code/autoregistry/proxy/docker.go

package main

import (
	"bufio"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"github.com/docker/docker/api/types/image"
	"github.com/docker/docker/client"
	"io"
	"log"
	"os"
	"regexp"
	"strings"
	"time"
)

// based on an example from https://www.loginradius.com/blog/engineering/build-push-docker-images-golang/

type ErrorLine struct {
	Error       string      `json:"error"`
	ErrorDetail ErrorDetail `json:"errorDetail"`
}

type ErrorDetail struct {
	Message string `json:"message"`
}

// docker errors are so critical that the safest thing is to just exit and
// get restarted.
func exitOnDockerError() {
	if err := recover(); err != nil {
		log.Fatalf("Exiting the proxy because of a docker error\n", err)
		os.Exit(1)
	}
}

func print(rd io.Reader) error {
	var lastLine string

	scanner := bufio.NewScanner(rd)
	for scanner.Scan() {
		lastLine = scanner.Text()
		log.Println(scanner.Text())
	}

	errLine := &ErrorLine{}
	json.Unmarshal([]byte(lastLine), errLine)
	if errLine.Error != "" {
		return errors.New(errLine.Error)
	}

	if err := scanner.Err(); err != nil {
		return err
	}

	return nil
}

func GetDockerClient() *client.Client {
	cli, err := client.NewClientWithOpts(client.FromEnv, client.WithAPIVersionNegotiation())
	if err != nil {
		panic(err)
	}
	return cli
}

func GetDockerImageId(registry, image_name, tag_name string) (imageId, imageName string) {
	defer exitOnDockerError()
	full_image := registry + "/" + image_name
	if strings.HasPrefix(tag_name, "sha256:") || strings.HasPrefix(tag_name, "sha512:") {
		full_image += "@" + tag_name
	} else {
		full_image += ":" + tag_name
	}
	cli := GetDockerClient()

	images, err := cli.ImageList(context.Background(), image.ListOptions{})
	if err != nil {
		panic(err)
	}
	for _, image_obj := range images {
		for _, tag := range image_obj.RepoTags {
			if tag == full_image {
				return image_obj.ID, full_image
			}
		}
		for _, tag := range image_obj.RepoDigests {
			if tag == full_image {
				// now we need to find an image tag that is in the
				// registry and that has a regular tag so we can push it.
				for _, pushTag := range image_obj.RepoTags {
					if strings.HasPrefix(pushTag, registry+"/") {
						return image_obj.ID, pushTag
					}
				}
			}
		}
	}
	return "", ""
}

var lockChannel = make(chan string, 1)

func PushDockerImage(full_image string) {
	defer exitOnDockerError()
	log.Printf("Image %s is unavailable in backend", full_image)

	// only do one push at a time to be sure.
	select {
	case lockChannel <- "locking":
		{
			defer func() {
				<-lockChannel
			}()
		}
	case <-time.After(2 * time.Minute):
		{
			// kubernetes will retry anyway when a pull fails.
			log.Printf("Lock not acquired within the timout, client will have to retry pull later")
			return
		}
	}
	log.Printf("Got lock for pushing %s, starting push", full_image)

	cli := GetDockerClient()
	closer, err := cli.ImagePush(context.Background(), full_image,
		image.PushOptions{
			RegistryAuth: "abc123", // dummy
		})
	if err != nil {
		panic(err)
	}
	defer closer.Close()
	err = print(closer)
	if err != nil {
		panic(err)
	}
}

func TestDocker(host, port string) {
	cli, err := client.NewClientWithOpts(client.FromEnv, client.WithAPIVersionNegotiation())
	if err != nil {
		panic(err)
	}

	images, err := cli.ImageList(context.Background(), image.ListOptions{})
	if err != nil {
		panic(err)
	}
	for _, image := range images {
		for _, tag := range image.RepoTags {
			log.Println(image.ID, tag)
		}
	}

	// Now push an image
	closer, err := cli.ImagePush(context.Background(), host+":"+port+"/alpine:latest",
		image.PushOptions{
			All:           false,
			RegistryAuth:  "abc123", // dummy
			PrivilegeFunc: nil,
			Platform:      nil,
		})
	if err != nil {
		panic(err)
	}
	defer closer.Close()

	err = print(closer)
	if err != nil {
		panic(err)
	}

	// parsing image and tag from a context path

	path := "v2/alpine/manifests/latest"
	r := regexp.MustCompile("^v2/(.*)/manifests/([^/]+)$")
	matches := r.FindStringSubmatch(path)
	fmt.Println("Matches ", len(matches), matches)
	if len(matches) == 3 {
		fmt.Println("Match ", matches[1], matches[2])
	} else {
		fmt.Println("No match", matches)
	}

}

func CheckDockerAvailable() {
	log.Printf("Checking connection to docker daemon\n")
	client := GetDockerClient()
	_, err := client.ImageList(context.Background(), image.ListOptions{})
	if err != nil {
		panic(err)
	}
}