reactor-core/src/main/java/reactor/core/publisher/Flux.java
public static Flux<Long> interval(Duration period, Scheduler timer) {
		return onAssembly(new FluxInterval(period.toMillis(), period.toMillis(), TimeUnit.MILLISECONDS, timer));
	}
public static Flux<Long> interval(Duration period, Scheduler timer) {
		return onAssembly(new FluxInterval(period.toMillis(), period.toMillis(), TimeUnit.MILLISECONDS, timer));
	}
Create a {@link Flux} that emits long values starting with 0 and incrementing at
specified time intervals, on the specified {@link Scheduler}. If demand is not
produced in time, an onError will be signalled with an {@link Exceptions#isOverflow(Throwable) overflow}
{@code IllegalStateException} detailing the tick that couldn't be emitted.
In normal conditions, the {@link Flux} will never complete.
<p>
<img class="marble" src="doc-files/marbles/interval.svg" alt="">

@param period the period {@link Duration} between each increment
@param timer a time-capable {@link Scheduler} instance to run on

@return a new {@link Flux} emitting increasing numbers at regular intervals