lock2.ts

const ACQUIRE_FREQ = 1000;

function tryAcquire(currentLease?): Observable<number> {
  // attempt to acquire the lock...
}

function acquire(): Observable<number> {
  return Observable
    .interval(ACQUIRE_FREQ)
    .switchMap(v => tryAcquire())
    .filter(v => !!v)
    .take(1);
}

function hold(lease: number): Observable<boolean> {
  let leaseTimes = new Subject();
  return leaseTimes
    .switchMap(lease => Observable
      .timer(lease, -1)
      .switchMap(_ => tryAcquire(lease)))
    .map(lease => {
      if (!!lease) {
        leaseTimes.next(lease);
        return true;
      } else {
        return false;
      }
    })
    .filter(v => !v)
    .take(1);
}

function lock(): Observable<boolean> {
  return acquire()
    .switchMap(lease => Observable.concat(
      Observable.of(true),
      hold(lease)))
    .repeat();
}