SpringOne Platform 2018 Rethinking Legacy and Monolithic Systems - Vaughn Vernon

1. Rethinking
Legacy and
Monolithic Systems
Copyright © 2018 Vaughn Vernon. All rights reserved.

2. Everyone Is Going
Microservices
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3. So We Want to Go
Microservices
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4. Business Wants
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5. You Want
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6. Definitions
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de•scrip•tion (dĭ-skrĭpˈshən)►
n. The act, process, or technique of describing.
n. A statement or an account describing something:
published a description of the journey; gave a vivid
description of the game.
n. A pictorial representation: Monet's ethereal descriptions
of haystacks and water lilies.

7. Legacy
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8. Legacy: Monolith
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9. Legacy: BBoM
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10. Anemic Domain
Model
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11. Anemic Domain Model
@Entity
public class Client {
@Id
private String id;
@Column
private String name;
@Column
private String address1;
@Column
private String address2;
@Column
private String city;
@Column
private String stateOrProv;
...
}
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12. Microservice
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?

13. @VaughnVernon
100
LoC

14. @VaughnVernon
400
LoC

15. @VaughnVernon
1000?

16. 100 LoC Now
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17. Dependencies?
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18. ONLY $400/mo!
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19. 100 Then * $400/mo
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20. And...
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21. Complex System
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2,000,000 LoC?
5,000,000 LoC?

22. 2,000,000 LoC
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2MM / 100 = 20,000 MS
20K * $400/mo = $8MM/mo
$8MM * 12 = $96MM/yr

23. 5,000,000 LoC
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5MM / 100 = 50,000 MS
50K * $400/mo = $20MM/mo
$20MM * 12 = $240MM/yr

24. Bounded Context
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25. Identify
Strategic Drivers
"Our problem is that our
software implements
ordinary business process
but stops short of seeking
strategic advantage."

26. Tell!
public class Client extends Entity {
public void name(String name) {
...
}
public void address(PostalAddress address) {
...
}
public void relocateTo(PostalAddress address) {
...
}
public void telephone(Telephone telephone) {
...
}
...
}

27. Explicit, Testable,
Less Code
public class Client {
public void relocateTo(PostalAddress address) {
this.postalAddress = address;
emit(new ClientRelocated(...));
}
}
public class ClientTests {
public void testThatClientRelocates() {
...
}
}

28. Bounded Context
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29. Monolith to
Microservices
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30. BBoM To BC—How?
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31. Rewrite
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32. Eat an Elephant
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One bite at a time.
●
Change-driven
●
Value-driven
●
Test-driven

33. Strangler (1)
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34. Strangler (2)
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● Debezium: http://debezium.io/
● Oracle Golden Gate

35. Restructured (1)
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36. Restructured (2)
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37. Restructured (3)
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38. @VaughnVernon

39. @VaughnVernon

40. @VaughnVernon

41. @VaughnVernon

42. @VaughnVernon

43. Reactive Rework
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44. Reactive DDD
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45. Contact: vaughn@kalele.io
Open Source
Reactive Platform
Web: vlingo.io
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