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Web server

Linux adoption - Web servers
Linux-based solution stacks come with all the general advantages and benefits of free and open-source software. Some more commonly known examples are:

The LAMP stack is probably one of the primary reasons for the very high Linux adoption rate among web servers. In the meantime there are several variations of the LAMP stack available and also completely new ones, such as, e.g. the LYME stack, which is written in Erlang (programming language) and implements functional programming. According to the Netcraft the Apache HTTP Server has the highest market share.

World Wide Web - Web servers
The primary function of a web server is to deliver web pages on the request to clients. This means delivery of HTML documents and any additional content that may be included by a document, such as images, style sheets and scripts.

NeXT Computer - Creation of the first web server and the first web browser
A NeXT Computer and its object oriented development tools and libraries were used by Tim Berners-Lee and Robert Cailliau at CERN to develop the world's first web server software, CERN HTTPd, and also used to write the first web browser, WorldWideWeb.

Web server The term 'web server' can refer to either the computer hardware|hardware (the computer) or the software (the computer application) that helps to deliver web content that can be accessed through the Internet.

Web server The most common use of web servers is to host websites, but there are other uses such as Online game|gaming, data storage or running Enterprise software|enterprise applications.

Web server - Overview The primary function of a web server is to deliver web pages to Client (computing)|clients. The communication between client and server takes place using the Hypertext Transfer Protocol|Hypertext Transfer Protocol (HTTP). Pages delivered are most frequently HTML|HTML documents, which may include images, Style sheet (web development)|style sheets and Java script|scripts in addition to text content.

Web server - Overview The resource is typically a real file on the server's secondary memory|secondary storage, but this is not necessarily the case and depends on how the web server is Implementation|implemented.

Web server - Overview While the primary function is to serve content, a full implementation of HTTP also includes ways of receiving content from clients. This feature is used for submitting Form (web)|web forms, including uploading of files.

Web server - Overview This means that the behaviour of the web server can be scripted in separate files, while the actual server software remains unchanged

Web server - Overview The web server may then be used as a part of a system for monitoring and/or administering the device in question

Web server - History In 1989 Tim Berners-Lee proposed a new project to his employer CERN, with the goal of easing the exchange of information between scientists by using a hypertext system. The project resulted in Berners-Lee writing two programs in 1990:

Web server - History Between 1991 and 1994, the simplicity and effectiveness of early technologies used to surf and exchange data through the World Wide Web helped to port them to many different operating systems and spread their use among scientific organizations and universities, and then to industry.

Web server - History In 1994 Tim Berners-Lee decided to constitute the World Wide Web Consortium (W3C) to regulate the further development of the many technologies involved (HTTP, HTML, etc.) through a standardization process.

Web server - Common features
* Virtual hosting to serve many web sites using one IP address

* Large file support to be able to serve files whose size is greater than 2GB on 32 bit Operating system|OS

* Bandwidth throttling to limit the speed of responses in order to not saturate the network and to be able to serve more clients

Web server - Path translation
Web servers are able to map the path component of a Uniform Resource Locator ('URL') into:

* A local file system resource (for static requests)

* An internal or external program name (for dynamic requests)

For a static request the URL path specified by the client is relative to the web server's root directory.

Consider the following URL as it would be requested by a client:

The client's user agent will translate it into a connection to with the following HTTP 1.1 request:

The web server on will append the given path to the path of its root directory. On an Apache server, this is commonly /home/www (On Unix machines, usually /var/www). The result is the local file system resource:

The web server then reads the file, if it exists and sends a response to the client's web browser. The response will describe the content of the file and contain the file itself or an error message will return saying that the file does not exist or is unavailable.

Web server - Kernel-mode and user-mode web servers
A web server can be either implemented into the Operating System|OS kernel (computing)|kernel, or in user space (like other regular applications).

An in-kernel web server (like Microsoft Internet Information Services|IIS on Windows or TUX web server|TUX on GNU/Linux) will usually work faster, because, as part of the system, it can directly use all the hardware resources it needs, such as non-paged memory, CPU time-slices, network adapters, or buffers.

Web servers that run in user-mode have to ask the system for permission to use more memory or more CPU resources. Not only do these requests to the kernel take time, but they are not always satisfied because the system reserves resources for its own usage and has the responsibility to share hardware resources with all the other running applications. Executing in user mode can also mean useless buffer copies which are another handicap for user-mode web servers.

Web server - Load limits
A web server (program) has defined load limits, because it can handle only a limited number of concurrent client connections (usually between 2 and 80,000, by default between 500 and 1,000) per IP address (and TCP port) and it can serve only a certain maximum number of requests per second depending on:

* the Personal computer hardware|hardware and Computer software|software limitations of the OS of the computer on which the web server runs.

When a web server is near to or over its limit, it becomes unresponsive.

Web server - Causes of overload
At any time web servers can be overloaded because of:

* Too much legitimate web traffic. Thousands or even millions of clients connecting to the web site in a short interval, e.g., Slashdot effect;

* Distributed Denial of Service attacks. A denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a computer or network resource unavailable to its intended users;

* Computer worms that sometimes cause abnormal traffic because of millions of infected computers (not coordinated among them);

* XSS Worm|XSS viruses can cause high traffic because of millions of infected browsers and/or web servers;

* Internet bots Traffic not filtered/limited on large web sites with very few resources (bandwidth, etc.);

* Internet (network) slowdowns, so that client requests are served more slowly and the number of connections increases so much that server limits are reached;

* Web servers (computers) partial unavailability. This can happen because of required or urgent maintenance or upgrade, hardware or software failures, back-end (e.g., database) failures, etc.; in these cases the remaining web servers get too much traffic and become overloaded.

Web server - Symptoms of overload
* Requests are served with (possibly long) delays (from 1 second to a few hundred seconds).

* The web server returns an List of HTTP status codes|HTTP error code, such as 500, 502, 503, 504, 408, or even HTTP 404|404, which is inappropriate for an overload condition.

* The web server refuses or resets (interrupts) Transmission control protocol|TCP connections before it returns any content.

* In very rare cases, the web server returns only a part of the requested content. This behavior can be considered a Software bug|bug, even if it usually arises as a symptom of overload.

Web server - Anti-overload techniques
To partially overcome above average load limits and to prevent overload, most popular web sites use common techniques like:

* Managing network traffic, by using:

** Firewall (computing)|Firewalls to block unwanted traffic coming from bad IP sources or having bad patterns

** HTTP traffic managers to drop, redirect or rewrite requests having bad HTTP patterns

** Bandwidth management and traffic shaping, in order to smooth down peaks in network usage

* Deploying web cache techniques

* Using different domain names to serve different (static and dynamic) content by separate web servers, i.e.:

* Using different domain names and/or computers to separate big files from small and medium sized files; the idea is to be able to fully web cache|cache small and medium sized files and to efficiently serve big or huge (over MB) files by using different settings

* Using many web servers (programs) per computer, each one bound to its own network card and IP address

* Using many web servers (computers) that are grouped together behind a load balancer so that they act or are seen as one big web server

* Adding more hardware resources (i.e. RAM, Disk storage|disks) to each computer

* Tuning OS parameters for hardware capabilities and usage

* Using more efficient computer programs for web servers, etc.

* Using other workarounds, especially if dynamic content is involved

Web server - Market share
[ Survey May, June, July 2013].

Slowloris - Affected web servers
This affects a number of webservers that use threaded processes and ironically attempt to limit that to prevent memory exhaustion - fixing one problem but creating another. This includes but is not necessarily limited to the following:

* WebSense block pages (unconfirmed)

* Trapeze Wireless Web Portal (unconfirmed)

* Verizon's MI424-WR FIOS Cable modem (unconfirmed)

* Verizon's Motorola Set-top box (port 8082 and requires auth - unconfirmed)

* BeeWare WAF (unconfirmed)

Because Slowloris exploits C10k problem|problems handling thousands of connections, the attack has less of an effect on servers that handle large numbers of connections well:

Web analytics - Web server logfile analysis
Web servers record some of their transactions in a logfile. It was soon realized that these logfiles could be read by a program to provide data on the popularity of the website. Thus arose web log analysis software.

In the early 1990s, web site statistics consisted primarily of counting the number of client requests (or hits) made to the web server

A page view was defined as a request made to the web server for a page, as opposed to a graphic, while a visit was defined as a sequence of requests from a uniquely identified client that expired after a certain amount of inactivity, usually 30 minutes

The emergence of Web crawler|search engine spiders and robots in the late 1990s, along with Proxy server|web proxies and Dynamic Host Configuration Protocol|dynamically assigned IP addresses for large companies and Internet service provider|ISPs, made it more difficult to identify unique human visitors to a website. Log analyzers responded by tracking visits by HTTP cookie|cookies, and by ignoring requests from known spiders.

The extensive use of web caches also presented a problem for logfile analysis. If a person revisits a page, the second request will often be retrieved from the browser's cache, and so no request will be received by the web server. This means that the person's path through the site is lost. Caching can be defeated by configuring the web server, but this can result in degraded performance for the visitor and bigger load on the servers.

HTTP pipelining - Implementation in web servers
Implementing pipelining in web servers is a relatively simple matter of making sure that network buffers are not discarded between requests. For that reason, most modern web servers handle pipelining without any problem.

Session (computer science) - Web server session management
For example, once a user has been authenticated to the web server, the user's next HTTP request (GET or POST) should not cause the web server to ask for the user's account and password again

The session information is stored on the web server using the session identifier Session ID generated as a result of the first (sometimes the first authenticated) request from the end user running a web browser. The storage of Session IDs and the associated session data (user name, account number, etc.) on the web server is accomplished using a variety of techniques including, but not limited to, local memory, flat files, and databases.

In situations where multiple web servers must share knowledge of session state (as is typical in a computer cluster|cluster environment) session information must be shared between the cluster nodes that are running web server software

If session information is considered transient, volatile data that is not required for non-repudiation of transactions and does not contain data that is subject to compliance auditing (in the U.S

In a service-oriented architecture, Simple Object Access Protocol or SOAP messages constructed with Extensible Markup Language (XML) messages can be used by consumer applications to cause web servers to create sessions.

Java (software platform) - Web server and enterprise use
The Java platform has become a mainstay of enterprise IT development since the introduction of the Enterprise Edition in 1998, in two different ways:

# Through the coupling of Java to the web server, the Java platform has become a leading platform for integrating the Web with enterprise backend systems

#* The Java platform has matured into an Enterprise Integration role in which legacy systems are unlocked to the outside world through bridges built on the Java platform. This trend has been supported for Java platform support for Enterprise application integration|EAI standards like messaging and Web services and has fueled the inclusion of the Java platform as a development basis in such standards as Software Communications Architecture|SCA, XAM and others.

#* Java has become the standard development platform for many companies' IT departments, which do most or all of their corporate development in Java. This type of development is usually related to company-specific tooling (e.g. a booking tool for an airline) and the choice for the Java platform is often driven by a desire to leverage the existing Java infrastructure to build highly intelligent and interconnected tools.

# The Java platform has become the main development platform for many software tools and platforms that are produced by third-party software groups (commercial, open source and hybrid) and are used as configurable (rather than programmable) tools by companies. Examples in this category include Web servers, application servers, databases, enterprise service buses, business process management (BPM) tools and content management systems.

Enterprise use of Java has also long been the main driver of open source interest in the platform

Cherokee (web server) 'Cherokee' is an open-source cross-platform web server that runs on Linux, BSD|BSD variants, Solaris (operating system)|Solaris, , and Microsoft Windows. It is a lightweight, high-performance web server/reverse proxy licensed under the GNU General Public License. Its goal is to be fast and fully functional yet still light. Major features of 'Cherokee' include a graphical administration interface named cherokee-admin, and a modular light-weight design.

Cherokee (web server) Independent tests have shown Cherokee to be better performing than Apache HTTP Server|Apache when serving up both static and dynamic content.

Cherokee (web server) Cherokee is maintained and developed by an Free software community|open source community.[ Contributors and metrics about Cherokee Project] Debian provides official packages of Cherokee.[ Debian's official packages for Cherokee webserver]

Cherokee (web server) - Web server features
* Transport Layer Security|TLS and SSL

* URL rewriting and redirections supporting regular expressions

* Authentication via htdigest, htpasswd, LDAP, MySQL, Pluggable Authentication Modules|PAM, plain, and fixed list.

* Custom and Apache HTTP Server|Apache compatible log format.

* Ability to Spawn (computing)|launch web applications on demand

* Streaming media|Audio/video streaming

* Resilient to the c10k problem|10000 simultaneous connections barrier

* Graphical configuration interface

* Point click deployments through an application market

Cherokee (web server) - Web applications
Configuration Wizard (software)|wizards are provided to automatically configure the web server to perform specific tasks, or run frameworks and applications. These provide support for:

Nginx - HTTP Proxy and Web server features
* Ability to handle c10k problem|more than 10,000 simultaneous connections with a low memory footprint (~2.5MB per 10k inactive HTTP persistent connection|HTTP keep-alive connections)

* Handling of static files, index files, and auto-indexing

* Load balancing (computing)|Load balancing with in-band health checks

* Fault-tolerant design|Fault tolerance

* Transport Layer Security|TLS/SSL with Server Name Indication|SNI and OCSP stapling support, via OpenSSL.

* WebSockets and HTTP/1.1 Upgrade header|HTTP/1.1 Upgrade (101 Switching Protocols)

* Web page access authentication

* Response rate and concurrent requests limiting

Catalyst (software) - Web server support
For development and testing, Catalyst has a built-in simple HTTP server. For production use, Apache HTTP Server|Apache, lighttpd, Hiawatha (web server)|Hiawatha, Cherokee (Webserver)|Cherokee or Nginx with FastCGI or mod_perl support is recommended, but any web server with CGI or FastCGI support will work. On Apache, mod_perl can help with performance considerably, though its use might be an issue because it can be unsafe to share multiple applications under mod_perl.

Since early 2008, Catalyst applications can also be deployed using the engine[ engine] which provides for the deployment of high performance Catalyst applications without a separate web server.

Starting with the release of Catalyst 5.9, Catalyst also outputs to the PSGI spec thus it can be run on any Plack (software)|Plack server and along with any server or protocol that supports the PSGI spec, including Mongrel2.

Tornado (web server) 'Tornado' is a scalable, Asynchronous IO|non-blocking web server and web application framework written in Python (programming language)|Python. It was developed for use by FriendFeed; the company was acquired by Facebook in 2009 and Tornado was Open-sourcing|open-sourced soon after.

Tornado (web server) - Modules
* A module called [ asyncmongo] exists, which allows easy integration with MongoDB.

Tornado (web server) - Modules
* [ corduroy] and [ trombi] similarly integrate with CouchDB.

Yaws (web server) 'Yaws' (Yet another web server) is a web server written in Erlang (programming language)|Erlang by Claes (klacke) Wikström.

Yaws (web server) Yaws can be embedded into other Erlang-based applications or run as a regular standalone web server.[ Steve Vinoski article at the IEEE Internet Computing review, July/August 2011]

Yaws (web server) Because Yaws uses Erlang's lightweight threading system, it performs well under high concurrency. A load test conducted in 2002 comparing Yaws and Apache found that with the hardware tested, Apache HTTP Server|Apache with the worker MPM failed at 4,000 concurrent connections, while Yaws continued functioning with over 80,000 concurrent connections.

Jetty (web server) The web server is used in products such as Apache ActiveMQ, Alfresco (software)|Alfresco, Apache Geronimo, Apache Maven, Google App Engine, Eclipse (software)|Eclipse, Fuse Services Framework|FUSE, HOSEbird|Twitter's Streaming API and Zimbra

Jetty (web server) - Overview
Developed as an independent open source project, in 2009 Jetty moved to Eclipse (software)|Eclipse. Jetty provides Web services in an embedded system|embedded Java application and it is already a component of the Eclipse (software)|Eclipse IDE. It supports Apache JServ Protocol|AJP, JASPI, JMX, JNDI, OSGi, WebSocket and other Java technologies.

Jetty (web server) - Use in Hadoop
Hadoop|Apache Hadoop is an example of how Jetty is used in a framework. Hadoop uses Jetty as a web server for different uses in several modules:

* The NameNode and the JobTracker use Jetty to serve their admin pages.

* The TaskTracker uses Jetty to receive the map, reduce and shuffle operations from the JobTracker.

In Hadoop 0.23, Jetty has been replaced by Netty (software)|Netty in the TaskTracker for shuffle operations.

Jetty (web server) - History
Originally developed in the Sydney suburb of Balmain, New South Wales|Balmain by software engineer Greg Wilkins, Jetty was originally a HTTP server component of Mort Bay Server; Mort Bay being an area of Balmain.

Jetty was originally called IssueTracker (its original application) and then MBServler (Mort Bay SERVLet servER). Neither of these were much liked, so Jetty was finally picked.

Jetty was started in 1995 and was hosted by MortBay, creating version 1.x and 2.x, until 2000

Spyglass, Inc. - Web server technology
Spyglass created and marketed the first commercially-supported web server. This product, variously marketed as the Spyglass Server and Server SDK, became available in July Before that date, the only web servers available were free and unsupported.

The Spyglass Server was also notable for being the first web server to include an application programming interface that allowed server-side applications to run in the server's process.

Spyglass did not offer their server as a retail product, instead licensing it to original equipment manufacturers to distribute. The largest licensee was Oracle Corporation.

Linux-based solution stacks come with all the Free and open-source software#Advantages and benefits of free and open-source software|general advantages and benefits of free and open-source software. Some more commonly known examples are:

According to the Netcraft the Apache HTTP Server has the highest market share.Netcraft, [ Survey] May, June, July 2013

SAP Logon Ticket - Web Server Filter
The filter is available from SAP Enterprise Portal 5.0 onwards

Hiawatha (web server) 'Hiawatha' is a web server available for multiple platforms. It has been developed by Hugo Leisink since 2002.[ About page of Hiawatha webserver]

Hiawatha (web server) - History
A CGI process [under other web servers] can run forever

The January 2009 edition of Linux Magazine contained an article about the Hiawatha web server.

* 1.0: September A basic but functional web server.

* 2.0: March Use of multithreading instead of forking.

* 4.0: December A CGI-wrapper[ Manual page cgi-wrapper - Hiawatha webserver] for improved security was included.

* 5.0: October FastCGI support for improved CGI speed.

* 5.12: August URL rewriting support.

* 6.10 : October Prevent cross-site request forgery added.

* 7.0: February Remote monitoring support.

* 8.0: January Autoconf replaced with CMake, OpenSSL replaced with PolarSSL.

Hiawatha (web server) - Features
Hiawatha web server implements all important functions of a modern web server, such as:

* Common Gateway Interface|CGI and Load balancing (computing)|load balancing FastCGI support

* Reverse proxy functionality

* Secure Sockets Layer|SSL and Transport Layer Security|TLS support

* Basic and digest HTTP authentication

* Upload speed control by traffic shaping

* Support for WebDAV applications

* Support for Server Name Indication included in v8.6

Hiawatha has many security features that no other web server has, like preventing SQL injection|SQL-injection, cross-site scripting (Cross-site scripting|XSS), Cross-site request forgery (CSRF) prevention, denial-of-service protection, control external image linking, banning of potential hackers and limiting the runtime of Common Gateway Interface|CGI applications.[ List of features] The author worked on Server Name Indication|RFC3546 support, but the OpenSSL documentation [on this subject] is just extremely poor so progress was difficult

Hiawatha (web server) - Performance
Although security is the main focus, Hiawatha is also doing quite well in terms of speed and performance

Web2py - Web servers Web2py can service requests via HTTP and HTTPS with its built-in Rocket server,[ How to run the built-in SSL server] with Apache HTTP Server|Apache,[ Web2py with Apache and mod_ssl] Lighttpd,[ Web2py with Lighttpd and FastCGI] Cherokee HTTP Server|Cherokee,[ Web2py with Cherokee] Hiawatha (web server)|Hiawatha, Nginx and almost any other web server through Common Gateway Interface|CGI, FastCGI, Web server gateway interface|WSGI, mod_proxy,[ Apache Module mod_proxy][ Web2py with mod_proxy][ Web2py with mod_proxy and mod_proxy_html] and/or mod_python.

FastCGI - Web Servers that implement FastCGI
:Note: unless stated, completeness of FastCGI implementation is unknown

** Implemented by [ mod_fcgid]. This module used to be third-party, but was granted to the Apache Software Foundation|ASF as an Apache HTTP Server subproject in 2009, shepherded by Chris Darroch.[ FastCGI apache module mod_fcgid] It only supports UNIX sockets, no TCP sockets.[ Debian bug #450748: Please add support for TCP/IP FastCGI servers]

** A third-party module mod_fastcgi is also being used. For a while, this module no longer compiled properly under Apache 2.4.x,[ Issues with Apache 2.4 and PHP-FPM] although that problem has been solved with a fork of the original project.[ libapache-mod-fastcgi on Github]

** Multiplexing of requests through a single connection is prohibited by Apache 1.x design,[ FastCGI – The Forgotten Treasure/ Section 2.3.] so this isn't supported

** In Apache 2.4, [ mod_proxy_fcgi] was added, supporting TCP FastCGI servers.

* Cherokee (web server)|Cherokee [ FastCGI for Cherokee]

** Supports chrooted FastCGI servers

Web Server Gateway Interface
The 'Web Server Gateway Interface' is a specification for simple and universal interface (computer science)|interface between web servers and web applications or web application framework|frameworks for the Python (programming language)|Python programming language

Web Server Gateway Interface - Idea
Python web application frameworks have been a problem for new Python users because the choice of web framework would limit the choice of usable web servers, and vice versa. Python applications were often designed for only one of Common Gateway Interface|CGI, FastCGI, mod_python or some other custom API of a specific web-server.

Web Server Gateway Interface - Idea
WSGI was created as a low-level interface (computer science)|interface between web servers and web applications or frameworks to promote common ground for portable web application development.

Web Server Gateway Interface - Specification overview
The WSGI has two sides: the server (computing)|server or gateway side, and the application or framework side. To process a WSGI request, the server side provides environment information and a callback function to the application side. The application processes the request, and returns the response to the server side using the callback function it was provided.

So-called WSGI middleware implements both sides of the API so that it can intermediate between a WSGI server and a WSGI application: the middleware acts as an application from some WSGI server's point of view and as a server from some WSGI application's point of view. A middleware component can perform such functions as:

* Routing a request to different application objects based on the target Uniform Resource Locator|URL, after changing the environment variables accordingly.

* Allowing multiple applications or frameworks to run side-by-side in the same process (computing)|process

* Load balancing (computing)|Load balancing and remote processing, by forwarding requests and responses over a computer network|network

* Perform content postprocessing, such as applying XSLT stylesheets

Web Server Gateway Interface - Example application
A WSGI-compatible “Hello World” application written in Python (programming language)|Python:

* Line 1 defines a callable named application, which takes two parameters, environ and start_response. environ is a dictionary containing Common Gateway Interface#Environment variables|environment variables in CGI. start_response is a callable taking two required parameters status and response_headers.

* Line 2 calls start_response, specifying 200 OK as the status and a Content-Type header.

* Line 3 returns the body of response as a string literal.

Web Server Gateway Interface - Example of calling an application
return status_headers[0], status_headers[1], .join(body)

Web Server Gateway Interface - Example of calling an application
status, headers, body = call_application(app, )

There are numerous web application frameworks supporting WSGI:
Web Server Gateway Interface - WSGI-compatible applications and frameworks There are numerous web application frameworks supporting WSGI:

Web Server Gateway Interface - Wrappers
The server or gateway invokes the application callable once for each request it receives from an HTTP client, that is directed at the application.

Web Server Gateway Interface - Wrappers
Currently wrappers are available for FastCGI, Common Gateway Interface|CGI, SCGI, Apache JServ Protocol|AJP (using flup), Twisted_(software)|twisted.web, Apache (using mod_wsgi or mod_python) and Internet Information Services|Microsoft IIS (using [ WFastCGI], [ isapi-wsgi], [ PyISAPIe], or an Active Server Pages|ASP gateway).

Web Server Gateway Interface - WSGI and Python 3
The separation of binary and text data in Python 3 poses a problem for WSGI, as it specifies that header data should be strings, while it sometimes needs to be binary and sometimes text. This works in Python 2 where text and binary data both are kept in string variables, but in Python 3 binary data is kept in bytes variables and string variables are for unicode text data. An updated version of the WSGI specification that deals with this is PEP 3333.

Mongrel (web server) 'Mongrel' is an open-source software HTTP Library (computing)|library and web server written in Ruby (programming language)|Ruby by Zed Shaw

Mongrel (web server) Mongrel was the first web server used by Twitter, and inspired Node.js according to Ryan Dahl.

Mongrel (web server) Shaw subsequently created Mongrel2, an open-source Language-independent specification|language agnostic web server and the successor to Mongrel server.

Mongrel (web server) - Deployment
One popular configuration was to run Apache HTTP Server 2.2 as a load balancer using mod_proxy|mod_proxy_balancer in conjunction with several Mongrel instances. Each Mongrel instance would run on a separate Port (computer networking)|TCP port, configured via the mongrel_cluster management utility. Until recently, Twitter was a notable instance of this configuration.[ Unicorn Power], Twitter Engineering Blog, March 30, 2010

Mongrel (web server) - Deployment
Mongrel was capable of serving Ruby on Rails powered sites without requiring any other web servers, though as a Single threading|single-threaded application this configuration is unsuitable for all but light loads.

Mongrel (web server) - Deprecation
After the original author Zed Shaw left the Ruby on Rails-scene the releases of Mongrel stopped. The current release is no longer able to install in Ruby versions higher than which is recommended for Rails 3, the fix is to use the much older pre2 release of Mongrel which isn't stable.

Mongrel (web server) - Deprecation
A new and maintained server, called Thin, uses the Mongrel parser.

Frontaccounting - Database Web server
FrontAccounting uses MySQL as database management system. Recommended HTTP web servers are Apache HTTP Server|Apache Internet Information Services.

IceWarp Mail Server - Web Server
IceWarp's web server was introduced in February 2005 and is used principally for webmail.

Microsoft Personal Web Server
'Microsoft Personal Web Server' ('PWS') is a scaled-down web server software for Microsoft Windows|Windows Operating Systems

Personal Web Server was originally created by Vermeer Technologies, the same company which created Microsoft FrontPage,[ History of the FrontPage Personal Web Server] before they were acquired by Microsoft. It was installed by FrontPage versions 1.1 to 98 as well.

NT Workstation 4.0 shipped with 'Peer Web Services', which was based on IIS 2.0 and 3.0. With IIS 4.0, this was renamed to Personal Web Server to be consistent with the name used in 95/98.

Since Windows 2000, PWS was renamed to the same IIS name used in server versions of Windows as a standard Windows component. Windows Me and Windows XP|Windows XP Home Edition support neither PWS nor IIS, although PWS can be installed on Windows Me. In other editions of Windows XP, Internet Information Services|IIS is included as standard.

Before Microsoft Visual Studio 2005, PWS was useful in developing web applications on the localhost before deploying to a production web server. The IDE of Visual Studio 2005 (and later versions) now contains a built-in lightweight web server for such development purposes.

File Transfer Protocol|FTP, SMTP, HTTP and the usual web languages such as PHP and Perl are supported by PWS. It also supports basic CGI (Common Gateway Interface) conventions and a subset of Active Server Pages|Classic ASP.[ Getting Started with Active Server Pages] Using these technologies, web applications running on PWS are capable of performing and interpreting database queries and results.

Microsoft also produced a version of Personal Web Server for the Macintosh based on code acquired in its acquisition of ResNova Software in November 1996.

Rack (web server interface)
'Rack' provides a minimal, modular and adaptable interface for developing web applications in Ruby programming language|Ruby. By wrapping Http request#Request message|HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.

Rack is used by almost all Ruby web frameworks and libraries, such as Ruby On Rails and Sinatra (software)|Sinatra. It is available as a Ruby RubyGems|Gem.

Rack has already inspired a JavaScript framework[ jack - introduction]. Jackjs.org. Retrieved on (jackjs) and a Perl one (Plack (software)|Plack), a Common Lisp project called clack, and has resulted in the Ruby developer quasi-standard of rack-compliant.[ Pancake: How To Stack and Loosely Couple Rack-Based Webapps Together]. Rubyinside.com ( ). Retrieved on

Rack (web server interface) - Example application
A Rack-compatible Hello World application in Ruby (programming language)|Ruby syntax:

Run BASIC - Web server model
If needed, it can be proxy server|proxied behind another web server, such as Apache

Apache (web server) In 2009, it became the first web server software to serve more than 100 million websites.

Apache (web server) Apache is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation

What Is The Apache Web Server?

Apache (web server) - Name
According to the FAQ in the Apache project website, the name Apache was chosen out of respect to the Native American tribe Apache and its superior skills in warfare and strategy

Apache (web server) - Features
Apache supports a variety of features, many implemented as Compiler|compiled Modular programming|modules which extend the core functionality

Popular compression methods on Apache include the external extension module, mod_gzip, implemented to help with reduction of the size (weight) of web pages served over HTTP. ModSecurity is an open source intrusion detection and prevention engine for web applications. Apache logs can be analyzed through a web browser using free scripts such as AWStats/W3Perl or Visitors (program)|Visitors.

Virtual hosting allows one Apache installation to serve many different websites. For example, one machine with one Apache installation could simultaneously serve test47.test-server.example.edu, etc.

Apache features configurable error messages, Database management system|DBMS-based authentication databases, and content negotiation. It is also supported by several graphical user interfaces (GUIs).

It supports password authentication and digital certificate authentication. Because the source code is freely available, anyone can adapt the server for specific needs, and there is a large public library of Apache add-ons.[ What is Apache Web server? - A Word Definition From the Webopedia Computer Dictionary. (n.d.). Webopedia: Online Computer Dictionary for Computer and Internet Terms and Definitions. Retrieved November 12, 2012]

Apache (web server) - Performance
Although the main design goal of Apache is not to be the fastest web server, Apache does have performance similar to other high-performance web servers

Apache (web server) - Performance
The Apache 2.2 series was considered significantly slower than nginx for delivering static pages, although remaining significantly faster for dynamic pages

Apache (web server) - Licensing
The Apache HTTP Server codebase was relicensed to the Apache License|Apache 2.0 License (from the previous 1.1 license) in January 2004, and Apache HTTP Server and were the first Software release life cycle|releases using the new license.

Apache (web server) - Licensing
The OpenBSD project did not like the change and continued the use of pre-2.0 Apache versions, effectively forking Apache 1.3.x for its purposes.

Apache (web server) - Development
The Apache HTTP Server Project is a collaborative software development effort aimed at creating a robust, commercial-grade, feature-rich and freely-available source code implementation of an HTTP (Web) server

Oracle iPlanet Web Server
'Oracle iPlanet Web Server' is a web server designed for medium and large business applications. Oracle iPlanet Web Server builds on the earlier Sun ONE Web Server, iPlanet Web Server, and Netscape Enterprise Server products.

In January 2009, Sun open sourced core components of Sun Java System Web Server 7.0 under the BSD licenses|BSD license as Open Web Server. The open source version was kept in sync with commercial releases until January 2010 (7.0 update 8). Since Oracle's acquisition of Sun, there have been no further open source releases.

In 2010, Oracle renamed the product from Sun Java System Web Server to Oracle iPlanet Web Server,[ Sun Software Products map] although documentation and links are still in the process of being updated to reflect this.

Network monitoring - Web server monitoring process
Third-party application performance monitoring tools provide additional web server monitoring, alerting and reporting capabilities.

Mongoose (web server) 'Mongoose' is a cross-platform web server written by Sergey Lyubka. With just over 130KB source code and an executable footprint of 40 kB on Linux 2.6 i386, Mongoose is one of the smallest web servers. Via API it can be also embedded into other programs.[ Mongoose: an Embeddable Web Server in C], LinuxJournal, Michel J. Hammel,

Mongoose (web server) * Common Gateway Interface|CGI, Secure Sockets Layer|SSL, Server Side Includes|SSI, Digest access authentication|Digest (MD5) authorization, Websocket, WebDAV support

* Resumed download, Rewrite engine|URL rewrite support
Mongoose (web server) * Resumed download, Rewrite engine|URL rewrite support

Mongoose (web server) * IP-based Access control list|ACL, Windows service, Hypertext_Transfer_Protocol#Request_methods|GET, POST, HEAD, PUT, DELETE methods

Mongoose (web server) * Excluding files from serving by Uniform resource identifier|URI pattern

* Python (programming language)|Python Language binding|bindings
Mongoose (web server) * Python (programming language)|Python Language binding|bindings

Mongoose (web server) - License change
In August 2013 the original author announced[ Mongoose project status and licensing change], mongoose-users mailing list, that he is changing the project license from the original MIT license to a dual GPLv2 / commercial licensing scheme.

Mongoose (web server) - License change
A fork using the original MIT license exists at with additions like C++ interface.

Caudium (web server) 'Caudium' is an open source web server. It was originally created as a fork of the Roxen (web server)|Roxen Challenger server. The server is written in C (programming language)|C and Pike programming language|Pike, and Pike is also used to create extensions to the server.

Caudium (web server) Caudium is very different from the Apache HTTP Server|Apache.This article about the lists some differences to Apache

Boa (web server) 'Boa' is an open source|open-source, small-footprint web server that is suitable for embedded applications. Originally written by Paul Phillips (poker player)|Paul Phillips, it is now maintained by Larry Doolittle and Jon Nelson.

Slashdot and Fotolog use Boa to serve images.
Boa (web server) Slashdot and Fotolog use Boa to serve images.

As of January 2006, Boa has the following limitations
Boa (web server) As of January 2006, Boa has the following limitations

* No access control features (HTTP Basic access authentication, etc.)
Boa (web server) * No access control features (HTTP Basic access authentication, etc.)

Boa (web server) * No Server Side Includes (deemed incompatible with server performance goals)

Boa (web server) * No SSL support although there are some patches against that introduce SSL support

Zeus Web Server 'Zeus Web Server' is a Proprietary software|proprietary web server for Unix and Unix-like platforms (currently Solaris (operating system)|Solaris, FreeBSD, HP-UX and Linux). It was developed by Zeus Technology, a software company located in Cambridge, England. The original authors and company founders are University of Cambridge graduates Damian Reeves and Adam Twiss.

Support for AIX, Tru64, and OS X|Mac OS X was dropped on 10 June 2008.
Zeus Web Server Support for AIX, Tru64, and OS X|Mac OS X was dropped on 10 June 2008.

ZWS seems to be dead since it hasn't been updated since January 2010,
Zeus Web Server ZWS seems to be dead since it hasn't been updated since January 2010,

Zeus Web Server and the company no longer offers a similar server solution. In July 2011, the company was acquired by Riverbed Technology

and is ending product support November 30, 2014.
Zeus Web Server and is ending product support November 30, 2014.

Zeus Web Server Zeus is designed to be a high-performance web server and was commonly used by hardware vendors submitting Standard Performance Evaluation Corporation|SPECweb99 benchmarks for their hardware. The SPECweb99 benchmark was retired in 2005 and replaced by SPECweb2005. While some SPECweb2005 submissions were made using Zeus, as of 2008 it is no longer among the top performers.

Zeus Web Server NSAPI and ISAPI are supported to ease migrations from Internet Information Services|Microsoft IIS and Sun Java System Web Server.

Saetta Web Server 'Saetta Web Server' is a web server with a strong focus on high Concurrency (computer science)|concurrency, performance and low Random-access memory|memory usage.

Saetta Web Server - Overview
Saetta Web Server can deploy dynamic HTTP content on a network using SAAPIs, server-side applications written in the C (programming language)|C or C++ programming language, or in PHP with the embedded PHP module for PHP web pages, or the CGI handler for scripting language|scripts.

Saetta Web Server - Overview
Like Nginx, Saetta Web Server uses an asynchronous system|asynchronous event (computing)|event-driven approach for handling requests, instead of the Apache HTTP Server model that defaults to a Thread (computer science)|threaded or Process (computing)|process-oriented approach. Event-driven approaches provide more predictable performance under high loads.

Saetta Web Server - Basic HTTP features
* Ability to handle c10k problem|more than simultaneous connections with a low memory footprint.

* Reload configuration on fly

* Framework via SAAPIs. Includes APIs for the generation of HTML documents, management of the GET/POST/HEAD HTTP methods, handling of uploaded files. SAAPIs are supported as global filters for virtual directories, single filters and handlers.

Saetta Web Server - SAAPI
SAAPI applications can be written using any language that allows the calling of cdecl|standard C functions and that can be compiled into a shared object (for example the C, C++ and assembly programming languages).

SAAPI Extensions are true applications that run in the address space of Saetta Web Server. They have access to all of the functionality provided by the web server. These extensions are implemented as shared objects that are loaded into the web server process.

Clients can access SAAPI extensions in the same way they access a static HTML page. Server side certain file extensions, full directories and whole web sites can be mapped to be handled by a SAAPI extension.

SAAPIs can be used to generate dynamic content and to serve many concurrent clients requiring little memory resources.

Web accelerator - Web server accelerator
Other web accelerators are targeted at the web site or web application owners. This type of web accelerator is installed in front of web servers and application servers and use a variety of the above techniques to improve performance to all users accessing the accelerated web sites or web applications. Sometimes referred to as a reverse proxy.

Web accelerator - Web server accelerator
This type of server side accelerator has the added benefit of off-loading transactions and connection managements from the web or applications servers and hence, reducing its CPU utilisation and increasing web server or application scalability to handle more users with less bandwidth.

Roxen (web server) 'Roxen' is a free software web server produced by Roxen Internet Software, a company based in Linköping, Sweden and named after the nearby lake Roxen

Roxen (web server) Roxen was often ahead of its time,[ Product Review: The Roxen Challenger Web Server] featuring a web-based Graphical user interface (GUI) administration interface,[ Install Roxen web server on centos] loadable modules that could be written in several languages including Pike (programming language)|Pike and later Java (programming language)|Java, dynamic content generation with a comprehensive caching system, replication systems for multi-headed servers, and an embedded SQL server for data-heavy server operations (as well as broad support for other databases).[ Roxen: How Much Is Too Much Functionality?] Roxen was built to meet the needs of content creators, so its features and facilities were superb.[ Roxen: How Much Is Too Much Functionality?]

Roxen (web server) - RXML
Much of Roxen's power is in an innocuous feature that was born in Roxen's early history: a server-side markup/scripting language called RXML (RoXen Macro Language[ Roxen Concepts])

Roxen modules typically provide their functionality by extending RXML, but the suite provided off-the-shelf was pretty comprehensive:

Notable tags include:

* lt;ifgt;[ If Tags] for conditional content (as well as tags for else, case, for, etc.)

* lt;tablifygt;[ ] for automatically transforming data into pretty tables

* lt;cachegt;[ ] for controlling the caching of dynamic content to reduce page fetch times/server loading

* lt;gbuttongt;[ ] and lt;gtextgt;[ ] image generation tags

* lt;diagramgt;[ ] for converting data into graphical charts/graphs

* lt;emitgt;[ ] for generating content based on LDAP, SQL or filesystem queries (its trivial to build your own photo gallery with thumbnails using Roxen)

All RXML tags contain inline documentation which is used to fill out the online manual that is included on both Roxen's documentation site[ Roxen's documentation site] and with every default server installation.

RXML also provides a variable system; all variables exist within a domain or scope, e.g. form fields passed to the query are accessible as form.'fieldname', user defined variables are stored in the 'var' scope. Unfortunately, in its attempt to explain the two methods of variable instantiation, the documentation confuses most people.

In most cases, variables are referred to by name, but it is also possible to instantiate (insert the value of) a variable anywhere, in- or out-side of tags/markup, using an XML entity-style markup, e.g. 'amp;page.path;'. Optionally, one can specify encoding/escaping of the instance, e.g. 'amp;form.username:mysql;' to insert a user-submitted value from a form safely into an SQL database or 'amp;page.path:js;' to make a variable javascript safe.

Much of the functionality achieved by RXML can be accomplished using an interpreted programming language like PHP which is embedded within a standard web server such as Apache as a plug-in (computing)|plug-in

Google Web Server The 'Google platform' refers to the computer software and large hardware resources Google uses to provide their services.

Google Web Server This article describes the technological infrastructure behind Google's websites as presented in the company's public announcements.

Google Web Server - Original hardware
The original hardware (circa 1998) that was used by Google when it was located at Stanford University included:. Stanford University (provided by Internet Archive). Retrieved on July 10, 2006.

* Sun Microsystems Ultra II with dual 200Hertz|MHz processors, and 256Megabyte|MB of Random access memory|RAM. This was the main machine for the original History of Google#Beginning|Backup system.

* 2 × 300MHz dual Pentium II servers donated by Intel, they included 512MB of RAM and 10 × 9Gigabyte|GB hard drives between the two. It was on these that the main search ran.

* F50 IBM RS/6000 donated by IBM, included 4 processors, 512MB of memory and 8 × 9GB hard disk drives.

* Two additional boxes included 3 × 9GB hard drives and 6 x 4GB hard disk drives respectively (the original storage for Backup). These were attached to the Sun Ultra II.

Google Web Server - Production hardware
Google uses commodity computing|commodity-class x86 Server (computing)|server computers running customized versions of Linux

According to Google their global data center operation electrical power ranges between 500 and 681 megawatts.[ Google Green infographics][ Analytics Press Growth in data center electricity use 2005 to 2010]

The combined processing power of these servers might have reached from 20 to 100 FLOPS|petaflops in 2008.[ Google Surpasses Supercomputer Community, Unnoticed?], May 20, 2008.

Google Web Server - Network topology
Details of the Google world wide private networks are not publicly available but Google publications make references to the Atlas Top 10 report that ranks Google as the third largest ISP behind Level 3 Communications|Level 3.

In order to run such a large network with direct connections to as many ISP as possible at the lowest possible cost Google has a very open peering policy.

From this site we can see that the Google network can be accessed from 67 public exchange points and 69 different locations across the world. As of May 2012 Google had 882 Gbit/s of public connectivity (not counting private peering agreements that Google has with the largest ISPs). This public network is used to distribute content to Google users as well as to crawl the Internet to build its search indexes.

The private side of the network is a secret but recent disclosure from Google indicate that they use custom built high-radix switch-routers (with a capacity of 128 × 10 Gigabit Ethernet port) for the wide area network. Running no less than two routers per datacenter (for redundancy) we can conclude that the Google network scales in the terabit per second range (with two fully loaded routers the bi-sectional bandwidth amount to 1,280 Gbit/s).

These custom switch-routers are connected to Wavelength-division multiplexing|DWDM devices to interconnect data centers and point of presences (PoP) via dark fibre.

From a datacenter view, the network starts at the rack level, where 19-inch racks are custom-made and contain 40 to 80 servers (20 to 40 1Rack unit|U servers on either side, while new servers are 2U rackmount systems.[ Web Search for a Planet: The Google Cluster Architecture] (Luiz André Barroso, Jeffrey Dean, Urs Hölzle) Each rack has a Ethernet switch|switch)

A Google cluster has thousands of server (computing)|servers and once the client has connected to the server additional load balancing is done to send the queries to the least loaded web server

Google has numerous data centers scattered around the world

Google Web Server - Project 02
One of the largest Google data centers is located in the town of The Dalles, Oregon, on the Columbia River, approximately 80 miles from Portland, Oregon|Portland

Google Web Server - Summa papermill
In February 2009, Stora Enso announced that they had sold the Summa paper mill in Hamina, Finland to Google for 40 million Euros. Google plans to invest 200 million euros on the site to build a data center. Google chose this location due to the availability and proximity of renewable energy sources.[ Finland – First Choice for Siting Your Cloud Computing Data Center.] Accessed 4 August 2010.

Google Web Server - Modular container data centers
Since 2005, Google has been moving to a containerized Google Modular Data Center|modular data center. Google filed a patent application for this technology in 2003.

Google Web Server - Software
Most of the software stack that Google uses on their servers was developed in-house

The software that runs the Google infrastructure includes:

* Google Web Server (GWS) custom Linux-based Web server that Google uses for its online services.

** Google File System and its successor, Colossus

** BigTable structured storage built upon GFS/Colossus

** Spanner (distributed database technology)|Spanner planet-scale structured storage system, next generation of BigTable stack

** Google F1 a distributed, quasi-SQL DBMS based on Spanner, substituting a custom version of MySQL.

* Distributed lock manager#Google's Chubby lock service|Chubby lock service

* MapReduce and Sawzall (programming language)|Sawzall programming language

** TeraGoogle Google's large search index (launched in early 2006), designed by Anna Patterson of Cuil fame.

** Caffeine (Percolator) continuous indexing system (launched in 2010).

** Hummingbird major search index update, including complex search and voice search.

Google has developed several abstractions which it uses for storing most of its data:

* Protocol Buffers Google's lingua franca for data, a binary serialization format which is widely used within the company.

* SSTable (Sorted Strings Table) a persistent, ordered, immutable map from keys to values, where both keys and values are arbitrary byte strings. It is also used as one of the building blocks of BigTable.[ ]

* RecordIO a sequence of variable sized records.

Google Web Server - Software development practices
Most operations are read-only. When an update is required, queries are redirected to other servers, so as to simplify consistency issues. Queries are divided into sub-queries, where those sub-queries may be sent to different ducts in Parallel computing|parallel, thus reducing the latency time.

Google Web Server - Software development practices
To lessen the effects of unavoidable Computer hardware|hardware failure, software is designed to be fault tolerant. Thus, when a system goes down, data is still available on other servers, which increases reliability.

Google Web Server - Index
Like most search engines, Google indexes documents by building a data structure known as inverted index. Such an index allows obtaining a list of documents by a query word. The index is very large due to the number of documents stored in the servers.

The index is partitioned by document IDs into many pieces called Shard (database architecture)|shards

In June 2010, Google rolled out a next-generation indexing and serving system called Caffeine which can continuously crawl and update the search index

Google Web Server - Server types
Google's server infrastructure is divided into several types, each assigned to a different purpose:

* Web servers coordinate the execution of queries sent by users, then format the result into an HTML page. The execution consists of sending queries to index servers, merging the results, computing their rank, retrieving a summary for each hit (using the document server), asking for suggestions from the spelling servers, and finally getting a list of advertisements from the ad server.

* Data-gathering servers are permanently dedicated to web crawler|spidering the Web. Google's web crawler is known as GoogleBot. They update the index and document databases and apply Google's algorithms to assign ranks to pages.

* Each index server contains a set of index shards. They return a list of document IDs (docid), such that documents corresponding to a certain docid contain the query word. These servers need less disk space, but suffer the greatest CPU workload.

* Document servers store documents. Each document is stored on dozens of document servers. When performing a search, a document server returns a summary for the document based on query words. They can also fetch the complete document when asked. These servers need more disk space.

* Spelling servers make suggestions about the spelling of queries.

Web servers The term 'web server', also written as 'Web server', can refer to either the computer hardware|hardware (the computer) or the software (the computer application) that helps to deliver web content that can be accessed through the Internet.

Web servers - Overview The primary function of a web server is to store, process and deliver web pages to Client (computing)|clients. The communication between client and server takes place using the Hypertext Transfer Protocol|Hypertext Transfer Protocol (HTTP). Pages delivered are most frequently HTML|HTML documents, which may include images, Style sheet (web development)|style sheets and JavaScript|scripts in addition to text content.

Web servers - Market share
Apache, IIS and Nginx are the most used web servers on the Internet.

TUX web server The 'TUX web server' is an in-kernel web server for Linux licensed under the GNU General Public License (GPL). It was maintained by Ingo Molnár.

TUX web server It is currently limited to serving static web pages and coordinating between kernelspace Module (Linux)|modules, userspace modules, and regular userspace web server daemon (computer software)|daemons that provide dynamic content. Regular userspace web servers do not need to be altered in any way for TUX to coordinate with them. However, userspace code has to use a new interface based on the tux(2) system call.

The main differences between TUX and other webservers include:
TUX web server The main differences between TUX and other webservers include:

TUX web server *TUX runs partly within a customized version of the Linux kernel and partly as a userspace daemon.

TUX web server *With a capable network card, TUX enables vectored I/O|scatter-gather Direct Memory Access|DMA from the page cache directly to the network.

*TUX is only able to serve static web pages.
TUX web server *TUX is only able to serve static web pages.

TUX web server This is largely due to its place directly within the kernel, where it can improve performance by taking advantage of facilities not available to traditional web servers, which run outside of the kernel

TUX web server TUX can also redirect any request it cannot process to a traditional userspace web server daemon, for example Apache HTTP Server|Apache or lighttpd

TUX web server One major component was the Native POSIX Thread Library, which, with the right tuning parameters, allows userspace web servers to serve web pages at a speed very close to that of a kernelspace web server like TUX but without its limitations

The web - Web servers The primary function of a web server is to deliver web pages in response to client requests. This means delivery of HTML documents and any additional content that may be included by a document, such as images, style sheets and scripts.

In-kernel web server An 'in-kernel web server' is an unlimited HTTP server that runs in kernel space or equivalent. It is also called accelerator.

In-kernel web server - Benefits
* Performance. The path taken by data from disk to network. Proper asynchronous zero-copy interfaces would make this available from user-space.

In-kernel web server - Benefits
* Scalability with respect to number of simultaneous clients. Event notification of comparable scalability seems unlikely in user-space.

In-kernel web server - Drawbacks
*Portability. Every kernel needs a specific implementation route.

In-kernel web server - Drawbacks
*Reliability. Failure in the webserver may crash the OS.

Michael Holve - Apache Web Server
Author of one of the first GUIs for managing the Apache web server, TkApache v1.0 ( was released into the public domain and dedicated to the Open Source and Linux communities at ApacheCon on October 15, 1998 ([ TkApache release announcement, sourcefiles.org, October 1998] TkApache release announcement,[ TkApache article, Linux Gazette #34] Tkapache article, Linux Gazette)

Embedded Web server An 'embedded HTTP server' is a component of a software system that implements the Hypertext Transfer Protocol|HTTP Communications protocol|protocol. Examples of usage within an application might be:

Embedded Web server * To provide Database index|indexing, reporting, and debugging tools during the development stage.

Embedded Web server * To implement a protocol for the distribution and acquisition of information to be displayed in the regular interface — possibly a web service, and possibly using XML as the Serialization|data format.

There are a few advantages to using HTTP to perform the above:
Embedded Web server There are a few advantages to using HTTP to perform the above:

Embedded Web server * HTTP is a well studied cross-platform protocol and there are mature implementations freely available.

Embedded Web server * HTTP is seldom blocked by Firewall (computing)|firewalls and intranet Router (computing)|routers.

Embedded Web server * HTTP clients (e.g. web browsers) are readily available with all modern computers.

Embedded Web server * There is a growing tendency of using embedded HTTP servers in applications that parallels the rising trends of Home network|home-networking and ubiquitous computing.

Embedded Web server - Typical requirements
Natural limitations of the platforms where an embedded HTTP server runs contribute to the list of the non-functional requirements of the embedded, or more precise, embeddable HTTP server. Some of these requirements:

* Small Random-access memory|RAM and Read-only memory|ROM footprint. The exact size depends on the system, but in many cases anything over several megabytes is not embeddable.

* Cross compilation support for multiple CPU and operating system combinations.

* Easy integration with an existing application, including static linking with the operating system and application.

* Serving Web page|pages from Application software|application Computer memory|memory if there is no file system.

* Single Thread (computing)|thread and Multithreading (software)|multi-thread support.

For every specific project, requirements can vary significantly. For example, ROM and RAM footprints can be a very serious constraint and limit the choices of the system designer. C++ or Java Virtual Machine|JVM availability for the system can be another constraint. Frequently performance is an issue, because typical embedded systems run multiple simultaneous tasks and an HTTP server is only one of them and may be configured as a low Scheduling (computing)|priority Task (computing)|task.

Apache web server In 2009, it became the first Web server software to serve more than 100 million Web sites.

Apache web server , Apache was estimated to serve 54.2% of all active website|Web sites and 53.3% of the top servers across all domains.[ sage of web servers for websites][ Information about the Apache Web Server

Apache web server - Name
When Apache is running, its process name is 'httpd', which is short for HTTP daemon.

Apache web server - Features
Virtual hosting allows one Apache installation to serve many different Web sites. For example, one machine with one Apache installation could simultaneously serve test47.test-server.example.edu, etc.

Apache web server - Features
It supports password authentication and digital certificate authentication. Because the source code is freely available, anyone can adapt the server for specific needs, and there is a large public library of Apache add-ons.[ What is Apache Web server? - A Word Definition From the Webopedia Computer Dictionary. (n.d.). Webopedia: Online Computer Dictionary for Computer and Internet Terms and Definitions. Retrieved November 12, 2012]

Apache web server - Performance
Instead of implementing a single architecture, Apache provides a variety of MultiProcessing Modules (MPMs), which allow Apache to run in a process-based, hybrid (process and thread) or event-hybrid mode, to better match the demands of each particular infrastructure

Apache web server - Performance
For delivery of static pages, Apache 2.2 series was considered significantly slower than nginx.[ Serving static files: a comparison between Apache, Nginx, Varnish and G-WAN] To address this issue, the Apache version considered by the Apache Foundation as providing high-performance is the multi-threaded version, which mixes the use of several processes and several threads per process.[ Apache MPM worker] This architecture, and the way it was implemented in the Apache 2.4 series, provides for performance equivalent or slightly better than event-based Web servers, as is claimed by the president of the Apache Foundation, Jim Jagielski.[ Apache httpd 2.4] However, some independent benchmarks show that it still half as fast as nginx.[ Apache 2.4 Faster Than Nginx?][ Performance of Apache 2.4 with the event MPM compared to Nginx]

Apache web server - Licensing
The OpenBSD project did not like the change and continued the use of pre-2.0 Apache versions, effectively forking Apache 1.3.x for its purposes. Later it switched to nginx.[ OpenBSD Upgrade Guide: 5.1 to 5.2][ OpenBSD Following -current]

Information explosion - Web servers
As of August 2005, there were over 70 million web servers. there were over 135 million web servers.

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