LaunchDarkly Cloudflare SDK

The LaunchDarkly Cloudflare SDK is designed primarily for use in multi-user Cloudflare workers. It follows the server-side LaunchDarkly model for multi-user contexts. It is not intended for use in desktop and embedded systems applications.

This SDK is a replacement of launchdarkly-cloudflare-edge-sdk. Please consider updating your application to use this package instead.

For more information, see the complete reference guide for this SDK.

Install

npm i @launchdarkly/cloudflare-server-sdk

Then turn on the Node.js compatibility flag in your wrangler.toml. This allows the SDK to use node:events:

compatibility_flags = [ "nodejs_compat" ]

Quickstart

Initialize the ldClient with your client side sdk key and the Cloudflare KV namespace:

import { init as initLD } from '@launchdarkly/cloudflare-server-sdk';

export default {
  async fetch(request: Request, env: Bindings): Promise<Response> {
    const sdkKey = 'test-sdk-key';
    const flagKey = 'testFlag1';
    const context = { kind: 'user', key: 'test-user-key-1' };

    // init the ldClient, wait and finally evaluate
    const client = initLD(sdkKey, env.LD_KV);
    await client.waitForInitialization();
    const flagValue = await client.variation(flagKey, context, false);

    return new Response(`${flagKey}: ${flagValue}`);
  },
};

See the full example app.

Developing this SDK

# at js-core repo root
yarn && yarn build && cd packages/sdk/cloudflare

# run tests
yarn test

About LaunchDarkly

• LaunchDarkly is a continuous delivery platform that provides feature flags as a service and allows developers to iterate quickly and safely. We allow you to easily flag your features and manage them from the LaunchDarkly dashboard. With LaunchDarkly, you can:
  • Roll out a new feature to a subset of your users (like a group of users who opt-in to a beta tester group), gathering feedback and bug reports from real-world use cases.
  • Gradually roll out a feature to an increasing percentage of users, and track the effect that the feature has on key metrics (for instance, how likely is a user to complete a purchase if they have feature A versus feature B?).
  • Turn off a feature that you realize is causing performance problems in production, without needing to re-deploy, or even restart the application with a changed configuration file.
  • Grant access to certain features based on user attributes, like payment plan (eg: users on the ‘gold’ plan get access to more features than users in the ‘silver’ plan). Disable parts of your application to facilitate maintenance, without taking everything offline.
• LaunchDarkly provides feature flag SDKs for a wide variety of languages and technologies. Read our documentation for a complete list.
• Explore LaunchDarkly
  • launchdarkly.com for more information
  • docs.launchdarkly.com for our documentation and SDK reference guides
  • apidocs.launchdarkly.com for our API documentation
  • blog.launchdarkly.com for the latest product updates