图解 Redis 和 Zookeeper 分布式锁 | 京东云技术团队

//lua脚本如下luaScript =  " if redis.call('get',key) == value then                  return redis.call('del',key)                else                   return 0                end;"

uuid = getUUID();//加锁lockResut = redisClient.setNx(key,uuid,timeOut);if(!lockResult){    return;}try{   //执行业务逻辑}finally{    //解锁    redisClient.eval(delLuaScript,keys,values)}//解锁的lua脚本delLuaScript =  " if redis.call('get',key) == value then                     return redis.call('del',key)                   else                      return 0                   end;"

uuid = getUUID();//加锁lockResut = redisClient.setNx(key,uuid,timeOut);if(!lockResult){    return;}//开启一个定时任务new Scheduler(key,time,uuid,scheduleTime)try{   //执行业务逻辑}finally{    //删除锁    redisClient.eval(delLuaScript,keys,values)    //取消定时任务    cancelScheduler(uuid);}

luaScript = "if redis.call('get',key) == value) then                return redis.call('expire',key,timeOut);             else                return 0;             end；"

//锁不存在if (redis.call('exists', key) == 0) then    redis.call('hset', key, uuid, 1);     redis.call('expire', key, time);     return 1;end;//锁存在，判断是否是自己的锁if (redis.call('hexists', key, uuid) == 1) then    redis.call('hincrby', key, uuid, 1);     redis.call('expire', key, uuid);    return 1; end; //锁不是自己的，返回加锁失败return 0；

//判断锁是否是自己的,不是自己的直接返回错误if (redis.call('hexists', key，uuid) == 0) then    return 0;end;//锁是自己的，则对加锁次数-1local counter = redis.call('hincrby', key, uuid, -1);if (counter > 0) then     //剩余加锁次数大于0，则不能释放锁，重新设置过期时间    redis.call('expire', key, uuid);     return 1;else//等于0，代表可以释放锁了    redis.call('del', key);     return 1; end; 

uuid = getUUID();//加锁lockResut = redisClient.eval(addLockLuaScript,keys,values);if(!lockResult){    return;}//开启一个定时任务new Scheduler(key,time,uuid,scheduleTime)try{   //执行业务逻辑}finally{    //删除锁    redisClient.eval(delLuaScript,keys,values)    //取消定时任务    cancelScheduler(uuid);}

zookeeper.exists("/watchpath",new Watcher() {    @Override    public void process(WatchedEvent event) {  System.out.println("进入监听器");  System.out.println("监听路径Path："+event.getPath());  System.out.println("监听事件类型EventType："+event.getType());            }      });  

//加锁路径String lockPath;//用来阻塞线程CountDownLatch cc = new CountDownLatch(1);//创建锁节点的路径Sting LOCK_ROOT_PATH = "/locks"
//先创建锁public void createLock(){    //lockPath = /locks/lock_01     lockPath = zkClient.create(LOCK_ROOT_PATH+"/lock_", CreateMode.EPHEMERAL_SEQUENTIAL);}
//获取锁public boolean acquireLock(){    //获取当前加锁路径下所有的节点    allLocks = zkClient.getChildren("/locks");    //按节点顺序大小排序    Collections.sort(allLocks);    //判断自己是否是第一个节点    int index = allLocks.indexOf(lockPath.substring(LOCK_ROOT_PATH.length() + 1));    //如果是第一个节点，则加锁成功    if (index == 0) {        System.out.println(Thread.currentThread().getName() + "获得锁成功, lockPath: " + lockPath);        return true;    } else {        //不是序号最小的节点，则监听前一个节点        String preLock = allLocks.get(index - 1);        //创建监听器        Stat status = zkClient.exists(LOCK_ROOT_PATH + "/" + preLockPath, watcher);        // 前一个节点不存在了，则重新获取锁        if (status == null) {            return acquireLock();        } else {             //阻塞当前进程，直到前一个节点释放锁            System.out.println(" 等待前一个节点锁释放，prelocakPath："+preLockPath);            //唤醒当前线程，继续尝试获取锁            cc.await();            return acquireLock();        }    }}
private Watcher watcher = new Watcher() {    @Override    public void process(WatchedEvent event) {         //监听到前一个节点释放锁，唤醒当前线程         cc.countDown();    }}

//利用Map记录线程持有的锁ConcurrentMap<Thread, LockData> lockMap = Maps.newConcurrentMap();public Boolean lock(){    Thread currentThread = Thread.currentThread();    LockData lockData = lockMap.get(currentThread);    //LockData不为空则说明已经有锁    if (lockData != null)        {       //加锁次数加一       lockData.lockCount.increment();       return true;    }    //没有锁则尝试获取锁    Boolean lockResult = acquireLock();    //获取到锁    if (lockResult)    {        LockData newLockData = new LockData(currentThread,1);        lockMap.put(currentThread, newLockData);        return true;    }    //获取锁失败    return false;}

public Boolean releaseLock(){    LockData lockData = lockMap.get(currentThread);    //没有锁    if(lockData == null){       return false;     }    //有锁则加锁次数减一    lockCount = lockData.lockCount.decrement();    if(lockCount > 0){        return true;    }     //加锁次数为0    try{        //删除节点        zkClient.delete(lockPath);        //断开连接        zkClient.close();    finally{        //删除加锁记录        lockMap.remove(currentThread);    }    return true;}