main.go

package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"strings"
	"time"

	"github.com/samuel/go-zookeeper/zk"
)

type Property struct {
	Key   string
	Value string
}

var (
	zookeeper   *string
	namespace   *string
	srcTemplate *string
	destConf    *string
	command     *string
	aSync       *bool

	conn                *zk.Conn
	zookeeperProperties []Property
	eventChannel        <-chan zk.Event
	child               []string
)

func flags() {
	zookeeper = flag.String("zookeeper", "192.168.120.81:2181,192.168.120.82:2181", "Zookeeper server list example: 192.168.120.1:2181,192.168.120.2:2181,..")
	namespace = flag.String("namespace", "/watch", "Namespace to watch on")
	srcTemplate = flag.String("template", "", "srcTemplate absolut path")
	destConf = flag.String("destConf", "", "Generated config absolut path")
	aSync = flag.Bool("aSync", false, "Asyncron command execution")
	command = flag.String("cmd", "", "Command execute after regenerate config")

	flag.Parse()
}

func main() {
	flags()

	if *srcTemplate != "" && *destConf == "" {
		println("destConf option must be set")
		flag.Usage()
		os.Exit(2)
	}

	if *srcTemplate == "" && *destConf != "" {
		println("srcTemplate option must be set")
		flag.Usage()
		os.Exit(2)
	}

	if *command == "" && *srcTemplate == "" {
		println("At least you have to set srcTemplate path or a command to execute after change event")
		flag.Usage()
		os.Exit(2)
	}

	splittedCommand := strings.Split(*command, " ")
	cmd := &Command{
		Cmd:   splittedCommand[0],
		Args:  splittedCommand[1:],
		Async: *aSync,
	}

	conf := &Config{
		Template: *srcTemplate,
		Dest:     *destConf,
	}
	conf.Init()
	defer conf.Close()

	conn, _, _ = zk.Connect(strings.Split(*zookeeper, ","), time.Second)
	defer conn.Close()

	log.Printf("connected to zookeepers: %v", *zookeeper)
	log.Printf("Watch on: %s", *namespace)

	eventChannel, zookeeperProperties = getChildW(*namespace)
	conf.GenerateConfig(zookeeperProperties)

	for true {
		zookeeperProperties = []Property{}

		<-eventChannel
		eventChannel, zookeeperProperties = getChildW(*namespace)
		conf.GenerateConfig(zookeeperProperties)
		cmd.Execute()
	}
}

func getChildW(namespace string) (ch <-chan zk.Event, properties []Property) {

	child, _, ch, _ = conn.ChildrenW(namespace)

	for _, key := range child {
		value, _, _ := conn.Get(fmt.Sprintf("%s/%s", namespace, key))

		// bypass directory
		if string(value) != "" {
			properties = append(properties, Property{
				Key:   key,
				Value: string(value),
			})
		}
	}

	return
}