executeTasks.java

Observable<Lease> leaseObservable = leaseService.find(timeSlice)
        .filter(lease -> lease.getOwner() == null)
        .map(lease -> lease.setOwner(owner));
Observable<Boolean> acquiredObservable = leaseObservable.flatMap(leaseService::acquire)
        .filter(acquired -> acquired);
Observable.zip(leaseObservable, acquiredObservable, ((lease, acquired) -> lease))
        .flatMap(lease -> findTasks(lease, taskType))
        .map(executeTasksSegment)
        .flatMap(this::rescheduleTask)
        .flatMap(taskContainer -> rxSession.execute(queries.deleteTasks.bind(
                taskContainer.getTaskType().getName(), timeSlice.toDate(),
                taskContainer.getSegment())))
        //.collect()
        // When all of the result sets are available and only if all tasks completed 
        // successfully do I then want to mark the lease finished