NestJS HttpService 同时调用多个端点

Question

I am using NestJS HttpModule to make GET request for one end point. The code is somewhat like this:

@Injectable
export class AnimalService {
  constructor(private httpService: HttpService){}
  
  getAnimalData(variant: string): Observable<AxiosResponse<Animal>> {
    return this.httpService
      .get(`http://animal.test/${variant}`)
      .pipe(map((response) => response.data));
  }
}

And now I want to create a method which calls multiple endpoints simultaneously.

getAllAnimalsData() {
  // const variants = ['birds', 'cats', 'dogs'];
  // call 
  //   http://animal.test/birds
  //   http://animal.test/cats
  //   http://animal.test/dogs
  // simultaneously
  // and process the response data
}

How can I achieve this using NestJS HttpModule ? How can I process every result? How can I handle if there is a partial error (eg 1 of 3 request has an error)?

Answer 1

If you want to make multiple http requests simultaneously you can use the RxJS forkJoin operator. I also added a catchError to each Observable so that any errors will be passed to the subscribe callback. The subscribe callback triggers when all Observables are finished.

getAllAnimalsData() {
  const variants = ['birds', 'cats', 'dogs'];
  
  forkJoin(
    variants.map(v => 
      getAnimalData(v).pipe(catchError(e => of(e)))
    )
  )
  .subscribe(([r1, r2, r3]) => /* ... */)
}