job_scheduling

Scheduled

• dependency: spring-boot-starter-data-jpa
• Use @Scheduled on method to define the task
• Use @EnableScheduling on main method to enable @Scheduled

@Component
public class MyScheduledTask {
 
    @Scheduled(fixedRate = 5000)
    public void runTask() {
        System.out.println("Running Scheduled Task every 5 seconds!");
    }
}
 
// -------------------------------------------------------------
 
@SpringBootApplication
@EnableScheduling
public class SchedulingTasksApplication {
 
	public static void main(String[] args) {
		SpringApplication.run(SchedulingTasksApplication.class);
	}
}

• More Options:
  • @Scheduled(fixedRate = 5000): 5ms
  • @Scheduled(fixedDelay = 5000)
  • @Scheduled(cron = "0 0 * * * ?"): hourly run task
• Considerations in distributed systems
  • multiple microservices try to run the same task, hence more than one task gets executed
    • Use distributed locks, spring boot supports:
      • Redis: spring-boot-starter-data-redis
      • Zookeeper, Hazelcast etc.
  • The timing is off because of timezone difference in microservices
  • It covers only simple cases. For more complex cases you can use distributed job scheduler like Quartz
    • Dependency: spring-boot-starter-quartz
• ref: https://medium.com/hprog99/mastering-job-scheduling-in-spring-boot-from-basics-to-best-practices-74ab938d80fa