Nowadays developers actively talk about DevOps, build pipelines are a reality in most teams and the majority of companies have a well-defined code review and continuous integration processes. We're rapidly evolving in terms of infrastructure but we also need to talk about the mindset that we - developers - need to have as we embark on the Continuous Delivery journey. What are the techniques and good practices out there that will help us release software more frequently? Feature toggling is one of them but it’s often labeled simply as a branching strategy practice but in reality, it is at the core of enabling Continuous Delivery. This talk covers different ways to toggle/switch/flag features in and out throughout the code and explores the different kinds of feature toggling. Also, the consequences and discipline required to evolve a working software product and Continuous Delivery. Example available on github: https://github.com/Pragmateam/feature-toggles

1. Release your
software anytime
Feature Toggles

2. Alabe Duarte
@alabeduarte
Software Engineer

3. The need to
release
frequently

4. Competitive
Advantage

5. Accurate
Decisions

6. Continuous Delivery
https://electric-cloud.com/solutions/continuous-delivery/

7. Small
Releases

8. Risk
Reduction

9. Confidence

10. https://spotifylabscom.files.wordpress.com/2014/03/spotify-engineering-culture-part1.jpeg

11. Constraints....

12. The Starting
Point

13. Continuous Delivery - deployment pipeline
Commit
Stage
Acceptance
Test
Staging Production

14. Continuous Delivery != Continuous Deployment
Commit
Stage
Acceptance
Test
Staging Production
Commit
Stage
Acceptance
Test
Staging Production
Continuous Delivery
Continuous Deployment
MANUAL
AUTO

15. The software
has to work

16. Who practices CD?

17. Continuous
Delivery is a
journey

18. Tech
Process
People

19. Tech
✓ Deployment Pipeline
✓ Test coverage
✓ Automation

20. Process
✓ Communication
✓ Value driven
✓ Feedback loop

21. People
✓ Quality Mindset
✓ Team player
✓ Discipline

22. “Everybody has
responsibility for the
release process”

23. https://electric-cloud.com/solutions/continuous-delivery/

24. Feature
Toggles
(Flags/Switch/Flipping)

26. if (featureToggle.isOn) {
// display flash sale
// hide top downloaded games
} else {
// display top downloaded games
}

27. Situations where feature toggles may be applied
• White-labeled product
• Seasonal releases
• Experiment toggles
• Operational toggles
• Release toggles

28. White-labeled product

29. Seasonal Releases

30. Experimental toggles
http://growthmetricsco.com/ab-testing-your-shopping-cart-page/

31. Release toggles

32. fork
commit pull requestcommit
master
merge

33. Let’s say we have a team
A TEAM

34. fork
commit pull requestcommit
master
merge
fork
commit pull requestcommit merge

35. “Every commit must be
production ready, it may
be released to the
customer any time.”

36. fork
commit pull request
master
merge
fork
commit pull request merge
Release toggles (feature branches example)

37. Example

38. Feature #1
Heart Beating
Status

40. it('indicates that heart is beating', () => {
const dataIntervals = [
{ timestamp: '2017-03-16T06:00', signal: 1 },
{ timestamp: '2017-03-16T06:30', signal: 0 },
{ timestamp: '2017-03-16T07:00', signal: 1 },
];
expect(heartMonitor.getStatus(dataIntervals)).to.eql(HeartBeating);
});

41. it('indicates that heart has stopped beating when signal remains the same', () => {
const dataIntervals = [
{ timestamp: '2017-03-16T06:00', signal: 0 },
{ timestamp: '2017-03-16T06:30', signal: 0 },
{ timestamp: '2017-03-16T07:00', signal: 0 },
];
expect(heartMonitor.getStatus(dataIntervals)).to.eql(StoppedBeating);
});

42. class HeartMonitor {
getStatus (dataIntervals) {
const allSignals = dataIntervals.map( (data) => data.signal );
const flatLine = allSignals.every( (signal) => signal === 0 );
return flatLine ? STATUS.STOPPED_BEATING : STATUS.HEART_BEATING;
}
}

43. HeartMonitor
✓ indicates that heart has stopped beating when signal remains the same
✓ indicates that heart is beating
2 passing

44. Feature #2
Indicates Stop
Beating Status
when the line is
flat

45. Stopped Beating!

46. describe('HeartMonitor', () => {
const featureToggle = { stopBeatingWhenSignalRemainsTheSame: true };
const heartMonitor = new HeartMonitor(featureToggle);
it('indicates that heart is beating', () => {
// ...
expect(heartMonitor.getStatus(dataIntervals)).to.eql(HeartBeating);
});
it('indicates that heart has stopped beating when all signals are zero', () => {
// ...
expect(heartMonitor.getStatus(dataIntervals)).to.eql(StoppedBeating);
});
it('indicates that heart has stopped beating when signal remains the same', () => {
// ...
expect(heartMonitor.getStatus(dataIntervals)).to.eql(StoppedBeating);
});
describe('when toggle is OFF', () => {
const featureToggle = { stopBeatingWhenSignalRemainsTheSame: false };
const heartMonitor = new HeartMonitor(featureToggle);
it('indicates that heart is beating when non zero signals remain the same', () => {
// ...
expect(heartMonitor.getStatus(dataIntervals)).to.eql(HeartBeating);
});
});
// ...

47. class HeartMonitor {
constructor(featureToggle) {
this.featureToggle = featureToggle;
}
getStatus (dataIntervals) {
const flatLine = this.isFlatLine(dataIntervals);
return flatLine ? STATUS.STOPPED_BEATING : STATUS.HEART_BEATING;
}
isFlatLine (dataIntervals) {
const allSignals = dataIntervals.map( (data) => data.signal );
return allSignals.every( (signal) => {
return this.featureToggle.stopBeatingWhenSignalRemainsTheSame ?
signal === allSignals[0] : signal === 0;
});
}
}

48. HeartMonitor
✓ indicates that heart is beating
✓ indicates that heart is beating when non zero signals remain the same
✓ indicates that heart has stopped beating when signal remains the same
when toggle is OFF
✓ indicates that heart is beating when non zero signals remain the same
✓ indicates that heart has stopped beating when all signals are zero
4 passing

49. Visualising flag statuses
http://blog.launchdarkly.com/launched-flag-status-indicators/

50. Toggle recycling

53. Pragmateam/feature-toggles
github.com

54. Stability
&
Flexibility

55. open/close
principle from
S.O.L.I.D

56. Branch by Abstraction
A B
F
C

57. Branch by Abstraction
A B
F
C
F’

58. Branch by Abstraction
A B C
F’
F F

59. Branch by Abstraction
A B C
F’
F F

60. Branch by Abstraction
A B C
F’
F

61. https://www.greenbird.com/2016/09/02/microservices-hitting-the-brick-wall-once-again/
Microservices

62. Microservices - Serverless Architecture
https://softwareengineeringdaily.com/2016/08/23/serverless-architecture-with-mike-roberts/

63. Microservices - Event Driven Architecture
https://dzone.com/articles/publish-subscribe-pubsub-taken-to-the-next-level-w

64. “The art of
destroying
Software”
by Greg Young

65. Wrapping up

66. Don’t let your
team down

67. Be aware of
your boundaries

68. Small
Releases

69. Release
Frequently

70. ➔ https://continuousdelivery.com/
➔ http://continuous-delivery.co.uk/
➔ https://pragprog.com/book/mnee/release-it
➔ https://martinfowler.com/articles/feature-toggles.html
➔ https://martinfowler.com/bliki/BranchByAbstraction.html
References

71. https://goo.gl/VJEbQ3
#PragmaThanks