project reactor always runs in the main thread when the logs get prints - reactive-programming

Question

I am new to project reactor, while I am studying the project reactor I observed one thing, always project rector logs get print as the main tread. if reactor runs without caring the thread, how that happens? and how I get verified reactive codes run on different different threads?

Answer 1

as default Reactor runs base on the thread that you subscribed. if you subscribe from your own thread, the reactor runs base on that thread. which means that not every time the main thread.
you can run this test code to verify that. here is the flux created on the main thread. and that flux subscribed from another thread that was newly created. after running the application, see the logs. the logs will prove it. the logs have been run on the new thread that we newly created.
public void testTheThread() throws InterruptedException {
//the flux created on the main thread.
Flux<String> stringFlux = Flux
.fromArray(new String[]{"a", "b"})
.map(String::toUpperCase)
.log();
//the subscriber runs on another new thread. [my-new-thread]
Thread newThread = new Thread(() -> {
stringFlux.subscribe(s -> {
System.out.println("String is = " + s);
});
});
newThread.setName("my-new-thread");
newThread.start();
//sleep the main thread until get the data from my-new-thread
//otherwise the log will not be printed.
Thread.sleep(1000);
}
the logs will be like this.
17:04:30.867 [my-new-thread] INFO reactor.Flux.MapFuseable.1 - | onSubscribe([Fuseable] FluxMapFuseable.MapFuseableSubscriber)
17:04:30.874 [my-new-thread] INFO reactor.Flux.MapFuseable.1 - | request(unbounded)
17:04:30.874 [my-new-thread] INFO reactor.Flux.MapFuseable.1 - | onNext(A)
s = A
17:04:30.880 [my-new-thread] INFO reactor.Flux.MapFuseable.1 - | onNext(B)
s = B
17:04:30.881 [my-new-thread] INFO reactor.Flux.MapFuseable.1 - | onComplete()
Process finished with exit code 0