> For the complete documentation index, see [llms.txt](https://www.learnrxjs.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://www.learnrxjs.io/learn-rxjs/operators/error_handling/retrywhen.md).

# retryWhen

#### signature: `retryWhen(receives: (errors: Observable) => Observable, the: scheduler): Observable`

## Retry an observable sequence on error based on custom criteria.

### Examples

**Example 1: Trigger retry after specified duration**

( [StackBlitz](https://stackblitz.com/edit/typescript-zpbsw6?file=index.ts\&devtoolsheight=100) | [jsBin](http://jsbin.com/miduqexalo/1/edit?js,console) | [jsFiddle](https://jsfiddle.net/btroncone/49mkhsyr/) )

```js
// RxJS v6+
import { timer, interval } from 'rxjs';
import { map, tap, retryWhen, delayWhen } from 'rxjs/operators';

//emit value every 1s
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 6 seconds
      delayWhen(val => timer(val * 1000))
    )
  )
);
/*
  output:
  0
  1
  2
  3
  4
  5
  "Value 6 was too high!"
  --Wait 6 seconds then repeat
*/
const subscribe = example.subscribe(val => console.log(val));
```

**Example 2: Customizable retry with increased duration**

( [StackBlitz](https://stackblitz.com/edit/angular-cwnknr?file=app%2Frxjs-utils.ts) )

```js
import { Observable, throwError, timer } from 'rxjs';
import { mergeMap, finalize } from 'rxjs/operators';

export const genericRetryStrategy = ({
  maxRetryAttempts = 3,
  scalingDuration = 1000,
  excludedStatusCodes = []
}: {
  maxRetryAttempts?: number,
  scalingDuration?: number,
  excludedStatusCodes?: number[]
} = {}) => (attempts: Observable<any>) => {
  return attempts.pipe(
    mergeMap((error, i) => {
      const retryAttempt = i + 1;
      // if maximum number of retries have been met
      // or response is a status code we don't wish to retry, throw error
      if (
        retryAttempt > maxRetryAttempts ||
        excludedStatusCodes.find(e => e === error.status)
      ) {
        return throwError(error);
      }
      console.log(
        `Attempt ${retryAttempt}: retrying in ${retryAttempt *
          scalingDuration}ms`
      );
      // retry after 1s, 2s, etc...
      return timer(retryAttempt * scalingDuration);
    }),
    finalize(() => console.log('We are done!'))
  );
};
```

```js
import { Component, OnInit } from '@angular/core';
import { catchError, retryWhen  } from 'rxjs/operators';
import { of } from 'rxjs';
import { genericRetryStrategy } from './rxjs-utils';
import { AppService } from './app.service';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent implements OnInit  {
  constructor(private _appService: AppService) {}

  ngOnInit() {
    this._appService
      .getData(500)
      .pipe(
        retryWhen(genericRetryStrategy()),
        catchError(error => of(error))
      )
      .subscribe(console.log);

    // excluding status code, delay for logging clarity
    setTimeout(() => {
    this._appService
      .getData(500)
      .pipe(
        retryWhen(genericRetryStrategy({
          scalingDuration: 2000,
          excludedStatusCodes: [500]
        })),
        catchError(error => of(error))
      )
      .subscribe(e => console.log('Exluded code:', e.status));

    }, 8000);
  }
}
```

### Additional Resources

* [retryWhen](https://rxjs.dev/api/operators/retryWhen) 📰 - Official docs
* [Error handling operator: retry and retryWhen](https://egghead.io/lessons/rxjs-error-handling-operator-retry-and-retrywhen?course=rxjs-beyond-the-basics-operators-in-depth) 🎥 💵 - André Staltz

***

> 📁 Source Code: <https://github.com/ReactiveX/rxjs/blob/master/packages/rxjs/src/internal/operators/retryWhen.ts>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://www.learnrxjs.io/learn-rxjs/operators/error_handling/retrywhen.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.