execute cmd on multiple server via ssh

go-ssh.go

package main

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"os"
	"time"

	"code.google.com/p/go.crypto/ssh"
)

func exitIf(err error) {
	if err != nil {
		fmt.Println("error:", err)
		os.Exit(-1)
	}
}

func makeKeyAuth(keyname string) ssh.AuthMethod {
	fp, err := os.Open(keyname)
	exitIf(err)
	defer fp.Close()

	buf, err := ioutil.ReadAll(fp)
	exitIf(err)

	signer, err := ssh.ParsePrivateKey(buf)
	exitIf(err)

	return ssh.PublicKeys(signer)
}

func executeCmd(cmd, hostname string, config *ssh.ClientConfig) string {
	conn, err := ssh.Dial("tcp", hostname, config)
	exitIf(err)

	session, err := conn.NewSession()
	exitIf(err)

	defer session.Close()

	var stdoutBuf bytes.Buffer
	session.Stdout = &stdoutBuf
	session.Run(cmd)

	return hostname + ": " + stdoutBuf.String()
}

func main() {
	cmd := os.Args[1]
	hosts := os.Args[2:]

	results := make(chan string, 10)
	config := &ssh.ClientConfig{
		User: os.Getenv("LOGNAME"),
		Auth: []ssh.AuthMethod{
			makeKeyAuth(os.Getenv("HOME") + "/.ssh/id_rsa"),
		},
	}

	for _, hostname := range hosts {
		go func(hostname string) {
			results <- executeCmd(cmd, hostname, config)
		}(hostname)
	}

	timeout := time.After(30 * time.Second)
	for i := 0; i < len(hosts); i++ {
		select {
		case res := <-results:
			fmt.Print(res)
		case <-timeout:
			fmt.Println("Timed out!")
			return
		}
	}
}