This pattern is used to structure distributed systems with decoupled components. These components can interact with each other by remote service invocations. A broker component is responsible for the coordination of communication among components.

Servers publish their capabilities (services and characteristics) to a broker. Clients request a service from the broker, and the broker then redirects the client to a suitable service from its registry.

Usage
Message broker software such as Apache ActiveMQ, Apache Kafka, RabbitMQ, Websphere MQ and JBoss Messaging.

This pattern can be used to structure systems which produce and process a stream of data. Each processing step is enclosed within a filter component. Data to be processed is passed through pipes. These pipes can be used for buffering or for synchronization purposes.

Usage
Compilers. The consecutive filters perform lexical analysis, parsing, semantic analysis, and code generation.
Workflows in bioinformatics.

This pattern consists of two parties; master and slaves. The master component distributes the work among identical slave components, and computes a final result from the results which the slaves return.

Usage
In database replication, the master database is regarded as the authoritative source, and the slave databases are synchronized to it.
Peripherals connected to a bus in a computer system (master and slave drives).