Graceful Shutdown & Spring Boot

I am assuming that you already know Java & Spring Boot

What is graceful shutdown?

Graceful shutdown refers to the process of stopping a software application or service in a way that allows it to complete its ongoing tasks and operations before shutting down. This approach ensures that the application finishes any pending processes, handles ongoing transactions, and releases resources properly, finished logging.

The PreDestroy annotation is used on methods as a callback notification to signal that the instance is in the process of being removed by the container. The method annotated with PreDestroy is typically used to release resources that it has been holding. 

You can check the rules for using this annotation here

      package com.dsabyte;
import jakarta.annotation.PreDestroy;
import org.springframework.stereotype.Service;
import java.time.Instant;

@Service
public class DsaByte {
  @PreDestroy
  public void preDestroy() throws InterruptedException {
    System.out.println("Cleaning Resource: " + Instant.now());
    Thread.sleep(1000); // simulate an asynchronous cleaning
    System.out.println("Cleaned Resource: " + Instant.now());
  }
}

    

We have created a class named DsaByte and a method preDestroy. We have added @Service annotation on the class level so that Spring Boot can recognise it. We have added @PreDestroy annotation on the preDestroy method so that it can be invoked by the container on any termination event received on the container level. 

When you run the above code, you'll get to the following output

      Cleaning Resource: 2023-11-16T00:31:28.863389Z
Cleaned Resource: 2023-11-16T00:31:29.868606Z