podex.go

/*
Copyright 2014 Google Inc. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

// podex is a command line tool to bootstrap kubernetes container
// manifest from docker image metadata.
//
// Manifests can then be edited by a human to match deployment needs.
//
// Example usage:
//
// $ docker pull google/nodejs-hello
// $ podex -yaml google/nodejs-hello > google/nodejs-hello/pod.yaml
// $ podex -json google/nodejs-hello > google/nodejs-hello/pod.json

package main

import (
	"encoding/json"
	"flag"
	"log"
	"os"
	"strconv"
	"strings"

	"github.com/GoogleCloudPlatform/kubernetes/pkg/api/v1beta1"
	dockerclient "github.com/fsouza/go-dockerclient"
	"github.com/ghodss/yaml"
)

const usage = "usage: podex [-json|-yaml] [-id PODNAME] IMAGES"

var generateJSON = flag.Bool("json", false, "generate json manifest")
var generateYAML = flag.Bool("yaml", false, "generate yaml manifest")
var podName = flag.String("id", "", "set pod name")

func main() {
	flag.Parse()

	if flag.NArg() < 1 {
		log.Fatal(usage)
	}
	if *podName == "" {
		if flag.NArg() > 1 {
			log.Fatal(usage)
		}
		_, *podName = parseDockerImage(flag.Arg(0))
	}

	if (!*generateJSON && !*generateYAML) || (*generateJSON && *generateYAML) {
		log.Fatal(usage)
	}

	dockerHost := os.Getenv("DOCKER_HOST")
	if dockerHost == "" {
		log.Fatalf("DOCKER_HOST is not set")
	}
	docker, err := dockerclient.NewClient(dockerHost)
	if err != nil {
		log.Fatalf("failed to connect to %q: %v", dockerHost, err)
	}

	podContainers := []v1beta1.Container{}

	for _, imageName := range flag.Args() {
		parts, baseName := parseDockerImage(imageName)
		container := v1beta1.Container{
			Name:  baseName,
			Image: imageName,
		}

		// TODO(proppy): use the regitry API instead of the remote API to get image metadata.
		img, err := docker.InspectImage(imageName)
		if err != nil {
			log.Fatalf("failed to inspect image %q: %v", imageName, err)
		}
		for p := range img.Config.ExposedPorts {
			port, err := strconv.Atoi(p.Port())
			if err != nil {
				log.Fatalf("failed to parse port %q: %v", parts[0], err)
			}
			container.Ports = append(container.Ports, v1beta1.Port{
				Name:          strings.Join([]string{baseName, p.Proto(), p.Port()}, "-"),
				ContainerPort: port,
				Protocol:      v1beta1.Protocol(strings.ToUpper(p.Proto())),
			})
		}
		podContainers = append(podContainers, container)
	}

	// TODO(proppy): add flag to handle multiple version
	manifest := v1beta1.ContainerManifest{
		Version:    "v1beta1",
		ID:         *podName + "-pod",
		Containers: podContainers,
		RestartPolicy: v1beta1.RestartPolicy{
			Always: &v1beta1.RestartPolicyAlways{},
		},
	}

	if *generateJSON {
		bs, err := json.MarshalIndent(manifest, "", "  ")
		if err != nil {
			log.Fatalf("failed to render JSON container manifest: %v", err)
		}
		os.Stdout.Write(bs)
	}
	if *generateYAML {
		bs, err := yaml.Marshal(manifest)
		if err != nil {
			log.Fatalf("failed to render YAML container manifest: %v", err)
		}
		os.Stdout.Write(bs)
	}
}

// parseDockerImage split a docker image name of the form [REGISTRYHOST/][USERNAME/]NAME[:TAG]
// TODO: handle the TAG
// Returns array of images name parts and base image name
func parseDockerImage(imageName string) (parts []string, baseName string) {
	// Parse docker image name
	// IMAGE: [REGISTRYHOST/][USERNAME/]NAME[:TAG]
	// NAME: [a-z0-9-_.]
	parts = strings.Split(imageName, "/")
	baseName = parts[len(parts)-1]
	return
}