DoWhile.java

Observable<ServiceResult> pollService() {
    final PollingState state = new PollingState();
    return Statement.doWhile(delayFetch(), state.shouldContinue())
        .doOnNext(serverResult -> serverResult.isProcessing()
                ? pollingState.increment()
                : pollingState.resultObtained())
        .filter(result -> !result.isProcessing());
}

private Observable<ServiceResult> delayFetch() {
    return Observable.timer(2, TimeUnit.SECONDS)
        .flatMap(tick -> fetchResult());
}