ConfigDirectorDOCS
Server SDKs

Node.js

Node.js SDK
Node.js SDK

Introduction

The Node.js SDK is a server-side SDK that evaluates configs and their targeting rules. Upon initialization, it retrieves configs and targeting rules from ConfigDirector services. From that point on, it evaluates configs locally for any user context, and receives updates via server sent events (SSE) when configs are updated on the dashboard or via the admin API.

The minimum Node.js version supported is 18.0.

The minimum Deno version supported is 2.0.

The minimum Bun version supported is 1.0.

Installation

The SDK can be installed from NPM: https://www.npmjs.com/package/@configdirector/server-sdk

npm install --save @configdirector/server-sdk

Configure and initialize the client

  1. Create an instance of the client providing your server SDK key. You can retrieve a server SDK key under your project settings in the Environments & SDK Keys tab.
  2. Initialize the client to initiate its connection lifecycle.
config-director-setup.ts (Initialize the client)
import { createClient } from "@configdirector/server-sdk";

// IMPORTANT: Do not commit the server SDK key to your source code, it is a secret value.
export const client = createClient("YOUR-SERVER-SDK-KEY");
await client.initialize();
Server SDK keys are secret values. Do not commit them to your source code repository. Provide them at runtime via environment variables instead.

Additional configuration options

metadata

The metadata option allows you to provide your application's name and version. These values can be used in targeting rules conditionals. For example, if a certain feature should only be enabled starting with a certain version of your application.

config-director-setup.ts
import { createClient } from "@configdirector/server-sdk";

export const client = createClient("YOUR-SERVER-SDK-KEY", {
  metadata: {
    appName: "YOUR-APP-NAME",
    appVersion: "1.0.2",
  },
});

await client.initialize();

logger

By default, the SDK logs to the console and it is set to log warnings and errors only. You can configure a logger by either creating a ConfigDirector console logger with a different log level, or by implementing the ConfigDirectorLogger interface to provide your own logger. The interface can be used to create an adapter to another logging library.

Configure the ConfigDirector console logger to a different level:

config-director-setup.ts
import { createClient, createConsoleLogger } from "@configdirector/server-sdk";

export const client = createClient("YOUR-SERVER-SDK-KEY", {
  logger: createConsoleLogger("debug"),
});

await client.initialize();

Implement your own logger adapter:

config-director-setup.ts
import { createClient, ConfigDirectorLogger } from "@configdirector/server-sdk";

const myLogger: ConfigDirectorLogger = {
  debug: function (message: string, ...args: any): void {
    // your specific logging library implementation here
  },
  info: function (message: string, ...args: any): void {
    // your specific logging library implementation here
  },
  warn: function (message: string, ...args: any): void {
    // your specific logging library implementation here
  },
  error: function (message: string, ...args: any): void {
    // your specific logging library implementation here
  },
};

export const client = createClient("YOUR-SERVER-SDK-KEY", {
  logger: myLogger,
});

await client.initialize();

connection

The connection object accepts three optional values:

  • mode
    • The connection mode, which can be either streaming or polling. It is recommended to use the default of streaming unless you have a specific need to use polling instead.
    • Defaults to streaming
  • timeout
    • The timeout, in milliseconds, to be used in initialization. This is how long the initialize method will wait for data from ConfigDirector services before resolving its Promise. If the timeout is reached, initialize will return but the client will still be in an unready status and returning default values. The client will continue to attempt to connect and retrieve config values in the background.
    • Defaults to 3000 milliseconds
  • url
    • The base URL used to connect to ConfigDirector services
    • This should only be provided if your environment requires you to configure a proxy server in order to connect to ConfigDirector services
config-director-setup.ts
import { createClient } from "@configdirector/server-sdk";

export const client = createClient("YOUR-SERVER-SDK-KEY", {
  connection: {
    mode: "streaming",
    timeout: 2_000, // 2,000 milliseconds initialization timeout
  },
});

await client.initialize();

telemetry

Telemetry tunning. It is unlikely these settings need to be adjusted. However, in cases where your application has a large number of evaluations per second, you can adjust these settings to tune the memory footprint and frequency of telemetry requests.

Keep in mind that ConfigDirector relies on these telemetry events to provide insights and features related to the configs being used.

The telemetry object accepts the following optional values:

  • eventQueueLimit
    • The size limit of telemetry event queues. If the size limit is reached before the events are flushed to the network, older events will be dropped.
    • ConfigDirector keeps a count of dropped events. If the number of dropped events is higher than 50% of the total events, ConfigDirector will issue a notification alert in the dashboard.
    • A number between 100 and 100,000. Defaults to 5,000.
  • flushInterval
    • How often events are flushed and sent over the network in milliseconds.
    • Decrease this number if your application consistently captures a large number of events in short periods of time in order to reduce memory footprint from a large event queue.
    • Defaults to 30,000 milliseconds (30 seconds).
config-director-setup.ts
import { createClient } from "@configdirector/server-sdk";

export const client = createClient("YOUR-SERVER-SDK-KEY", {
  telemetry: {
    eventQueueLimit: 5_000,
    flushInterval: 30_000,
  },
});

await client.initialize();

Hooks

Hooks are events you can subscribe to in order to be notified of some key actions from the client. In order to subscribe to hooks you can provide a handler (or an array of handlers) in the options:

config-director-setup.ts
import { createClient } from "@configdirector/server-sdk";

export const client = createClient("YOUR-SERVER-SDK-KEY", {
  hooks: {
    configEvaluated: (event) => { console.log("Received configEvaluated:", event); },
  },
});

await client.initialize();

The following hooks are available:

  • clientReady
    • Emitted when the client is initialized. When this event is emitted it means the client has received a payload from the ConfigDirector servers and is ready to evaluate configs.
  • configsUpdated: { keys: string }
    • Emitted when a payload is received from the ConfigDirector servers with config data. It is emitted during initialization when an entire config payload is received. After initialization, it is emitted when updates are pushed from the server (or discovered via polling if that connection mode is used).
    • keys - A string array listing the config keys that were included in the payload from the server.
  • configEvaluated: { evaluation: ConfigEvaluation }
    • Emitted whenever a config is evaluated. This includes calls to getValue and evaluations delivered to listeners via watch.
    • evaluation - A ConfigEvaluation object containing the details of the evaluation:
      • key: string - The config key that was evaluated
      • value: string | number | boolean | object | ConfigEnumLikeType - The value the config evaluated to. It can be the default value provided to getValue or watch. For example, if the config was evaluated before the client was initialized.
      • valueId: string | undefined - The value ID, which is a stable hash of the value that can be used for analytics or other third parties rather than sending the value. This can be useful for large values, like a JSON config, or to avoid disclosing the values themselves to third parties. It may be undefined if the evaluation had to fall back to the default value.
      • isDefaultValue: boolean - Whether or not the evaluation fell back to the default value provided in code.
      • reason: EvaluationReason - The reason for the evaluation resolution. In the case the config successfully evaluated based on server-provided targeting rules, it will be found-match. If the evaluation had to fall back to the default value, the reason will encode why the fallback was required:
        • client-not-ready - The evaluation happened before the client finished initialization
        • config-state-missing - The requested config key was not present in the payload received from the server. This could be due to an incorrect config key, or a config that was not enabled to be available to client SDKs.
        • invalid-number - The config was requested as a number but the value received from the server could not be converted to a number.
        • invalid-boolean - The config was requested as a boolean but the value received from the server could not be converted to a boolean.
        • invalid-json - The config was requested as a JSON object but the value received from the server could not be converted to a JSON object.
        • type-mismatch - The config was requested with a data type that did not match the type of the config and no reasonable type conversion was possible.
      • context: ConfigDirectorContext | undefined - The user context that was provided to the evaluation function, or undefined if no context was provided.

Retrieve config values

Retrieving config values via getValue, and subscribe to updates via watch:

main.ts
import { client } from "./config-director-setup"

// Retrieve the current value
client.getValue("my-config-key", false);

// Subscribe to value updates
const unwatchMyKey = client.watch("my-config-key", false, (newValue) => {
  console.log("Value updated:", newValue);
});

unwatchMyKey(); // Call the unwatch function returned to remove the listener

client.unwatch("my-config-key"); // Removes all listeners for that key

Evaluate config values with a user context

getValue accepts three arguments, the first argument is the config key, the second one is the default value to be returned if the client is not yet initialized, and the third and optional argument is a user context to be used for targeting rules evaluation:

main.ts
client.getValue("my-string-config-key", "Default");

client.getValue("my-boolean-config-key", false, { id: "user-id", name: "Example User" });

client.getValue<MyEnum>("my-enum-config-key", MyEnum.SomeDefaultValue, {
  id: "user-id",
  traits: { region: "Australia" },
});

watch accepts four arguments, the first is the config key, the second argument is the default value, the third argument is a callback function that will be executed when the config value is updated, and the fourth and optional argument is a user context:

main.ts
const unwatchMyKey = client.watch(
  "my-string-config-key",
  "Default",
  (newValue) => {
    console.log("Value updated:", newValue);
  },
  { id: "user-id", name: "Example User", traits: { region: "North America" } }, // User context
);

unwatchMyKey(); // Call the unwatch function returned to remove the observer

Other useful client features

The client provides additional properties and methods.

isReady

Returns a boolean indicating if the client has been successfully initialized and is ready to evaluate configs. It is initially false and becomes true after initialize succeeds.

unwatchAll

Removes all listeners for all config keys that were previously created via watch.

dispose

Removes all listeners and observers, and closes all connections to ConfigDirector services. Only call dispose when your application shuts down and it will no longer make use of the client instance.

It is generally not needed for applications to call dispose explicitly.

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