reactor-core/src/main/java/reactor/core/publisher/Flux.java
public final Flux<Tuple2<Long, T>> timestamp(Scheduler scheduler) {
		Objects.requireNonNull(scheduler, "scheduler");
		return map(d -> Tuples.of(scheduler.now(TimeUnit.MILLISECONDS), d));
	}
public final Flux<Tuple2<Long, T>> timestamp(Scheduler scheduler) {
		Objects.requireNonNull(scheduler, "scheduler");
		return map(d -> Tuples.of(scheduler.now(TimeUnit.MILLISECONDS), d));
	}
Emit a {@link reactor.util.function.Tuple2} pair of T1 the current clock time in
millis (as a {@link Long} measured by the provided {@link Scheduler}) and T2
the emitted data (as a {@code T}), for each item from this {@link Flux}.

<p>
<img class="marble" src="doc-files/marbles/timestampForFlux.svg" alt="">

@param scheduler the {@link Scheduler} to read time from
@return a timestamped {@link Flux}