refactor: Split up code for readability and add docs
This commit is contained in:
Vincent Ambo
parent
1c2d087ec4
commit
fa43472a5d
4 changed files with 242 additions and 159 deletions
12
const.go
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12
const.go
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@ -0,0 +1,12 @@
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package main
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// HTTP content types
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const ImageConfigMediaType string = "application/vnd.docker.container.image.v1+json"
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const ManifestMediaType string = "application/vnd.docker.distribution.manifest.v2+json"
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const LayerMediaType string = "application/vnd.docker.image.rootfs.diff.tar.gzip"
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// HTTP header names
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const ContentType string = "Content-Type"
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const DigestHeader string = "Docker-Content-Digest"
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158
image.go
158
image.go
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@ -1,28 +1,150 @@
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// The code in this file creates a Docker image layer containing the binary of the
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// application itself.
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package main
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import "time"
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import (
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"archive/tar"
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"bytes"
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"compress/gzip"
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"crypto/sha256"
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"encoding/json"
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"fmt"
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"io/ioutil"
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"log"
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"os"
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"time"
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)
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type RootFs struct {
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DiffIds []string `json:"diff_ids"`
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Type string `json:"type"`
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// This function creates a Docker-image digest (i.e. SHA256 hash with
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// algorithm-specification prefix)
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func Digest(b []byte) string {
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hash := sha256.New()
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hash.Write(b)
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return fmt.Sprintf("sha256:%x", hash.Sum(nil))
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}
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type History struct {
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Created time.Time `json:"created"`
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CreatedBy string `json:"created_by"`
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func GetImageOfCurrentExecutable() Image {
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binary := getCurrentBinary()
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tarArchive := createTarArchive(&map[string][]byte{
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"/main": binary,
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})
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configJson, configElem := createConfig([]string{Digest(tarArchive)})
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compressed := gzipArchive("Quinistry image", tarArchive)
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manifest := createManifest(&configElem, &compressed)
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manifestJson, _ := json.Marshal(manifest)
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return Image{
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Layer: compressed,
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LayerDigest: Digest(compressed),
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Manifest: manifestJson,
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ManifestDigest: Digest(manifestJson),
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Config: configJson,
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ConfigDigest: Digest(configJson),
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}
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}
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type ImageConfig struct {
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Cmd []string
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Env []string
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func getCurrentBinary() []byte {
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path, _ := os.Executable()
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file, _ := ioutil.ReadFile(path)
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return file
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}
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type Config struct {
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Created time.Time `json:"created"`
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Author string `json:"author"`
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Architecture string `json:"architecture"`
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Os string `json:"os"`
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Config *ImageConfig `json:"config"`
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RootFs RootFs `json:"rootfs"`
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History []History `json:"history"`
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func createTarArchive(files *map[string][]byte) []byte {
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buf := new(bytes.Buffer)
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w := tar.NewWriter(buf)
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for name, file := range *files {
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hdr := &tar.Header{
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Name: name,
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// Everything is executable \o/
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Mode: 0755,
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Size: int64(len(file)),
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}
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w.WriteHeader(hdr)
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w.Write(file)
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}
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if err := w.Close(); err != nil {
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log.Fatalln(err)
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os.Exit(1)
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}
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return buf.Bytes()
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}
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func gzipArchive(name string, archive []byte) []byte {
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buf := new(bytes.Buffer)
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w := gzip.NewWriter(buf)
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w.Name = name
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w.Write(archive)
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if err := w.Close(); err != nil {
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log.Fatalln(err)
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os.Exit(1)
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}
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return buf.Bytes()
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}
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func createConfig(layerDigests []string) (configJson []byte, elem Element) {
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now := time.Now()
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imageConfig := &ImageConfig{
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Cmd: []string{"/main"},
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Env: []string{"PATH=/"},
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}
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rootFs := RootFs{
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DiffIds: layerDigests,
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Type: "layers",
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}
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history := []History{
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{
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Created: now,
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CreatedBy: "Quinistry magic",
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},
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}
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config := Config{
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Created: now,
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Author: "tazjin",
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Architecture: "amd64",
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Os: "linux",
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Config: imageConfig,
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RootFs: rootFs,
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History: history,
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}
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configJson, _ = json.Marshal(config)
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elem = Element{
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MediaType: ImageConfigMediaType,
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Size: len(configJson),
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Digest: Digest(configJson),
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}
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return
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}
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func createManifest(config *Element, layer *[]byte) Manifest {
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layers := []Element{
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{
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MediaType: LayerMediaType,
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Size: len(*layer),
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// Layers must contain the digest of the *gzipped* layer.
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Digest: Digest(*layer),
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},
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}
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return Manifest{
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SchemaVersion: 2,
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MediaType: ManifestMediaType,
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Config: *config,
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Layers: layers,
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}
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}
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152
main.go
152
main.go
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@ -1,92 +1,18 @@
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package main
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import (
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"archive/tar"
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"bytes"
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"compress/gzip"
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"crypto/sha256"
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"encoding/json"
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"fmt"
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"io/ioutil"
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"log"
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"net/http"
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"os"
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"time"
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)
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const ImageContentType string = "application/vnd.docker.container.image.v1+json"
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const ManifestContentType string = "application/vnd.docker.distribution.manifest.v2+json"
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const LayerContentType string = "application/vnd.docker.image.rootfs.diff.tar.gzip"
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const DigestHeader string = "Docker-Content-Digest"
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type Element struct {
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MediaType string `json:"mediaType"`
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Size int `json:"size"`
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Digest string `json:"digest"`
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}
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type Manifest struct {
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SchemaVersion int `json:"schemaVersion"`
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MediaType string `json:"mediaType"`
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Config Element `json:"config"`
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Layers []Element `json:"layers"`
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}
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// A really "dumb" representation of an image, with a data blob (tar.gz image) and its hash as the type expected
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// in the manifest.
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type Image struct {
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Data []byte
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TarDigest string
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GzipDigest string
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}
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func main() {
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log.Println("Starting quinistry")
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img := getImage()
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now := time.Now()
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image := GetImageOfCurrentExecutable()
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config := Config{
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Created: now,
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Author: "tazjin",
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Architecture: "amd64",
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Os: "linux",
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Config: &ImageConfig{
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Cmd: []string{"main"},
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Env: []string{"PATH=/"},
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},
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RootFs: RootFs{
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DiffIds: []string{
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img.TarDigest,
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},
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Type: "layers",
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},
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History: []History{
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{
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Created: now,
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CreatedBy: "quinistry magic",
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},
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},
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}
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configJson, _ := json.Marshal(config)
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manifest := Manifest{
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SchemaVersion: 2,
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MediaType: ManifestContentType,
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Config: Element{
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MediaType: ImageContentType,
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Size: len(configJson),
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Digest: digest(configJson),
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},
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Layers: []Element{
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{
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MediaType: LayerContentType,
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Size: len(img.Data),
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Digest: img.GzipDigest,
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},
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},
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}
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layerUri := fmt.Sprintf("/v2/quinistry/blobs/%s", image.LayerDigest)
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configUri := fmt.Sprintf("/v2/quinistry/blobs/%s", image.ConfigDigest)
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log.Fatal(http.ListenAndServe(":8080", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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// Acknowledge that we speak V2
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@ -99,29 +25,26 @@ func main() {
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// Serve manifest
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if r.RequestURI == "/v2/quinistry/manifests/latest" {
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logRequest("Serving manifest", r)
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w.Header().Add("Content-Type", ManifestContentType)
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resp, _ := json.Marshal(manifest)
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w.Header().Add(DigestHeader, digest(resp))
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w.Write(resp)
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w.Header().Set(ContentType, ManifestMediaType)
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w.Header().Add(DigestHeader, image.ManifestDigest)
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w.Write(image.Manifest)
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return
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}
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// Serve actual image layer
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layerUri := fmt.Sprintf("/v2/quinistry/blobs/%s", img.GzipDigest)
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if r.RequestURI == layerUri {
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logRequest("Serving image layer blob", r)
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w.Header().Add(DigestHeader, img.GzipDigest)
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w.Write(img.Data)
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w.Header().Add(DigestHeader, image.LayerDigest)
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w.Write(image.Layer)
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return
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}
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// Serve image config
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configUri := fmt.Sprintf("/v2/quinistry/blobs/%s", digest(configJson))
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if r.RequestURI == configUri {
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logRequest("Serving config", r)
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w.Header().Set("Content-Type", ImageContentType)
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w.Header().Set(DigestHeader, digest(configJson))
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w.Write(configJson)
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w.Header().Set("Content-Type", ImageConfigMediaType)
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w.Header().Set(DigestHeader, image.ConfigDigest)
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w.Write(image.Config)
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return
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}
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@ -132,56 +55,3 @@ func main() {
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func logRequest(msg string, r *http.Request) {
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log.Printf("%s: %s %s\n", msg, r.Method, r.RequestURI)
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}
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func digest(b []byte) string {
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hash := sha256.New()
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hash.Write(b)
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return fmt.Sprintf("sha256:%x", hash.Sum(nil))
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}
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// Creates an image of the currently running binary (spooky!)
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func getImage() *Image {
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// Current binary, imagine this is some other output or whatever
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path, _ := os.Executable()
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// don't care about error! :O
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file, _ := ioutil.ReadFile(path)
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// First create tar archive
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tarBuf := new(bytes.Buffer)
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tarW := tar.NewWriter(tarBuf)
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hdr := &tar.Header{
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Name: "/main",
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Mode: 0755,
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Size: int64(len(file)),
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}
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tarW.WriteHeader(hdr)
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tarW.Write(file)
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if err := tarW.Close(); err != nil {
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log.Fatalln(err)
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os.Exit(1)
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}
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tarBytes := tarBuf.Bytes()
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// Then GZIP it
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zBuf := new(bytes.Buffer)
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zw := gzip.NewWriter(zBuf)
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zw.Name = "Docker registry fake test"
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zw.Write(tarBytes)
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if err := zw.Close(); err != nil {
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log.Fatal(err)
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os.Exit(1)
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}
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gzipData := zBuf.Bytes()
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return &Image{
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TarDigest: digest(tarBytes),
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GzipDigest: digest(gzipData),
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Data: gzipData,
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}
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}
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79
types.go
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79
types.go
Normal file
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@ -0,0 +1,79 @@
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package main
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import "time"
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// This type represents the rootfs-key of the Docker image config.
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// It specifies the digest (i.e. usually SHA256 hash) of the tar'ed, but NOT
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// compressed image layers.
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type RootFs struct {
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// The digests of the non-compressed FS layers.
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DiffIds []string `json:"diff_ids"`
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// Type should always be set to "layers"
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Type string `json:"type"`
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}
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// This type represents an entry in the Docker image config's history key.
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// Every history element "belongs" to a filesystem layer.
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type History struct {
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Created time.Time `json:"created"`
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CreatedBy string `json:"created_by"`
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}
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// This type represents runtime-configuration for the Docker image.
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// A lot of possible keys are omitted here, see:
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// https://github.com/docker/docker/blob/master/image/spec/v1.2.md#image-json-description
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type ImageConfig struct {
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Cmd []string
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Env []string
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}
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// This type represents the Docker image configuration
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type Config struct {
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Created time.Time `json:"created"`
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Author string `json:"author"`
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// Architecture should be "amd64"
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Architecture string `json:"architecture"`
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// OS should be "linux"
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Os string `json:"os"`
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// Configuration can be set to 'nil', in which case all options have to be
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// supplied at container launch time.
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Config *ImageConfig `json:"config"`
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// Filesystem layers and history elements have to be in the same order.
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RootFs RootFs `json:"rootfs"`
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History []History `json:"history"`
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}
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// This type represents any manifest
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type Element struct {
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MediaType string `json:"mediaType"`
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Size int `json:"size"`
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Digest string `json:"digest"`
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}
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// This type represents a Docker image manifest as used by the registry
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// protocol V2.
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type Manifest struct {
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SchemaVersion int `json:"schemaVersion"` // Must be 2
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MediaType string `json:"mediaType"` // Use ManifestMediaType const
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Config Element `json:"config"`
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Layers []Element `json:"layers"`
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}
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// A really "dumb" representation of an image, with its data blob and related
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// metadata.
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// Note: This is not a registry API type.
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type Image struct {
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Layer []byte
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LayerDigest string
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Manifest []byte
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ManifestDigest string
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Config []byte
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ConfigDigest string
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}
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