Spring execute a block of code after a delay

Question

I have a Spring boot controller which makes two service calls. The second call should occur only after 10 secs, after getting response from first call.

public SomeResponse myAction() {
    res = serviceCallA();
    waitFor(10) {
        serviceCallB();
    }
    return res;
}

The action doesn't have to wait for the response from serviceCallB(), to return response. Call to serviceCallB() just has to be triggered in separate thread.

Whats the best way to implement this? I need something like a ThreadPoolTaskExecutor, but with a delay.

Sample code would awesome..

Answer 1

Very straightforward answer;

SomeResponse myAction() {
  res = serviceCallA();
  serviceCallB();
  return res;
}

@Async
void serviceCallB() {
  Thread.sleep(10000) // 10 secs
  // do service B call stuff
}

More on @Async with Spring also this

Beware though, since these calls will be running these serviceCallB() logic in new threads, and if used without proper control, might cause memory issues & kill your server.

Answer 2

Use a promise, not the horrible Thread.sleep from 1999 that wastes precious system resources. Your options are CompletableFuture, RxJava Publisher constructs, Spring's own Project Reactor.

Let serviceCallA return Mono<Something> (Project Reactor). Then:

res.delayElement(Duration.ofSeconds(10))
  .doOnEach(unused -> serviceCallB())
  .block();

There's probably 6 ways to do this in each library, the above being one.