Why messaging middleware

Enterprise messaging is at the core of an ESB architecture. In this chapter we will explore Message Oriented Middleware MOM and what it contributes to an enterprise integration strategy.

A MOM is a key part of the ESB architecture, as it provides the underpinnings of the network of virtual channels that an ESB uses to route messages throughout an extended enterprise and beyond. Term of the Day. Best of Techopedia weekly. News and Special Offers occasional. Also, MOM allows various software components to talk to each other or share data. In visual models, this type of middleware is often represented as a central station with lines that connect different technologies involving message origination and delivery destinations.

Users sometimes describe MOM and other types of middleware as linking up front and back end systems. Tools known as application programming interfaces API are used to develop effective middleware solutions. Figure 1—3 shows the way a MOM system can enable communication between two synchronous messaging systems for example, two RPC-based systems. The left side of the figure shows an application that distributes client, server, and data store components on different networked nodes for improved performance.

This is a discount airline reservation system: an end user pays a fee to use this service, which allows it to find the lowest available fare for given destinations and times. The data store holds information about registered users and about airlines that participate in this program. The right side of the picture would be replicated for as many airlines as the discounter is connected to.

For each such airline, the data store would hold information about available flights seating, flight times, and prices. The server component would update that information in response to data input by the end user. The airline server also subscribes to the MOM service, accepting requests for information from the discount reservation system and returning seating and pricing information. If a customer decides to purchase a discounted ticket on a PanWorld flight, the server component for that system would update the information in the data store and then either generate a ticket for the requester or send a message to the discounting service to generate the ticket.

The difference in the way in which distributed components are coupled has already been mentioned. Another difference is that while RPC systems are often used to distribute and connect client and server components in which the client component is directly accessed by an end-user, with MOM systems, client components are often heterogeneous software systems that can only interoperate by means of asynchronous messaging.

To resolve this problem, a standard messaging interface is needed. Such an interface should be simple to learn but provide enough features to support sophisticated messaging applications. Get in touch. The primary disadvantage of many message-oriented middleware systems is that they require an extra component in the architecture, the message transfer agent message broker.

As with any system, adding another component can lead to reductions in performance and make the system as a whole more difficult and expensive to maintain. When introduced due to lack of standards governing the use of message-oriented middleware has caused problems.

Most of the major vendors have their own implementations, each with its own application programming interface API and management tools. MOM — Implementation. The message queue is a fundamental concept within MOM. Queues provide the ability to store messages on a MOM platform. MOM clients are able to send and receive messages to and from a queue. Queues are central to the implementation of the asynchronous interaction model within MOM.

Usually the messages contained within a Queue is sorted in a particular order. The standard queue found in a messaging system is the First-In First-Out FIFO queue; as the name suggests, the first message sent to the queue is the first message to be retrieved from the queue.

Many attributes of a queue can be configured. Typically each application may have its own queue, or applications may share a queue, there is no restriction on the set-up. MOM platforms support multiple queue types for different purposes. MOM — Messaging Models. A solid understanding of the available messaging models within MOM is key to appreciate the unique capabilities it provides. Both of these models are based on the exchange of messages through a channel queue.