Multithread

By default if there is no delay, it will be running on single thread.

However we can specify publishOn() or .parallel().runOn() to specify the thread that we want

For example

flux.parallel().runOn(Schedulers.parallel()).subscribe(s -> {  
  System.out.println("s = " + s);  
  System.out.println("In thread s = " + Thread.currentThread().getId());  
});

Or

flux.publishOn(Schedulers.parallel()).subscribe(s -> {  
  System.out.println("s = " + s);  
  System.out.println("In thread s = " + Thread.currentThread().getId());  
});