Question
What is the best way to programmatically schedule a job in Spring with a dynamically adjustable fixed rate?
@Scheduled(fixedRateString = "${myRate}")
public void getSchedule() {
System.out.println("in scheduled job");
}
// This is not suitable for dynamic adjustments.
Answer
In Spring, if you want to schedule a job with a dynamically adjustable fixed rate, you cannot solely rely on annotations like @Scheduled since they are evaluated at startup. Instead, we can leverage the Spring Task Scheduler programmatically for achieving this flexibility. This approach allows you to change the scheduling parameters at runtime without needing to redeploy the application.
import org.springframework.scheduling.TaskScheduler;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
import org.springframework.stereotype.Component;
@Component
@EnableScheduling
public class SchedulerService {
private final TaskScheduler taskScheduler;
private ScheduledFuture<?> scheduledFuture;
public SchedulerService() {
this.taskScheduler = new ThreadPoolTaskScheduler();
((ThreadPoolTaskScheduler) taskScheduler).initialize();
}
public void startScheduling(long rate) {
stopScheduling(); // Stops any existing task before starting a new one
scheduledFuture = taskScheduler.scheduleAtFixedRate(() -> {
System.out.println("in scheduled job");
}, rate);
}
public void stopScheduling() {
if (scheduledFuture != null) {
scheduledFuture.cancel(false);
}
}
} // Example method to start the task programmatically.
Causes
- Using the @Scheduled annotation restricts flexibility for dynamic scheduling.
- Property-based scheduling does not allow changes at runtime.
Solutions
- Use the Spring `ScheduledExecutorService` for customized scheduling.
- Implement a `Runnable` task and schedule it with adjustable parameters.
Common Mistakes
Mistake: Using @Scheduled with static rates prevents dynamic adjustments.
Solution: Use a programmatic approach with ScheduledExecutorService.
Mistake: Not stopping existing scheduled tasks before starting new ones.
Solution: Ensure to cancel existing tasks to avoid concurrency issues.
Helpers
- Spring scheduling
- dynamic fixed rate
- Spring Task Scheduler
- programmatically schedule Spring jobs
- @Scheduled annotation limitations