. The first alpha release of Apache 2 was in March 2000 with the first general availability release in May 2002.
Version 2.2 introduced a new auth API that allows for more flexibility. It also features improved cache modules and proxy modules.
All text used in this article is available under the GNU Free Documentation License. It uses material from the Wikipedia article "Apache HTTP Server".