gistB

val cacheObservable:Observable<Data> = cacheSourceObservable
val remoteObservable:Observable<Data> = remoteSourceObservable.doOnNext { data ->
        saveDataToCache(data)
    }
val sourceObservable = Observable.concat(
    cacheObservable.onErrorResumeNext(Function<Throwable, Observable<DriverStatsEntity>> { Observable.empty() /*ignore any errors from serving data from cache*/ }),
    remoteObservable.onErrorResumeNext(Function<Throwable, Observable<DriverStatsEntity>> { throwable ->
        if (!cache.hasCachedData()) Observable.error<Throwable>(throwable) /*show error from server since there is no data to be served*/
        Observable.empty() /*ignore any errors from remote server and continue serving data from cache*/
    })
)