@weaverslab/feature-flags

A robust feature flag management service for CodeWeavers applications. This library provides a simple and efficient way to manage feature flags in your application with PostgreSQL support and real-time updates.

Features

• 🚀 Real-time feature flag updates using PostgreSQL notifications
• 💾 LRU caching for improved performance
• 🔄 Event-based updates for seamless flag changes
• 📦 TypeScript support
• 🔒 Type-safe API

Installation

npm install @weaverslab/feature-flags
# or
yarn add @weaverslab/feature-flags
# or
pnpm add @weaverslab/feature-flags

Prerequisites

• PostgreSQL database
• Node.js 14 or higher
• TypeScript (for TypeScript projects)

Configuration

1. Set up your environment variables:

   DATABASE_URL=postgresql://user:password@localhost:5432/database

2. Create the required database table:

   CREATE TABLE hub_feature_flag (
     name VARCHAR(255) PRIMARY KEY,
     enabled BOOLEAN NOT NULL DEFAULT false
   );

3. Set up the notification trigger in PostgreSQL:

   CREATE OR REPLACE FUNCTION notify_feature_flag_changes()
   RETURNS trigger AS $$
   BEGIN
     PERFORM pg_notify('feature_flag_changes', NEW.name);
     RETURN NEW;
   END;
   $$ LANGUAGE plpgsql;
   
   CREATE TRIGGER feature_flag_changes_trigger
   AFTER UPDATE ON hub_feature_flag
   FOR EACH ROW
   EXECUTE FUNCTION notify_feature_flag_changes();

Usage

import { FeatureFlagService } from '@weaverslab/feature-flags'

// Initialize the service
const featureFlags = new FeatureFlagService()

// Check if a feature is enabled
if (featureFlags.isEnabled('my-feature')) {
   // Feature is enabled
   console.log('Feature is active!')
}

// Listen for feature flag updates
featureFlags.onUpdate(() => {
   console.log('Feature flags have been updated!')
})

// Set database URL programmatically (optional)
FeatureFlagService.setDatabaseUrl('postgresql://user:password@localhost:5432/database')

API Reference

FeatureFlagService

The main class for managing feature flags.

Methods

• isEnabled(flagName: string): boolean

  • Checks if a specific feature flag is enabled
  • Returns false if the flag doesn't exist

• onUpdate(callback: () => void): void

  • Registers a callback to be called when feature flags are updated

• static setDatabaseUrl(url: string): void

  • Sets the database URL programmatically

Database Schema

The library expects a PostgreSQL table with the following structure:

CREATE TABLE hub_feature_flag (
  name VARCHAR(255) PRIMARY KEY,
  enabled BOOLEAN NOT NULL DEFAULT false
);

Performance Considerations

• The library uses an LRU cache with a maximum of 100 entries and a TTL of 60 seconds
• Real-time updates are handled through PostgreSQL notifications
• Database connections are managed efficiently using connection pooling

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT © CodeWeavers