nats-autocluster.go

package main

import (
	"fmt"
	"net"
	"os/exec"
	"strconv"
	"strings"
	"sync"

	"github.com/nats-io/go-nats"
)

func main() {
	var ourIP net.IP
	var network *net.IPNet

	ifaces, _ := net.Interfaces()
	for _, i := range ifaces {
		fmt.Println("interface:", i.Name)

		addrs, _ := i.Addrs()
	iface:
		for _, a := range addrs {
			ip, ipnet, _ := net.ParseCIDR(a.String())
			if strings.HasPrefix(ipnet.IP.String(), "192.168.") {
				network = ipnet
				ourIP = ip
				break iface
			}
		}
	}

	lastSep := strings.LastIndex(network.IP.String(), ".")
	lastOct, _ := strconv.Atoi(network.IP.String()[lastSep+1:])
	routes := []string{"-cluster", "nats://0.0.0.0:5222", "-routes"}
	rLock := sync.Mutex{}
	wg := sync.WaitGroup{}

	for i := lastOct + 1; i < 50; i++ {
		address := fmt.Sprintf(network.IP.String()[:lastSep+1]+"%d", i)
		if address == ourIP.String() {
			fmt.Println("skipping our IP", ourIP.String())
			continue
		}

		wg.Add(1)
		go func() {
			fmt.Println("Dialing", address)
			_, err := nats.Connect("nats://" + address + ":4222")
			if err == nil {
				rLock.Lock()
				routes = append(routes, "nats://"+address+":5222")
				rLock.Unlock()
			}
			wg.Done()
		}()
	}

	wg.Wait()
	fmt.Println("Starting gnatsd and joining cluster through", routes)
	cmd := exec.Command("gnatsd", routes...)
	cmd.Run()
}