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Question:
I'm currently developing a web application using spring boot and I have a problem in the service layer.
I have a heavy method on my service layer. If multiple users call that same service, the applications stops due to low memory. So I want to limit the no of parallel running threads of that method only. So far I have come out with using <strong>synchronized</strong> on that method. But it will limit it to single threaded method.
@Service
public class DocumentService{
private synchronized void doReplacement(){
//should have limited no of multi threads (eg. 3)
}
private void normalMethod(){
//no restrictions
}
}
What can I do to achieve this task. Any help would be appreciated.
Answer1:You may be better of with using some sort of request throttling (i.e. number of requests per second) than with the number of threads that can execute a method simultaneously. For instance using <a href="https://dzone.com/articles/ratelimiter-discovering-google" rel="nofollow">Guava's RateLimiter</a> directly, or maybe event <a href="https://www.javacodegeeks.com/2015/07/throttle-methods-with-spring-aop-and-guava-rate-limiter.html" rel="nofollow">adding declarative support for with Spring's AOP</a>.
If you still want to go with threads, my suggestion would be to use an ExecutorService:
@Service
public class DocumentService {
private final ExecutorService executor;
@Autowired
public DocumentService(
@Value("${some.config.property}") int maxConcurrentThreads) {
// will allow only the given number of threads
executor = Executors.newFixedThreadPool(maxConcurrentThreads);
}
private void doReplacementWithLimitedConcurrency(String s, int i){
Future<?> future = executor.submit(() -> doReplacement(s, i));
future.get(); // will block until a thread picks up the task
// and finishes executing doReplacement
}
private void doReplacement(String s, int i){
}
// other methods
@PreDestroy
public void performThreadPoolCleanup() throws Exception {
executor.shutdown();
executor.awaitTermination(10, TimeUnit.SECONDS);
executor.shutdownNow();
}
}
