Latest overflow strategy with size 1 or any alternatives - reactive-programming

Question

I have a gui events producer. I want to take the latest emission from it and have it processed on a different thread. While processing the emission I need gui producer emissions to be dropped. After emission is processed I want to take latest emission from gui producer.
I was trying to use onBackpressureLatest() overflow strategy but queue size is my problem. With the default 256 queue size I get the expected behaviour but must process 255 emissions which are useless for me. Decreasing queue size to 16 leaves me with 15 useless emissions. I imagine I would achieve expected behaviour with a queue size=1 but 16 is the min value.
I attach code described in the previous paragraph.
import reactor.core.publisher.Flux;
import reactor.core.scheduler.Schedulers;
import java.util.concurrent.TimeUnit;
public class App {
public static void main(String[] args) throws InterruptedException {
System.setProperty("reactor.bufferSize.small", "16");
guiEventsProducer()
.onBackpressureLatest()
.log()
.publishOn(Schedulers.single())
.subscribe(next -> {
System.out.println("Processing " + next);
try {
TimeUnit.MILLISECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Processing " + next + " done");
});
TimeUnit.SECONDS.sleep(60);
}
private static Flux<Integer> guiEventsProducer() {
return Flux.range(0, 10000);
}
}

Answer 1

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.core.scheduler.Schedulers;
import java.util.concurrent.TimeUnit;
public class App {
public static void main(String[] args) throws InterruptedException {
Flux.range(1, 10000)
.log()
.onBackpressureLatest()
.log()
.flatMap(next -> Mono.just(next).subscribeOn(Schedulers.single()), 1, 1)
.subscribe(integer -> {
System.out.println("[" + Thread.currentThread().getName() + "] result=" + integer);
try {
TimeUnit.MILLISECONDS.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
});
TimeUnit.SECONDS.sleep(60);
}
}