Angular and RxJS: Ensuring continuous interval execution in the event of an error

Question

Angular and RxJS: Ensuring continuous interval execution in the event of an error

Every 10 seconds, I make a call to a RESTful service through an Angular service called "myservice" and a function called "foo."

 ngOnInit ()
 {
      interval (10000).pipe (startWith (0), mergeMap (obs =>
      this.myservice.foo ())).subscribe (resp =>
      {
        this.data = resp;
      },
      error =>
      {
        console.log ("error");
      }
      );
 }

The current setup works fine when the connection to the REST service is active. However, when the REST service is down, the interval stops as well.

How can I modify the code to keep the interval running, even when the REST service is unavailable?

angular typescript rxjs

Answer 1

Answer №1

Have you considered handling errors at the level of the "inner" observable (the one that could potentially generate errors) rather than the entire stream? Perhaps something like this:

ngOnInit () {
  interval(10000).pipe(
    startWith(0),
    mergeMap(obs => this.myservice.foo().pipe(
      catchError((error) => {
        console.log(error);
        return empty(); // or return of(error) and take appropriate action in the subscribe block
      }),
    ),
  )).subscribe(resp => this.data = resp);
}

Answer 2

Have you considered handling errors at the level of the "inner" observable (the one that could potentially generate errors) rather than the entire stream? Perhaps something like this:

ngOnInit () {
  interval(10000).pipe(
    startWith(0),
    mergeMap(obs => this.myservice.foo().pipe(
      catchError((error) => {
        console.log(error);
        return empty(); // or return of(error) and take appropriate action in the subscribe block
      }),
    ),
  )).subscribe(resp => this.data = resp);
}

Answer 3

Answer №2

This response does not directly address the specific situation at hand (I prefer to test solutions on StackBlitz before sharing any code suggestions). However, I have included a screenshot from a video by Ward Bell that discusses effective error isolation methods.

https://i.sstatic.net/2T7Qp.png

Take note of the "wrong way" and "right way" labels above the two code snippets in the screenshot.

You can view this section of the video here: https://www.youtube.com/watch?v=q--U25yPTrA&feature=youtu.be&t=1240

Answer 4

This response does not directly address the specific situation at hand (I prefer to test solutions on StackBlitz before sharing any code suggestions). However, I have included a screenshot from a video by Ward Bell that discusses effective error isolation methods.

https://i.sstatic.net/2T7Qp.png

Take note of the "wrong way" and "right way" labels above the two code snippets in the screenshot.

You can view this section of the video here: https://www.youtube.com/watch?v=q--U25yPTrA&feature=youtu.be&t=1240

Answer 5

Answer №3

To handle errors, utilize the retryWhen operator

interval(10000)
  .pipe(
    startWith(0),
    switchMap(obs => this.myservice.foo()),
    retryWhen(error => {
      return error.flatMap((error: any) => {
          if (error.status === 503) {
              return Observable.of(true);
          }
          return Observable.throw({error: 'No retry'});
      });
);

Answer 6

To handle errors, utilize the retryWhen operator

interval(10000)
  .pipe(
    startWith(0),
    switchMap(obs => this.myservice.foo()),
    retryWhen(error => {
      return error.flatMap((error: any) => {
          if (error.status === 503) {
              return Observable.of(true);
          }
          return Observable.throw({error: 'No retry'});
      });
);

Answer 7

Answer №4

Utilize flatMap to map the value to an inner observable that manages errors. Within the inner observable, include a catchError handler in the pipeline to handle errors quietly with an empty observable. See the example below:

interval(10000).pipe(
  flatMap(num => of(num).pipe(
    mergeMap(num => this.myservice.foo()),
    catchError((error) => {
      console.log ("error");
      return empty();
    })
  ))
).subscribe(resp => {
  console.log(resp)
});

Stackblitz

Answer 8

Utilize flatMap to map the value to an inner observable that manages errors. Within the inner observable, include a catchError handler in the pipeline to handle errors quietly with an empty observable. See the example below:

interval(10000).pipe(
  flatMap(num => of(num).pipe(
    mergeMap(num => this.myservice.foo()),
    catchError((error) => {
      console.log ("error");
      return empty();
    })
  ))
).subscribe(resp => {
  console.log(resp)
});

Angular and RxJS: Ensuring continuous interval execution in the event of an error

Answer №1

Answer №2

Answer №3

Answer №4

Stackblitz

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