Implement Distributed Scheduled Tasks with Spring Cloud Alibaba SchedulerX

Background

Scheduled tasks run at fixed times or intervals and are used for asynchronous data processing, automated operations, system monitoring, and data synchronization. In monolithic Java applications developers often use java.util.Timer, ScheduledExecutorService, or Spring’s @Scheduled annotation.

Challenges in Microservices

When a service is deployed on multiple nodes, each instance runs its own timer, causing duplicate executions. Distributed scheduling must prevent repeats, support sharding, and control parallelism.

Spring Cloud Alibaba SchedulerX Module

Spring Cloud Alibaba provides a Scheduling module (pull request #3732) that offers a lightweight, open‑source, high‑availability solution for distributed scheduled tasks. The implementation mode is selected via spring.cloud.scheduling.distributed-mode:

schedulerx : integrates with Alibaba Cloud SchedulerX, a managed scheduling platform.

shedlock : uses the open‑source ShedLock library with JDBC, Zookeeper, Redis, etc., for distributed locking.

Quick Start (Maven)

Add the starter dependency:

<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-schedulerx</artifactId>
    <version>{version}</version>
</dependency>

Configure the mode in application.properties or YAML:

spring.cloud.scheduling.distributed-mode=schedulerx   # or shedlock

Using Alibaba SchedulerX

Create a SchedulerX instance in the Alibaba Cloud console, obtain the access credentials, and use the provided web UI for task creation, monitoring, sharding and parallelism.

Using ShedLock (local open‑source)

Add JDBC lock dependencies:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.33</version>
</dependency>

Configure the datasource (example for MySQL):

spring.datasource.url=jdbc:mysql://127.0.0.1:3306/testdb?useUnicode=true&characterEncoding=utf-8&useSSL=false
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

ShedLock creates a shedlock table at startup to coordinate task execution.

Sample Application

Enable scheduling and the lock manager:

@SpringBootApplication
@EnableScheduling
@EnableSchedulerLock(defaultLockAtMostFor = "3m")
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

Define jobs with @Scheduled and @SchedulerLock annotations:

@Component
public class SpringJob {
    @Scheduled(cron = "0 */5 * * * ?")
    @SchedulerLock(name = "SpringJob.job1", lockAtMostFor = "2m", lockAtLeastFor = "1m")
    public void job1() {
        System.out.println("time=" + DateTime.now().toString("YYYY-MM-dd HH:mm:ss") + " do job1...");
    }

    @Scheduled(fixedRate = 5000)
    @SchedulerLock(name = "SpringJob.job2", lockAtMostFor = "4s", lockAtLeastFor = "4s")
    public void job2() {
        System.out.println("time=" + DateTime.now().toString("YYYY-MM-dd HH:mm:ss") + " do job2...");
    }

    @Scheduled(fixedDelay = 5000)
    @SchedulerLock(name = "SpringJob.job3", lockAtMostFor = "4s", lockAtLeastFor = "4s")
    public void job3() throws InterruptedException {
        System.out.println("time=" + DateTime.now().toString("YYYY-MM-dd HH:mm:ss") + " do job3...");
        Thread.sleep(10000);
    }
}

Future Plans

The module will integrate additional open‑source schedulers such as Quartz and XXL‑Job, allowing a single @Scheduled method to run on different back‑ends and providing features like task sharding and concurrency limits.

References

Scheduling task module PR: https://github.com/alibaba/spring-cloud-alibaba/pull/3732

Spring Framework scheduling docs: https://docs.spring.io/spring-framework/docs/5.3.37/reference/html/integration.html#scheduling

Example project: https://github.com/alibaba/spring-cloud-alibaba/blob/2023.x/spring-cloud-alibaba-examples/spring-cloud-scheduling-example/README.md

ShedLock repository: https://github.com/lukas-krecan/ShedLock