public final ParallelFlux<T> doOnSubscribe(Consumer<? super Subscription> onSubscribe){
  Objects.requireNonNull(onSubscribe,"onSubscribe");
  return doOnSignal(this,null,null,null,null,null,onSubscribe,null,null);
}

public final ParallelFlux < T > doOnSubscribe ( Consumer < ? super Subscription > onSubscribe ) { Objects . requireNonNull ( onSubscribe , "onSubscribe" ) ; return doOnSignal ( this , null , null , null , null , null , onSubscribe , null , null ) ; }
call the specified callback when a ' rail ' receives a subscription from its upstream .
