Angular 2 Http RetryWhen

Question

I am trying to use retryWhenin HTTP calls.

It works great when trying to use like this:

return this.http.get(`${environment.apiUrl}/track/${this.user.instance._id}/${this.currentPlayer.playlist.id}/next?s=${this.playerCounter}`, options)
      .timeout(500, new TimeoutError(`Timeout trying to get next track. [instanceId=${this.user.instance._id}]`))
      .retryWhen(attempts => {
        return Observable.range(1, 3).zip(attempts, i => i).flatMap(i => 3 === i ? Observable.throw(attempts) : Observable.timer(i * 1000));
      })

It makes a maximum of 3 attempts if it receives a timeout error.

But I always have buuut, I want to make it more abstract for use in various use cases, and for this I need to check the type of error.

Only TechnicalErros will be re-reviewed.

So, I tried this without success.

.retryWhen(attempts => {
    return attempts.flatMap(error => {
      if(error instanceof TechnicalError) {
        return Observable.range(1, 3).zip(attempts, i => i).flatMap(i => 3 === i ? Observable.throw(attempts) : Observable.timer(i * 1000));
      } else {
        Observable.throw(error);
      }
    });
  })

He stops on the first try and does not execute Observable.timer(), either Observable.throw().

I am almost sure that the problem is in the first flatMap, I have already tried to use it mergeMapwithout success.

Thanks in advance!

Answer 1

RxJS 5 flatMap() mergeMap():).

, retryWhen(). , , , Observable, .

Observable attempts.flatMap, .zip(attempts, i => i). zip , , attempts.flatMap. , Observable.range(1, 3) .

, . thet:

• retryWhen() .
• attempts.flatMap() , .

, , , :

var source = Observable.create(obs => {
        obs.next(1);
        obs.next(2);
        obs.error(new TechnicalError('error from source'));
    })
    .retryWhen(attempts => {
        console.log('retryWhen callback');
        let count = 0;

        return attempts.flatMap(error => {
            if (error instanceof TechnicalError) {
                console.log(error);
                return ++count >= 3 ? Observable.throw(error) : Observable.timer(count * 1000);
            } else {
                return Observable.throw(error);
            }
        });
    })
    .subscribe(
        val => console.log(val),
        err => console.log('subscribe error', err),
        _ => console.log('complete')
    );

:

1
2
retryWhen callback
TechnicalError { msg: 'error from source' }
1
2
TechnicalError { msg: 'error from source' }
1
2
TechnicalError { msg: 'error from source' }
subscribe error TechnicalError { msg: 'error from source' }

-: https://jsbin.com/hobeda/3/edit?js,console

Answer 2

, :

  var source = Observable.create(obs => {
  obs.next(1);
  obs.next(2);
  obs.error(new TechnicalError('error from source'));
})
  .retryWhen(error => {
    console.log("Error occured, retryWhen initialized");
    return error.zip(Observable.range(1, 4), (error, i) => {
      return {
        ErrorObj: error,
        RetryCount: i
      }
    })
      .map(obj => {
        if (error instanceof TechnicalError) {
          if (obj.RetryCount > 3)
            throw obj.ErrorObj;
          //Retry every one sec for 3 times
          console.log('Retry # ' + obj.RetryCount);
          return Observable.timer(obj.RetryCount * 1000);
        }
        else {
          throw obj.ErrorObj;
        }
      }).concatAll()
  })
  .subscribe(
  val => console.log(val),
  err => console.log('subscribe error', err),
  _ => console.log('complete')
  );

, , (retryWhen callback), , zip-