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Feature Flag all the things!

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CO-OP

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All out

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5

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6

mec.ca

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7

safety

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X

X

X

X

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  1. monitoring & alerting
  2. test automation
  3. feature flags

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feature flag:

mechanism to dynamically control what feature is accessed or used at a given point in time

aka feature toggle

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if ( featureIsEnabled("new-feature") ) {

runNewAlgorithm()

} else {

runOldAlgorithm()

}

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Toggle feature without deploying new code

Off

On

Feature A

Feature B

Feature C

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Kill switch

Off

On

Integration with 3rd party service or newly released feature

aka ops toggle

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Dark launch

Off

On

New feature under active development

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Incremental rollout

Off

On

New feature

aka canary release

0%

100%

10% of users get the new feature first week

50% of users get the new feature next week

100% the week after

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Split test

Off

On

New feature

aka A/B test

0%

100%

Experiment to measure impact of new feature vs current state

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Release toggle

Fallback

Latest

Front-end build version

​

Latest: { "bundle": "build-588" }

Fallback: { "bundle": "build-575" }

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Feature bypass

Off

On

Recaptcha on login

Off Whitelist: Test automation agent hosts

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Flag configuration

Impressions

SDK / Agent

Flag check

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  • almost all new or modified code is behind a flag
  • adding a feature flag is the first step in any change
  • feature flags named after associated Jira ticket
  • feature flags should be disabled by default across all environments
  • enabling feature flag is independent of release; enabled by the person accountable for the feature
  • flags are tagged by type

Practices

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  • code duplication within a flag is okay
  • perform regular flag cleanup
  • test all flag conditions (enable/disable)
  • beware of flag leakage
  • do not feature flag bugs

Lessons

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  • synchronizing automated integration tests and flags
  • interdependencies between flags

Puzzles

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Thanks!

(we’re hiring!)