Dennis van der Stelt is a software architect with nearly 20 years of experience in distributed systems, offering coaching and training on software development and architecture. He emphasizes the importance of messaging for reducing coupling in systems and discusses concepts like the CAP theorem and eventual consistency in distributed transactions. His work includes insights on monolithic design challenges, the complexities of distributed transactions, and the necessity of idempotency in message delivery.

1. Dennis van der Stelt
of distributed systems
Dennis van der Stelt
Software Architect
http://dennis.bloggingabout.net/
dennis@bloggingabout.net
NServiceBus Community Champ
PRINCIPLES
@dvdstelt
#sdnevent

2. Dennis van der Stelt
YOUR PRESENTER
Dennis van der Stelt
http://dennis.bloggingabout.net/
Software Architect
Professional Services
Provides coaching & training
About Dennis
Innovative software architect
Almost 20 years of experience in development of
distributed systems. Has a continuous drive to
learn and improve knowledge in different
architectural styles, including quality in software
development. Highly motivated to share his
knowledge via articles, presentations and his
blog.
Awards
NServiceBus Champ
Typemock MVP
Certified Trainer
• Presentations
• Software & Architecture audits
• SOA & Microservices advice
• Unit Testing training
• NServiceBus training
Presentations
October 15th at Blaak Selectie / Betabit
Reliable systems using messaging

3. Dennis van der Stelt
AGENDA

4. Dennis van der Stelt
A monolithic design is characterized by such tight coupling
among modules that they really have no independent existence.
monolithic

5. Dennis van der Stelt
MONOLITHIC DESIGN
How does my clean code become a big ball of mud?
Database

6. Dennis van der Stelt
MONOLITHIC DESIGN
How does my clean code become a big ball of mud?
Database

7. Dennis van der Stelt

8. Dennis van der Stelt
What’s your problem, dude?

9. Dennis van der Stelt
PROBLEM STATEMENT
Layering
Problem #1

10. Dennis van der Stelt

11. Dennis van der Stelt
lightweight servicebus

12. Dennis van der Stelt
PROBLEM STATEMENT
“little computers
passing messages”
Problem #2
alan kay http://bit.ly/alankay-oo

13. reduce
coupling

14. Dennis van der Stelt
SpatialTemporalPlatform
coupling aspects

15. Dennis van der Stelt
TEMPORAL
Store Front End Shipping Service

16. Dennis van der Stelt
TEMPORAL
Store Front End Shipping ServiceShipping Service

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TEMPORAL
Store Front End Shipping ServiceOrder Queue

18. Dennis van der Stelt
TEMPORAL
Store Front End Shipping ServiceOrder Queue

19. Dennis van der Stelt
TEMPORAL
Store Front End Shipping ServiceOrder Queue

20. Dennis van der Stelt
Messaging
 Reduces spatial coupling
 Solves platform coupling
 Asynchronous for temporal coupling

21. Dennis van der Stelt
CAP Theorem
Eric Brewer, PODC Conference 2000

22. Dennis van der Stelt
CAP THEOREM
You can only pick 2

23. Dennis van der Stelt
CAP THEOREM
You can only pick 2
centralized
system
partition tolerantconsistencyavailability

24. Dennis van der Stelt
CAP THEOREM
You can only pick 2
centralized
system
partition tolerantconsistencyavailability

25. Dennis van der Stelt
CAP THEOREM
You can only pick 2
centralized
system
partition tolerantconsistencyavailability
distributed
system
partition tolerantconsistencyavailability

26. Dennis van der Stelt
CAP THEOREM
You can only pick 2
centralized
system
partition tolerantconsistencyavailability
distributed
system
partition tolerantconsistencyavailability
when there’s network partition,
which do you sacrifice?

27. Dennis van der Stelt
Match the business perspective

28. Dennis van der Stelt

29. Dennis van der Stelt

30. Dennis van der Stelt

31. Dennis van der Stelt
But I can’t drop consistency!

32. Dennis van der Stelt
Basically Available
BASE
What is BASE?
Soft state
Eventually consistent

33. Dennis van der Stelt
Eventual Consistency
Because 100% consistency isn’t the only option

34. Dennis van der Stelt

35. Dennis van der Stelt
Eventual Consistency

36. Dennis van der Stelt
Eventual Consistency

37. Dennis van der Stelt
Eventual Consistency
your “enterprise” is already eventual consistent with reality

38. Dennis van der Stelt
Eventual Consistency
your “enterprise” is already eventual consistent with reality

39. Dennis van der Stelt
“Allow things to be inconsistent and find ways to
compensate for mistakes, versus trying to prevent
mistakes altogether.”
EVENTUAL CONSISTENCY
Eric Brewer
VP of Infrastructure at Google, Professor at UC Berkeley

40. Dennis van der Stelt
Some ideas on messaging

41. Dennis van der Stelt
100% synchronized
that‘s eventual consistency.
Udi Dahanin 2010

42. Dennis van der Stelt
Distributed Transactions
Are they as evil as you think? Perhaps even more?

43. Dennis van der Stelt
Who uses distributed transactions?

44. Dennis van der Stelt
using (var scope = new TransactionScope()))
{
var queue = new
MessageQueue(@".Private$Customers");
var message = queue.Receive();
var con = new SqlConnection();
var cmd = new SqlCommand("update customers ...");
cmd.ExecuteNonQuery();
}
DISTRIBUTED TRANSACTIONS
Microsoft Distributed Transaction Coordinator (MSDTC)
Code

45. Dennis van der Stelt
using (var scope = new TransactionScope()))
{
var queue = new
MessageQueue(@".Private$Customers");
var message = queue.Receive();
var con = new SqlConnection();
var cmd = new SqlCommand("update customers ...");
cmd.ExecuteNonQuery();
}
DISTRIBUTED TRANSACTIONS
Microsoft Distributed Transaction Coordinator (MSDTC)
Code
MSDTC

46. Dennis van der Stelt

47. Dennis van der Stelt
Distributed Transactions

48. Dennis van der Stelt49
Idempotency
Once and only once delivery is hard!

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50. Dennis van der Stelt
IDEM POTENCY
Solving the distributed transactionissues
Sender
{0C836F44-6587-416E-B97A-5615615600D5}

51. Dennis van der Stelt
IDEM POTENCY
Solving the distributed transactionissues
Sender
{0C836F44-6587-416E-B97A-5615615600D5}

52. Dennis van der Stelt
IDEM POTENCY
Solving the distributed transactionissues
Sender
Event
Subscriber
{5EDC4993-AB01-4F17-A238-71C4521F750F}
{0C836F44-6587-416E-B97A-5615615600D5}

53. Dennis van der Stelt
IDEM POTENCY
Solving the distributed transactionissues
Sender
Event
Subscriber
{5EDC4993-AB01-4F17-A238-71C4521F750F}
{0C836F44-6587-416E-B97A-5615615600D5}

54. Dennis van der Stelt

55. Dennis van der Stelt
find me.
http://dennis.bloggingabout.net
dvdstelt@outlook.com