What is a suitable alternative to forkJoin for executing parallel requests that can still complete even if one of them fails?

Question

What is a suitable alternative to forkJoin for executing parallel requests that can still complete even if one of them fails?

Is there a more robust method than forkJoin to run multiple requests in parallel and handle failed subscriptions without cancelling the rest? I need a solution that allows all requests to complete even if one fails. Here's a scenario:

const posts = this.http.get("https://myApi.com/posts?userId=1");
const albums = this.http.get("https://myApi.com/albums?userId=1");

forkJoin([posts, albums]).subscribe((result) => {
  this.combineResults(result[0], result[1]);
});

combineResults(res1, res2) {
  const message = res1.text + res2.text;
  console.log(message);
}

javascript angular typescript rxjs observable

Answer 1

Answer №1

To achieve this, utilize the forkJoin method. However, it is essential to manage errors for each individual sub Observable by using catchError to avoid interrupting the stream in case of any errors.

You can implement something similar to the code below:

// import { catchError } from 'rxjs/operators';
// import { forkJoin, of } from 'rxjs';

const posts = this.http
  .get('https://myApi.com/posts?userId=1')
  .pipe(catchError((err) => of(err)));
const albums = this.http
  .get('https://myApi.com/albums?userId=1')
  .pipe(catchError((err) => of(err)));

forkJoin([posts, albums]).subscribe((result) => {
  this.print(result[0], result[1]);
});

Answer 2

To achieve this, utilize the forkJoin method. However, it is essential to manage errors for each individual sub Observable by using catchError to avoid interrupting the stream in case of any errors.

You can implement something similar to the code below:

// import { catchError } from 'rxjs/operators';
// import { forkJoin, of } from 'rxjs';

const posts = this.http
  .get('https://myApi.com/posts?userId=1')
  .pipe(catchError((err) => of(err)));
const albums = this.http
  .get('https://myApi.com/albums?userId=1')
  .pipe(catchError((err) => of(err)));

forkJoin([posts, albums]).subscribe((result) => {
  this.print(result[0], result[1]);
});

Answer 3

Answer №2

To enhance reusability and facilitate unit testing, I propose creating a custom function called forkJoinReplaceErrors. This function takes an array of Observables and an ObservableInput as parameters. It then maps each Observable in the array to catch any errors and replace them with the provided ObservableInput.

function forkJoinReplaceErrors<T,R>(
  observables: Observable<T>[],
  ifError: ObservableInput<R>
) {
  const returnIfError = () => ifError;
  const modifiedArray = observables.map(
    observable => observable.pipe(
      catchError(returnIfError)
    )
  );
  return forkJoin(...modifiedArray);
}

This custom function can be used instead of calling forkJoin directly, making it more reusable and easier to test individual components.

Answer 4

To enhance reusability and facilitate unit testing, I propose creating a custom function called forkJoinReplaceErrors. This function takes an array of Observables and an ObservableInput as parameters. It then maps each Observable in the array to catch any errors and replace them with the provided ObservableInput.

function forkJoinReplaceErrors<T,R>(
  observables: Observable<T>[],
  ifError: ObservableInput<R>
) {
  const returnIfError = () => ifError;
  const modifiedArray = observables.map(
    observable => observable.pipe(
      catchError(returnIfError)
    )
  );
  return forkJoin(...modifiedArray);
}

This custom function can be used instead of calling forkJoin directly, making it more reusable and easier to test individual components.

What is a suitable alternative to forkJoin for executing parallel requests that can still complete even if one of them fails?

Answer №1

Answer №2

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