Unlocking Scalability and Resilience with Event-Driven Architecture: A Smart Home Showcase

Are you looking to build a system that’s scalable, efficient, and resilient to failure? Event-driven architecture (EDA) might be the answer. In this article, we’ll walk through the design of a Smart Home application to illustrate the power of EDA. From handling real-time events with producers and consumers to ensuring independent, fault-tolerant components, we’ll break down the system design process step by step. Let’s dive in!

A bit of theory 

Event-driven architecture (EDA) relies on events to connect decoupled services in your system. Producers are responsible for detecting changes (user click, sensor measurement) and triggering messages to the broker. When consumers listen for specific types of messages and respond with the appropriate behavior. At the heart of an EDA system is the event - a single change in state. Every action or change in your system is represented as an individual event.

Applications built with EDA(Event-Driven architecture) are easy to scale because new producers/consumers can be created independently. This allows us to maintain and deploy them separately, using one or multiple languages. Systems are also fault-tolerant - errors on consumers will not be propagated to other services.

Smart Home driven by events

To showcase the system design process, we’ll use the example of building a Smart Home application. In the next steps, we’ll go through system requirements, identify all the necessary components, and define the application’s behavior flows.

System requirements

Our clients gave us a few user stories to describe how the system should work:

• I want to be able to close all blinds and gates from a mobile app
• I want my sprinkles to run automatically each day at 7 AM.
• I want to start sprinkles from the mobile app
• When the sun rises, I want my blinds to open.

System components

In Event-Driven systems, we identify two main types of components - producers and consumers. In our case, a light sensor, house scheduler, and mobile application will be the producers and will be responsible for event generation. Once sprinkler systems, entry gates, and blinds (consumers) implement logic, they are responsible for handling system events. System design  All components are defined, and we know what our requirements are, so let’s jump straight to shaping the application’s behaviour.

First, let’s start with the events that may occur in our system (state changes).

• LightLevel -Events coming from light sensor informing us about current light level
• HouseLock - Event trigger by mobile application to lock all of the blinds and gates
• SprinklersChange - Used to turn on/off sprinklers, can be triggered manually via mobile application or by house clock scheduler

Now, let’s define the behaviours of our controllers (consumers).

• Sprinklers controller - listens for changes coming from SprinklersChange either to turn them on or off.
• Gate controller - The gate will be closed and locked whenever the controller receives the HouseLock event.
• Blind controller - this controller will interact with two types of events LightLevel and HouseLock . The blinds will open automatically whenever the level of light is higher than a threshold. But when the user triggers the event lock house, the blinds will close themselves.

Below is an animation of how the final system is going to work.

Future proof

As you can easily see, adding new elements to our Smart Home will not require a dozen changes in already existing components. For example, if we want to create a new Door Controller that will lock the door when a user selects it from a mobile app, we need to implement our service to handler LockHouse events.

Final note

Companies such as Uber or Netflix use Event-Driven systems to handle millions of messages on the daily basis. But don’t be afraid to design even smaller applications or parts of them using this approach. For example, you can use EDA for building logging handling in your distributed system or handling async tasks such as triggering email/notifications sending.