Message-oriented middleware (MOM) is software or hardware infrastructure supporting sending and receiving messages between

distributed system A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another from any system. Distributed computing is a field of computer sci ...

s. MOM allows application modules to be distributed over heterogeneous platforms and reduces the complexity of developing applications that span multiple

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

s and

network protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...

s. The

middleware Middleware is a type of computer software that provides services to software applications beyond those available from the operating system. It can be described as "software glue". Middleware makes it easier for software developers to implement co ...

creates a distributed communications layer that insulates the

application developer A computer programmer, sometimes referred to as a software developer, a software engineer, a programmer or a coder, is a person who creates computer programs — often for larger computer software. A programmer is someone who writes/creates ...

from the details of the various operating systems and network interfaces.

API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software Interface (computing), interface, offering a service to other pieces of software. A document or standa ...

s that extend across diverse platforms and networks are typically provided by MOM. This middleware layer allows software components (applications, Enterprise JavaBeans, servlets, and other components) that have been developed independently and that run on different networked platforms to interact with one another. Applications distributed on different network nodes use the application interface to communicate. In addition, by providing an administrative interface, this new, virtual system of interconnected applications can be made reliable and secure. MOM provides software elements that reside in all communicating components of a client/server architecture and typically support asynchronous calls between the client and server applications. MOM reduces the involvement of application developers with the complexity of the master-slave nature of the client/server mechanism.

Middleware categories

Remote procedure call In distributed computing, a remote procedure call (RPC) is when a computer program causes a procedure (subroutine) to execute in a different address space (commonly on another computer on a shared network), which is coded as if it were a normal (l ...

or RPC-based middleware *

Object request broker In distributed computing, an object request broker (ORB) is a middleware which allows program calls to be made from one computer to another via a computer network, providing location transparency through remote procedure calls. ORBs promote interop ...

or ORB-based middleware *Message Oriented Middleware or MOM-based middleware All these models make it possible for one software component to affect the behavior of another component over a network. They are different in that RPC- and ORB-based middleware create systems of tightly coupled components, whereas MOM-based systems allow for a

loose coupling In computing and systems design, a loosely coupled system is one # in which components are weakly associated (have breakable relationships) with each other, and thus changes in one component least affect existence or performance of another comp ...

of components. In an RPC- or ORB-based system, when one procedure calls another, it must wait for the called procedure to return before it can do anything else. In these

synchronous messaging Synchronization is the coordination of events to operate a system in unison. For example, the Conductor (music), conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are sai ...

models, the middleware functions partly as a super-linker, locating the called procedure on a network and using network services to pass function or method parameters to the procedure and then to return results.

Advantages

Central reasons for using a message-based communications

protocol Protocol may refer to: Sociology and politics * Protocol (politics), a formal agreement between nation states * Protocol (diplomacy), the etiquette of diplomacy and affairs of state * Etiquette, a code of personal behavior Science and technolog ...

include its ability to store (buffer), route, or transform

message A message is a discrete unit of communication intended by the source for consumption by some recipient or group of recipients. A message may be delivered by various means, including courier, telegraphy, carrier pigeon and electronic bus. A ...

s while conveying them from senders to receivers. Another advantage of messaging provider mediated messaging between clients is that by adding an administrative interface, you can monitor and tune performance. Client applications are thus effectively relieved of every problem except that of sending, receiving, and processing messages. It is up to the code that implements the MOM system and up to the administrator to resolve issues like interoperability, reliability, security, scalability, and performance.

Asynchronicity

Using a MOM system, a client makes an API call to send a message to a destination managed by the provider. The call invokes provider services to route and deliver the message. Once it has sent the message, the client can continue to do other work, confident that the provider retains the message until a receiving client retrieves it. The message-based model, coupled with the mediation of the provider, makes it possible to create a system of loosely coupled components. MOM comprises a category of inter- application

communication software Communication software is used to provide remote access to systems and exchange files and messages in text, audio and/or video formats between different computers or users. This includes terminal emulators, file transfer programs, chat and instant ...

that generally relies on

asynchronous Asynchrony is the state of not being in synchronization. Asynchrony or asynchronous may refer to: Electronics and computing * Asynchrony (computer programming), the occurrence of events independent of the main program flow, and ways to deal with ...

message-passing In computer science, message passing is a technique for invoking behavior (i.e., running a program) on a computer. The invoking program sends a message to a process (which may be an actor or object) and relies on that process and its supporting ...

, as opposed to a request-response architecture. In asynchronous systems,

message queue In computer science, message queues and mailboxes are software-engineering components typically used for inter-process communication (IPC), or for inter- thread communication within the same process. They use a queue for messaging – the ...

s provide temporary storage when the destination program is busy or not connected. In addition, most asynchronous MOM systems provide

persistent storage In computer science, persistence refers to the characteristic of state of a system that outlives (persists more than) the process that created it. This is achieved in practice by storing the state as data in computer data storage. Programs have t ...

back up In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is " back up", ...

the message queue. This means that the sender and receiver do not need to connect to the network at the same time ( asynchronous delivery), and problems with intermittent connectivity are solved. It also means that should the receiver application fail for any reason, the senders can continue unaffected, as the messages they send will simply accumulate in the

for later processing when the receiver restarts.

Routing

Many message-oriented middleware implementations depend on a

system. Some implementations permit routing logic to be provided by the messaging layer itself, while others depend on client applications to provide routing information or allow for a mix of both paradigms. Some implementations make use of

broadcast Broadcasting is the distribution of audio or video content to a dispersed audience via any electronic mass communications medium, but typically one using the electromagnetic spectrum ( radio waves), in a one-to-many model. Broadcasting began ...

multicast In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused with ...

distribution paradigms.

Transformation

In a message-based middleware system, the message received at the destination need not be identical to the message originally sent. A MOM system with built-in intelligence can

transform Transform may refer to: Arts and entertainment * Transform (scratch), a type of scratch used by turntablists * ''Transform'' (Alva Noto album), 2001 * ''Transform'' (Howard Jones album) or the title song, 2019 * ''Transform'' (Powerman 5000 album ...

messages and route to match the requirements of the sender or of the recipient. In conjunction with the routing and broadcast/

facilities, one application can send a message in its own native format, and two or more other applications may each receive a copy of the message in their own native format. Many modern MOM systems provide sophisticated message transformation (or mapping) tools which allow

programmer A computer programmer, sometimes referred to as a software developer, a software engineer, a programmer or a coder, is a person who creates computer programs — often for larger computer software. A programmer is someone who writes/creates ...

s to specify transformation rules applicable to a simple

GUI The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...

drag-and-drop In computer graphical user interfaces, drag and drop is a pointing device gesture in which the user selects a virtual object by "grabbing" it and dragging it to a different location or onto another virtual object. In general, it can be used to ...

operation.

Disadvantages

The primary disadvantage of many message-oriented middleware systems is that they require an extra component in the

architecture Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and constructing building ...

, the message transfer agent (

message broker A message broker (also known as an integration broker or interface engine) is an intermediary computer program module that translates a message from the formal messaging protocol of the sender to the formal messaging protocol of the receiver. Mess ...

). As with any

system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment (systems), environment, is described by its boundaries, ...

, adding another component can lead to reductions in

performance A performance is an act of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function. Management science In the work place ...

and reliability, and can also make the system as a whole more difficult and expensive to maintain. In addition, many inter-application communications have an intrinsically

synchronous Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are said to be synchronou ...

aspect, with the sender specifically wanting to wait for a reply to a message before continuing (see

real-time computing Real-time computing (RTC) is the computer science term for hardware and software systems subject to a "real-time constraint", for example from event to system response. Real-time programs must guarantee response within specified time constrai ...

and

near-real-time Real-time computing (RTC) is the computer science term for hardware and software systems subject to a "real-time constraint", for example from event to system response. Real-time programs must guarantee response within specified time constrai ...

for extreme cases). Because message-based

communication Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...

inherently functions asynchronously, it may not fit well in such situations. That said, most MOM systems have facilities to group a request and a response as a single pseudo-synchronous transaction. With a synchronous messaging system, the calling function does not return until the called function has finished its task. In a loosely coupled asynchronous system, the calling client can continue to load work upon the recipient until the resources needed to handle this work are depleted and the called component fails. Of course, these conditions can be minimized or avoided by monitoring performance and adjusting message flow, but this is work that is not needed with a synchronous messaging system. The important thing is to understand the advantages and liabilities of each kind of system. Each system is appropriate for different kinds of tasks. Sometimes, a combination of the two kinds of systems is required to obtain the desired behavior.

Standards

Historically, there was a lack of

standards Standard may refer to: Symbols * Colours, standards and guidons, kinds of military signs * Standard (emblem), a type of a large symbol or emblem used for identification Norms, conventions or requirements * Standard (metrology), an object th ...

governing the use of message-oriented middleware that has caused problems. Most of the major vendors have their own implementations, each with its own

application programming interface An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how t ...

(API) and management tools. One of the long-standing standards for message oriented middleware is X/Open group's XATMI specification (Distributed Transaction Processing: The XATMI Specification) which standardizes API for

interprocess communication In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categori ...

s. Known implementations for this API is ATR Baltic's

Enduro/X Enduro/X is an open-source middleware platform for distributed transaction processing. It is built on proven APIs such as X/Open group's XATMI and XA. The platform is designed for building real-time microservices based applications with a cl ...

middleware and

Oracle An oracle is a person or agency considered to provide wise and insightful counsel or prophetic predictions, most notably including precognition of the future, inspired by deities. As such, it is a form of divination. Description The word '' ...

Tuxedo Black tie is a semi-formal Western dress code for evening events, originating in British and American conventions for attire in the 19th century. In British English, the dress code is often referred to synecdochically by its principal element fo ...

. The

Advanced Message Queuing Protocol The Advanced Message Queuing Protocol (AMQP) is an open standard application layer protocol for message-oriented middleware. The defining features of AMQP are message orientation, queuing, routing (including point-to-point and publish-and-su ...

(AMQP) is an approved

OASIS In ecology, an oasis (; ) is a fertile area of a desert or semi-desert environment'ksar''with its surrounding feeding source, the palm grove, within a relational and circulatory nomadic system.” The location of oases has been of critical imp ...

and ISO standard that defines the protocol and formats used between participating application components, so implementations are interoperable. AMQP may be used with flexible routing schemes, including common messaging paradigms like point-to-point,

fan-out In digital electronics, the fan-out is the number of gate inputs driven by the output of another single logic gate. In most designs, logic gates are connected to form more complex circuits. While no logic gate input can be fed by more than one ...

, publish/subscribe, and request-response (note that these are intentionally omitted from v1.0 of the protocol standard itself, but rely on the particular implementation and/or underlying network protocol for routing). It also supports transaction management, queuing, distribution, security, management, clustering, federation and heterogeneous multi-platform support. Java applications that use AMQP are typically written in Java JMS. Other implementations provide APIs for C#, C++, PHP, Python, Ruby, and other languages. The

High-Level Architecture The High Level Architecture (HLA) is a standard for distributed simulation, used when building a simulation for a larger purpose by combining (federating) several simulations. The standard was developed in the 1990s under the leadership of the US ...

(HLA IEEE 1516) is an

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operation ...

and SISO standard for simulation interoperability. It defines a set of services, provided through an API in C++ or Java. The services offer publish/subscribe based information exchange, based on a modular Federation Object Model. There are also services for coordinated data exchange and time advance, based on logical simulation time, as well as synchronization points. Additional services provide transfer of ownership, data distribution optimizations and monitoring and management of participating Federates (systems). The

MQ Telemetry Transport MQTT (originally an initialism of MQ Telemetry Transport) is a lightweight, publish-subscribe, machine to machine network protocol for Message queue/ Message queuing service. It is designed for connections with remote locations that have devic ...

(MQTT) is an ISO standard (ISO/IEC PRF 20922) supported by the OASIS organization. It provides a lightweight publish/subscribe reliable messaging transport protocol on top of TCP/IP suitable for communication in M2M/IoT contexts where a small code footprint is required and/or network bandwidth is at a premium. The

Object Management Group The Object Management Group (OMG) is a computer industry standardization, standards consortium. OMG Task Forces develop enterprise integration standards for a range of technologies. Business activities The goal of the OMG was a common portabl ...

's Data Distribution Service (DDS) provides message-oriented Publish/Subscribe (P/S) middleware standard that aims to enable scalable, real-time, dependable, high performance and interoperable data exchanges between publishers and subscribers. The standard provides interfaces to C++, C++11, C, Ada, Java and Ruby. The eXtensible Messaging and Presence Protocol (

XMPP Extensible Messaging and Presence Protocol (XMPP, originally named Jabber) is an open communication protocol designed for instant messaging (IM), presence information, and contact list maintenance. Based on XML (Extensible Markup Language), it ...

) is a communications protocol for message-oriented middleware based on XML (Extensible Markup Language). Designed to be extensible, the protocol has also been used for publish-subscribe systems, signalling for VoIP, video, file transfer, gaming, Internet of Things applications such as the smart grid, and social networking services. Unlike most instant messaging protocols, XMPP is defined in an open standard and uses an open systems approach of development and application, by which anyone may implement an XMPP service and interoperate with other organizations' implementations. Because XMPP is an open protocol, implementations can be developed using any software license; although many server, client, and library implementations are distributed as free and open-source software, numerous freeware and proprietary software implementations also exist. The Internet Engineering Task Force (IETF) formed an XMPP working group in 2002 to formalize the core protocols as an IETF instant messaging and presence technology. The XMPP Working group produced four specifications (RFC 3920, RFC 3921, RFC 3922, RFC 3923), which were approved as Proposed Standards in 2004. In 2011, RFC 3920 and RFC 3921 were superseded by RFC 6120 and RFC 6121 respectively, with RFC 6122 specifying the XMPP address format. In addition to these core protocols standardized at the IETF, the XMPP Standards Foundation (formerly the Jabber Software Foundation) is active in developing open XMPP extensions. XMPP-based software is deployed widely across the Internet, according to the XMPP Standards Foundation, and forms the basis for the Department of Defense (DoD) Unified Capabilities Framework. The

Java EE Jakarta EE, formerly Java Platform, Enterprise Edition (Java EE) and Java 2 Platform, Enterprise Edition (J2EE), is a set of specifications, extending Java SE with specifications for enterprise features such as distributed computing and web serv ...

programming environment provides a standard API called JMS (Java Message Service), which is implemented by most MOM vendors and aims to hide the particular MOM API implementations; however, JMS does not define the format of the messages that are exchanged, so JMS systems are not interoperable. A similar effort is with the actively evolving OpenMAMA project, which aims to provide a common API, particularly to C clients. However, at the moment (August 2012) it is primarily appropriate for distributing market-oriented data (e.g. stock quotes) over pub-sub middleware.

Message queuing

Message queue In computer science, message queues and mailboxes are software-engineering components typically used for inter-process communication (IPC), or for inter- thread communication within the same process. They use a queue for messaging – the ...

s allow the exchange of information between distributed applications. A message queue can reside in memory or disk storage. Messages stay in the queue until the time they are processed by a service consumer. Through the message queue, the application can be implemented independently - they do not need to know each other's position, or continue to implement procedures to remove the need for waiting to receive this message.

Trends

* Advanced Message Queuing Protocol (AMQP) provides an open standard application layer protocol for message-oriented middleware. * The

's Data Distribution Service (DDS) has added many new standards to the basic DDS specification. Se
Catalog of OMG Data Distribution Service (DDS) Specifications
for more details. *

is a communications protocol for message-oriented middleware based on XML (Extensible Markup Language). * Streaming Text Oriented Messaging Protocol (STOMP), formerly known as TTMP, is a simple text-based protocol, provides an interoperable wire format that allows STOMP clients to talk with any Message Broker supporting the protocol. * An additional trend sees message-oriented middleware functions being implemented in hardware - usually

FPGA A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term '' field-programmable''. The FPGA configuration is generally specified using a hardware de ...

s or other specialized silicon chips.Are You Soft in the Middle? The future of enterprise IT rests in hardware applications

References

External links

* {{Cite book, title=Get started with IBM MQ , url=https://developer.ibm.com/series/badge-ibm-mq-developer-essentials/ Enterprise application integration Middleware Systems engineering