monitor docker events

sumosource.go

package main

import (
	"flag"
	"fmt"
	"os"
	"text/template"
	"io/ioutil"

	dockerapi "github.com/fsouza/go-dockerclient"
)

func main() {
	var sourceDir = flag.String("dir", "/etc/sumo", "Directory path where the new source config will be written")
	var dockerSocket = flag.String("socket", "unix:///var/run/docker.sock", "Docker socket")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
		fmt.Fprintf(os.Stderr, "  %s [options]\n\n", os.Args[0])
		flag.PrintDefaults()
	}

	flag.Parse()
	fmt.Println("dir=%s", *sourceDir)
	fmt.Println("socket=%s", *dockerSocket)

	dockerHost := os.Getenv("DOCKER_HOST")
	if dockerHost == "" {
		os.Setenv("DOCKER_HOST", "unix:///tmp/docker.sock")
	}
	docker, err := dockerapi.NewClient(*dockerSocket)
	if err != nil {
		fmt.Println("error")
	}
	events := make(chan *dockerapi.APIEvents)
	fmt.Println("listening for docker events...")
	docker.AddEventListener(events)
	quit := make(chan struct{})
	for msg := range events {
		switch msg.Status {
		case "start":
			fmt.Println("container started: %+v", msg)
			///TODO: create sumo source config file here
			parseTemplate("templates/app.tmpl", msg)
		case "die":
			fmt.Println("container died: %+v", msg)
		}
	}

	<-quit
}

func parseTemplate(path string, event *dockerapi.APIEvents) bool {
	tmplStr, err := getTemplate(path)
	if err != nil {
		return false
	}
	tmpl, err := template.New("tmpl").Parse(tmplStr)	
	if err != nil {
		return false
	}
	data := struct {
		HostName string
		AppName string
		Prefix string
	}{
		HostName: "i-wei-speedtest",
		AppName: event.Actor.Attributes["name"],
		Prefix: "THOR_",
	}
	err = tmpl.Execute(os.Stdout, data)
	if err != nil {
		return false
	}
	return true
}

func getTemplate(path string) (string, error) {
	file, err := os.Open(path)
	if err != nil {
		return "", err
	}

	str, err := ioutil.ReadAll(file)
	if err != nil {
		return "", err
	}
	
	return string(str), nil
}