How to stop execution of CompletableFuture after timeout? - asynchronous

Question

I have a use case where CompletableFuture is running in a separate thread pool. We use Java8, so I have implemented a timeout mechanism using ScheduledExecutorService.
CompletableFuture<Void> cf = CompletableFuture.runAsync(() -> {
// run some code asynchronously
}, executorService);
Below is the timeout mechanism I used, reference:
final CompletableFuture<Void> responseFuture = within(cf, Duration.ofSeconds(3));
responseFuture
        .thenAccept(s -> log.info("Completed Asynchronous Processing"))
        .exceptionally(throwable -> {
            log.error("Unrecoverable error", throwable);
            return null;
        });
public CompletableFuture<Void> within(CompletableFuture<Void> future, Duration duration) {
    final CompletableFuture<Void> timeout = failAfter(duration);
    return future.applyToEither(timeout, Function.identity());
}
public CompletableFuture<Void> failAfter(Duration duration) {
    final CompletableFuture<Void> promise = new CompletableFuture<>();
    scheduler.schedule(() -> {
        final TimeoutException ex = new TimeoutException("Timeout after " + duration);
        return promise.completeExceptionally(ex);
    }, duration.toMillis(), MILLISECONDS);
    return promise;
}
I am manually testing the TimeOutException by adding Thread.sleep() - After the timeout takes place, it goes in the exceptionally block and logs the error but continues the execution. I want the cf which is running in the executorService to stop processing after timeout.
My understanding is that, since cf is running in a separate threadpool it is not aware of the TimeOutException and hence continues processing. How do I achieve this? Am I approaching this right?