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本文主要研究一下PowerJob的LockService

LockService

tech/powerjob/server/extension/LockService.java

public interface LockService {

    /**
     * 上锁（获取锁），立即返回，不会阻塞等待锁
     * @param name 锁名称
     * @param maxLockTime 最长持有锁的时间，单位毫秒（ms）
     * @return true -> 获取到锁，false -> 未获取到锁
     */
    boolean tryLock(String name, long maxLockTime);

    /**
     * 释放锁
     * @param name 锁名称
     */
    void unlock(String name);
}

LockService接口定义了tryLock、unlock方法

DatabaseLockService

tech/powerjob/server/extension/defaultimpl/DatabaseLockService.java

@Slf4j
@Service
public class DatabaseLockService implements LockService {

    private final String ownerIp;

    private final OmsLockRepository omsLockRepository;

    @Autowired
    public DatabaseLockService(OmsLockRepository omsLockRepository) {

        this.ownerIp = NetUtils.getLocalHost();
        this.omsLockRepository = omsLockRepository;

        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
            int num = omsLockRepository.deleteByOwnerIP(ownerIp);
            log.info("[DatabaseLockService] execute shutdown hook, release all lock(owner={},num={})", ownerIp, num);
        }));
    }

    @Override
    public boolean tryLock(String name, long maxLockTime) {

        OmsLockDO newLock = new OmsLockDO(name, ownerIp, maxLockTime);
        try {
            omsLockRepository.saveAndFlush(newLock);
            return true;
        } catch (DataIntegrityViolationException ignore) {
        } catch (Exception e) {
            log.warn("[DatabaseLockService] write lock to database failed, lockName = {}.", name, e);
        }

        OmsLockDO omsLockDO = omsLockRepository.findByLockName(name);
        long lockedMillions = System.currentTimeMillis() - omsLockDO.getGmtCreate().getTime();

        // 锁超时，强制释放锁并重新尝试获取
        if (lockedMillions > omsLockDO.getMaxLockTime()) {

            log.warn("[DatabaseLockService] The lock[{}] already timeout, will be unlocked now.", omsLockDO);
            unlock(name);
            return tryLock(name, maxLockTime);
        }
        return false;
    }

    @Override
    public void unlock(String name) {

        try {
            CommonUtils.executeWithRetry0(() -> omsLockRepository.deleteByLockName(name));
        }catch (Exception e) {
            log.error("[DatabaseLockService] unlock {} failed.", name, e);
        }
    }

}

DatabaseLockService基于数据库实现了LockService，其构造器依赖OmsLockRepository，同时注册了ShutdownHook，在关闭的时候执行omsLockRepository.deleteByOwnerIP(ownerIp)；其tryLock方法创建OmsLockDO，然后执行omsLockRepository.saveAndFlush，若成功则返回，若有异常则通过omsLockRepository.findByLockName找到omsLockDO，计算加锁时间，若超过MaxLockTime则执行unlock再重新tryLock；其unlock执行omsLockRepository.deleteByLockName

NetUtils.getLocalHost

tech/powerjob/common/utils/NetUtils.java

    public static String getLocalHost() {
        if (HOST_ADDRESS != null) {
            return HOST_ADDRESS;
        }

        String addressFromJVM = System.getProperty(PowerJobDKey.BIND_LOCAL_ADDRESS);
        if (StringUtils.isNotEmpty(addressFromJVM)) {
            log.info("[Net] use address from[{}]: {}", PowerJobDKey.BIND_LOCAL_ADDRESS, addressFromJVM);
            return HOST_ADDRESS = addressFromJVM;
        }

        InetAddress address = getLocalAddress();
        if (address != null) {
            return HOST_ADDRESS = address.getHostAddress();
        }
        return LOCALHOST_VALUE;
    }

    public static InetAddress getLocalAddress() {
        if (LOCAL_ADDRESS != null) {
            return LOCAL_ADDRESS;
        }
        InetAddress localAddress = getLocalAddress0();
        LOCAL_ADDRESS = localAddress;
        return localAddress;
    }    

    private static InetAddress getLocalAddress0() {
        // @since 2.7.6, choose the {@link NetworkInterface} first
        try {
            InetAddress addressOp = getFirstReachableInetAddress( findNetworkInterface());
            if (addressOp != null) {
                return addressOp;
            }
        } catch (Throwable e) {
            log.warn("[Net] getLocalAddress0 failed.", e);
        }

        InetAddress localAddress = null;
        try {
            localAddress = InetAddress.getLocalHost();
            Optional<InetAddress> addressOp = toValidAddress(localAddress);
            if (addressOp.isPresent()) {
                return addressOp.get();
            }
        } catch (Throwable e) {
            log.warn("[Net] getLocalAddress0 failed.", e);
        }


        return localAddress;
    }    

NetUtils的getLocalHost先判断HOST_ADDRESS是否有值，有则直接返回，否则先从系统属性读取powerjob.network.local.address，读取不到则取LOCAL_ADDRESS，若LOCAL_ADDRESS为null则通过getLocalAddress0获取

OmsLockDO

tech/powerjob/server/persistence/remote/model/OmsLockDO.java

@Data
@Entity
@NoArgsConstructor
@Table(uniqueConstraints = {@UniqueConstraint(name = "uidx01_oms_lock", columnNames = {"lockName"})})
public class OmsLockDO {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "native")
    @GenericGenerator(name = "native", strategy = "native")
    private Long id;

    private String lockName;

    private String ownerIP;
    /**
     * 最长持有锁的时间
     */
    private Long maxLockTime;

    private Date gmtCreate;

    private Date gmtModified;

    public OmsLockDO(String lockName, String ownerIP, Long maxLockTime) {
        this.lockName = lockName;
        this.ownerIP = ownerIP;
        this.maxLockTime = maxLockTime;
        this.gmtCreate = new Date();
        this.gmtModified = this.gmtCreate;
    }
}

OmsLockDO定义lockName为唯一索引，它还定义了ownerIP、maxLockTime

OmsLockRepository

tech/powerjob/server/persistence/remote/repository/OmsLockRepository.java

public interface OmsLockRepository extends JpaRepository<OmsLockDO, Long> {

    @Modifying
    @Transactional(rollbackOn = Exception.class)
    @Query(value = "delete from OmsLockDO where lockName = ?1")
    int deleteByLockName(String lockName);

    OmsLockDO findByLockName(String lockName);

    @Modifying
    @Transactional(rollbackOn = Exception.class)
    int deleteByOwnerIP(String ip);
}

OmsLockRepository继承了JpaRepository，它定义了deleteByLockName、findByLockName、deleteByOwnerIP方法

小结

LockService接口定义了tryLock、unlock方法；DatabaseLockService基于数据库实现了LockService，其构造器依赖OmsLockRepository，同时注册了ShutdownHook，在关闭的时候执行omsLockRepository.deleteByOwnerIP(ownerIp)；其tryLock方法创建OmsLockDO，然后执行omsLockRepository.saveAndFlush，若成功则返回，若有异常则通过omsLockRepository.findByLockName找到omsLockDO，计算加锁时间，若超过MaxLockTime则执行unlock再重新tryLock；其unlock执行omsLockRepository.deleteByLockName。