LaunchDarkly Server-Side SDK for Node.js - Consul integration

This library provides a Consul-backed persistence mechanism (feature store) for the LaunchDarkly server-side Node.js SDK, replacing the default in-memory feature store. It uses the consul package.

The minimum version of the LaunchDarkly Node.js SDK for use with this library is 6.0.0.

For more information, see the SDK features guide.

TypeScript API documentation is here.

Quick setup

This assumes that you have already installed the LaunchDarkly Node.js SDK.

1. Install this package with npm:

    npm install launchdarkly-node-server-sdk-consul --save

2. Require the package:

    var ConsulFeatureStore = require('launchdarkly-node-server-sdk-consul');

3. When configuring your SDK client, add the Consul feature store:

    var store = ConsulFeatureStore({ consulOptions: { host: 'your-consul-host' } });
    var config = { featureStore: store };
    var client = LaunchDarkly.init('YOUR SDK KEY', config);

4. If you are running a LaunchDarkly Relay Proxy instance, or any other process that will prepopulate Consul with feature flags from LaunchDarkly, you can use daemon mode, so that the SDK retrieves flag data only from Consul and does not communicate directly with LaunchDarkly. This is controlled by the SDK's useLdd option:

    var config = { featureStore: store, useLdd: true };
    var client = LaunchDarkly.init('YOUR SDK KEY', config);

5. If the same Consul host is being shared by SDK clients for different LaunchDarkly environments, set the prefix option to a different short string for each one to keep the keys from colliding:

    var store = ConsulFeatureStore({ consulOptions: { host: 'your-consul-host' }, prefix: 'env1' });

Caching behavior

To reduce traffic to Consul, there is an optional in-memory cache that retains the last known data for a configurable amount of time. This is on by default; to turn it off (and guarantee that the latest feature flag data will always be retrieved from Consul for every flag evaluation), configure the store as follows:

    var store = ConsulFeatureStore('YOUR TABLE NAME', { cacheTTL: 0 });

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