Redis分布式锁不生效

Question

我正在使用go-redis distributed lock实现互斥访问，我的服务器是单线程服务器。但与此同时，许多请求得到 distributed lock.

func (redisMgrPtr *RedisMgr) getLock(key string) (int32) {
    encodeKey := transcoding.Base64Encode(key)
    _, err := redisMgrPtr.redisClient.SetNX(redisMgrPtr.ctx, 
    encodeKey, 1, TIMEOUT).Result()
    if err != nil {
        return -1
    }
    return 0
}

func (redisMgrPtr *RedisMgr) delLock(key string, sessionId string) {
    encodeKey := transcoding.Base64Encode(key)
    redisMgrPtr.redisClient.Del(redisMgrPtr.ctx, encodeKey)
    Log.Errorf("session[%s] del lock", sessionId)
}

获取锁码是这样的：

func (redisMgrPtr *RedisMgr) GetServer(name string, session string) () {
    for { 
        locRes := redisMgrPtr.getLock(name) 
        if locRes == 0 {
            break
        } else {
            time.Sleep(5 * time.Millisecond)
            continue
        }
    }
    defer redisMgrPtr.delLock(sceneLock, sessionId)
    Log.Errorf("session[%s] get lock", sessionId)
    // do something
}

我发现很多请求同时获得了锁，结果是

2021-09-08T15:05:21.073+0800 session[51776955325] get lock
2021-09-08T15:05:21.073+0800 session[91776955325] get lock
2021-09-08T15:05:21.073+0800 session[71776955325] get lock

我觉得同一时间只有一个session能拿到锁

Answer 1

问题似乎出在锁定功能上。它不检查值是否存在，它只检查错误。

func (redisMgrPtr *RedisMgr) getLock(key string) (int32) {
    encodeKey := transcoding.Base64Encode(key)
    wasSet, err := redisMgrPtr.redisClient.SetNX(redisMgrPtr.ctx, encodeKey, 1, TIMEOUT).Result()
    if err != nil || !wasSet {
        return -1
    }
    return 0
}

... 或使用布尔值更容易推理：

func (redisMgrPtr *RedisMgr) getLock(key string) (ok bool) {
    encodeKey := transcoding.Base64Encode(key)
    wasSet, err := redisMgrPtr.redisClient.SetNX(redisMgrPtr.ctx, encodeKey, 1, TIMEOUT).Result()
    return err == nil && wasSet
}

布尔版本 GetServer 可能如下所示：

func (redisMgrPtr *RedisMgr) GetServer(name string, session string) () {
    for { 
        if ok := redisMgrPtr.getLock(name); ok {
            break
        }
        time.Sleep(5 * time.Millisecond)
    }
    defer redisMgrPtr.delLock(sceneLock, sessionId)
    Log.Errorf("session[%s] get lock", sessionId)
    // do something
}

Redis分布式锁不生效

Redis distributed lock does not take effect

go

redis

go-redis