SEE UPDATED VERSION: https://www.slideshare.net/gsluthra/recipes-for-continuous-delivery-thoughtworks-geeknight In this presentation, I cover techniques and best practices for CD. The idea is to explain the rationale behind CI, Branching, Feature Branches, Trunk Based Development, Feature Toggles, and related techniques that aid in faster delivery. Special Thanks to Luminaries like Martin Fowler, Paul Hammant, Jez Humble, Pete Hodgson and many ThoughtWorkers for their material. I have mentioned links to them on respective slides.

1. RECIPES FOR
CONTINUOUS DELIVERY
Gurpreet Luthra - Lead Consultant, ThoughtWorks
1
_zenx_

2. TOPICS
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• Continuous Integration (CI)
• Continuous Deployment (CD?) / Continuous Delivery (CD)
• Phoenix Servers
• Branching for Release
• Feature Branches
• Trunk Based Development
• Pull Request Model
• Toggles
• Branch by Abstraction & Strangulation

3. 3
CONTINUOUS INTEGRATION

4. 3
CONTINUOUS INTEGRATION
https://www.thoughtworks.com/continuous-integration

5. 4

6. 4
https://www.thoughtworks.com/continuous-integration

7. THE PRACTICES
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• Maintain a single source repository
• Automate the build
• Make your build self-testing
• Every commit should build on an integration machine
• Keep the build fast
• Test in a clone of the production environment
• Make it easy for anyone to get the latest executable
• Everyone can see what’s happening
• Automate deployment

8. HOW TO DO IT
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• Developers check out code into their private workspaces.
• When done, commit the changes to the repository.
• The CI server monitors the repository and checks out
changes when they occur.
• The CI server builds the system and runs unit and
integration tests.
• The CI server releases deployable artefacts for testing.
• The CI server assigns a build label to the version of the
code it just built.
• The CI server informs the team of the successful build.

9. TEAM RESPONSIBILITIES
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• Check in frequently
• Don’t check in broken code
• Don’t check in untested code
• Don’t check in when the build is broken
• Don’t go home after checking in until the system builds

10. THE UNDERLYING ASSUMPTION
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• The quality and impact of your CI processes are solely
dependant on the quality of your TESTS.
• If you don’t write good quality tests, with reasonable
coverage, all the CI infrastructure in the world can’t
protect you.

11. THE UNDERLYING ASSUMPTION
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• The quality and impact of your CI processes are solely
dependant on the quality of your TESTS.
• If you don’t write good quality tests, with reasonable
coverage, all the CI infrastructure in the world can’t
protect you.
WRITE GOOD TESTS!!!

12. CONTINUOUS DELIVERY
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Image from: http://blog.crisp.se/2013/02/05/yassalsundman/continuous-delivery-vs-continuous-deployment

13. CONTINUOUS DELIVERY
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Image from: http://blog.crisp.se/2013/02/05/yassalsundman/continuous-delivery-vs-continuous-deployment

14. PHOENIX SERVERS
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• Configuration Drift
• Snowflake servers
• No SSH servers
• Immutable Servers
• Phoenix servers
PLEASE READ: http://martinfowler.com/bliki/PhoenixServer.html
and http://martinfowler.com/bliki/ImmutableServer.html

15. VM (OR CONTAINERS) AS BUILD AGENTS
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SLIDE COPIED FROM: http://decks.eric.pe/pantheon-ci/#9

16. BUILD AGENTS AS PHONEIX SERVERS
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17. BUILD AGENTS AS PHONEIX SERVERS
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18. BUILD AGENTS AS PHONEIX SERVERS
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19. PHOENIX SERVERS
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20. PHOENIX SERVERS
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Diagram and full article at: https://boxfuse.com/blog/no-ssh

21. BRANCHING FOR RELEASE
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Image from: http://paulhammant.com/blog/branch_by_abstraction.html

22. BRANCHING FOR RELEASE
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FOR EACH RELEASE HOW MUCH EFFORT DO YOU PUT
IN TO CREATE CI PIPELINES ?

23. FEATURES BRANCHES
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Image from: http://blogs.riskotech.com/riskfactor/post/An-Alternate-Branching-Strategy.aspx

24. THE REALITY OF FEATURE BRANCHES
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Image from: http://paulhammant.com/blog/branch_by_abstraction.html

25. BRANCH TRACKING
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26. A GIT BRANCHING MODEL
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27. A GIT BRANCHING MODEL
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Image from: http://nvie.com/posts/a-successful-git-branching-model/

28. TRUNK BASED DEVELOPMENT
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• Trunk Based Development (TBD) is where all developers
(for a particular deployable unit) commit to one shared
branch under source-control called “trunk” or “mainline”.
• Branches are made only for a release in the shared
repository.
• Trunk always stays GREEN.
• Developers never break the build with any commit.
Alternatively, broken commits are immediately rolled
back. Or such commits may be blocked before being
merged with the trunk.
• Developers don’t work in ISOLATION, in their “happy
branches” for days. Update your workstation daily!

29. TRUNK BASED DEVELOPMENT
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Image from: http://paulhammant.com/2014/01/08/googles-vs-facebooks-trunk-based-development/

30. PULL REQUEST MODEL
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master
fork’s master
Fork
branch
feature-1 branch
branch
Raise pull request
Update to latest
Raise pull request
feature-2 branch
review + no mergereview + merge
review + merge

31. PULL REQUEST MODEL
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Image from: code.tutsplus.com/tutorials/travis-ci-what-why-how--net-34771

32. TRUNK BASED DEVELOPMENT
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Feature branching is a poor man’s modular architecture,
instead of building systems with the ability to easily swap in
and out features at runtime/deploy time, you’re coupling
yourself to the source control providing this mechanism
through manual merging.
- Daniel Bodart
Mentioned By
http://martinfowler.com/bliki/FeatureBranch.html
AND
http://sethgoings.com/feature-branching

33. TRUNK BASED DEVELOPMENT
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OK. I WILL TRY & AVOID FEATURE BRANCHES. HOW DO
I ENSURE I CAN DEVELOP BIG FEATURES, YET, KEEP
TRUNK GREEN & STABLE?

34. FEATURE TOGGLES
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• Release Toggles
• Business Toggles
• Build Time Toggles
• Run Time Toggles
• A/B Testing
• Canary Releases
• Rollback in production
PLEASE READ
http://martinfowler.com/articles/feature-toggles.html
Pete Hodgson

35. EXAMPLES
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• Introduce a simple search box on your home page
• Add a new feature to favorite products + My Favorite page
(client side only, nothing on server side)
• Upgrade from Java7 and Java 8 (slowly across servers)
• Improve your search algo (in case it returns no results, then
apply, distance algo)
• Change upload logic for images (earlier each image was
assigned a thread). New logic: Create a queue, perform a de-
dup, assign to a thread, batch size of 5, upload.
• Add FB Integration (FB Like + Count -- pulled from FB)
• Change JS code to use Require.JS for dependencies
• Introduce dependency injection via Spring/Guice
• Change Repository code from Hibernate to Toplink

36. IMPLEMENTATION
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• Simple IF statement (top most layer)
• DB / File / Code based configuration
• Polymorphic Substitution / Injection
• Plugin Based / Dynamic JAR Lookup / Discovery
• Hook based extensions
• Toggle Based Frameworks (Use Google!)
• Many more..

37. BRANCH BY ABSTRACTION
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38. BRANCH BY ABSTRACTION
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39. BRANCH BY ABSTRACTION
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40. BRANCH BY ABSTRACTION
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41. BRANCH BY ABSTRACTION
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IMAGES AND ARTICLE:
http://martinfowler.com/bliki/BranchByAbstraction.html

42. BRANCH BY ABSTRACTION
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• Technique for making large scale changes in a gradual way
• Use an abstraction layer to allow multiple implementations to
co-exist
• Use the notion of one abstraction and multiple
implementations to perform the migration from one
implementation to the other
• Ensure that the system builds and runs correctly at all times
YES. IT’S JUST GOOD OBJECT ORIENTED DESIGN.

43. STRANGULATION PATTERN
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• Slowly strangulate one system for another.
• Slow strangulate one model / one component for another.
PLEASE READ
http://agilefromthegroundup.blogspot.in/2011/03/strangulation-pattern-of-choice-for.html
IMAGE FROM:
https://dzone.com/articles/legacy-java-applications

44. WHERE TO NEXT?
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• Write good tests. Make them blazing fast. Depend on them!
• Commit & push frequently to Trunk. Build should be ALWAYS
Green.
• Every morning, pull latest code to your machine.
• Consider using Immutable Servers / Phoenix Servers.
• Figure out creative ways to keep software ready-for-release.
• Plan for rollbacks, or for functionality switches.
• Consider strategies like Toggles or Branch-by-Abstraction.
• Don’t work in ISOLATED branches.
• Be thoughtful in your code… and in your design.

45. WHERE TO NEXT?
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• Write good tests. Make them blazing fast. Depend on them!
• Commit & push frequently to Trunk. Build should be ALWAYS
Green.
• Every morning, pull latest code to your machine.
• Consider using Immutable Servers / Phoenix Servers.
• Figure out creative ways to keep software ready-for-release.
• Plan for rollbacks, or for functionality switches.
• Consider strategies like Toggles or Branch-by-Abstraction.
• Don’t work in ISOLATED branches.
• Be thoughtful in your code… and in your design.
AIM FOR Continuous Delivery!

46. THANK YOU
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Gurpreet Luthra - Lead Consultant, ThoughtWorks
_zenx_
Thank you for all your thoughts on CI & CD by
Martin Fowler, Paul Hammant, Jez Humble, Pete Hodgson, ThoughtWorkers
and
of course Calvin & Hobbes