polling with rx

poll.js

    /*
     * create data STREAM
     * using RX observable timer which allows a starts with time plus interval vs,
     * flatMapLatest will always merge the last value from stream,
     * so we don't create multiple observers which are hanging in limbo
     * give me the first observable that satisfies our predicate, which then unsubscribes OR
     * unsubscribe after elapsed time of 1 minute
     */
	function pollData(dataMart) {
		return Rx.Observable.timer(2000, 15000)
	        .flatMapLatest(() => _getDMStatus(dataMart))
	        .first(response => response.data.resultset.length > 0)
	        .takeUntilWithTime(60000);
	}