[go-nuts] Why can net.Dial be very slow on a hostname defined in /etc/hosts?

[Peng Yu]

Hi,

I run the following go program using net.Dial(). Depending on whether
I specify a local hostname (defined in /etc/hosts) or an IP. I get
very different runtimes.

But `ping mymachine.local` resolves the hostname to an IP address
instantaneously. So the two calls of the go program should have the
same runtimes.

Can anybody reproduce the same runtime problem? Does anybody know what
is wrong with the implementation of net.Dial()? Thanks.

$ ./main mymachine.local:22
2021/02/22 14:14:25 before
2021/02/22 14:14:30 after
$ ./main 192.168.1.104:22
2021/02/22 14:14:30 before
2021/02/22 14:14:30 after
$ cat main.go
package main
import (
  "net"
  "log"
  "os"
)

func main() {
  dialAddr := os.Args[1]
  log.Println("before")
  _, err := net.Dial("tcp", dialAddr)
  log.Println("after")
  if err != nil {
    log.Fatalln(err)
  }
}

-- 
Regards,
Peng

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