Proper way to start new thread from service layer using spring

Question

I have a method that will be rarely called. This method collect garbage in db. I don't want to make user to wait for server response so i decided to call this method from new thread from my service layer. i'm using Spring. Service class:

@Service
@Transactional
public class UploadService {

    @Resource(name = "UploadDAO")
    private UploadDao uploadDao;

Method that i don't want to wait for

public void collectBlobGarbage(){
        Thread th = new Thread(new Runnable() {
            @Override
            public void run() {
                uploadDao.collectBlobGarbage();
            }
        });
        th.start();
    }

Is it a good way to do like this?

Answer 1

If you have Spring on your classpath you might as well use @Async

@Async
public CompletableFuture<Void> collectBlobGarbage() throws InterruptedException {
    CompletableFuture.completeFuture(uploadDao.collectBlobGarbage());
}

On your main class you need to use @EnableAsync like:

@SpringBootApplication
@EnableAsync
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

And you need an executor bean:

@Bean
public Executor asyncExecutor() {
    ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
    executor.setCorePoolSize(2);
    executor.setMaxPoolSize(2);
    executor.setQueueCapacity(500);
    executor.setThreadNamePrefix("Stackoverflow-");
    executor.initialize();
    return executor;
}

Answer 2

I think the provided solution can potentially cause a lot of threads on you server.

As an alternative, you can consider using Executors.newSingleThreadExecutor in such a way that you will get an executor service that is limited only to one thread—so you will never create more than one thread—and that is what you need.

Also as you are using Spring, consider configuring a SingleThreadExecutor instantiation as a separate bean—in such a way that you will be able to change the implementation of ExecutorService in the future.