Introduction to Event-Driven Architecture - ACloudGuru
Contents
- Introduction
- Legacy Event Processing
- Event-Driven Architecture
- Message vs Event
- A Word on Idempotency
- Summary
1. Introduction
- Event-driven architecture is a software architecture paradigm designed to promote the production, detection, consumption and reaction to events.
- An event-driven application is a program that responds to event input.
- Why is event-driven architecture important?
- Provides valuable Business Advantages
- Solves modern application problems
- Easier to implement than legacy applications
- Can be applied in any cloud platform
2. Legacy Event Processing
What’s covered: Events, Discuss how events are handled in legacy applications
What’s an event?
- “A thing that happens - especially one of importance.”
- Could be anything that happens.
Legacy strategy for working with events
Traditional multi-tier applications are built around a Database. Historically, programmers have approached events by inserting all events into a DB and executing queries against those events.
New events were acted on by a scheduled DB job at a somewhat regular interval.
4 problems facing the modern application
| Problem | Explanation |
|---|---|
| Availability | Traditionally, one monolithic application. In modern applications, we have microservices, each of which has to be available 99.999% of the time. i.e. < 5 mins of downtime per year (40 seconds of downtime per month). Includes event processing. |
| Scalability | Event processing needs to scale rapidly to meet the demand of applications without introducing latency. |
| Source of Truth | Need a single source of truth. Was easy before microservices as all the data resided in a single DB, but when applications share a DB, there will be problems like dependencies on schema changes or performance issues. Common solution to this problem: 1 DB per service. But this would mean dealing with distributed transactions and the complexity of maintaining multiple DBs. |
| Synchronous | Legacy event processing is often synchronous. In a typical request/response scenario, the client waits for the server to respond. So, it blocks all other activity until it receives a response or timeout expires. Problem: if the microservice has resource block, timeouts will occur exponentially, which will impact every other service. |
Why modern applications need a new approach:
- World is changing at an alarming pace and as a result
- companies operate globally
- companies create applications that integrate the entire organization
- 24/7 availability expected
Solution all these problems:
- Event-driven architecture to the rescue!
- “Organizations must provide real-time application communication, and in order to accomplish this, they must become event-driven.”
How event-driven architecture solves the 4 problems
| Problem | Solution |
|---|---|
| Availability |
3. Event-Driven Architecture
What’s covered: About event-driven architecture, Critical components of an event-driven application, messaging models, different styles of event processing, how an event-driven application works, examples of event-driven applications
4. Message vs Event
What’s covered: Compare and contrast messages and events
5. A Word on Idempotency
What’s covered: Idempotency as it relates to events