What Is a Message Broker?

A Message Broker is a centralized hub that simplifies communication among heterogeneous systems. A Message Broker is not a technological breakthrough, but a sensible solution to a common problem: a dramatic increase in number of point-to-point connections between applications in the enterprise.

If there are N applications, and every application links to every other application, the total number of point-to-point connections required is N * (N - 1)/2. If applications instead connect through a central Message Broker, this number is reduced to just N, as in Figure 11-1, where a tangled web of 36 connections is replaced with a tidy 9.

Point-to-point connections versus connections through a Message Broker
Figure 11-1. Point-to-point connections versus connections through a Message Broker

The argument is a straw man because no company ever requires anywhere near the mathematical maximum number of links. Worse than the quantity of connections is the quality: each connection potentially has its own transport mechanism and message format, and in many cases is poorly documented, hard to integrate, or hard to maintain. Some systems are new, some are legacy, some speak XML, some fixed-position text, and some obscure binary.

A Message Broker’s solution is, first, to be a central integration point with a well-documented and clearly understood interface. New applications requiring enterprise integration simply plug into this open architecture. ...

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