go redis锁

redis经常用作分布式锁，这里记录一个简单的锁代码如下：

package main

import (
    "crypto/rand"
    "encoding/base64"
    "fmt"
    "github.com/go-redis/redis"
    "io"
    "sync"
    "time"
)

func main() {
    addr := "192.168.100.30:6379"
    rdb := redis.NewUniversalClient(&redis.UniversalOptions{
        Addrs:    []string {addr},
        Password: "", // no password set
        DB:       0,  // use default DB
    })
    defer func() {
        _ = rdb.Close()
    }()

    key := "gavin-lock"
    uid, err := Lock(rdb, key, time.Second*1, time.Second*2)
    if err == nil {
        _ = Unlock(rdb, key, uid)
    }
}

var randMutex sync.Mutex
var randBytes []byte

// 获取随机字串
func randToken() string {
    randMutex.Lock()
    defer randMutex.Unlock()

    if len(randBytes) == 0 {
        randBytes = make([]byte, 16)
    }

    if _, err := io.ReadFull(rand.Reader, randBytes); err != nil {
        return ""
    }
    return base64.RawURLEncoding.EncodeToString(randBytes)
}

func Lock(redisClient redis.UniversalClient, lockKey string, acquireTimeOut, lockTimeOut time.Duration) (token string, err error) {
    token = randToken()
    var acquireDuration = acquireTimeOut

    for acquireDuration > 0 {
        ok, err := redisClient.SetNX(lockKey, token, lockTimeOut).Result()
        if err != nil {
            fmt.Printf("redis锁 - 加锁失败 key: %s, token: %s, ttl: %v, err: %v\r\n", lockKey, token, lockTimeOut, err)
            return "", err
        }

        if ok {
            fmt.Printf("redis锁 - 加锁成功 key: %s, token: %s, ttl: %v\r\n", lockKey, token, lockTimeOut)
            return token, nil
        }
        time.Sleep(time.Millisecond * 100) // next: sleep 500ms
        acquireDuration -= time.Millisecond * 100
    }
    fmt.Printf("redis锁 - 加锁超时 key: %s, token: %s, ttl: %v\r\n", lockKey, token, acquireTimeOut)
    return "", fmt.Errorf("获取redis锁超时: %v\r\n", acquireTimeOut)
}

func Unlock(redisClient redis.UniversalClient, lockKey, token string) error {
    const script = `if redis.call('GET', KEYS[1]) == ARGV[1] then return redis.call('DEL', KEYS[1]) else return 0 end`
    ret, err := redisClient.Eval(script, []string{lockKey}, token).Result()
    if err != nil {
        fmt.Printf("redis锁 - 解锁失败 key: %s, token: %s,  err: %v\r\n", lockKey, token, err)
        return err
    }

    if v, ok := ret.(int64); ok && v == 1 {
        fmt.Printf("redis锁 - 解锁成功 key: %s, token: %s\r\n", lockKey, token)
        return nil
    }

    fmt.Printf("redis锁 - 解锁失败 key: %s, token: %s, key已经过期\r\n", lockKey, token)
    return nil
}