Redis系列-10.Redis分布式锁（下）-阿里云开发者社区

Redis系列-10.Redis分布式锁（上）:https://developer.aliyun.com/article/1414722

Lua保证原子性

前面有一个问题就是 finally块的判断 + del删除操作不是原子性的

为了保证原子性，需要启用lua脚本编写redis分布式锁判断 + 删除判断代码

Redis调用Lua脚本通过eval命令保证代码执行的原子性，直接用return返回脚本执行后的结果值

解决

@Service
@Slf4j
public class InventoryService
{
    @Autowired
    private StringRedisTemplate stringRedisTemplate;
    @Value("${server.port}")
    private String port;
    private Lock lock = new ReentrantLock();
    public String sale()
    {
        String retMessage = "";
        String key = "zzyyRedisLock";
        String uuidValue = IdUtil.simpleUUID()+":"+Thread.currentThread().getId();
        while(!stringRedisTemplate.opsForValue().setIfAbsent(key, uuidValue,30L,TimeUnit.SECONDS))
        {
            //暂停毫秒
                     try { TimeUnit.MILLISECONDS.sleep(20); } catch (InterruptedException e) { e.printStackTrace(); }
        }
        try
        {
            //1 查询库存信息
            String result = stringRedisTemplate.opsForValue().get("inventory001");
            //2 判断库存是否足够
            Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);
            //3 扣减库存
            if(inventoryNumber > 0) {
                stringRedisTemplate.opsForValue().set("inventory001",String.valueOf(--inventoryNumber));
                retMessage = "成功卖出一个商品，库存剩余: "+inventoryNumber+"\t"+uuidValue;
                System.out.println(retMessage);
            }else{
                retMessage = "商品卖完了，o(╥﹏╥)o";
            }
        }finally {
            //V6.0 将判断+删除自己的合并为lua脚本保证原子性
            String luaScript =
                    "if (redis.call('get',KEYS[1]) == ARGV[1]) then " +
                        "return redis.call('del',KEYS[1]) " +
                    "else " +
                        "return 0 " +
                    "end";
            stringRedisTemplate.execute(new DefaultRedisScript<>(luaScript, Boolean.class), Arrays.asList(key), uuidValue);
        }
        return retMessage+"\t"+"服务端口号："+port;
    }
}

可重入锁 + 设计模型

如何兼顾锁的可重入性问题呢？

可重入锁

可重入锁又名递归锁

是指在同一个线程在外层方法获取锁的时候，再进入该线程的内层方法会自动获取锁(前提，锁对象得是同一个对象)，不会因为之前已经获取过还没释放而阻塞。

如果是1个有 synchronized 修饰的递归调用方法，程序第2次进入被自己阻塞了岂不是天大的笑话，出现了作茧自缚。

所以Java中ReentrantLock和synchronized都是可重入锁，可重入锁的一个优点是可一定程度避免死锁。

可重入锁的种类

隐式锁（即synchronized关键字使用的锁）默认是可重入锁

指的是可重复可递归调用的锁，在外层使用锁之后，在内层仍然可以使用，并且不发生死锁，这样的锁就叫做可重入锁。

简单的来说就是：在一个synchronized修饰的方法或代码块的内部调用本类的其他synchronized修饰的方法或代码块时，是永远可以得到锁的

与可重入锁相反，不可重入锁不可递归调用，递归调用就发生死锁。

public class ReEntryLockDemo
{
    public static void main(String[] args)
    {
        final Object objectLockA = new Object();
        new Thread(() -> {
            synchronized (objectLockA)
            {
                System.out.println("-----外层调用");
                synchronized (objectLockA)
                {
                    System.out.println("-----中层调用");
                    synchronized (objectLockA)
                    {
                        System.out.println("-----内层调用");
                    }
                }
            }
        },"a").start();
    }
}

public class ReEntryLockDemo
{
    public synchronized void m1()
    {
        System.out.println("-----m1");
        m2();
    }
    public synchronized void m2()
    {
        System.out.println("-----m2");
        m3();
    }
    public synchronized void m3()
    {
        System.out.println("-----m3");
    }
    public static void main(String[] args)
    {
        ReEntryLockDemo reEntryLockDemo = new ReEntryLockDemo();
        reEntryLockDemo.m1();
    }
}

Synchronized重入的实现机理

每个锁对象拥有一个锁计数器和一个指向持有该锁的线程的指针。

当执行monitorenter时，如果目标锁对象的计数器为零，那么说明它没有被其他线程所持有，Java虚拟机会将该锁对象的持有线程设置为当前线程，并且将其计数器加1。

在目标锁对象的计数器不为零的情况下，如果锁对象的持有线程是当前线程，那么 Java 虚拟机可以将其计数器加1，否则需要等待，直至持有线程释放该锁。

**当执行monitorexit时，Java虚拟机则需将锁对象的计数器减1。**计数器为零代表锁已被释放。

lock/unlock配合可重入锁进行AQS源码分析

如果还是当前线程，则nextc = c + acquires

可重入锁的计数问题，redis中那个数据类型可以代替

K，K，V

Map>

命令

hset key field value

hset redis锁名字(zzyyRedisLock) 某个请求线程的UUID+ThreadID 加锁的次数

总结

setnx，只能解决有无的问题，够用但是不完美

hset，不但解决有无，还解决可重入

思考+设计

目前有两条支线，目的是保证同一个时刻只能有一个线程持有锁进去redis做扣减库存动作

可重入
扣减原子性

Lua脚本

redis命令过程分析

加锁lua脚本lock

先判断redis分布式锁这个key是否存在

EXISTS key

返回零说明不存在，hset新建当前线程属于自己的锁 BY UUID ：ThreadID

HSET zzyyRedisLock 0c90d37cb6ec42268861b3d739f8b3a8:1 1

命令 key value = UUID:ThreadID 次数

返回一说明已经有锁，需进一步判断是不是当前线程自己的

返回零说明不是自己的

返回一说明是自己的锁，自增一次表示重入

上述设计修改为Lua脚本

if redis.call('exists','key') == 0 then
  redis.call('hset','key','uuid:threadid',1)
  redis.call('expire','key',30)
  return 1
elseif redis.call('hexists','key','uuid:threadid') == 1 then
  redis.call('hincrby','key','uuid:threadid',1)
  redis.call('expire','key',30)
  return 1
else
  return 0
end
相同部分是否可以替换处理？？？
hincrby命令可否替代hset命令

if redis.call('exists','key') == 0 or redis.call('hexists','key','uuid:threadid') == 1 then
  redis.call('hincrby','key','uuid:threadid',1)
  redis.call('expire','key',30)
  return 1
else
  return 0
end

测试

解锁lua脚本unlock

设计思路：有锁且还是自己的锁

HEXISTS key uuid：ThreadID

返回零，说明根本没有锁，程序块返回nil

不是零，说明有锁且是自己的锁，直接调用HINCRBY -1，表示每次减个一，解锁一次。直到它变为零表示可以删除该锁key。

全套流程

if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 0 then
 return nil
elseif redis.call('HINCRBY',KEYS[1],ARGV[1],-1) == 0 then
 return redis.call('del',KEYS[1])
else
 return 0
end

测试全套流程

将上述Lua脚本整个进入微服务Java程序

通过实现JUC里面的Lock接口，实现Redis分布式锁RedisDistributedLock

RedisDistributedLock

public class RedisDistributedLock implements Lock
{
    private StringRedisTemplate stringRedisTemplate;
    private String lockName;//KEYS[1]
    private String uuidValue;//ARGV[1]
    private long   expireTime;//ARGV[2]
    public RedisDistributedLock(StringRedisTemplate stringRedisTemplate, String lockName)
    {
        this.stringRedisTemplate = stringRedisTemplate;
        this.lockName = lockName;
        this.uuidValue = IdUtil.simpleUUID()+":"+Thread.currentThread().getId();//UUID:ThreadID
        this.expireTime = 30L;
    }
    @Override
    public void lock()
    {
        tryLock();
    }
    @Override
    public boolean tryLock()
    {
        try {tryLock(-1L,TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();}
        return false;
    }
    /**
     * 干活的，实现加锁功能，实现这一个干活的就OK，全盘通用
     * @param time
     * @param unit
     * @return
     * @throws InterruptedException
     */
    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException{
        if(time != -1L){
            this.expireTime = unit.toSeconds(time);
        }
        String script =
                "if redis.call('exists',KEYS[1]) == 0 or redis.call('hexists',KEYS[1],ARGV[1]) == 1 then " +
                        "redis.call('hincrby',KEYS[1],ARGV[1],1) " +
                        "redis.call('expire',KEYS[1],ARGV[2]) " +
                        "return 1 " +
                "else " +
                        "return 0 " +
                "end";
        System.out.println("script: "+script);
        System.out.println("lockName: "+lockName);
        System.out.println("uuidValue: "+uuidValue);
        System.out.println("expireTime: "+expireTime);
        while (!stringRedisTemplate.execute(new DefaultRedisScript<>(script,Boolean.class), Arrays.asList(lockName),uuidValue,String.valueOf(expireTime))) {
            TimeUnit.MILLISECONDS.sleep(50);
        }
        return true;
    }
    /**
     *干活的，实现解锁功能
     */
    @Override
    public void unlock()
    {
        String script =
                "if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 0 then " +
                "   return nil " +
                "elseif redis.call('HINCRBY',KEYS[1],ARGV[1],-1) == 0 then " +
                "   return redis.call('del',KEYS[1]) " +
                "else " +
                "   return 0 " +
                "end";
        // nil = false 1 = true 0 = false
        System.out.println("lockName: "+lockName);
        System.out.println("uuidValue: "+uuidValue);
        System.out.println("expireTime: "+expireTime);
        Long flag = stringRedisTemplate.execute(new DefaultRedisScript<>(script, Long.class), Arrays.asList(lockName),uuidValue,String.valueOf(expireTime));
        if(flag == null)
        {
            throw new RuntimeException("This lock doesn't EXIST");
        }
    }
    //===下面的redis分布式锁暂时用不到=======================================
    //===下面的redis分布式锁暂时用不到=======================================
    //===下面的redis分布式锁暂时用不到=======================================
    @Override
    public void lockInterruptibly() throws InterruptedException
    {
    }
    @Override
    public Condition newCondition()
    {
        return null;
    }
}

这样设计的问题？

考虑扩展，本次是redis实现分布式锁，以后是zookeeper、mysql呢？

引入工厂模式改造

DistributedLockFactory

@Component
public class DistributedLockFactory
{
    @Autowired
    private StringRedisTemplate stringRedisTemplate;
    private String lockName;
    public Lock getDistributedLock(String lockType)
    {
        if(lockType == null) return null;
        if(lockType.equalsIgnoreCase("REDIS")){
            lockName = "zzyyRedisLock";
            return new RedisDistributedLock(stringRedisTemplate,lockName);
        } else if(lockType.equalsIgnoreCase("ZOOKEEPER")){
            //TODO zookeeper版本的分布式锁实现
            return new ZookeeperDistributedLock();
        } else if(lockType.equalsIgnoreCase("MYSQL")){
            //TODO mysql版本的分布式锁实现
            return null;
        }
        return null;
    }
}

RedisDistributedLock

public class RedisDistributedLock implements Lock
{
    private StringRedisTemplate stringRedisTemplate;
    private String lockName;//KEYS[1]
    private String uuidValue;//ARGV[1]
    private long   expireTime;//ARGV[2]
    public RedisDistributedLock(StringRedisTemplate stringRedisTemplate, String lockName){
        this.stringRedisTemplate = stringRedisTemplate;
        this.lockName = lockName;
        this.uuidValue = IdUtil.simpleUUID()+":"+Thread.currentThread().getId();//UUID:ThreadID
        this.expireTime = 30L;
    }
    @Override
    public void lock(){
        tryLock();
    }
    @Override
    public boolean tryLock(){
        try {tryLock(-1L,TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();}
        return false;
    }
    /**
     * 干活的，实现加锁功能，实现这一个干活的就OK，全盘通用
     * @param time
     * @param unit
     * @return
     * @throws InterruptedException
     */
    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException{
        if(time != -1L){
            this.expireTime = unit.toSeconds(time);
        }
        String script =
                "if redis.call('exists',KEYS[1]) == 0 or redis.call('hexists',KEYS[1],ARGV[1]) == 1 then " +
                        "redis.call('hincrby',KEYS[1],ARGV[1],1) " +
                        "redis.call('expire',KEYS[1],ARGV[2]) " +
                        "return 1 " +
                "else " +
                        "return 0 " +
                "end";
        System.out.println("script: "+script);
        System.out.println("lockName: "+lockName);
        System.out.println("uuidValue: "+uuidValue);
        System.out.println("expireTime: "+expireTime);
        while (!stringRedisTemplate.execute(new DefaultRedisScript<>(script,Boolean.class), Arrays.asList(lockName),uuidValue,String.valueOf(expireTime))) {
            TimeUnit.MILLISECONDS.sleep(50);
        }
        return true;
    }
    /**
     *干活的，实现解锁功能
     */
    @Override
    public void unlock()
    {
        String script =
                "if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 0 then " +
                "   return nil " +
                "elseif redis.call('HINCRBY',KEYS[1],ARGV[1],-1) == 0 then " +
                "   return redis.call('del',KEYS[1]) " +
                "else " +
                "   return 0 " +
                "end";
        // nil = false 1 = true 0 = false
        System.out.println("lockName: "+lockName);
        System.out.println("uuidValue: "+uuidValue);
        System.out.println("expireTime: "+expireTime);
        Long flag = stringRedisTemplate.execute(new DefaultRedisScript<>(script, Long.class), Arrays.asList(lockName),uuidValue,String.valueOf(expireTime));
        if(flag == null)
        {
            throw new RuntimeException("This lock doesn't EXIST");
        }
    }
    //===下面的redis分布式锁暂时用不到=======================================
    //===下面的redis分布式锁暂时用不到=======================================
    //===下面的redis分布式锁暂时用不到=======================================
    @Override
    public void lockInterruptibly() throws InterruptedException
    {
    }
    @Override
    public Condition newCondition()
    {
        return null;
    }
}

InventoryService

@Service
@Slf4j
public class InventoryService
{
    @Autowired
    private StringRedisTemplate stringRedisTemplate;
    @Value("${server.port}")
    private String port;
    @Autowired
    private DistributedLockFactory distributedLockFactory;
    public String sale()
    {
        String retMessage = "";
        Lock redisLock = distributedLockFactory.getDistributedLock("redis");
        redisLock.lock();
        try
        {
            //1 查询库存信息
            String result = stringRedisTemplate.opsForValue().get("inventory001");
            //2 判断库存是否足够
            Integer inventoryNumber = result == null ? 0 : Integer.parseInt(result);
            //3 扣减库存
            if(inventoryNumber > 0)
            {
                inventoryNumber = inventoryNumber - 1;
                stringRedisTemplate.opsForValue().set("inventory001",String.valueOf(inventoryNumber));
                retMessage = "成功卖出一个商品，库存剩余: "+inventoryNumber+"\t服务端口:" +port;
                System.out.println(retMessage);
                return retMessage;
            }
            retMessage = "商品卖完了，o(╥﹏╥)o"+"\t服务端口:" +port;
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            redisLock.unlock();
        }
        return retMessage;
    }
}

进行可重入测试发现出现问题

DistributedLockFactory

@Component
public class DistributedLockFactory
{
    @Autowired
    private StringRedisTemplate stringRedisTemplate;
    private String lockName;
    private String uuidValue;
    public DistributedLockFactory()
    {
        this.uuidValue = IdUtil.simpleUUID();//UUID
    }
    public Lock getDistributedLock(String lockType)
    {
        if(lockType == null) return null;
        if(lockType.equalsIgnoreCase("REDIS")){
            lockName = "zzyyRedisLock";
            return new RedisDistributedLock(stringRedisTemplate,lockName,uuidValue);
        } else if(lockType.equalsIgnoreCase("ZOOKEEPER")){
            //TODO zookeeper版本的分布式锁实现
            return new ZookeeperDistributedLock();
        } else if(lockType.equalsIgnoreCase("MYSQL")){
            //TODO mysql版本的分布式锁实现
            return null;
        }
        return null;
    }
}

RedisDistributedLock

public class RedisDistributedLock implements Lock
{
    private StringRedisTemplate stringRedisTemplate;
    private String lockName;
    private String uuidValue;
    private long   expireTime;
    public RedisDistributedLock(StringRedisTemplate stringRedisTemplate, String lockName,String uuidValue)
    {
        this.stringRedisTemplate = stringRedisTemplate;
        this.lockName = lockName;
        this.uuidValue = uuidValue+":"+Thread.currentThread().getId();
        this.expireTime = 30L;
    }
    @Override
    public void lock()
    {
        this.tryLock();
    }
    @Override
    public boolean tryLock()
    {
        try
        {
            return this.tryLock(-1L,TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return false;
    }
    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException
    {
        if(time != -1L)
        {
            expireTime = unit.toSeconds(time);
        }
        String script =
                "if redis.call('exists',KEYS[1]) == 0 or redis.call('hexists',KEYS[1],ARGV[1]) == 1 then " +
                    "redis.call('hincrby',KEYS[1],ARGV[1],1) " +
                    "redis.call('expire',KEYS[1],ARGV[2]) " +
                    "return 1 " +
                "else " +
                    "return 0 " +
                "end";
        System.out.println("lockName: "+lockName+"\t"+"uuidValue: "+uuidValue);
        while (!stringRedisTemplate.execute(new DefaultRedisScript<>(script, Boolean.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime)))
        {
            try { TimeUnit.MILLISECONDS.sleep(60); } catch (InterruptedException e) { e.printStackTrace(); }
        }
        return true;
    }
    @Override
    public void unlock()
    {
        String script =
                "if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 0 then " +
                    "return nil " +
                "elseif redis.call('HINCRBY',KEYS[1],ARGV[1],-1) == 0 then " +
                    "return redis.call('del',KEYS[1]) " +
                "else " +
                        "return 0 " +
                "end";
        System.out.println("lockName: "+lockName+"\t"+"uuidValue: "+uuidValue);
        Long flag = stringRedisTemplate.execute(new DefaultRedisScript<>(script, Long.class), Arrays.asList(lockName), uuidValue, String.valueOf(expireTime));
        if(flag == null)
        {
            throw new RuntimeException("没有这个锁，HEXISTS查询无");
        }
    }
    //=========================================================
    @Override
    public void lockInterruptibly() throws InterruptedException
    {
    }
    @Override
    public Condition newCondition()
    {
        return null;
    }
}

自动续期

Redis分布式锁还存在一个问题就是续期问题。

//==============自动续期
if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 1 then
  return redis.call('expire',KEYS[1],ARGV[2])
else
  return 0
end

RedisDistributedLock

public class RedisDistributedLock implements Lock
{
    private StringRedisTemplate stringRedisTemplate;
    private String lockName;//KEYS[1]
    private String uuidValue;//ARGV[1]
    private long   expireTime;//ARGV[2]
    public RedisDistributedLock(StringRedisTemplate stringRedisTemplate,String lockName,String uuidValue)
    {
        this.stringRedisTemplate = stringRedisTemplate;
        this.lockName = lockName;
        this.uuidValue = uuidValue+":"+Thread.currentThread().getId();
        this.expireTime = 30L;
    }
    @Override
    public void lock()
    {
        tryLock();
    }
    @Override
    public boolean tryLock()
    {
        try {tryLock(-1L,TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();}
        return false;
    }
    /**
     * 干活的，实现加锁功能，实现这一个干活的就OK，全盘通用
     * @param time
     * @param unit
     * @return
     * @throws InterruptedException
     */
    @Override
    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException
    {
        if(time != -1L)
        {
            this.expireTime = unit.toSeconds(time);
        }
        String script =
                "if redis.call('exists',KEYS[1]) == 0 or redis.call('hexists',KEYS[1],ARGV[1]) == 1 then " +
                        "redis.call('hincrby',KEYS[1],ARGV[1],1) " +
                        "redis.call('expire',KEYS[1],ARGV[2]) " +
                        "return 1 " +
                        "else " +
                        "return 0 " +
                        "end";
        System.out.println("script: "+script);
        System.out.println("lockName: "+lockName);
        System.out.println("uuidValue: "+uuidValue);
        System.out.println("expireTime: "+expireTime);
        while (!stringRedisTemplate.execute(new DefaultRedisScript<>(script,Boolean.class), Arrays.asList(lockName),uuidValue,String.valueOf(expireTime))) {
            TimeUnit.MILLISECONDS.sleep(50);
        }
        this.renewExpire();
        return true;
    }
    /**
     *干活的，实现解锁功能
     */
    @Override
    public void unlock()
    {
        String script =
                "if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 0 then " +
                        "   return nil " +
                        "elseif redis.call('HINCRBY',KEYS[1],ARGV[1],-1) == 0 then " +
                        "   return redis.call('del',KEYS[1]) " +
                        "else " +
                        "   return 0 " +
                        "end";
        // nil = false 1 = true 0 = false
        System.out.println("lockName: "+lockName);
        System.out.println("uuidValue: "+uuidValue);
        System.out.println("expireTime: "+expireTime);
        Long flag = stringRedisTemplate.execute(new DefaultRedisScript<>(script, Long.class), Arrays.asList(lockName),uuidValue,String.valueOf(expireTime));
        if(flag == null)
        {
            throw new RuntimeException("This lock doesn't EXIST");
        }
    }
  // 上锁的情况
    private void renewExpire()
    {
        String script =
                "if redis.call('HEXISTS',KEYS[1],ARGV[1]) == 1 then " +
                        "return redis.call('expire',KEYS[1],ARGV[2]) " +
                        "else " +
                        "return 0 " +
                        "end";
        new Timer().schedule(new TimerTask()
        {
            @Override
            public void run()
            {
                if (stringRedisTemplate.execute(new DefaultRedisScript<>(script, Boolean.class), Arrays.asList(lockName),uuidValue,String.valueOf(expireTime))) {
                    renewExpire();
                }
            }
        },(this.expireTime * 1000)/3);
    }
    //===下面的redis分布式锁暂时用不到=======================================
    //===下面的redis分布式锁暂时用不到=======================================
    //===下面的redis分布式锁暂时用不到=======================================
    @Override
    public void lockInterruptibly() throws InterruptedException
    {
    }
    @Override
    public Condition newCondition()
    {
        return null;
    }
}

总结

synchronized单机版可以，但是上分布式死翘翘

nginx分布式微服务单机锁不行

如果取消宕机所，可以考虑上redis分布式锁setnx

但是只是加了锁，没有释放锁，出现异常的话，可能无法释放锁，必须要在代码层面finally释放锁

宕机了，部署了微服务代码层面根本没有走到finally这块，没办法保证解锁，这个key没有被删除，需要有lockkey的过期时间设定

为redis的分布式锁key，增加过期时间，此外，还必须要setnx+过期时间在同一行，保证原子性

且必须规定只能自己删除自己的锁，你不能把别人的锁删除了，防止张冠李戴

同时unlock变为Lua脚本保证

最后还需要考虑锁重入问题，使用hset替代setnx+lock变为lua脚本办证，以及自动续期问题

Redis系列-10.Redis分布式锁（下）

Lua保证原子性

解决

可重入锁 + 设计模型

可重入锁

可重入锁的种类

隐式锁（即synchronized关键字使用的锁）默认是可重入锁

Synchronized重入的实现机理

lock/unlock配合可重入锁进行AQS源码分析

可重入锁的计数问题，redis中那个数据类型可以代替

K，K，V

命令

总结

思考+设计

Lua脚本

redis命令过程分析

加锁lua脚本lock

上述设计修改为Lua脚本

测试

解锁lua脚本unlock

测试全套流程

将上述Lua脚本整个进入微服务Java程序

通过实现JUC里面的Lock接口，实现Redis分布式锁RedisDistributedLock

自动续期

RedisDistributedLock

总结

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