Event-Driven Architecture (EDA) is about using events as a way to communicate within a system. Generally, leveraging a message broker to publish and consume events asynchronously. The publisher is unaware of who is consuming an event and the consumers are unaware of each other. Event-Driven Architecture is simply a way of achieving loose coupling between services within a system.
What is an event?
An event is a data point that represents state changes in a system. It doesn't specify what should happen and how the change should modify the system, it only notifies the system of a particular state change. When a user makes an action, they trigger an event.
Components
Event-driven architectures have three key components:
- Event producers: Publishes an event to the router.
- Event routers: Filters and pushes the events to consumers.
- Event consumers: Uses events to reflect changes in the system.
Note: Dots in the diagram represents different events in the system.
Patterns
There are several ways to implement the event-driven architecture, and which method we use depends on the use case but here are some common examples:
Note: Each of these methods is discussed separately.
Advantages
Let's discuss some advantages:
- Decoupled producers and consumers.
- Highly scalable and distributed.
- Easy to add new consumers.
- Improves agility.
Challenges
Here are some challenges of event-drive architecture:
- Guaranteed delivery.
- Error handling is difficult.
- Event-driven systems are complex in general.
- Exactly once, in-order processing of events.
Use cases
Below are some common use cases where event-driven architectures are beneficial:
- Metadata and metrics.
- Server and security logs.
- Integrating heterogeneous systems.
- Fanout and parallel processing.
Examples
Here are some widely used technologies for implementing event-driven architectures:
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Table of contents
-
Getting Started
-
Chapter I
-
Chapter II
-
Chapter III
- N-tier architecture
- Message Brokers
- Message Queues
- Publish-Subscribe
- Enterprise Service Bus (ESB)
- Monoliths and Microservices
- Event-Driven Architecture (EDA)
- Event Sourcing
- Command and Query Responsibility Segregation (CQRS)
- API Gateway
- REST, GraphQL, gRPC
- Long polling, WebSockets, Server-Sent Events (SSE)
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Chapter IV
- …
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