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OpenFeature provider for Node.js (server-side) SDK

Read time: 3 minutes
Last edited: Jun 18, 2024

Overview

This topic documents how to get started with the LaunchDarkly OpenFeature provider for the Node.js (server-side) SDK.

Provider quick links

LaunchDarkly's OpenFeature providers are open source. In addition to this reference guide, we provide source, API reference documentation, and a sample application:

ResourceLocation
OpenFeature Provider API documentationProvider API docs
GitHub repositoryopenfeature-dotnet-server
Sample applicationSample OpenFeature Node.js (server-side) provider application
Published modulenpm

Get started

The LaunchDarkly OpenFeature provider for the Node.js (server-side) SDK is intended for use in multi-user systems such as web servers and application. It is not intended for use in desktop and embedded systems applications.

The provider is compatible with Node.js version 18 and above.

Follow these instructions to start using the LaunchDarkly OpenFeature provider for the Node.js (server-side) SDK in your application.

Install the provider

First, install the LaunchDarkly and OpenFeature packages:

npm install @openfeature/server-sdk
npm install @launchdarkly/node-server-sdk
npm install @launchdarkly/openfeature-node-server

Next, import the OpenFeature and LaunchDarkly namespaces in your application code:

import { OpenFeature } from '@openfeature/server-sdk';
import { LaunchDarklyProvider } from '@launchdarkly/openfeature-node-server';

Initialize the provider

After you install and import the provider, create a single, shared instance of LaunchDarklyProvider. Specify your SDK key here to authorize your application to connect to a particular environment within LaunchDarkly.

Here's how:

await OpenFeature.setProviderAndWait(new LaunchDarklyProvider("sdk-key-123abc"));
const client = OpenFeature.getClient();
The Node.js provider uses an SDK key

The LaunchDarkly Node.js (server-side) provider uses an SDK key. Keys are specific to each project and environment. They are available from the Environments list for each project. To learn more about key types, read Keys.

Construct a context

A context is a generalized way of referring to the people, services, machines, or other resources that encounter feature flags in your product. The OpenFeature specification calls these evaluation contexts.

In the LaunchDarkly provider, contexts:

  • always have a particular context kind. If you do not specify a kind, the provider treats the context as having a "user" kind. To specify a different kind, including a multi-context, you must include a kind attribute.
  • must have a targeting key. This is optional in the OpenFeature specification, but LaunchDarkly requires a key for evaluation. You can specify this using targetingKey, as in the OpenFeature specification, or key, which is the typical LaunchDarkly identifier for the targeting key.

Here are examples of a context:

const context = {
targetingKey: "user-key-123abc", // Could also use "key" instead of "targetingKey".
};

For additional examples, read OpenFeature specific considerations in the provider GitHub repository.

Evaluate a context

To evaluate feature flags for a context, use the OpenFeature Evaluation API. For example:

const flagValue = await client.getBooleanValue("flag-key-123abc", false, context);

Access the LaunchDarkly client

You may need access to the LDClient from within the LaunchDarkly Node.js (server-side) SDK if you are working on use cases not supported by OpenFeature, such as migration flags or sending custom events.

To access the LDClient, use getClient():

const ldClient = provider.getClient();