Video and slides synchronized, mp3 and slide download available at http://bit.ly/12bfeX3. Graham Brooks explores internal measurements used in a continuous delivery feedback mechanism in order to improve a system's design. Filmed at qconnewyork.com. Graham Brooks is a software developer. When not consulting with clients he works on open source projects, learns new programming languages and reads. He has been a practicing developer, architect and team lead since the early 80s when he first became interested in programming.

1. Feedback based
evolutionary design
Graham Brooks
gbrooks@thoughtworks.com
Twitter: @grahamcbrooks
Blog: http://www.grahambrooks.com/blog

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Watch the video with slide
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http://www.infoq.com/presentations
/feedback-continuous-delivery

3. Presented at QCon New York
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Purpose of QCon
- to empower software development by facilitating the spread of
knowledge and innovation
Strategy
- practitioner-driven conference designed for YOU: influencers of
change and innovation in your teams
- speakers and topics driving the evolution and innovation
- connecting and catalyzing the influencers and innovators
Highlights
- attended by more than 12,000 delegates since 2007
- held in 9 cities worldwide

4. Design

5. 90’s
UML and 4GL
is Design

6. Design Build Test

7. Design Build Test
Requirement Specifications
Architecture
Design
Detailed design
Modeling
Write
Code

8. Design!

9. Design TestDesign Design
Build Build Build

10. If code is the design
• Automated
• Fast
• Synchronized
• Measurable

11. Design Design Design Design
Build
Test
Build
Test
Build
Test
Build
Test

12. Design Design Design Design
Build
Test
Release
Build
Test
Release
Build
Test
Release
Build
Tes
R

13. Design Design Design Design
Time
Design Fragmentation

14. Report Management
Data Store
Customers
Analysts
CMS
Web Application
CMIS Store
Sales F
For Ide
ManageHTML Reports
Immutable Store
Data cleaning & View
Generation
Data
Data Administration

15. Just one more thing...

16. Design Design Design Design
Empirical Design

17. Feedback

18. Evaluating a build is
evaluating the design
The trick is knowing what to evaluate

19. Feedback

20. Feedback system
A B

21. Feedback system
A BComponent

22. Feedback system
A BComponent
BComponent
Component

23. Feedback system
A BComponent
BComponent
Component
√
7,000 request/s

24. Reinforcing feedback
• Positive Feedback
• Green Tests
• Simpler - Lower complexity
• Faster - Lower latency
• Cleaner - Lower coupling

25. Disruptive feedback
• Negative Feedback
• Failed Tests
• Complex - higher complexity
• Slower - Higher latency
• Dirty - High coupling
Why??!!

26. Good Feedback
• Fast
• Deterministic
• In Context
• Value degrades
• Small in number

27. • Static analysis
• Operational analysis
• Runtime

28. Automated functional
tests are
not enough

29. Measurements are
contextual

30. Internal Web App Algorithmic TradingPerformance
Monthly reports Social NetworkingAvailability
Single server Distributed devicesConsistency
Rebuild StartupResponsive

31. Too much feedback

33. Judgement
Total toxicity 7524
Bad
!!!!!

34. Antipatterns
• Test cases with no asserts to improve
coverage
• Classes with shared responsibilities to
reduce class/method length
• Averages - fixing problems makes the
average worse

36. • Javascript load order in the browser
significantly impacting user perceptions
Competing business drivers

37. • Javascript load order in the browser
significantly impacting user perceptions
• Advertising stakeholder - wants display
advertising to always load and load early
Competing business drivers

38. • Javascript load order in the browser
significantly impacting user perceptions
• Advertising stakeholder - wants display
advertising to always load and load early
• Business owner wants content to always
load and advertising to be optimistic
Competing business drivers

39. Rework
Competing business drivers

40. Acceptance Test
Competing business drivers

41. access.log

42. Design
Countermeasures
• Double over the wire encryption
• Encapsulation
• Microtype sensitive information
• Obfuscation
• String - byte or encrypted

43. Operational Change
100 1 2 3 4 5 6 7 8 9
10
0
1
2
3
4
5
6
7
8
9
Day
Latency100ms

45. Lifesaver

46. Incorporating Feedback
• Continuous (Integration) Delivery pipeline
• Static code analysis
• Load evaluations
• System Interaction analysis
• Security analysis

47. Humans

48. ThankYou
Graham Brooks
gbrooks@thoughtworks.com
Twitter: @grahamcbrooks
Blog: http://www.grahambrooks.com/blog
ReBar

49. • http://www.developerdotstar.com/mag/
articles/reeves_design.html