Pattern description

Unlike the content-based routing scenario which targets a single destination system, this scenario calls for the broadcast of an event to a variable number of interested consumers. Similar to the content-based routing pattern where the publisher of a request does not know who is consuming the information, the publish/subscribe pattern relies on decoupling the sender from the receiver(s). In a publish/subscribe scenario, a set of subscribers asynchronously receive a message in parallel to each other and independently act upon it. This pattern is very successful if you need a very loosely coupled, scalable way to funnel data to multiple recipients.

Ideally, a message broker in a publish/subscribe solution can provide a robust quality of service to the subscribers. This typically means that the broker can notify subscribers in parallel (versus sequentially), perform in a store-and-forward fashion so that downstream unavailability does not result in lost messages, and filter...