feature flag notes.md

feature flag notes

• UI

  • about:flags (or maybe about:features?)
  • similar to chrome://flags in Chromium
  • allow enabling/disabling/changing settings
    • also specifies if Mozilla has remotely changed flag and allows opting out

• Library / SDK

  • language-specific libraries (instead of libpref)
    • JS

      Chrome.utils.import("Features");
      let showFeature = Feature.variation("YOUR_FEATURE_KEY");
      if (showFeature) {
        ...
      } else {
        ...
      }
      

    • C++
    • Rust
  • declarative config (JSON file etc) that lists:
    • default state
      • (enabled, disabled, etc)
    • incompatibilities
      • some features are mutually exclusive
    • dependencies
      • some features depend on others
    • restartless
      • assume that features require restart unless otherwise specified
    • used by both UI and libraries

• References

  • https://dl.acm.org/citation.cfm?id=2901745
  • https://blog.launchdarkly.com/feature-flag-driven-development/
  • https://firebase.googleblog.com/2016/06/introducing-firebase-remote-config.html