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

This library provides a DynamoDB-backed persistence mechanism (feature store) for the LaunchDarkly Node.js SDK, replacing the default in-memory feature store. It uses the AWS SDK for Node.js.

The minimum version of the LaunchDarkly Node.js SDK for use with this library is 5.8.1.

For more information, see also: Using a persistent feature store.

TypeScript API documentation is here.

Quick setup

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

1. In DynamoDB, create a table which has the following schema: a partition key called "namespace" and a sort key called "key", both with a string type. The LaunchDarkly library does not create the table automatically, because it has no way of knowing what additional properties (such as permissions and throughput) you would want it to have.

2. Install this package with npm:

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

3. If your application does not already have its own dependency on the aws-sdk package, and if it will not be running in AWS Lambda, add aws-sdk as well:

    npm install aws-sdk --save
   

   The launchdarkly-node-server-sdk-dynamodb package does not provide aws-sdk as a transitive dependency, because it is provided automatically by the Lambda runtime and this would unnecessarily increase the size of applications deployed in Lambda. Therefore, if you are not using Lambda you need to provide aws-sdk separately.

4. Require the package:

    var DynamoDBFeatureStore = require('launchdarkly-node-server-sdk-dynamodb');
   

5. When configuring your SDK client, add the DynamoDB feature store:

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

   By default, the DynamoDB client will try to get your AWS credentials and region name from environment variables and/or local configuration files, as described in the AWS SDK documentation. You can also specify any valid DynamoDB client options like this:

    var dynamoDBOptions = { accessKeyId: 'YOUR KEY', secretAccessKey: 'YOUR SECRET' };
    var store = DynamoDBFeatureStore('YOUR TABLE NAME', { clientOptions: dynamoDBOptions });
   

   Alternatively, if you already have a fully configured DynamoDB client object, you can tell LaunchDarkly to use that:

    var store = DynamoDBFeatureStore('YOUR TABLE NAME', { dynamoDBClient: myDynamoDBClientInstance });
   

6. If you are running a LaunchDarkly Relay Proxy instance, or any other process that will prepopulate the DynamoDB table with feature flags from LaunchDarkly, you can use daemon mode, so that the SDK retrieves flag data only from DynamoDB 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);
   

7. If the same DynamoDB table 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 = DynamoDBFeatureStore('YOUR TABLE NAME', { prefix: 'env1' });
   

Caching behavior

To reduce traffic to DynamoDB, 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 DynamoDB for every flag evaluation), configure the store as follows:

    var store = DynamoDBFeatureStore('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. Check out 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
  • Feature Flagging Guide for best practices and strategies