Software Architecture Patterns, 2nd Edition

Chapter 5. Event-Driven Architecture

The event-driven architecture style has significantly gained in popularity and use over recent years, so much so that even the way we think about it has changed. This high adoption rate isn’t overly surprising given some of the hard problems event-driven architecture solves, such as complex nondeterministic workflows and highly reactive and responsive systems. Furthermore, new techniques, tools, frameworks, and cloud-based services have made event-driven architecture more accessible and feasible than ever before, and many teams are turning to event-driven architecture to solve their complex business problems.

Topology

Event-driven architecture is an architecture style that relies on asynchronous processing using highly decoupled event processors that trigger events and correspondingly respond to events happening in the system. Most event-driven architectures consist of the following architectural components: an event processor, an initiative event, a processing event, and an event channel. These components and their relationships are illustrated in Figure 5-1.

Figure 5-1. The main components of event-driven architecture

An event processor (today usually called a service) is the main deployment unit in event-driven architecture. It can vary in granularity from a single-purpose function (such as validating an order) to a large, complex process ...