PollerService.ts

import { Logger, OnModuleInit } from '@nestjs/common';
import { SchedulerRegistry } from '@nestjs/schedule';

type Fulfilled = 'fulfilled';
type Rejected = 'rejected';

export interface ResolvedItem<T> {
  status: Fulfilled;
  value: T;
}

export interface RejectedItem {
  status: Rejected;
  reason: Error;
}

export type SettledItem<T> = RejectedItem | ResolvedItem<T>;

export abstract class PollerService implements OnModuleInit {
  protected logger: Logger;

  private isRunning = false;

  constructor(
    private readonly schedulerRegistry: SchedulerRegistry,
    public readonly timeout: number = 1000,
  ) {
    this.logger = new Logger(this.constructor.name);
  }

  onModuleInit() {
    const interval = setInterval(async () => {
      if (this.isRunning) {
        this.logger.log('poll() was running, skipping this interval');
        return;
      }
      try {
        this.isRunning = true;
        await this.poll();
      } catch (e) {
        if (e instanceof Error) {
          this.logger.error(e.message, e.stack);
        } else {
          this.logger.error(e.toString());
        }
      } finally {
        this.isRunning = false;
      }
    }, this.timeout);

    // Add the interval to the registry, so that it is properly cleared when the application exits.
    this.schedulerRegistry.addInterval(
      `${this.constructor.name}_syncInterval`,
      interval,
    );
  }

  abstract async poll(): Promise<void>;

  protected logRejections<T>(rejectedResults: SettledItem<T>[]) {
    for (const result of rejectedResults) {
      if (result.status === 'rejected') {
        if (result.reason instanceof Error) {
          this.logger.error(result.reason.message, result.reason.stack);
        } else {
          this.logger.error(result.reason);
        }
      }
    }
  }
}


// ****************** USAGE

@Injectable()
export class CatService extends PollerService {
  
  constructor( 
    @Inject(SchedulerRegistry)
    schedulerRegistry: SchedulerRegistry
  ){
    super(schedulerRegistry , 5000)
  }

  async poll() {
    console.log('do your recurring job every 5 seconds!')
  }

}