@aarek/nest-stan

Table of Contents

• Description
• Usage
  • Install
  • Module Initialization
• Handling Messages
• Publishing Messages
• Connection Status
• ToDo

Description

Wrapper around node-nats-streaming for NestJS.

Usage

Install

npm install --save @aarek/nest-stan

or

yarn add @aarek/nest-stan

Module initialization

@Module({
  imports: [
    NestStanModule.forRoot({
      clientId: 'client-id-test1',
      clusterId: 'test-cluster',
      stanOptions: {
        url: 'nats://localhost:4222'
      }
    })
  ]
})
export class AppModule {}

or

@Module({
  imports: [
    NestStanModule.forRootAsync({
      imports: [ConfigModule]
      inject: [ConfigService],
      useFactory: (config: ConfigService) => config.nestStanConfig(),
    }),
  ]
})
export class AppModule {}

Handling messages

Nest Stan gives you two decorators StanSubscribe and AsyncStanSubscribe. AsyncStanSubscribe will automatically acknowledge message after successful Promise resolve. Both decorators accepts subject as first argument and optional config as second argument. Config object has two keys:

• setupSubscription - function accepting node-nats-streaming SubscriptionOptions and returning SubscriptionOptions
• messageParser - function accepting String or Buffer and returning parsed object

ex.:

@StanSubscribe('subject', {
    setupSubscription: options =>
      options.setStartAtTimeDelta(30 * 1000),
    messageParser: (data) => JSON.parse(data.toString()),
  },
)
export class Subscriber implements IStanSubscriber<Message> {
  handle(message: Message, context: IMessageHandlerContext): void {
    // Handle message
    return;
  }
}

@AsyncStanSubscribe('subject', {
    setupSubscription: options =>
      options
        .setStartAtTimeDelta(30 * 1000)
        .setDurableName(AsyncSubscriber.name),
    messageParser: (data) => JSON.parse(data.toString()),
  },
)
export class AsyncSubscriber implements IStanSubscriber<Message> {
  async handle(message: Message, context: IMessageHandlerContext): Promise<void> {
    // Handle message
    return;
  }
}

Publishing messages

In order to publish messages you first need to import NestStanModule for subjects that you would like to publish to:

@Module({
  imports: [NestStanModule.forSubjects(['subject'])],
  controllers: [TestController],
  providers: [],
})
export class TestModule {}

Nest Stan provides you with InjectPublisher decorator to inject publishers:

@Controller()
class TestController {
  constructor(
    @InjectPublisher('subject') private readonly publisher: IStanPublisher<Message>,
  ) {}

  @Post()
  async publishMessage() {
    const message: Message = {
      foo: 'bar',
    }

    await this.publisher.publish(message)
  }
}

Connection status

In order to check what is the current status of connection you can use InjectConnectionStatusIndicator:

@Injectable()
export class StanConnectionIndicator extends HealthIndicator {
  constructor(
    @InjectConnectionStatusIndicator() private readonly connectionStatus: ConnectionStatusIndicator
  ) {
    super();
  }

  async isHealthy(key: string): Promise<HealthIndicatorResult> {
    const isHealthy = this.connectionStatus.getStatus() === ConnectionStatus.CONNECTED;
    const lastError = this.connectionStatus.lastError()

    return this.getStatus(key, isHealthy, { lastError });
  }
}

ToDo

• Add linter
• Add classes documentation
• Implement github actions
• Collect coverage
• Provide example app