My April talk at boston-rb. The code examples can be found on github: https://github.com/bkaney/continuous-delivery-talk

1. Brian Kaney
brian@vermonster.com
bkaney, @bkaney
Continuous
Delivery
vermo nster

2. Here’s a Problem
Change
Time

3. Delivery Hazard
Change
The amount of risk
and uncertainty when
delivering change.
Time

4. Scheduled Releases
Change
Lots of time, lots of changes.
Larger area = larger hazard
Time

5. Scheduled Releases
• Lots of change over a lot of time
• High level of deployment hazard
• Scary, sweat, fear, etc.

6. Scheduled Releases
Deadlines

7. Scheduled Releases
Deadlines

8. Agile Manifesto
Individuals and interactions over processes and tools
Working software over comprehensive documentation
Customer collaboration over contract negotiation
Responding to change over following a plan
That is, while there is value in the items on the right, we
value the items on the left more.
http://agilemanifesto.org

9. Iterations
Sprint 4
Change Sprint 3
Sprint 2
Less time and less change
Less area = Less hazard
Sprint 1
Time

10. Iterations
• Less hazard per deploy
• “Production” deployments are routine
• Sprints are a series of micro-deadlines

11. Iterations
• Less hazard per deploy
• “Production” deployments are routine
• Sprints are a series of micro-deadlines
still has the word “dead”

12. What if...
Change
Release features individually
as soon as they are ready.
Lowest level of hazard
Time

13. Continuous Delivery
• Release features as soon as they are ready
• No prescribed deadlines
• Remove stigma from releasing to
production (because everyone has to
release often)

14. What does “Ready” Mean?
• Does it pass CI?
• Approved by Customer?
• SQA?
• Smoke Testing?

15. What does “Ready” Mean?
Depends on the team’s risk threshold...
Green CI Approval SQA Smoke Test
Faster Slower
Risker Safer

16. CD Challenges?
✓Determine Risk
• Project Management
• Technical Challenges

17. Kanban Intro
• Signboard
• Consisting of bins w/ two wells
• Pull-based

18. Signboard

19. Signboard
“Bins” arranged to
match flow

20. Signboard
WIP Limit

21. Signboard
Bifurcation
“in progress” and
“ready to pull”

22. Signboard

23. Signboard

24. Signboard

25. Signboard

26. Signboard
High Priority
Backlog Bottleneck!

27. Kanban Metrics?
• No time-boxed development
• No estimation
• Velocity is replaced by cycle time (e.g. takes
2 days to deploy a card)
• Throughput is development efficiency (e.g.
we are moving 5 cards a week)

28. Little’s Law
For a queueing system in steady state, the average
length of the queue is equivalent to the average
arrival rate multiplied by the average waiting time.
L = λW
- or -
WIP (L)
Cycle Time (W) =
Throughput (λ)

29. Decrease Cycle Time
• Less cycle time means more features out
faster!
• One way is to increase throughput
• Another is to decrease WIP

30. Decrease Cycle Time
• Less cycle time means more features out
faster!
• One way is to increase throughput
• Another is to decrease WIP
• We aim for 1.5-ish WIP cards per pair
• http://www.limitedwipsociety.org

31. Retrospective
• Weekly retrospective
• Candid review of week
• What did we do well, not so well, what
should we try to improve on

32. CD Challenges?
✓Determine Risk
✓Project Management
• Technical Challenges

33. Technical Challeges
• Code Management
• Continuous Integration
• New Feature Management
• Deployment

34. Twelve-Factor App
• http://www.12factor.net
• Codebase
• Config
• Dev/Prod Parity

35. Code Management
• Twelve-Factor - One codebase (multiple is
a system and not called an “app”)
• (Environmental) Feature Toggles
• Topic Branches

36. Continuous Integration
• One integrated branch of code (to test and
deploy)
• Consensus and experience for feature
toggles over complicated git strategies
• http://www.infoq.com/interviews/jez-
humble-martin-fowler-cd

37. Feature Toggle Challenges
• Different toggle states per bin
• “Pure”, unobtrusive feature toggles
• Database migrations?

38. Env. Feature Toggles
• Part of the config (twelve factor)
• Should be expressed as env vars
code_time.finally!

39. Dev/Prod Parity
• Minimize Difference
• Use the same stack locally that is used in
development.
• Persistence / backend services -- databases,
queues, caching servers
• Can be a challenge (e.g. Amazon AWS)

40. Brian Kaney
brian@vermonster.com
“bkaney”, @bkaney, etc.
Thanks!
vermo nster