src/main/java/io/reactivex/parallel/ParallelFlowable.java
@CheckReturnValue
    @NonNull
    public final ParallelFlowable<T> doOnRequest(@NonNull LongConsumer onRequest) {
        ObjectHelper.requireNonNull(onRequest, "onRequest is null");
        return RxJavaPlugins.onAssembly(new ParallelPeek<T>(this,
                Functions.emptyConsumer(),
                Functions.emptyConsumer(),
                Functions.emptyConsumer(),
                Functions.EMPTY_ACTION,
                Functions.EMPTY_ACTION,
                Functions.emptyConsumer(),
                onRequest,
                Functions.EMPTY_ACTION
                ));
    }
@CheckReturnValue
    @NonNull
    public final ParallelFlowable<T> doOnRequest(@NonNull LongConsumer onRequest) {
        ObjectHelper.requireNonNull(onRequest, "onRequest is null");
        return RxJavaPlugins.onAssembly(new ParallelPeek<T>(this,
                Functions.emptyConsumer(),
                Functions.emptyConsumer(),
                Functions.emptyConsumer(),
                Functions.EMPTY_ACTION,
                Functions.EMPTY_ACTION,
                Functions.emptyConsumer(),
                onRequest,
                Functions.EMPTY_ACTION
                ));
    }
@ CheckReturnValue @ NonNull public final ParallelFlowable < T > doOnRequest ( @ NonNull LongConsumer onRequest ) { ObjectHelper . requireNonNull ( onRequest , "onRequest is null" ) ; return RxJavaPlugins . onAssembly ( new ParallelPeek < T > ( this , Functions . emptyConsumer ( ) , Functions . emptyConsumer ( ) , Functions . emptyConsumer ( ) , Functions . EMPTY_ACTION , Functions . EMPTY_ACTION , Functions . emptyConsumer ( ) , onRequest , Functions . EMPTY_ACTION ) ) ; }
Call the specified consumer with the request amount if any rail receives a request.

@param onRequest the callback
@return the new ParallelFlowable instance
Call the specified consumer with the request amount if any rail receives a request .