A presentation I delivered at Digital Croydon (April 2015) on Event-driven Architecture

1. Event Driven Architecture
A short overview of
Andrew Easter

2. Who am I?
● Former Platform Architect at Gumtree.com
● Specialise in JVM (Java/Scala) development
● Currently contracting/freelancing/consulting
whilst validating startup ideas
● CTC Tech Specialist
● CTC Agile & Scrum Workshop Facilitator

3. “Event-driven architecture (EDA) is a
software architecture pattern promoting
the production, detection,consumption
of, and reaction to events”
Wikipedia says...

4. “The art of designing a system around the
principle of using events – concise descriptions
of state changes or significant occurrences in
the system – to drive behaviour both within and
between the applications that make up an
entire system”
Andrew Easter says...

5. Pub/Sub Pattern Revisited
Model View2
View1
View3

6. “To be successful with EDA, it needs to
become a fundamental mindset that
drives all design decisions, rather than
just a pattern that is used in some
isolated parts of a wider system”

7. Example: Entity changes as events
Bank
Account
Deposit
Made
Account
Created
Withdrawal
Made

8. Account
Created
Send Bank
Card
Send
Welcome
Email
Upsell
Reminder

9. Why do this?
(other than it just being cool)

10. Separation of concerns
Single responsibility principle
Extensibility

11. ...what does this enable?
But...

12. aka webhooks
The Evented Web

13. Business intelligence
Big Data (yuck)

14. Sexy dashboards
System Monitoring

15. “Logs as event streams”
(http://12factor.net/logs)
Log File Analysis

16. Given, When, Then
Behaviour-driven Development (BDD)

17. And finally...

18. Eventsourcing

19. Eventsourcing is an approach to persistence
that means the state of an entity is made up
of all the events (state changes) it has
emitted over time

20. AccountCreated
DepositMade
DepositMade
DepositMade
WithdrawalMade
InterestCredited
Time Replay BankAccount
(current state)

21. ● Very scalable. An event store can be as
simple as an append only log file
● Full history of every state change - great for
auditing and debugging
● Very BDD compatible
● Plays real nice with the CQRS pattern
Benefits

22. Any questions?

23. Contact me
@DrewEaster
http://www.dreweaster.com