redis分布式锁可重入锁

Redis分布式锁可重入锁是指同一个线程在持有锁的情况下可以再次获取该锁而不会被阻塞。这种锁的实现需要在锁的value中记录当前线程持有锁的次数，每次释放锁时将次数减1，直到次数为0时才真正释放锁。

实现可重入锁的代码如下：

def acquire_lock(conn, lockname, acquire_timeout=10, lock_timeout=10):
    identifier = str(uuid.uuid4())
    lock_key = 'lock:' + lockname
    lock_value = identifier + ':' + str(1)
    end = time.time() + acquire_timeout
    while time.time() < end:
        if conn.setnx(lock_key, lock_value):
            conn.expire(lock_key, lock_timeout)
            return identifier
        elif conn.ttl(lock_key) == -1:
            conn.expire(lock_key, lock_timeout)
        else:
            time.sleep(0.1)
    return False

def release_lock(conn, lockname, identifier):
    lock_key = 'lock:' + lockname
    pipe = conn.pipeline(True)
    while True:
        try:
            pipe.watch(lock_key)
            lock_value = pipe.get(lock_key)
            if not lock_value:
                return True
            if lock_value.decode('utf-8').split(':')[0] == identifier:
                if int(lock_value.decode('utf-8').split(':')[1]) > 1:
                    new_lock_value = identifier + ':' + str(int(lock_value.decode('utf-8').split(':')[1])-1)
                    pipe.multi()
                    pipe.set(lock_key, new_lock_value)
                    pipe.execute()
                    return True
                else:
                    pipe.multi()
                    pipe.delete(lock_key)
                    pipe.execute()
                    return True
            pipe.unwatch()
            break
        except redis.exceptions.WatchError:
            pass
    return False