Message broker

A message broker (also known as an integration broker or interface engine^[1]) is an intermediary中间的 computer program module that translates a message from the formal正式的 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.^[1] Message brokers are a building block of message-oriented middleware (MOM) but are typically not a replacement for traditional middleware like MOM and remote procedure call (RPC).^[2]^[3]

Purpose, functionality, and architecture

A message broker is an architectural pattern for message validation, transformation, and routing. It mediates传达 communication among applications, minimizing the mutual相互的 awareness that applications should have of each other in order to be able to exchange messages, effectively implementing decoupling.^[4]

The primary purpose of a broker is to take incoming messages from applications and perform some action on them. Message brokers can decouple end-points, meet specific non-functional requirements, and 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. The following represent other examples of actions that might be handled by the broker^[2]^[3]:

Route messages to one or more destinations
Transform messages to an alternative representation
Perform message aggregation, decomposing分解 messages into multiple messages and sending them to their destination, then recomposing改组 the responses into one message to return to the user
Interact with an external repository to augment a message or store it
Invoke web services to retrieve data
Respond to events or errors
Provide content and topic-based message routing using the publish–subscribe pattern

Message brokers are generally based on one of two fundamental architectures: hub-and-spoke and message bus. In the first, a central server acts as the mechanism that provides integration services, whereas with the latter, the message broker is a communication backbone主干网 or distributed service that acts on the bus.^[3] Additionally, a more scalable multi-hub approach can be used to integrate multiple brokers