src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final ConnectableFlowable<T> replay(final int bufferSize, final Scheduler scheduler) {
        ObjectHelper.requireNonNull(scheduler, "scheduler is null");
        return FlowableReplay.observeOn(replay(bufferSize), scheduler);
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final ConnectableFlowable<T> replay(final int bufferSize, final Scheduler scheduler) {
        ObjectHelper.requireNonNull(scheduler, "scheduler is null");
        return FlowableReplay.observeOn(replay(bufferSize), scheduler);
    }
Returns a {@link ConnectableFlowable} that shares a single subscription to the source Publisher and
replays at most {@code bufferSize} items emitted by that Publisher. A Connectable Publisher resembles
an ordinary Publisher, except that it does not begin emitting items when it is subscribed to, but only
when its {@code connect} method is called.
<p>
Note that due to concurrency requirements, {@code replay(bufferSize)} may hold strong references to more than
{@code bufferSize} source emissions.
<p>
<img width="640" height="515" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/replay.ns.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>This operator supports backpressure. Note that the upstream requests are determined by the child
Subscriber which requests the largest amount: i.e., two child Subscribers with requests of 10 and 100 will
request 100 elements from the underlying Publisher sequence.</dd>
<dt><b>Scheduler:</b></dt>
<dd>You specify which {@link Scheduler} this operator will use.</dd>
</dl>

@param bufferSize
the buffer size that limits the number of items that can be replayed
@param scheduler
the scheduler on which the Subscribers will observe the emitted items
@return a {@link ConnectableFlowable} that shares a single subscription to the source Publisher and
replays at most {@code bufferSize} items that were emitted by the Publisher
@see <a href="http://reactivex.io/documentation/operators/replay.html">ReactiveX operators documentation: Replay</a>