In computer programming, a message broker is an intermediary program module that translates a message from the formal messaging protocol of the sender to the formal messaging protocol of the receiver. Message brokers are elements in telecommunication or computer networks where software applications communicate by exchanging formally-defined messages. Message brokers are a building block of Message oriented middleware.
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Pattern
A message broker is an architectural pattern for message validation, transformation and routing. It mediates communication amongst applications, minimizing the mutual awareness that applications should have of each other in order to be able to exchange messages, effectively implementing decoupling.
The purpose of a broker is to take incoming messages from applications and perform some action on them. The following are examples of actions that might be taken in by the broker:
Broker functionality
Some messaging functions do not require an intermediary message broker. For example, end-point objects can take the roles of publisher and subscriber, as in the observer design pattern. Message brokers are used to decouple end-points and/or meet specific non-functional requirements and/or facilitate reuse of intermediary functions. For example, a message broker may be used to manage a workload queue or message queue for multiple receivers, providing reliable storage, guaranteed message delivery and perhaps transaction management.