gatsby-plugin-launchdarkly

A simple plugin that integrates LaunchDarkly into your Gatsby site. This will allow you to use feature flags to rollout new features on your site.

Installation

Add plugin to your Gatsby site:

npm install gatsby-plugin-launchdarkly

Then in your gatsby-config.js:

// gatsby-config.js
...
  plugins: [
    ...
    {
      resolve: 'gatsby-plugin-launchdarkly',
      options: {
        clientSideID: '<your-launchdarkly-project-client-side-id>',
        options: {
          // any LaunchDarkly options you may want to implement
          bootstrap: 'localStorage', // caches flag values in localStorage
        },
      },
    },
    ...
  ]
...

This plugin uses LaunchDarkly's React SDK. The SDK requires a client-side ID which you can retrieve from your LaunchDarkly Project settings page. This client-side ID needs to be stored in your gatsby-config.js.

Behind the scenes, this plugin uses the React SDK's withLDProvider function to initialize the client. Read the documentation on Initializing the React SDK to understand other configuration options you can provide.

To learn more about the configuration options available in the plugin's options property, read the documentation on configuration in the JavaScript SDK.

Basic usage

To use a LaunchDarkly feature flag in your component, first import the LaunchDarklyContext. This plugin uses React Context to make the LaunchDarkly SDK available to your Gatbsy components.

import { useFlags } from 'gatsby-plugin-launchdarkly'

Then within your component, you can do the following:

// In a functional component...
const Header = ({ siteTitle }) => {
  // The following contains all of the client-side flags. Flag names are
  // automatically converted to snake-case which will allow you to pull out
  // one or more flags directly through destructuring.
  const flags = useFlags()

  return (
    <header
      style={{
        background: flags.someNewFeature ? 'green' : 'gray'
      }}
    >
...

Note that the LaunchDarkly SDK will automatically convert flag names to snake-case.

In addition to the useFlags hook, the useLDClient hook gives you direct access to the LaunchDarkly client:

import React from 'react';
import { useFlags, useLDClient } from 'gatsby-plugin-launchdarkly';

const HooksDemo = () => {
  const { someNewFeature } = useFlags();
  const ldClient = useLDClient();

  const onLoginSuccessful = () => ldClient.identify({ kind: 'user', key: 'user-key-123abc' });

  return (
    <div>{someNewFeature ? 'Flag on' : 'Flag off'}</div>
  );
};

export default HooksDemo;

If you're using class components, you can use the withLDConsumer higher-order component to do this instead:

import { withLDConsumer } from 'gatsby-plugin-launchdarkly'

// In your class component...
class MyComponent extends React.Component {
  render() {
    // Wrapping your class component with the withLDConsumer HOC injects the
    // flags and ldClient props into your component
    const { flags, ldClient } = this.props;

    return
      <header
        style={{
          background: flags.someNewFeature ? 'green' : 'gray'
      }}
    ...
    >
  }
}

export default withLDConsumer()(MyComponent)

The withLDConsumer HOC injects the flags and ldClient as props to your class component.

Advanced usage

This plugin assumes that the end user viewing your site is anonymous, which is likely the case for most Gatsby sites. In this situation, the LaunchDarkly SDK uniquely tracks each end user and remembers what variation of each flag was served to them. This is transparent and you don't need to do anything else to make it work this way.

If you have a logged-in end user, and can identify that end user to LaunchDarkly and then target that end user for a feature. To do this, access the LDClient object directly:

import React from 'react';
import { useFlags, useLDClient } from 'gatsby-plugin-launchdarkly';

const HooksDemo = () => {
  const { someNewFeature } = useFlags();
  const ldClient = useLDClient();

  // Calling `identify` will cause the flags to be re-evaluated for the
  // new end user that's logged in. Changes in flag values will stream in and
  // could cause your component to re-render.
  const onLoginSuccessful = (user) => ldClient.identify({
    kind: 'user',
    key: user.id,
    firstName: user.firstName,
    lastName: user.lastName,
    anonymous: false,
  });

  return (
    <div>{someNewFeature ? 'Flag on' : 'Flag off'}</div>
  );
};

export default HooksDemo;

To learn more about changing the user context, read the identify documentation for the JavaScript SDK.

Contributing

We encourage pull requests and other contributions from the community. Check out our contributing guidelines for instructions on how to contribute to this plugin.

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