Event-driven architecture is an architectural design approach that relies on events to trigger actions across decoupled services. In this context, an event represents some sort of change in state – a customer logging in to an application, a shopper adding an item to a cart, or a user following a new account. Events may include information about the action that was taken. Or they may simply generate notifications that get consumed by other parts of the application.
Event-driven architecture can follow the pub / sub model, in which publishers push events to subscribers. After events are processed, they cannot be replayed. The alternative is the event streaming model where events get written to a log. Rather than subscribing to a specific stream, clients have access to the entire log and can replay certain events.
Great, but what does this all mean when it comes to deploying applications in the real world? Why are organizations turning to event-driven architecture now? What’s wrong with legacy approaches to IT architecture design? We answer these questions and more below.
The main components of event-driven architecture
Event-driven architecture consists of three components:
- Event producers
- Event routers
- Event consumers
Event producers are responsible for publishing events to event routers. In a typical event-driven architecture, producers generate events in near real-time, enabling applications to respond quickly to triggers. Furthermore, in event-driven architecture, event producers have no idea what event consumers are listening to them, which is part of what makes this architecture design model scalable and resilient.
Event routers filter and share events with event consumers. They are the crux of what makes event-driven architecture work. Everything that happens on the consumer side passes through a router so that it can be sent to the appropriate consumer. Routers act like buffers between producers and consumers, allowing both sides to operate freely. Routers also serve as a centralized location for auditing the performance of an application since every event that occurs has to pass through the router.
Event consumers are responsible for actually processing the events that get sent through by routers. Consumers don’t have to request events from producers. Instead, they stand by and wait for events to come through before executing some workflow.
This producer, router, consumer framework enables decoupling between producing and consuming – the secret sauce of event-driven architecture.
What are the advantages of event-driven architecture?
Event-driven architecture has several advantages over monolithic design patterns. First, it enables better application development agility. Engineers can add producers and consumers as needed without having to coordinate between the two. Teams can add or update individual services simultaneously, allowing different lanes to move faster on various priorities.
Event-driven architecture can also be less costly than alternative design approaches. Because consumers automatically receive events when they are generated, there is no wasted effort. Consumers don’t have to request events from producers that may not exist. Events are pushed when they happen, giving event-architecture its on-demand, pay-as-you-go nature.
The decoupling between producers and consumers is also what gives event-driven architecture its scalability. Expanding or shrinking individual services is easy because they are loosely tied to other parts of the application. Furthermore, this loose coupling makes event-driven applications more durable. Services that fail don’t affect other areas. Engineers can address issues locally without compromising performance more broadly.
To summarize, event-driven architecture empowers engineering teams to update, scale, and deploy loosely coupled services, which has many benefits in modern application development. It’s an effective way to accelerate innovation, increase development flexibility, and deploy more resilient products in the real world. At a time when organizations have to move faster without sacrificing quality, event-driven architecture may be the answer.
Anthony Loss is lead solutions architect at ClearScale.