A brief introduction to event sourcing, event collaboration and CQRS. Covers how they may be used together to enable microservice architecture, move data between services, renovate legacy architectures and provide a richer understanding of the entire organisation. Originally delivered at LAST conference 2016.

1. IT’S FULL OF STARS
BUILDING, MEASURING AND LEARNING WITH EVENTS
Brent Snook - @brentsnook

2. @brentsnook

3. What is the bank balance?
@brentsnook

4. Jeena deposited $100
Mal withdrew $50
Bron withdrew $60
Overdrawn fee charged of $2
Mal deposited $50
Account
Balance: $ 38
What is the bank balance?
@brentsnook

5. How much has been charged in fees?
Account
Balance: $ 38
@brentsnook

6. @brentsnook
we know that there
are known knowns
but there are also
unknown unknowns
How are we going to use our data?
(the ones we don’t know we don’t know)
@brentsnook

7. your
data
hoard
@brentsnook

8. e e
e
e
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e
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e
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e
e
e
e
ee
e
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ee
e
e
e
e
e
e
e
e
e
e
correlation
@brentsnook

9. projection
e
e
e
e
ee
e
e
e
e
@brentsnook

10. projection
e
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e
ee
e
e
e
e
@brentsnook

11. projection
e
e
e
e
ee
e
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e
@brentsnook

12. @brentsnook
LE POULPE COLOSSAL
or
L’INTÉGRATION VIA
LA BASE DE DONNÉES
Pierre Dénys de Montfort
1801
@brentsnook

14. Anatomy of an Event
{
"eventId": "F59774E7",
"sequenceId": 237893473,
"eventType": "withdrawalSuccess",
"createdAt": "2016-04-02 23239230",
"aggregateId": "5B7D5971",
"metadata": {
"correlationIds": [
"CD5B3E20",
"D12C18B7"
]
},
"data": {
"1.0": {
"accountId": "6CEB2C11",
"money": {
"currency": "AUD",
"amount": "34.45"
}
}
}
}
@brentsnook

15. request
collaboration
A B C D
@brentsnook

16. request
collaboration
A B C D
@brentsnook

17. event
collaboration
A B C D
@brentsnook

18. event
collaboration
A B C D
@brentsnook

19. event
collaboration
A B C D
e
e
@brentsnook

20. event
collaboration
A B C D
e
e
e
e
e
@brentsnook

21. SPLITTING THE MONOLITH
@brentsnook

22. SPLITTING THE MONOLITH
• EMIT EVENTS AT KEY PARTS OFTHE PROCESS
e e
@brentsnook

23. SPLITTING THE MONOLITH
• EMIT EVENTS AT KEY PARTS OFTHE PROCESS
• REACTTOTHEMTO ADD EVENT-DRIVEN SEAMS
e e
@brentsnook

24. SPLITTING THE MONOLITH
• EMIT EVENTS AT KEY PARTS OFTHE PROCESS
• REACTTOTHEMTO ADD EVENT-DRIVEN SEAMS
• MOVE RESPONSIBILITY BETWEENTWO SEAMS INTO A NEW SERVICE
e e
@brentsnook

25. SPLITTING THE MONOLITH
• EMIT EVENTS AT KEY PARTS OFTHE PROCESS
• REACTTOTHEMTO ADD EVENT-DRIVEN SEAMS
• MOVE RESPONSIBILITY BETWEENTWO SEAMS INTO A NEW SERVICE
• REPEAT
e e
@brentsnook

26. e e e e e e e e e e e e e e e e
Event Bus
MY GOD, IT’S FULL OF EVENTS …
ATM
Query
Event
Store
Billing
Internet
Banking
Web UI
Internet
Banking
API
Reports
User
Mgmt.
Accounts
Paper
Mail
@brentsnook

27. C H A L L E N G E S
@brentsnook

28. Q U E S T I O N S ?
@brentsnook

29. REFERENCES/FURTHER READING
• Event Collaboration
• http://martinfowler.com/eaaDev/EventCollaboration.html
• Event Sourcing
• http://martinfowler.com/eaaDev/EventSourcing.html
• https://www.thoughtworks.com/radar/techniques/event-sourcing
• Greg Young - Event Sourcing Talk at Code on the Beach 2014
• https://www.youtube.com/watch?v=JHGkaShoyNs
• Command/Query Responsibility Segregation (CQRS)
• http://martinfowler.com/bliki/CQRS.html
• Domain Driven Design incl. Aggregates, Bounded Contexts and Anti-Corruption Layers
• https://www.infoq.com/minibooks/domain-driven-design-quickly
• http://martinfowler.com/bliki/DDD_Aggregate.html
• http://martinfowler.com/bliki/BoundedContext.html
http://www.markhneedham.com/blog/2009/07/07/domain-driven-design-anti-corruption-layer/
• Event Storming
• http://ziobrando.blogspot.com.au/2013/11/introducing-event-storming.html
• Seams
• http://www.informit.com/articles/article.aspx?p=359417&seqNum=2
• Software Entropy
• https://en.wikipedia.org/wiki/Software_entropy
• AWS Technologies
• https://aws.amazon.com/kinesis/streams/
• https://aws.amazon.com/sqs/
• https://aws.amazon.com/sns/
• https://aws.amazon.com/lambda/details/
@brentsnook

30. IMAGES
• Images from “2001 - A Space Odyssey”
• COPYRIGHT © Metro-Goldwyn-Mayer Inc.; 3 April 1968; LP36136 (in copyright registry)
• © Renewed 1996 by Turner Entertainment Company
• Images from”Willy Wonka and the Chocolate Factory”
• COPYRIGHT © MCMLXXI BY WOLPER PICTURES, LTD. AND THE QUAKER OATS COMPANY ALL RIGHTS RESERVED
• © Renewed 1999 by Warner Bros., a division of Time Warner Entertainment Company, LP
• Rumsfeld
• https://commons.wikimedia.org/wiki/File:Donald_Rumsfeld_Defenselink.jpg
• Cluttered Store
• https://www.flickr.com/photos/tallkev/4082110101/
• Le Poulpe Colossal
• https://commons.wikimedia.org/wiki/File:Histoire_naturelle,_g%C3%A9n%C3%A9rale_et_particuli%C3%A8re_des_mollusques_(6261008252).jpg
• Dominoes
• https://www.flickr.com/photos/daxx13/6289764937/
• Stars
• https://www.flickr.com/photos/122323654@N05/15024418586/
• Waterfall
• https://www.flickr.com/photos/btf5/13958611932/
• Heart
• http://thegraphicsfairy.com/wp-content/uploads/2013/02/Anatomy-Heart-Images-Vintage-GraphicsFairy1.jpg
• Bear 1
• https://www.flickr.com/photos/deischi/7765087960/
• Bear 2
• https://www.flickr.com/photos/usfws_alaska/8384015991/
• Bear 3
• https://www.flickr.com/photos/deischi/7765098472/
• Bear 4
• https://www.flickr.com/photos/deischi/7765062054/
• Bucket Brigade
• http://digital.library.upenn.edu/women/brody/fire/4-100.jpeg
• Big Fire Engine Book by Virginia Brody (fl.1960), Illustrations by Mazoujian. New York, McGraw-Hill, 1958. Copyright not renewed.
• Paper Background
• https://www.flickr.com/photos/schmod/419640051
• Database
• https://commons.wikimedia.org/wiki/File:Database.svg
• Cloud
• https://commons.wikimedia.org/wiki/File:Emojione_2601.svg
@brentsnook