Apache HTTP Server

Apache HTTP Server
The Apache Software Foundation · Apache License 2.0 · source
Name	Apache HTTP Server
Developer	Apache Software Foundation
Released	1995
Latest release	2.4.x
Operating system	Unix-like, Microsoft Windows
License	Apache License 2.0

Apache HTTP Server Apache HTTP Server is an open-source web server software developed and maintained by the Apache Software Foundation. It serves HTTP requests for websites and web applications, running on Unix-like systems and Microsoft Windows while interoperating with systems such as Linux, FreeBSD, NetBSD, OpenBSD, Solaris, Microsoft Windows Server 2019, IBM AIX and HP-UX. Originally created to respond to early web growth, it became a cornerstone of web infrastructure used by organizations including NASA, CERN, White House web services and many academic institutions.

History

Apache HTTP Server originated in the mid-1990s from patches to the NCSA HTTPd server; contributors included members of the National Center for Supercomputing Applications, early web pioneers and volunteer developers who formed the Apache Group. The project incorporated influences from projects and entities such as Netscape Communications Corporation, Tim Berners-Lee's work at CERN, and standards from the Internet Engineering Task Force through RFCs like those authored by Roy Fielding. Over time stewardship moved to the Apache Software Foundation where governance, licenses and processes mirrored other ASF projects like Apache Tomcat and Apache HTTP Server 2.4 development practices. Major milestones paralleled events such as the rise of Dot-com bubble companies, adoption by enterprise vendors like IBM, Red Hat, Oracle Corporation, and integration in distributions by Debian, Ubuntu, CentOS and Fedora Project.

Features and Architecture

Apache implements core functionality for serving HTTP/1.0, HTTP/1.1 and, via modules, support for HTTP/2 and aspects of HTTP/3 experimental work influenced by QUIC research. The server architecture includes a parent process model and multiple MPMs (Multi-Processing Modules) such as the prefork, worker and event MPMs; these were designed with concepts used in systems like POSIX threads and select/epoll abstractions from Linux kernel. Content delivery is extensible through handler hooks and filters comparable in modularity to NGINX reverse-proxying strategies and interoperability with FastCGI and SCGI backends used by platforms like PHP, Python WSGI applications hosted with mod_wsgi, and Ruby on Rails apps via proxying to Phusion Passenger.

Configuration and Modules

Configuration relies on declarative files such as httpd.conf and per-directory .htaccess files, employing directives that interact with access control and URL rewriting influenced by standards like those from the World Wide Web Consortium. A rich module ecosystem includes official modules such as mod_ssl (integrating with OpenSSL), mod_proxy (supporting reverse proxy scenarios akin to HAProxy), mod_rewrite, mod_headers, mod_negotiation and mod_status, plus third-party modules from vendors and communities including Let's Encrypt ecosystem tooling, mod_security rulesets informed by operators like OWASP. Module development follows extension patterns similar to plugins for Apache Tomcat and packaging channels used by Red Hat Software Collections and community repositories managed by distributions such as Gentoo and Arch Linux.

Security and Performance

Security practices for Apache involve using TLS via integrations with OpenSSL and BoringSSL-based tooling, adherence to vulnerability disclosure policies like those established by the Open Source Initiative and coordination with CERT teams such as US-CERT for advisories. Performance tuning uses parameters and approaches seen in systems engineering at organisations like Facebook and Google — tuning MPMs, keepalive, worker threads and integrating caching layers such as Varnish and content delivery networks like Akamai. Hardening techniques include privilege separation, chroot-style isolation inspired by Unix conventions, SELinux policies maintained by NSA-authored tooling in distributions like Red Hat Enterprise Linux, and automated patch management via vendors like Canonical and SUSE.

Deployment and Use Cases

Apache is deployed for a wide array of use cases including traditional virtual-hosted websites, reverse proxies, API gateways, static content serving for media platforms operated by entities like BBC and The New York Times, and as front-ends for application servers such as Apache Tomcat, GlassFish, WildFly and Node.js backends. Common deployment topologies integrate orchestration and management tools like Ansible, Puppet, Chef and container platforms such as Docker and Kubernetes for microservice environments used by enterprises like Salesforce and Netflix.

Development and Community

Development is managed through the Apache governance model under the Apache Software Foundation with contributors drawn from corporations like IBM, Intel, Microsoft, Amazon Web Services and independent developers. The project coordinates via mailing lists and issue trackers similar to practices in Linux kernel development, holds community events and tracks roadmaps akin to other ASF projects such as Apache HTTP Server modules collaborations and cross-project efforts with Apache Lounge. Licensing under the Apache License encourages adoption and commercial redistribution by firms including Red Hat, Oracle Corporation and cloud providers like Google Cloud Platform and Microsoft Azure.

Category:Web server software