let arr = [1,2,3,4,'random',6,7,8,9,10];

​

Rx.Observable.from(arr)

  .concatMap(val => {

    let attempts = 0;

​

    return Rx.Observable.of(val)

      .delay(500)

      .concatMap(val => randomFunc(val)

        .catch((err, caught) => {

          console.log('log error');

          if (attempts++ === 1) {

            return Rx.Observable.of(err);

          } else {

            return caught;

          }

        })

      );

​

  })

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

​

function randomFunc(dt) {

  return Rx.Observable.create(observer => {

    if (dt === 'random') {

      observer.error(`error received ${dt}`);

    } else {

      observer.next(dt);

      observer.complete();

    }

  });

}