How to publish data in Spring webflux hierarchy?

Question

I'm developing a proxy application with spring webflux. The client sends a request to fetch first 100 records. The server 1(Spring webflux project) sends a request to server 2, and fetch first 100 records(Flux<MyData>) and then applies a filter on it(reject some data), Now server 1 has less than 100 records, So It has to send another request to fetch exactly 100 correct records. But I can't do it dynamically with Spring webflux. How can I collect 100 records dynamically?

Note: I have fetchData method that send request via WebClient erto get max records from first record.

Flux<MyData> fetchData(int first, int max){
   ...
}