Multiple Spring @Scheduled tasks simultaneously

Question

I'm trying to run multiple scheduled tasks at the same time on spring boot, but in practice they run queuing (one after the other, not parallel)

This is my simple service:

import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Service;

@Service
public class MyScheduleDemo {

    @Scheduled(fixedDelay = 5000, initialDelay = 1000)
    public void taskA() throws InterruptedException {
        System.out.println("[A] Starting new cycle of scheduled task");

        // Simulate an operation that took 5 seconds.
        long startTime = System.currentTimeMillis();
        while (System.currentTimeMillis() - startTime <= 5000);

        System.out.println("[A] Done the cycle of scheduled task");
    }

    @Scheduled(fixedDelay = 5000, initialDelay = 2000)
    public void taskB() throws InterruptedException {
        System.out.println("[B] Starting new cycle of scheduled task");

        System.out.println("[B] Done the cycle of scheduled task");
    }
}

Output:

[A] Starting new cycle of scheduled task
[A] Done the cycle of scheduled task
[B] Starting new cycle of scheduled task
[B] Done the cycle of scheduled task

But, It should be like:

[A] Starting new cycle of scheduled task
[B] Starting new cycle of scheduled task
[B] Done the cycle of scheduled task
[A] Done the cycle of scheduled task

What am I doing wrong?

This is my configuration:

@Configuration
@EnableAsync
@EnableScheduling
public class AsyncConfiguration implements AsyncConfigurer {

    @Override
    @Bean(name = "taskExecutor")
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(6);
        executor.setMaxPoolSize(50);
        executor.setQueueCapacity(100);
        executor.setThreadNamePrefix("customer-Executor-");
        executor.initialize();
        return executor;
    }
}

Dorina

You are confusing TaskExecutor with TaskScheduler you haven't configured the latter and thus everything runs in sync mode (the default). – Gaby

Thanks @M.Deinum !! – Dorina

Answer 1

You should use TaskScheduler for your purpose

@Bean
public ThreadPoolTaskScheduler threadPoolTaskScheduler() {
    ThreadPoolTaskScheduler threadPoolTaskScheduler = new ThreadPoolTaskScheduler();
    threadPoolTaskScheduler.setPoolSize(THREADS_COUNT);
    return threadPoolTaskScheduler;
}

Where THREADS_COUNT - total count of tasks which should be executed in parallel. If I understand you correctly, you have only 2 jobs, so you need 2 threads

Bail

And keep in mind that every default @Async annotation uses this scheduler, too. If you use @Scheduled and call @Async methods thery aren't executed until a thread is available. – Tilly

Answer 2

Alternatively, you can configure this property in your application.properties:

spring.task.scheduling.pool.size=2

Monolingual

Simple and easy fix. Worked like a charm. My context was that I had 5 @Scheduled(fixedDelay=5000) methods. Threads were fighting for priority. Setting the pool size to 5 fixed the issue. Thanks again. – Rustproof