Apache Overview HOWTO - Linux Documentation …

1 Apache Overview HOWTOT able of ContentsApache Overview Lopez ASF Where to find more Contacting the Open Content Open Publication Apache Software Structure of this Apache based Web Apache Processing and filter Performance and CGI Development Platform for other Interfaces for Apache Overview HOWTOiTable of ContentsApache Overview Protocol Virtual Commercial ASF Applications and (Java Apache Mail Enterprise Server).. Content Parsers and Document Access Portable Code and Where to find more Apache Overview HOWTOiiTable of ContentsApache Overview Support Contacting the Open Content Open Publication REQUIREMENTS ON BOTH UNMODIFIED AND MODIFIED SCOPE OF REQUIREMENTS ON MODIFIED GOOD PRACTICE LICENSE Apache Overview HOWTOiiiApache Overview HOWTOD aniel Lopez Ridruejo, 2002 10 10 This document gives you an Overview of the different Apache projects, such as the Apache HTTP server andthe Tomcat Servlet and JSP engine.

2 It provides pointers for further information and implementation Apache Software Foundation Structure of this document 2. Architecture Security Proxy Performance and scalability CGI scripts Development Platform Integration Management Publishing Protocol modules Virtual Hosting Commercial support 3. ASF Applications and Frameworks Presentation Parsers and Document Access libraries Interoperability Development Testing 4. Where to find more Websites Books Support forums Apache Overview HOWTO15. Contacting the Translations 6. Open Content Open Publication REQUIREMENTS ON BOTH UNMODIFIED AND MODIFIED VERSIONS COPYRIGHT SCOPE OF LICENSE REQUIREMENTS ON MODIFIED WORKS GOOD PRACTICE RECOMMENDATIONS LICENSE OPTIONS 1. IntroductionThis document gives you an Overview of the Apache world, including Apache Software Foundation projectssuch as the Apache web server and commercial and open source third party software.

3 Apache is the mostpopular server on the Internet. New Apache users, especially those coming from a Windows background, areoften unaware of the possibilities of Apache , its useful addons and, more in general, how everything workstogether. This document aims to show a general picture of such possibilities with a brief description of eachone and pointers for further information. The information has been gathered from many sources, includingprojects' web pages, conference talks, mailing lists, Apache websites and my own hands on experience. Fullcredit is given to these authors. Without them and their work, this document would not have been possible 2002 Daniel Lopez RidruejoPermission is granted to copy, distribute and/or modify this document under the terms of the Open ContentOpen Publication License, Version A copy of the license is included in the appendix entitled "OpenContent Open Publication License", or at Apache Software FoundationThe Apache Software Foundation provides support for the Apache community of open source softwareprojects.

4 The Apache projects are characterized by a collaborative, consensus based development process, anopen and pragmatic software license, and a desire to create high quality software that leads the way in itsfield. We consider ourselves not simply a group of projects sharing a server, but rather a community ofdevelopers and ASF is home to many successful Open Source projects, such as the Tomcat Servlet/JSP engine and theANT build can learn more about the foundation Structure of this documentThe first part of this document deals with the Apache Web Server and related modules. It covers the history,architecture and capabilities of the server and describes ways in which you can extend and customize it. Apache Overview HOWTO5. Contacting the Author2 The second part of this document covers projects of the Apache Software Foundation, such as those form theJakarta and Java XML communities.

5 Rather than organizing the projects around a certain programminglanguage or technology, they are organized based on functionality ApacheApache is the leading internet web server, with over 60% market share, according to the Netcraft key factors have contributed to Apache 's success:The Apache license. It is an open source, BSD like license that allows for both commercial andnon commercial uses of Apache . Talented community of developers with a variety of backgrounds and an open development processbased on technical merits. Modular architecture. Apache users can easily add functionality or tailor Apache to their specificenviroment. Portable: Apache runs on nearly all flavors of Unix (and Linux ), Windows, BeOs, Robustness and security. Many commercial vendors have adopted Apache based solutions for their products, including Oracle, RedHat and IBM. In addition, Covalent provides add on modules and 24x7 support for following websites use Apache or derivatives.

6 Chances are that if Apache is good enough for them, it isalso good enough for you :) Yahoo! W3 Consortium Financial Times Apple Stanford >From the Apache website:The Apache HTTP Server Project is an effort to develop and maintain an open source HTTP server formodern operating systems including UNIX and Windows NT. The goal of this project is to provide a secure,efficient and extensible server that provides HTTP services in sync with the current HTTP started its life as modifications to the NCSA Web server, one of the first HTTP servers. You can learnmore about Apache 's history here:The Apache project has grown beyond building just a web server into developing other critical server sidetechnologies. The Apache Software Foundation, described in a later section, serves as an umbrella for ArchitectureThere are two main versions of Apache , the series and the series.

7 Although both versions areconsidered production quality, they differ in architecture and capabilities. Apache Overview HOWTO2. Apache has been ported to a great variety of Unix platforms and is the most widely deployed Web serveron the based Web serverApache on Unix is a process based Web server. The Apache program forks several children at means that a parent process makes identical copies of itself, called children. Each one of the childrencan serve a request independent of the others. This approach has the advantage of improved stability: If one ofthe children misbehaves (runs out of control or has memory leaks) it can be terminated without affecting theothers. The stability comes with a performance penalty. In most Unix operating systems, creating processesand context switching (assigning processor time to each process) are expensive operations.

8 Since processesare isolated from each other, they cannot easily share code and data, consuming system supportApache is the first version of Apache to support Windows, although the port is not considered to be asstable as its Unix counterparts. This is due to the fact that the server had been designed with Unix in mind andthe Windows port was a later addition that did not integrate very has a modular architecture. You can enable or disable modules to add and remove Web serverfunctionality. You can customize Apache to improve performance and security. In addition to modulesbundled with the server, there is a great number of third party modules, providing extended Apache is the latest and greatest version of the Apache server. The architecture contains significantimprovements over the series. The following are some of Processing ModulesApache abstracts the request processing architecture in special server modules, called Multi Processingmodules (MPMs).

9 This means that Apache can be configured to be a pure process based server, a purelythreaded server or a mixture of those models. Threads are contained inside processes and run processes, threads can share data and code. Threads are thus more "lighweight" than processes, and inmost cases threaded servers scale better than process based servers. The disadvantage is that the server is lessreliable, since if a thread misbehaves it can corrupt data or code belonging to other ModulesThe protocol handling has been encapsulated in its own layer in Apache That means it is possible to writemodules to serve protocols other than HTTP, such as POP3 for mail or FTP for file transfer. These protocolmodules can take advantage of a solid server framework and module functionality, such as authentication anddynamic content generation. This means that, for example, you can authenticate your POP3 users against thesame user database Apache uses for web requests and that FTP content can be generated dynamically usingPHP, CGI or any other technologies explained later in this document.

10 Apache Overview Apache and filter maintains the modular architecture and adds an additional extension mechanism: filters. Filtersallow modules to modify the content generated by other modules. They can encrypt, scan for viruses orcompress not only static files but dynamically generated issuesUnfortunately, though the module API is similar between versions, they are not identical and Apache need to be ported to the new architecture. Most mainstream modules such as PHP and mod_perlalready have Apache versions and others, such as mod_dav and mod_ssl, are now part of the serverdistribution. Running modules on a threaded architecture requires specific changes to modules. Modulesdistributed with Apache have undergone those changes and are considered `thread safe', but third partymodules or libraries may not. If you need one of those, you will be limited to running Apache as a pureprocess based runs equally well now on Windows and Unix platforms thanks to the Apache Portable Runtime(APR) library.