Nestjs-unleash NPM

Setup

$ npm install --save nestjs-unleash

Import the module with UnleashModule.forRoot(...) or UnleashModule.forRootAsync(...).

Synchronous configuration

Use UnleashModule.forRoot(). Available options are described in the UnleashModuleOptions interface.

@Module({
  imports: [
    UnleashModule.forRoot({
      url: "https://example.com/unleash",
      appName: "my-app-name",
      instanceId: "my-unique-instance",
    }),
  ],
})
export class MyModule {}

Asynchronous configuration

If you want to use your Unleash options dynamically, use UnleashModule.forRootAsync(). Use useFactory and inject to import your dependencies. Example using the ConfigService:

@Module({
  imports: [
    UnleashModule.forRootAsync({
      useFactory: (config: ConfigService) => ({
        url: config.get("UNLEASH_URL"),
        appName: config.get("UNLEASH_APP_NAME"),
        instanceId: config.get("UNLEASH_INSTANCE_ID"),
        refreshInterval: config.get("UNLEASH_REFRESH_INTERVAL"),
        metricsInterval: config.get("UNLEASH_METRICS_INTERVAL"),
      }),
      inject: [ConfigService],
    }),
  ],
})
export class MyModule {}

Usage in controllers or providers

In your controller use the UnleashService or the @IfEnabled(...) route decorator:

import { UnleashService } from "nestjs-unleash";

@Controller()
@UseGuards(UserGuard)
export class AppController {
  constructor(private readonly unleash: UnleashService) {}

  @Get("/")
  index(): string {
    // the UnleashService can be used in all controllerrs and provideers
    return this.unleash.isEnabled("test")
      ? "feature is active"
      : "feature is not active";
  }

  // Throws a NotFoundException if the feature is not enabled
  @IfEnabled("test")
  @Get("/foo")
  getFoo(): string {
    return "my foo";
  }
}

Custom context

The UnleashContext grants access to request related information like user ID or IP address.

In addition, the context can be dynamically enriched with further information and subsequently used in a separate strategy:

export interface MyCustomData {
  foo: string;
  bar: number;
}

@Injectable()
class SomeProvider {
  constructor(private readonly unleash: UnleashService<MyCustomData>) {}

  someMethod() {
    return this.unleash.isEnabled("someToggleName", undefined, {
      foo: "bar",
      bar: 123,
    })
      ? "feature is active"
      : "feature is not active";
  }
}

// Custom strategy with custom data:
@Injectable()
export class MyCustomStrategy implements UnleashStrategy {
  name = "MyCustomStrategy";

  isEnabled(
    _parameters: unknown,
    context: UnleashContext<MyCustomData>
  ): boolean {
    return context.customData?.foo === "bar";
  }
}

Configuration

NestJS-Unleash can be configured with the following options:

interface UnleashModuleOptions {
  /**
   * If "true", registers `UnleashModule` as a global module.
   * See: https://docs.nestjs.com/modules#global-modules
   *
   * @default true
   */
  global?: boolean;

  /**
   * URL of your Unleash server
   *
   * @example http://unleash.herokuapp.com/api/client
   */
  url: string;

  /**
   * Name of the application seen by unleash-server
   */
  appName: string;

  /**
   * Instance id for this application (typically hostname, podId or similar)
   */
  instanceId: string;

  /**
   * Additional options for the HTTP request to the Unleash server, e.g. custom
   * HTTP headers
   */
  http?: AxiosRequestConfig;

  /**
   * At which interval, in milliseconds, will this client update its feature
   * state
   */
  refreshInterval?: number;

  /**
   * At which interval, in milliseconds, will this client send metrics
   */
  metricsInterval?: number;

  /**
   * Array of custom strategies. These classes mus implement the `UnleashStrategy` interface.
   */
  strategies?: Type<UnleashStrategy>[];

  /**
   * `nestjs-unleash` sends an initial registration request to the unleash server at startup. This behavior can be disabled by this option.
   */
  disableRegistration?: boolean;

  /**
   * Some strategies depend on the user ID of the currently logged in user. The
   * user ID is expected by default in `request.user.id`. To customize this
   * behavior, a custom user ID factory can be provided.
   */
  userIdFactory?: (request: Request<{ id: string }>) => string;
}

Default strategies

This module supports the official standard activation strategies. They do not need to be activated separately and work out of the box.

Custom strategies

In order to create a custom strategy you have to create a class wich inplements the UnleashStrategy interface:

import { UnleashContext } from "nestjs-unleash";

export interface UnleashStrategy {
  /**
   * Must match the name you used to create the strategy in your Unleash
   * server UI
   */
  name: string;

  /**
   * Determines whether the feature toggle is active
   *
   * @param parameters Custom paramemters as configured in Unleash server UI
   * @param context applicaton/request context, i.e. UserID
   */
  isEnabled(parameters: unknown, context: UnleashContext): boolean;
}

Example custom strategy:

import { Injectable } from "@nestjs/common";
import { UnleashContext, UnleashStrategy } from "nestjs-unleash";

@Injectable()
export class MyCustomStrategy implements UnleashStrategy {
  name = "MyCustomStrategy";

  isEnabled(parameters: any, context: UnleashContext): boolean {
    return Math.random() < 0.5;
  }
}

Now you can use it your module setup as follows:

import { MyCustomStrategy } from "./my-custom-strategy";

@Module({
  imports: [
    UnleashModule.forRoot({
      // ...
      strategies: [MyCustomStrategy],
    }),
  ],
})
export class ApplicationModule {}