As an essential part of cloud native architecture, microservices are applications built from loosely coupled, independently deployable services. Microservices usually communicate with each other via lightweight protocols like HTTP, messaging queues, or event streams. Event-driven architecture is often the best way to implement microservices, because it promotes greater modularity, fault tolerance, and scalability.
Event-driven architecture (EDA) is a pattern of software design that enables systems to detect, process, communicate, and respond to events in real time. EDA communicates events as soon as they happen, enabling any person, service, or event-driven application that needs to know about an event to respond in real time.
Asynchronous messaging and loose coupling are two important aspects of event-driven architecture. Asynchronous communication replaces the traditional “request and response” architecture in which services must wait for a reply before moving on to perform a task. This allows for easier integration and makes systems more scalable, since they can handle higher volumes of real-time data with low latency. It also allows for related systems to be decoupled or loosely coupled. This means apps and services can communicate with each other by publishing and consuming events without knowing much else about the other system. As a result, event-driven systems can scale quickly and are highly resilient to failure, since the system can continue functioning even if one component is unavailable. EDA also is well suited for real-time processing and handling large volumes of data, as components can react to events — and process data as it arrives — without waiting for a complete dataset.
What is an event?
An event is any change in the state of something within a business system: an object added to a bucket, a new record added to a database, an item placed in a shopping cart, or a password that was reset. It is something that happened in the past, normally in JSON or YAML format.
Why is event-driven architecture necessary?
All business processes are driven by events, and the ability to react quickly to events is essential to productivity, efficiency, and competitiveness. The faster that applications, services, and people can get information about events, the more effectively an organization can operate.
In this environment, event-driven architecture is important because it communicates about events as soon as they happen, in contrast to architectural approaches like APIs that wait for systems to update periodically.
What are the components of event-driven architecture?
Event-driven architecture includes software and hardware components that are deployed and connected to provide real-time communication and messaging around events. These components include:
- Event publishers: These sources of events — also known as event producers — generate an event and then publish it to an event channel or event bus.
- Event bus: This includes event brokers, message queues, and an event channel. It is the path through which events are communicated from event producers to event consumers. Event channels enable the asynchronous and decoupled nature of EDA, enhancing flexibility and scalability of systems as well as the organization of related messaging groups.
- Event subscribers: Also known as event consumers or event listeners, event subscribers receive, process, and respond to events. Responses may involve things like updating a database, performing a task, initiating a process, or generating new events.
How does event-driven architecture work?
Here are the steps involved in communicating events within an event-driven architecture:
- An event publisher produces an event and publishes that data to a channel (or channels) on the event bus.
- The event subscriber “listens” for events on the channel(s) that it cares about, and it responds when a relevant event is published. It can potentially trigger other workflows, actions, or events.
Event-driven architecture is typically deployed in a publish/subscribe (pub/sub) model or an event streaming model.
- Pub/sub: In this model, also known as the event messaging model, event consumers subscribe to a class of messages published by event producers. When producers publish an event, the information is communicated to all subscribers who want to consume it. This is usually performed through a message broker that receives event messages, translates them if needed, manages the order of messages, makes them available to subscribers, and deletes messages once they have been consumed.
- Event streaming: In this model, event consumers subscribe to streams of events that are sent by publishers to brokers and recorded in logs. Rather than receiving and consuming each event as it’s published, consumers can enter the stream at any point and consume only the events they’re interested in. Events may be retained for a period of time, allowing consumers to receive them at any time. Some event streaming processes use a data streaming platform like Apache Kafka to manage ingestion, processing, and transformation of the event stream. Event streaming can also be used for complex event processing, in which consumers process a large number of events simultaneously.
What are the benefits of event-driven architecture?
Event-driven architecture offers many benefits for organizations in every industry.
- Enhanced system flexibility: The loosely coupled nature of an event-driven architecture allows organizations to easily modify, add, or remove components without affecting the entire system, making it adaptable to changing requirements. For developers, EDA reduces complexity by making it possible to break down monolithic workflows into a series of simple, decoupled services that can be managed independently and communicated asynchronously through event messages.
- Improved scalability: EDA supports easy horizontal scaling, allowing businesses to handle increased workloads or traffic by adding more instances of components or services as needed.
- Increased system resiliency: EDA’s asynchronous communication and decoupled components contribute to improved fault tolerance, as the failure of one component does not necessarily cause a system-wide outage.
- Real-time processing capabilities: EDA enables real-time processing of large data volumes and complex event patterns, making it suitable for businesses that require immediate insights or responses to rapidly changing real-world conditions.
- Optimized resource usage: By reacting to events only when they occur, EDA helps optimize resource utilization and reduces the need for continuously running processes, potentially leading to cost savings and improved efficiency.
- Faster speed: EDA can speed up your systems because different components don’t have to wait for each other.
What are use cases for event-driven architecture?
The most common use cases for event-driven architecture include:
- Real-time monitoring: Rather than waiting on the results of periodic check-ins and updates, EDA enables applications, services, and teams to receive immediate alerts about any anomalies, changes, and updates to systems.
- Data replication: EDA makes it easy to share a single event between multiple services, which can copy its event data into various databases. EDA can also coordinate systems operating in different regions and accounts.
- Redundancy: When a service goes down, events may persist within a router until the service is back up and able to consume events again.
- Parallel processing: With EDA, a single event can trigger multiple processes at once.
- Integration and interoperability: Event-driven architecture enables systems running on different stacks to share information without needing to be tightly coupled.
What are examples of event-driven architecture?
Event-driven architecture is used in a broad array of industries and systems.
- Ecommerce: EDA enables ecommerce companies to respond immediately whenever an item is placed in a shopping cart, a purchase is made, a payment is processed, or a package is shipped.
- IoT: Event-driven architecture is critical to collecting data in Internet of Things (IoT) systems, triggering actions when IoT devices detect certain conditions or metrics.
- Stock market: When market conditions change, EDA can trigger automated trading strategies.
- Real-time analytics: EDA can instantly trigger analysis of real-time events to detect fraud, monitor traffic, and make better decisions based on real-time conditions.
- Online gaming: EDA enables online games to identify and respond to events such as players’ actions, moving characters, or completing tasks.
- Smart homes: Sensors and smart devices within the home can respond to changes in temperature, motion, lighting, and other events.
- Workflow automation: EDA enables organizations to automate many steps in a complex workflow, where one event triggers new steps in a process.
Frequently Asked Questions
Within event-driven systems, decoupling and loose coupling are related concepts. Decoupling is the process of eliminating dependencies between different components within the system so that neither component is reliant on the other. This allows components to be more independent and creates a more flexible and resilient system. Loose coupling is a form of decoupling that minimizes dependence while not completely separating components. Components may still interact with one another, but in ways that don’t create a lasting dependence.
Serverless computing is a computing paradigm in which developers can access back-end services on demand, allowing them to focus on writing code while not having to worry about managing the underlying servers and infrastructure. It is based on event-driven architecture, in which functions are triggered by events such as HTTP requests, file uploads, and database updates to simplify the application architecture and improve scalability.
