Fire and forget with reactor

Question

I have a method like below in my Spring boot app.

public Flux search(SearchRequest request) {
  Flux<         


        

Answer 1

1, If your fire-and-forget is already async returning Mono/Flux

public Flux search(SearchRequest request)
{
    return searchService.search(request)
                        .collectList()
                        .doOnNext(data -> doThisAsync(data).subscribe())  // add error logging here or inside doThisAsync
                        .flatMapMany(Flux::fromIterable);
}

public Mono doThisAsync(List data) {
    //do some async/non-blocking processing here like calling WebClient
}

2, If your fire-and-forget does blocking I/O

public Flux search(SearchRequest request)
{
    return searchService.search(request)
                        .collectList()
                        .doOnNext(data -> Mono.fromRunnable(() -> doThisAsync(data))
                                              .subscribeOn(Schedulers.elastic())  // delegate to proper thread to not block main flow
                                              .subscribe())  // add error logging here or inside doThisAsync
                        .flatMapMany(Flux::fromIterable);
}

public void doThisAsync(List data) {
    //do some blocking I/O on calling thread
}

Note that in both of the above cases you lose backpressure support. If the doAsyncThis slows down for some reason, then the data producer won't care and keep producing items. This is a natural consequence of the fire-and-foget mechanism.