Feature Flags

Overview

Feature flags allow admins to toggle platform features at runtime without code changes or redeployments. The system uses OpenFeature with a flagd provider. Flag state is stored in a JSON file watched by the flagd daemon — changes propagate within 5 seconds.

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Workflow

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Flag Structure (flags.json)

{
  "flags": {
    "chat-enabled": {
      "state": "ENABLED",
      "defaultVariant": "on",
      "variants": { "on": true, "off": false }
    },
    "polls-enabled": {
      "state": "ENABLED",
      "defaultVariant": "on",
      "variants": { "on": true, "off": false }
    }
  }
}

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Step-by-Step: Toggle a Feature Flag

1. Navigate to Admin → Feature Flags (/admin/feature-flags).
2. The current flag list is shown with ON/OFF toggles.
3. Toggle the desired flag.
4. Click "Save".
5. Changes propagate within 5 seconds — no server restart required.

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Frontend Integration

The frontend uses the useFeatureFlag(flagKey) hook:

const chatEnabled = useFeatureFlag('chat-enabled');
if (!chatEnabled) return null; // Hide feature

The OpenFeatureProvider wraps the app and provides real-time flag updates.

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Application Properties

Property	Default	Description	When to Change
rcb.flagd.host	localhost	flagd server hostname	In Docker, use service name
rcb.flagd.port	8013	flagd gRPC port	Only if port conflicts
rcb.flagd.tls	false	TLS for flagd connection	Enable in production
rcb.flagd.flags-file-path	infra/flagd/flags.json	Path to flags file	Use absolute path in production

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Security Notes

• ADMIN only for viewing and editing feature flags.
• Flags file is written server-side — clients cannot directly modify the flags file.
• Disabling a feature flag removes the feature from the UI and blocks the backend API endpoint.
• No restart required — flagd watches the file and propagates changes automatically.

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QA Checklist

• Toggle flag OFF → feature hidden from all users within 5 seconds
• Toggle flag ON → feature restored within 5 seconds
• Access admin flags as non-admin → 403 Forbidden
• flagd server down → FeatureFlagService returns configured default (typically false) — fail-safe