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本文讲述如何使用shedlock给spring schedule上锁，保证集群内部调度任务不会重复执行，避免资源浪费。

maven

        <dependency>
            <groupId>net.javacrumbs.shedlock</groupId>
            <artifactId>shedlock-spring</artifactId>
            <version>0.16.1</version>
        </dependency>

        <dependency>
            <groupId>net.javacrumbs.shedlock</groupId>
            <artifactId>shedlock-provider-jdbc-template</artifactId>
            <version>0.16.1</version>
        </dependency>

shedlock提供了mongo、redis、zookeeper、jdbc等的锁实现，这里使用jdbc。

shedlock配置

@Configuration
@EnableScheduling
public class ShedlockConfig {

    @Bean
    public LockProvider lockProvider(DataSource dataSource) {
        return new JdbcTemplateLockProvider(dataSource);
    }

    @Bean
    public ScheduledLockConfiguration scheduledLockConfiguration(LockProvider lockProvider) {
        return ScheduledLockConfigurationBuilder
                .withLockProvider(lockProvider)
                .withPoolSize(10)
                .withDefaultLockAtMostFor(Duration.ofMinutes(10))
                .build();
    }
}

这里使用了jdbc的lock provider，同时设定默认最大的lock expire时间为10分钟

shedlock表

CREATE TABLE shedlock(
    name VARCHAR(64),
    lock_until TIMESTAMP(3) NULL,
    locked_at TIMESTAMP(3) NULL,
    locked_by  VARCHAR(255),
    PRIMARY KEY (name)
)

这个需要手工建立，不过可以优化一下，自动建表。

实例

    @Scheduled(fixedDelay = 10*1000 /**ms**/,initialDelay = 10*1000)
    @SchedulerLock(name = "demoLockTask", lockAtMostFor = 5*1000)
    public void checkTask(){
        LOGGER.error("checkTask executed");
    }

doc

• ShedLock