按时间中断net.LookupHost时golang内存泄漏

Question

I use this function to limit response time from DNS server

func LookupHost(hostname string, timeout time.Duration) ([]string, error) {
    c1 := make(chan []string)
    c2 := make(chan error)

    go func() {
        var ipaddr []string
        ipaddr, err := net.LookupHost(hostname)
        if err != nil {
            c2 <- err
            close(c2)
        }

        c1 <- ipaddr
        close(c1)
    }()

    select {
    case ipaddr := <-c1:
        return ipaddr, nil
    case err := <-c2:
        return []string{}, err
    case <-time.After(timeout):
        return []string{}, errors.New("timeout")
    }

}

The problem is that this function eat memory.
I think it is because I break net.LookupHost(hostname) syscall.

Any way to avoid this?
May be some other way how to query DNS servers with timeouts?

Answer 1

You can check an alternative implementation proposed in bogdanovich/dns_resolver

Its dns_resolver.go does include timeout management

resolver := dns_resolver.New([]string{"8.8.8.8", "8.8.4.4"})
// OR
// resolver := dns_resolver.NewFromResolvConf("resolv.conf")

// In case of i/o timeout
resolver.RetryTimes = 5

You can then wrap the all call in a goroutine, in order for the call to not break abruptly net.LookupHost().

ip, err := resolver.LookupHost("google.com")
if err != nil {
    log.Fatal(err.Error())
}
log.Println(ip)
// Output [216.58.192.46]