private void startDurationUpdate() {
        if (subscription != null && !subscription.isUnsubscribed()) {
            subscription.unsubscribe();
        }
        subscription = getTimerObservable()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .doOnNext(new Action1<Long>() {
                    @Override
                    public void call(Long integer) {

                    }
                })
                .subscribe(new Action1<Long>() {
                    @Override
                    public void call(Long seconds) {
                        getMVPView().onDurationUpdate(seconds * 1000);
                    }
                }, new Action1<Throwable>() {
                    @Override
                    public void call(Throwable throwable) {
                        throwable.printStackTrace();
                    }
                });
        subscriptions.add(subscription);
    }

    private Observable<Long> getTimerObservable() {
        return Observable.timer(ONE_SECOND, TimeUnit.SECONDS);
//        Observable.interval(ONE_SECOND, TimeUnit.SECONDS);
//        return Observable.create(new Observable.OnSubscribe<Integer>() {
//            @Override
//            public void call(final Subscriber<? super Integer> subscriber) {
//
//                try {
//                    int counter = 0;
//                    while (!subscriber.isUnsubscribed()) {
//                        TimeUnit.SECONDS.sleep(ONE_SECOND);
//
//                        if (!subscriber.isUnsubscribed()) {
//                            subscriber.onNext(counter++);
//                        }
//                    }
//                } catch (Exception e) {
//                    if (!subscriber.isUnsubscribed()) {
//                        subscriber.onError(e);
//                    }
//                }
//            }
//        });
    }