Broker

The broker is an architecture pattern for structuring a distributed system out of decoupled components that interact through, usually remote, service invocations rather than calling one another directly. A broker component sits between callers and providers, coordinating the communication between them. It forwards requests to the right provider, and transmits the results or exceptions that come back, so that neither side needs to know the other’s location or how to reach it.

This is the same coordinating role played by a message broker in asynchronous, message-based systems, and by the registry and stub components in a remote procedure call (RPC) system, both of which are broker-pattern instances specialized to their own style of invocation.