retryWhen

Returns an Observable that mirrors the source Observable with the exception of an error. If the source Observable calls error, this method will emit the Throwable that caused the error to the Observable returned from notifier. If that Observable calls complete or error then this method will call complete or error on the child subscription. Otherwise this method will resubscribe to the source Observable.

retryWhen<T>(notifier: (errors: Observable<any>) => Observable<any>): MonoTypeOperatorFunction<T>

Parameters

Returns

MonoTypeOperatorFunction<T>: A function that returns an Observable that mirrors the source Observable with the exception of an error.

Description

Retry an observable sequence on error based on custom criteria.

Example

import { timer, interval } from 'rxjs';
import { map, tap, retryWhen, delayWhen } from 'rxjs/operators';

const source = interval(1000);
const example = source.pipe(
  map(val => {
    if (val > 5) {
      // error will be picked up by retryWhen
      throw val;
    }
    return val;
  }),
  retryWhen(errors =>
    errors.pipe(
      // log error message
      tap(val => console.log(`Value ${val} was too high!`)),
      // restart in 5 seconds
      delayWhen(val => timer(val * 1000))
    )
  )
);

const subscribe = example.subscribe(val => console.log(val));

// results:
//   0
//   1
//   2
//   3
//   4
//   5
//   "Value 6 was too high!"
//  --Wait 5 seconds then repeat