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An enterprise service bus (ESB) implements a communication system between mutually interacting software applications in a
service-oriented architecture In software engineering, service-oriented architecture (SOA) is an architectural style that focuses on discrete services instead of a monolithic design. By consequence, it is also applied in the field of software design where services are provid ...
(SOA). It represents a
software architecture Software architecture is the fundamental structure of a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements and relations. ...
for distributed computing, and is a special variant of the more general client-server model, wherein any application may behave as server or client. ESB promotes agility and flexibility with regard to high-level protocol communication between applications. Its primary use is in
enterprise application integration Enterprise application integration (EAI) is the use of software and computer systems' architectural principles to integrate a set of enterprise computer applications. Overview Enterprise application integration is an integration framework comp ...
(EAI) of heterogeneous and complex service landscapes.


Architecture

The concept of the enterprise service bus is analogous to the bus concept found in computer hardware architecture combined with the modular and concurrent design of high-performance computer operating systems. The motivation for the development of the architecture was to find a standard, structured, and general purpose concept for describing implementation of loosely coupled software components (called services) that are expected to be independently deployed, running, heterogeneous, and disparate within a network. ESB is also a common implementation pattern for
service-oriented architecture In software engineering, service-oriented architecture (SOA) is an architectural style that focuses on discrete services instead of a monolithic design. By consequence, it is also applied in the field of software design where services are provid ...
, including the intrinsically adopted network design of the
World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web ...
. No global standards exist for enterprise service bus concepts or implementations. Most providers of
message-oriented middleware Message-oriented middleware (MOM) is software or hardware infrastructure supporting sending and receiving messages between distributed systems. MOM allows application modules to be distributed over heterogeneous platforms and reduces the comple ...
have adopted the enterprise service bus concept as ''de facto'' standard for a service-oriented architecture. The implementations of ESB use event-driven and standards-based message-oriented middleware in combination with message queues as technology frameworks. However, some software manufacturers relabel existing middleware and communication solutions as ESB without adopting the crucial aspect of a bus concept.


Functions

An ESB applies the design concept of modern
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s to independent services running within networks of disparate and independent computers. Like concurrent operating systems, an ESB provides commodity services in addition to adoption, translation and routing of client requests to appropriate answering services. The primary duties of an ESB are: * Route messages between services * Monitor and control routing of message exchange between services * Resolve contention between communicating service components * Control deployment and versioning of services * Marshal use of redundant services * Provide commodity services like event handling, data transformation and mapping, message and event queuing and sequencing, security or
exception handling In computing and computer programming, exception handling is the process of responding to the occurrence of ''exceptions'' – anomalous or exceptional conditions requiring special processing – during the execution of a program. In general, an ...
, protocol conversion and enforcing proper quality of communication service.


History

The first published usage of the term "enterprise service bus" is attributed to Roy W. Schulte from the Gartner Group 2002 and the book ''The Enterprise Service Bus'' by David Chappell. Although a number of companies take credit for coining the phrase, in an interview, Schulte said that the first time he heard the phrase was from a company named Candle and went on to say: "The most direct ancestor to the ESB was Candle’s Roma product from 1998" whose Chief Architect and patent application holder was Gary Aven. Roma was first sold in 1998 making it the first commercial ESB in the market, but that Sonic's product from 2002 was also one of the early ESBs on the market. * Service - denotes non-iterative and autonomously executing programs that communicate with other services through message exchange * Bus - is used in analogy to a computer hardware bus * Enterprise - the concept has been originally invented to reduce complexity of enterprise application integration within an enterprise; the restriction has become obsolete since modern Internet communication is no longer limited to a corporate entity


ESB as software

The ESB is implemented in software that operates between the business applications, and enables communication among them. Ideally, the ESB should be able to replace all direct contact with the applications on the bus, so that all communication takes place via the ESB. To achieve this objective, the ESB must encapsulate the functionality offered by its component applications in a meaningful way. This typically occurs through the use of an enterprise message model. The message model defines a standard set of messages that the ESB transmits and receives. When the ESB receives a message, it routes the message to the appropriate application. Often, because that application evolved without the same message model, the ESB has to transform the message into a format that the application can interpret. A software adapter fulfills the task of effecting these transformations, analogously to a physical adapter. ESBs rely on accurately constructing the enterprise message model and properly designing the functionality offered by applications. If the message model does not completely encapsulate the application functionality, then other applications that desire that functionality may have to bypass the bus, and invoke the mismatched applications directly. Doing so violates the principles of the ESB model, and negates many of the advantages of using this architecture. The beauty of the ESB lies in its platform-agnostic nature and the ability to integrate with anything at any condition. It is important that
Application Lifecycle Management Application lifecycle management (ALM) is the product lifecycle management (governance, development, and maintenance) of computer programs. It encompasses requirements management, software architecture, computer programming, software testing, ...
vendors truly apply all the ESB capabilities in their integration products while adopting SOA. Therefore, the challenges and opportunities for EAI vendors are to provide an integration solution that is low-cost, easily configurable, intuitive, user-friendly, and open to any tools customers choose.


Characteristics

¹ ''Some do not regard process choreography as an ESB function. For example, see M.Richards. ² ''While process choreography supports implementation of complex business processes that require coordination of multiple
business Business is the practice of making one's living or making money by producing or buying and selling products (such as goods and services). It is also "any activity or enterprise entered into for profit." Having a business name does not separ ...
services (usually using BPEL), service orchestration enables coordination of multiple implementation services (most suitably exposed as an aggregate service) to serve individual requests.'' These solutions often focus on low-level ESB functions, such as connectivity, routing and transformation, and require coding or scripting to implement orchestration. Developers operating at a project or tactical level, e.g., just trying to fix a problem, often gravitate toward lightweight service bus technologies, but there is often ongoing tension between these initiatives and an enterprise architecture whose goal it is to optimize infrastructure across multiple projects. If the message broker, the ESB software, translates a message from one format to another, then as with any translation, there is the issue of semantics of the message. For example, a record can be translated from JSON to XML, but the same set of fields can be interpreted differently by different applications, specifically in the case of the various corner cases that are usually known only to developers that have extensive experience with the application that is connected to the ESB. For the known corner cases the number of tests that cover all corner cases increases exponentially with every application that is connected to the ESB, because every ESB-connected application must be tested against every other application that is connected to the ESB.


Key benefits

* Scales from point-solutions to enterprise-wide deployment (distributed bus) * More configuration rather than integration coding * No central rules-engine, no central broker * Easy plug-in and plug-out and loosely coupling system


Key disadvantages

* Slower communication speed, especially for those already compatible services *
Single point of failure A single point of failure (SPOF) is a part of a system that, if it fails, will stop the entire system from working. SPOFs are undesirable in any system with a goal of high availability or reliability, be it a business practice, software ap ...
, can bring down all communications in the Enterprise * High configuration and maintenance complexity


Products

Notable products include: * Proprietary ** Candle's Roma ESB - bought by IBM and became WebSphere ESB ** IBM App Connect, formerly IBM Integration Bus and IBM WebSphere ESB ** InterSystems Ensemble **
Information Builders Information Builders (ibi), founded in 1975, was a privately held software company headquartered in New York City. Information Builders (ibi) provided services in the fields of Business Intelligence, Data Integration and Data Quality solutions ...
iWay Service Manager **
Microsoft Azure Microsoft Azure, often referred to as Azure ( , ), is a cloud computing platform operated by Microsoft for application management via around the world-distributed data centers. Microsoft Azure has multiple capabilities such as software as a ...
Service Bus **
Microsoft BizTalk Server Microsoft BizTalk Server is an inter-organizational middleware system (IOMS) that automates business processes through the use of ''adapters'' which are tailored to communicate with different software systems used in an enterprise. Created by M ...
**
Mule The mule is a domestic equine hybrid between a donkey and a horse. It is the offspring of a male donkey (a jack) and a female horse (a mare). The horse and the donkey are different species, with different numbers of chromosomes; of the two po ...
ESB **
Oracle Enterprise Service Bus Oracle Enterprise Service Bus (Oracle ESB), a fundamental component of Oracle's Services-Oriented Architecture suite of products, provides integration of data and enterprise applications within an organisation and their connected ( "extended" or ...
**
Progress Software Progress Software Corporation (Progress) is an American public company that offers software for creating and deploying business applications. Headquartered in Burlington, Massachusetts with offices in 16 countries, the company posted revenues ...
Sonic ESB (acquired by
Trilogy A trilogy is a set of three works of art that are connected and can be seen either as a single work or as three individual works. They are commonly found in literature, film, and video games, and are less common in other art forms. Three-part wor ...
) **
SAP Process Integration SAP NetWeaver Process Integration (SAP PI) is SAP's enterprise application integration (EAI) software, a component of the NetWeaver product group used to facilitate the exchange of information among a company's internal software and systems and tho ...
** TIBCO Software ActiveMatrix BusinessWorks **
webMethods webMethods was an enterprise software company focused on application integration, business process integration and B2B partner integration. Founded in 1996, the company sold systems for organizations to use web services to connect software app ...
enterprise service bus (acquired by
Software AG Founded in 1969, Software AG is an enterprise software company with over 10,000 enterprise customers in over 70 countries. The company is the second largest software vendor in Germany, and the seventh largest in Europe. Software AG is traded on t ...
) **
Sonic ESB Progress Software Corporation (Progress) is an American public company that offers software for creating and deploying business applications. Headquartered in Burlington, Massachusetts with offices in 16 countries, the company posted revenues ...
from Aurea ** XIATech Single Data View *
Open-source software Open-source software (OSS) is computer software that is released under a license in which the copyright holder grants users the rights to use, study, change, and distribute the software and its source code to anyone and for any purpose. ...
**
Apache Camel Apache Camel is an open source framework for message-oriented middleware with a rule-based routing and mediation engine that provides a Java object-based implementation of the Enterprise Integration Patterns using an application programming in ...
**
Apache ServiceMix Apache ServiceMix is an open-source software project to implement a distributed enterprise service bus (ESB). Architecture ServiceMix is based on the service-oriented architecture (SOA) model. It is a project of the Apache Software Foundation ...
** Apache Synapse **
Fuse ESB Red Hat Fuse is an open source integration platform based on Apache Camel. It is a distributed integration platform that provides a standardized methodology, infrastructure, and tools to integrate services, microservices, and application compo ...
from
Red Hat Red Hat, Inc. is an American software company that provides open source software products to enterprises. Founded in 1993, Red Hat has its corporate headquarters in Raleigh, North Carolina, with other offices worldwide. Red Hat has become a ...
** JBoss ESB ** NetKernel **
Open ESB ''OpenESB'' is a Java-based open-source software, open-source enterprise service bus. It can be used as a platform for both enterprise application integration and service-oriented architecture. OpenESB allows developers to integrate legacy systems ...
** Petals ESB **
Spring Integration Spring Integration is an open source framework for enterprise application integration. It is a framework that builds upon the core Spring framework. It is designed to enable the development of integration solutions typical of event-driven ar ...
**
UltraESB UltraESB is a lightweight enterprise service bus (ESB) capable of supporting many transports and message formats natively. It allows messages to be mediated via Java or JSR 223 scripting languages through an API, and is the first ESB to claim sup ...
** WSO2 ESB


See also

*
Enterprise Integration Patterns ''Enterprise Integration Patterns'' is a book by Gregor Hohpe and Bobby Woolf and describes 65 patterns for the use of enterprise application integration and message-oriented middleware in the form of a pattern language. The integration (messa ...
* Event-driven messaging *
Java Business Integration Java Business Integration (JBI) is a specification developed under the Java Community Process (JCP) for an approach to implementing a service-oriented architecture (SOA). The JCP reference is JSR 208 for JBI 1.0 and JSR 312 for JBI 2.0. JSR 312 w ...
*
Business Process Management Business process management (BPM) is the discipline in which people use various methods to discover, model, analyze, measure, improve, optimize, and automate business processes. Any combination of methods used to manage a company's business p ...
* Universal Integration Platform *
Enterprise application integration Enterprise application integration (EAI) is the use of software and computer systems' architectural principles to integrate a set of enterprise computer applications. Overview Enterprise application integration is an integration framework comp ...
* Business Service Provider *
Message Oriented Middleware Message-oriented middleware (MOM) is software or hardware infrastructure supporting sending and receiving messages between distributed systems. MOM allows application modules to be distributed over heterogeneous platforms and reduces the comple ...
* Complex event processing * Event Stream Processing * Event-driven programming *
Comparison of Business Integration Software This article is a comparison of notable business integration and business process automation software. General Scope Scope of this comparison: * Service-oriented architecture implementations; * Message-oriented middleware and message brokers ...
* Comparison of BPEL engines * Comparison of BPMN 2.0 Engines * Composite application *
Event-driven SOA Event-driven SOA is a form of service-oriented architecture (SOA), combining the intelligence and proactiveness of event-driven architecture with the organizational capabilities found in service offerings. Before event-driven SOA, the typical SOA ...
* Integration Platform as a service (iPaaS)


References


Further reading

* David Chappell, "Enterprise Service Bus" (O’Reilly: June 2004, ) * Binildas A. Christudas, "Service-oriented Java Business Integration" (Packt Publishers: February 2008, ; ) * Michael Bell, "Service-Oriented Modeling: Service Analysis, Design, and Architecture" (2008 Wiley & Sons, )


External links


"Lasting concept or latest buzzword?"
(Nicolas Farges, 2003)

(July 22, 2005)
JSR-208: Java Business Integration
(August 2005)
The Role of the Enterprise Service Bus (InfoQ - Video Presentation)
(October 23, 2006)
ESB Roundup Part One: Defining the ESB (InfoQ)
(July 13, 2006)
ESB Roundup Part Two: Use Cases (InfoQ)
(July 5, 2006)
"Services Fabric—Fine Fabrics for New Era Systems"
(Binildas A. Christudas, 2007)

(Dennis Byron, September 20, 2007)
Aggregate Services in ServiceMix JBI ESB: PACKT Publishers
(Binildas A. Christudas, November 30, 2007)
ESB Topology alternatives
(InfoQ, A. Louis, May 23, 2008)
Rethinking the ESB: Building a Simple, Secure, Scalable Service Bus with a SOA Gateway
(Computerworld, J. Ryan, 2011) *

(IBM developer Works, Greg Flurry and Kim Clark, May 2011) {{DEFAULTSORT:Enterprise Service Bus Enterprise application integration Message-oriented middleware Service-oriented (business computing) Software architecture