The document discusses event driven architecture and how it compares to service oriented architecture. It defines key concepts in event driven architecture like events, commands, autonomous components, event producers and consumers. It also provides an example of how the .NET library MassTransit implements concepts like loose coupling and publish/subscribe using messages and events.

1. EVENT DRIVEN
ARCHITECTURE
Chris Patterson
Senior Architect, RelayHealth
Chris@PhatBoyG.com

2. Agenda
Review Enterprise Application Integration
Introduce Event Driven Architecture
Define Events
.NET sample using MassTransit

3. About Me
Enterprise Software Architect
20+ years in commercial software development
12+ years at a Fortune 15 company
Proven history with distributed, real-time systems
2009 - Awarded Microsoft Visual C# MVP

4. ENTERPRISE APPLICATION
INTEGRATION

5. ENTERPRISE APPLICATION
INTEGRATION
Linking applications in an organization together to
simplify and automate business processes

6. Shared Database
Multiple applications coupled to single schema
Unclear ownership of schema
Blurred application boundaries
Linked servers (SQL to SQL RPC)
Changes often affect multiple applications

7. File Transfer

8. File Transfer
Extract - Transform - Load (ETL)

9. File Transfer
Extract - Transform - Load (ETL)
Asynchronous

10. File Transfer
Extract - Transform - Load (ETL)
Asynchronous
Simple interoperability through common formats

11. File Transfer
Extract - Transform - Load (ETL)
Asynchronous
Simple interoperability through common formats
Timeliness of data can lead to inconsistencies

12. File Transfer
Extract - Transform - Load (ETL)
Asynchronous
Simple interoperability through common formats
Timeliness of data can lead to inconsistencies
Large data volume containing unrelated data

13. File Transfer
Extract - Transform - Load (ETL)
Asynchronous
Simple interoperability through common formats
Timeliness of data can lead to inconsistencies
Large data volume containing unrelated data
Ownership of files, cleanup, versioning

14. Web Services
Explicit Contract (WSDL, DataContract)
Synchronous Operation leads to sequencing
Services must be available at invocation
Nested call stacks fragile, consume resources
Remote Procedure Call (RPC, COM, CORBA)
The network is unreliable

15. RPC Exchange
Prepare Call
Return Process

16. RPC Exchange
Prepare Call
Return Process

17. RPC Exchange
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Prepare Call
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Return Process
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18. MESSAGING

19. Message Exchange
Create Process
Send Receive

20. A-Synchronicity
Message producers are non-blocking
Fire and forget
Message consumers run in their own process
Introduces a more complex programming model

21. Minimized Coupling
Eliminates temporal coupling
Enables isolated testing of services
Reduces dependencies, increasing service reuse

22. Explicit Contract
Agreement between producer and consumer
Internal data structure remains private
Integration points remain at the application’s edge
Eliminates propagation of internal changes

23. Fault Tolerance
Messages improve recoverability
Durable message transports

24. Data Availability
Enables small, frequent transfers of related content
Distribute system load over a wider time window

25. EVENT DRIVEN
ARCHITECTURE

26. EVENT DRIVEN
ARCHITECTURE
A method of building enterprise systems in which events
flow between decoupled components and services

27. Another Architecture?
Service Oriented Event Driven
Architecture Architecture

28. Service Oriented Event Driven
Architecture Architecture
Complimentary

29. Service Oriented Event Driven
Architecture Architecture
Complimentary

30. SOA 1.0
Applications are composed using a designer
Synchronous programming model
Step-by-step (F10) flow through services
Majority of interactions are request/response

31. Event Driven Architecture
Components are assembled at run-time
Asynchronous programming model
Reactive behavior
Leverages one way, fire and forget, messaging

32. Autonomous Components
Defined by responsibility
Independent
Self-governing - makes decisions on how to react
Self-controlling - responsible for execution context
Self-contained - not part of an application

33. Event Producers
Publish events
Oblivious to consumer reactions
Unaffected by high number of consumers

34. Event Consumers
React to events
Subscribe by topic/type/selector
Asynchronous operation

35. Business Components
Logical grouping of autonomous components
Represent a complete business process

36. COMMANDS

37. Commands
Tell a component or service to do something
Initiated by an event, interaction, etc.
Use correlation for tracing, idempotence
Sent using messaging (not published)

38. Reset Password
User initiates a password reset
Password service sends reset email
User clicks link in email

39. Message Body
public class ResetPassword
{
public Guid RequestId { get; set; }
public string Username { get; set; }
}

40. Compared To...
public void ResetPassword(string username)
public class ResetPassword
{
public Guid RequestId { get; set; }
public string Username { get; set; }
}

41. EVENTS

42. Pablo’s Fiesta!
February 26, 27, 28
Austin, TX
Open Spaces
fiesta.lostechies.com

43. EVENTS

44. EVENTS
Represent a change in state

45. Self Contained
A pure and complete representation of a specific event
Time relevant, not time sensitive
Avoid references to internal data
Reduces dependencies, loosens coupling

46. Identified
Each event should have its own unique identifier

47. Related
Related events should share a common identifier
Allows event tracing (the new F11)
Assists in combining events into processes

48. Observed
Events are published as messages
Multiple components can subscribe to the same event

49. EVENT TYPES

50. Business Events
Map to real world events that occur in business
Item Added to Cart
Invoice Received
Order Shipped
Payment Requested

51. Lifecycle Events
Notifications related to the life of a state or process
Preparing Shipment / Shipment Prepared
Authorizing Payment / Payment Authorization
Complete
Session Started / Session Completed

52. Management Events
Relate events to time, ranges, limits
Timely Service Guarantee Exceeded
Your order within five minutes, or it’s free
Popular Item Notification
Items with a 5x increase in sales in an hour

54. MassTransit Key Points
Lightweight Service Bus Implementation
Loose coupling via publish/subscribe
Active Service Pattern
Supports MSMQ, RabbitMQ, ActiveMQ, TIBCO EMS
Open Source, Apache 2.0 License

55. “EVENT DRIVEN
ARCHITECTURE IS...
programming without a call stack.”
-Gregor Hohpe, Google

56. Testing
Individual components testable in isolation
Fully unit-testable using mocks and stubs
Test-first development helps improve data contract

57. Logging
Thorough logging with correlation information
Log level configurable at runtime

58. Visualization Tools
Present code-based logic in a visual form
Aid in identifying composition problems
Should be viewable on operational systems

59. GITTING
MASSTRANSIT

60. Source Repository

61. Latest Build

62. Documentation

63. FOR MORE
INFORMATION

64. Reading Material

65. Reading Material

66. Reading Material

67. Reading Material

68. Reading Material

69. Reading Material

70. Reading Material

71. CONTACT ME
Chris@PhatBoyG.com
http://PhatBoyG.LosTechies.com
twitter: @PhatBoyG
voice: text “cmp” to 50500