Message broker

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 networks where software applications communicate by exchanging formally-defined messages. Message brokers are a building block of Message oriented middleware.

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:

• Route messages to one or more of many destinations
• Transform messages to an alternative representation
• Perform message aggregation, decomposing messages into multiple messages and sending them to their destination, then recomposing 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

Broker functionality

Many messaging patterns (like publish–subscribe) can work without a message broker. One pattern that requires a message broker is workload queues, that is message queues that are handled by multiple receivers. Such queues must be managed, transacted, and usually stored reliably, at a single point.

List of message broker software

• Apache ActiveMQ
• Apache Kafka
• Apache Qpid
• Celery Task Queue
• Cloverleaf (E-Novation Lifeline)
• Comverse Message Broker (Comverse Technology)
• Financial Fusion Message Broker (Sybase)
• Fuse Message Broker (enterprise ActiveMQ)
• Gearman
• IBM Integration Bus
• JBoss Messaging (JBoss)
• JORAM
• Microsoft BizTalk Server (Microsoft)
• Microsoft Azure Service Bus (Microsoft)
• Open Message Queue
• Oracle Message Broker (Oracle Corporation)
• QDB (Apache License 2.0, supports message replay by timestamp)
• RabbitMQ (Mozilla Public License, written in Erlang)
• SAP PI (SAP AG)
• Spread Toolkit
• Tarantool, a NoSQL database, with a set of stored procedures for message queues
• WSO2 Message Broker

See also

• Publish–subscribe pattern
• Comparison of business integration software
• Message-oriented middleware