feature-flags

Feature Flag Routing with Legacy/New Path SWITCH

Your app has a new checkout UI, but you only want to show it to flagged users. This workflow checks the flag status for a user (from LaunchDarkly), routes through a SWITCH to either the new feature path (v2 UI), legacy path (v1 UI), or default path, and logs the flag usage.

Workflow

userId, featureName
        |
        v
+-------------------+
| ff_check_flag     |   flagStatus: enabled/disabled, source: "launchdarkly"
+-------------------+
        |
        v
   SWITCH on flagStatus
   +--"enabled"----------+--"disabled"---------+--default-----------+
   | ff_new_feature      | ff_legacy_path      | ff_default_path    |
   | path: "new"         | path: "legacy"      | path: "default"    |
   | uiVersion: "v2"     | uiVersion: "v1"     | uiVersion: "v1"    |
   +---------------------+---------------------+--------------------+
        |
        v
   +------------------+
   | ff_log_usage     |   logged: true
   +------------------+

Workers

CheckFlagWorker -- Checks flag featureName for userId. Returns flagStatus: "enabled"/"disabled", rolloutPercent, source: "launchdarkly".

NewFeatureWorker -- Renders the new feature path. Returns path: "new", uiVersion: "v2", rendered: true.

LegacyPathWorker -- Renders the legacy path. Returns path: "legacy", uiVersion: "v1".

DefaultPathWorker -- Renders the default path. Returns path: "default", uiVersion: "v1".

LogUsageWorker -- Logs the flag usage decision. Returns logged: true.

Tests

12 unit tests cover flag checking, all three routing paths, and usage logging.

Running

See ../../RUNNING.md for setup and execution instructions.