Glossary · System coordination, integration and orchestration
Message broker
Also known as: Broker
German: Message Broker
In software architecture, a message broker is a middleware component that receives messages from producers and delivers them to consumers, decoupling them in time and location, usually through topics or queues with publish/subscribe or point-to-point semantics.
- System integration
In one sentence
A message broker is middleware that receives messages from producers and routes them to consumers through topics or queues, decoupling both sides.
Example
Edge gateways publish machine states to an MQTT broker, and the MES, a historian and a dashboard subscribe to the topics they need.
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
How it applies
- Engineering: Common brokers in industrial settings are MQTT brokers, AMQP brokers and the pub/sub transport of OPC UA over MQTT. Define the topic structure, payload format, quality-of-service levels and retention before connecting many clients.
- Operation: The broker becomes a central dependency. Plan for redundancy, monitoring and what clients do when the broker is unreachable.
- Security: Authenticate and authorize clients per topic and encrypt connections; an open broker lets anyone publish commands or read production data.
- Documentation: Document the topic namespace, message schemas and versioning in the interface specification, and state which messages may trigger actions on machines.
Message broker vs. protocol gateway
A broker distributes messages between many parties using one messaging protocol. A Protocol gateway translates between different protocols, for example from a fieldbus to OPC UA or MQTT. A gateway often publishes into a broker.
A broker carries messages but does not guarantee that consumers interpret them the same way; that is the job of a shared Data model and Schema (data).