Broker Pattern
A broker may be implemented in either a Pub/sub model or Point-to-point (P2P) model.
- The publish-and-subscribe (pub/sub) model is intended for a one-to-many broadcast（Multicast） of information
- The point-to-point (P2P) model is intended for a one-to-one communication （Unicast） between two specific applications.
Pub/sub model
In the pub/sub model, multiple consumers may register an interest with, or subscribe to, a topic. A producer sends a message on that channel by publishing on that topic. Each subscriber receives a copy of that message.
Point-to-point (P2P) model
In the point-to-point model, only one consumer may receive a message that is sent to a queue.
A point-to-point queue may have multiple consumers listening for the purposes of load-balancing or “hot backup”; however, only one receiver may consume each individual message.
There may also be no receivers listening, in which case the message stays in the queue until a receiver attaches itself to the queue to retrieve messages.
In the publish-and-subscribe model, messages not flagged as reliable can be discarded if no subscribers are registered to receive them at the time they are published.