Confidence SDK

JavaScript implementation of the Confidence SDK, enables event tracking and feature flagging capabilities in conjunction with the OpenFeature Web SDK.

Usage

Adding the dependencies

To add the packages to your dependencies run:

yarn add @spotify-confidence/sdk

Initializing the SDK

Run the Confidence.create function to obtain a root instance of Confidence.

The SDK initialization requires an API key (clientSecret) to work. This key obtained through the Confidence console.

import { Confidence } from '@spotify-confidence/sdk';

const confidence = Confidence.create({
  clientSecret: 'my secret',
  region: 'eu', // or 'us'
  environment: 'client', // or 'backend'
  timeout: 1000,
});

Region

The region option is used to set the region for the network request to the Confidence backend. When the region is not set, the default (global) region will be used. The current regions are: eu and us.

Timeout

The timeout option is used to set the timeout for the feature flag resolve network request to the Confidence backend. When the timeout is reached, default values will be returned.

Logging

During your integration and when debugging, you can get helpful logging information by defining a logger when creating the Confidence instance. The Logger is an interface for you to implement. It's very similar to the console object, but all the logging functions (debug, info, warn etc) are optional, so you just provide the ones you are interested in. Providing console as the logger will log everything to the console. If you don't want any logging you can provide {} which is also a valid Logger implementation. If no logger is provided it will default to logging info or higher in development, but no logging in production.

import { Confidence } from '@spotify-confidence/sdk';

const myLogger = {
  warn: message => {
    console.log('Confidence warning: ', message);
  },
  error: message => {
    console.log('Confidence error: ', message);
  },
};

const confidence = Confidence.create({
  clientSecret: 'mysecret',
  region: 'eu',
  environment: 'client',
  logger: myLogger,
  timeout: 1000,
});

Setting the context

You can set the context manually by using setContext({}):

confidence.setContext({ 'pants-color': 'yellow' });

or obtain a "child instance" of Confidence with a modified context by using withContext({})

const childInstance = confidence.withContext({ 'pants-color': 'blue', 'pants-fit': 'slim' });

At this point, the context of childInstance is 'pants-color': 'blue', 'pants-fit': 'slim' while the context of confidence remains {'pants-color': 'yellow'}.

[!IMPORTANT] When using the SDK in a server environment, you should call withContext rather than setContext. This will give you a new instance scoped to the request and prevent context from leaking between requests.

Accessing flags

Flags can be accessed with two different API's.

The flag value API returns the Confidence assigned flag value or the passed in default value if no value was returned. The evaluate API returns a FlagEvaluation type that also contain information about variant, reason and possible error details.

const flag = await confidence.getFlag('tutorial-feature', {});
const flagEvaluation = await confidence.evaluateFlag('tutorial-feature', {});

Dot notation

Both the "flag value", and the "evaluate" API's support dot notation, meaning that if the Confidence flag has a property enabled or title on the flag, you can access them directly:

const enabled = await confidence.getFlag('tutorial-feature.enabled', false);
const messageEvaluation = await confidence.evaluateFlag('tutorial-feature.message', 'default message');
const message = messageEvaluation.value;

Synchronous access

In a client application (where environment is set to client), the SDK fetches and caches all flags when the context is updated. This means the flags can be accessed synchronously after that.

Caching

Flag evaluations are cached in memory on the Confidence instance with the evaluation context and flag name as a cache key. This is done to reduce network calls when evaluating multiple flags using the same context.

const confidence = Confidence.create({...});
const flag = confidence.getFlag('flag', {})
// subsequent calls to getFlag will return the same value

If you need to always fetch the latest flag values (e.g., for testing, debugging or an other use case), you can bypass the cache by always get a fresh Confidence instance (and an empty cache):

const confidence = Confidence.create({...});
const flag = confidence.withContext({}).getFlag('flag', {})

Event tracking

Use confidence.track() from any Confidence instance to track an event in Confidence. Any context data set on the instance will be appended to the tracking event.

confidence.track('event_name', { 'message-detail1': 'something interesting' });

Auto track

Confidence supports automatically tracking certain things out of the box and supports API's for you to extend that functionality.

Visitor ID (web)

Confidence can provide all flag resolves and tracking events with a browser specific identifier. We call this visitor_id.
The visitor_id is stored in a cookie named cnfdVisitorId. To add a generated visitor_id to the context, use the following:

import { visitorIdentity } from './trackers';
confidence.track(visitorIdentity());

Page Views (web)

Confidence can automatically track page views on events such as load, pushState, replaceState, popstate and hashchange. To automatically track page views, use the following:

import { Confidence, pageViews } from '@spotify-confidence/sdk';
confidence.track(pageViews());

Web vitals (web)

To automatically send tracking events containing web vitals data, use:

import { Confidence, webVitals } from '@spotify-confidence/sdk';
confidence.track(webVitals());