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

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

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.

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

Version compatibility

The LaunchDarkly OpenFeature provider for the Node.js (server-side) SDK is compatible with the OpenFeature Node.js SDK v1.x.

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

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:

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import { OpenFeature } from '@openfeature/server-sdk';
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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:

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await OpenFeature.setProviderAndWait(new LaunchDarklyProvider("YOUR_SDK_KEY"));
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const client = OpenFeature.getClient();

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:

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

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:

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

Track metrics

To associate metrics with actions customers take in your application, use the OpenFeature Tracking API. For example:

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client.track('example-event-key', context, { "optionalCustomData": "optionalCustomValue"});

To learn more, read track.

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():

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const ldClient = provider.getClient();