用shedlock实现分布式定时任务锁

添加包

<dependency>

    <groupId>net.javacrumbs.shedlock</groupId>

    <artifactId>shedlock-spring</artifactId>

    <version>2.2.0</version>

</dependency>

<dependency>

    <groupId>net.javacrumbs.shedlock</groupId>

    <artifactId>shedlock-provider-jdbc-template</artifactId>

    <version>2.2.0</version>

</dependency>

添加表

CREATE TABLE `shedlock` (
`name` varchar(64) COLLATE utf8mb4_unicode_ci NOT NULL,
`lock_until` timestamp(3) NULL DEFAULT NULL,
`locked_at` timestamp(3) NULL DEFAULT NULL,
`locked_by` varchar(255) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
PRIMARY KEY (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

添加config

import net.javacrumbs.shedlock.core.LockProvider;
import net.javacrumbs.shedlock.provider.jdbctemplate.JdbcTemplateLockProvider;
import net.javacrumbs.shedlock.spring.ScheduledLockConfiguration;
import net.javacrumbs.shedlock.spring.ScheduledLockConfigurationBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableScheduling;

import javax.sql.DataSource;
import java.time.Duration;

@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();
    }
}
具体的定时任务

import net.javacrumbs.shedlock.core.SchedulerLock;
import net.javacrumbs.shedlock.spring.annotation.EnableSchedulerLock;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

@Component
@Configuration
@EnableScheduling
@EnableSchedulerLock(defaultLockAtMostFor = "PT30S") //重点地方
public class MarkRefreshScheduler {

    private final static Logger logger = LoggerFactory.getLogger(MarkRefreshScheduler.class);

    //每周一早上5点执行一次，用户的热度值和hot标识归零
    @Scheduled(cron = "0 0/2 * * * ? ")
    @SchedulerLock(name = "headNumCronName", lockAtMostFor = 5 * 1000, lockAtLeastFor = 5 * 1000)//重点地方
    public void refreshHotSumAndIsOnTop() {
        logger.info("begin refreshHotSumAndIsOnTop...");
        //do something
        logger.info("begin refreshHotSumAndIsOnTop...");

    }
}
结果

通过修改数据库表中的数据实现锁

里面有四个字段

主键name：每个定时任务的一个名字

locked_at：锁的开始时间

lock_until：锁的结束时间

再定时开始时，会更新这两个时间，在时间之内的定时是不会被执行的