This document summarizes key concepts in distributed systems including: The CAP theorem states that a distributed system can only guarantee two of three properties: consistency, availability, and partition tolerance. Fallacies of distributed systems include assuming the network is reliable with zero latency and infinite bandwidth, that the topology does not change, and there is a single administrator. The document discusses patterns like CQRS which separates commands from queries, event sourcing which stores an entire stream of events, and publisher/subscriber which allows applications to send messages to interested receivers without knowing their identities. It provides an overview of an agenda covering distributed system definitions, CAP theorem, design problems and solutions, and demonstrates a pub/sub pattern in

1. Design Patterns in
Distributed System
Tom Huynh
tom.huynh@thfins.com

2. Agenda
O What is distributed system?
O CAP theorem
O Fallacies of Distributed system
O Some distributed design problems and solutions
O CQRS & Event Sourcing
O Enterprise Service Bus
O Publisher/Subscriber pattern
O Demo pub/sub pattern in AngularJS SPA
O QA

3. What is Distributed System?
N1 N2
N3 N4
LAN/WAN Fiber, cable,
satellite, etc

4. CAP theorem
O Consistency
O Availability
O Partition Tolerance
1
4
2
3
Can have ONLY maximum 2 promises
at same time

5. CAP theorem - Proof
1 2

6. Fallacies of Distributed system
O Network is reliable.
O Latency is zero.
O Bandwidth in infinite.
O Network is secure.
O Topology does not change.
O There is one administrator.
O Transport cost is zero.
O Network is homogeneous.

7. CAP Theorem - Fallacies
O Network not reliable
O Latency is zero
O Bandwidth is infinite
O Network is secure
O Topology doesn’t change
O 1 administrator
O Transport cost is zero
O Network is homogeneous
O Consistency
O Availability
O Partition Tolerance

8. CAP Theorem - Fallacies

9. Agenda
O What is distributed system?
O CAP theorem
O Fallacies of Distributed system
O Some distributed design problems and solutions
O CQRS & Event Sourcing
O Enterprise Service Bus
O Publisher/Subscriber pattern
O Demo pub/sub pattern in AngularJS SPA
O QA

10. CQRS
O A pattern
O Not an architecture
O Not an architectural style
O Not a principle
O Command Query Responsibility Segregation
O Domain applicable

11. CQRS - Durability (Cont.)

12. CQRS - Scaling (Cont.)

13. Event Sourcing

14. Enterprise Service Bus

15. ESB – 2 kinds
O Decentralized
O Independently configurable
services
O Collaboration among teams
O Services make all decisions
O NServiceBus
O MassTransit
O Rhino Service Bus
O Brokered
O Single point of config
O Single governing body
O Middleware makes some
decisions
O TIBCO
O BizTalk
O Web Sphere

16. Publisher/Subscriber pattern
O Problem:
O How an application send messages to other
applications that are interested in receiving
the messages without knowing the identities
of the receivers?
O Tight coupling of sender and receiver
applications
O Solution: P/S
Sender
Receiver 2
Receiver 1

17. Publisher/Subscriber pattern
Publisher
Event 1
Event 2
SubScriber1
SubScriber1
SubScriber1

18. Pub/sub demo
O AngularJS
O Controllers
Root scope
Scope 2Scope 1
Scope 4Scope 3

19. Reference
O Farm Credit Service of America knowledge
base.
O Presentations of Michael L Perry, Dino
Esposito, Greg Young, etc.

20. Q&A