redigo不同池连接到单个服务器

Question

因此，我有必要连接到3 redis服务器。我创建了3个连接池，并初始化每个连接池。但是redigo似乎只连接到单个redis服务器，尽管我使用不同的池获得连接。

使用redigo，下面是我的代码

import (
    "fmt"
    "time"
    "github.com/garyburd/redigo/redis"
)

var poolA *redis.Pool
var poolB *redis.Pool
var poolC *redis.Pool

func main() {
    poolA = &redis.Pool{}
    poolB = &redis.Pool{}
    poolC = &redis.Pool{}

    connections := []string{"localhost:6379", "localhost2:6379", "localhost3:6379"}

    for k, v := range connections {
        redisPool := &redis.Pool{
            Dial: func() (redis.Conn, error) {
                return redis.Dial("tcp", v)
            },
            TestOnBorrow: func(c redis.Conn, t time.Time) error {
                if time.Since(t) < time.Minute {
                    return nil
                }
                _, err := c.Do("PING")
                return err
            },
            IdleTimeout: time.Duration(10) * time.Second,
            MaxActive:   100,
            MaxIdle:     100 / 2,
            Wait:        true,
        }

        if k == 0 {
            fmt.Println("poolA:", v)
            poolA = redisPool
        }
        if k == 1 {
            fmt.Println("poolB:", v)
            poolB = redisPool
        }
        if k == 2 {
            fmt.Println("poolC:", v)
            poolC = redisPool
        }
    }

    con := poolA.Get()
    defer con.Close()
    count, err := redis.Int(con.Do("SADD", "any:test", 3246))
    if err != nil {
        fmt.Println("error querying redis:", err.Error())
    }
    fmt.Println("count=", count)

    con2 := poolB.Get()
    defer con2.Close()
    count, err = redis.Int(con2.Do("SADD", "any:test", 3246))
    if err != nil {
        fmt.Println("error querying redis:", err.Error())
    }
    fmt.Println("count=", count)

    con3 := poolC.Get()
    defer con3.Close()
    count, err = redis.Int(con3.Do("SADD", "any:test", 3246))
    if err != nil {
        fmt.Println("error querying redis:", err.Error())
    }
    fmt.Println("count=", count)
}

问题是，所有三个池都连接到最后一个服务器/连接，结果如下所示。知道吗？

poolA: localhost:6379
poolB: localhost2:6379
poolC: localhost3:6379
error querying redis: dial tcp: lookup localhost3: no such host
count= 0
error querying redis: dial tcp: lookup localhost3: no such host
count= 0
error querying redis: dial tcp: lookup localhost3: no such host
count= 0

Process finished with exit code 0

Answer 1

拨号函数使用单变量v。函数使用调用时分配给v的最后一个值。

要解决这个问题，请在for循环的作用域中声明一个变量，并在拨号函数中使用该变量：

for k, v := range connections {
    v := v // Declare variable scoped inside for loop 
    redisPool := &redis.Pool{
        Dial: func() (redis.Conn, error) {
            return redis.Dial("tcp", v)  // uses variable scoped inside for loop
        },
    ...

与此问题不同，池设置没有意义。由于池被配置为丢弃已空闲10秒的连接，因此，对借入函数的测试永远不会触发服务器。