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moby--moby/image/tarexport/save.go

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package tarexport // import "github.com/docker/docker/image/tarexport"
import (
"encoding/json"
"fmt"
"io"
"os"
"path"
"path/filepath"
"time"
"github.com/docker/distribution"
"github.com/docker/distribution/reference"
"github.com/docker/docker/image"
v1 "github.com/docker/docker/image/v1"
"github.com/docker/docker/layer"
"github.com/docker/docker/pkg/archive"
"github.com/docker/docker/pkg/system"
"github.com/opencontainers/go-digest"
"github.com/pkg/errors"
)
type imageDescriptor struct {
refs []reference.NamedTagged
layers []string
image *image.Image
layerRef layer.Layer
}
type saveSession struct {
*tarexporter
outDir string
images map[image.ID]*imageDescriptor
savedLayers map[string]struct{}
diffIDPaths map[layer.DiffID]string // cache every diffID blob to avoid duplicates
}
func (l *tarexporter) Save(names []string, outStream io.Writer) error {
images, err := l.parseNames(names)
if err != nil {
return err
}
// Release all the image top layer references
defer l.releaseLayerReferences(images)
return (&saveSession{tarexporter: l, images: images}).save(outStream)
}
// parseNames will parse the image names to a map which contains image.ID to *imageDescriptor.
// Each imageDescriptor holds an image top layer reference named 'layerRef'. It is taken here, should be released later.
func (l *tarexporter) parseNames(names []string) (desc map[image.ID]*imageDescriptor, rErr error) {
imgDescr := make(map[image.ID]*imageDescriptor)
defer func() {
if rErr != nil {
l.releaseLayerReferences(imgDescr)
}
}()
addAssoc := func(id image.ID, ref reference.Named) error {
if _, ok := imgDescr[id]; !ok {
descr := &imageDescriptor{}
if err := l.takeLayerReference(id, descr); err != nil {
return err
}
imgDescr[id] = descr
}
if ref != nil {
if _, ok := ref.(reference.Canonical); ok {
return nil
}
tagged, ok := reference.TagNameOnly(ref).(reference.NamedTagged)
if !ok {
return nil
}
for _, t := range imgDescr[id].refs {
if tagged.String() == t.String() {
return nil
}
}
imgDescr[id].refs = append(imgDescr[id].refs, tagged)
}
return nil
}
for _, name := range names {
ref, err := reference.ParseAnyReference(name)
if err != nil {
return nil, err
}
namedRef, ok := ref.(reference.Named)
if !ok {
// Check if digest ID reference
if digested, ok := ref.(reference.Digested); ok {
id := image.IDFromDigest(digested.Digest())
if err := addAssoc(id, nil); err != nil {
return nil, err
}
continue
}
return nil, errors.Errorf("invalid reference: %v", name)
}
if reference.FamiliarName(namedRef) == string(digest.Canonical) {
imgID, err := l.is.Search(name)
if err != nil {
return nil, err
}
if err := addAssoc(imgID, nil); err != nil {
return nil, err
}
continue
}
if reference.IsNameOnly(namedRef) {
assocs := l.rs.ReferencesByName(namedRef)
for _, assoc := range assocs {
if err := addAssoc(image.IDFromDigest(assoc.ID), assoc.Ref); err != nil {
return nil, err
}
}
if len(assocs) == 0 {
imgID, err := l.is.Search(name)
if err != nil {
return nil, err
}
if err := addAssoc(imgID, nil); err != nil {
return nil, err
}
}
continue
}
id, err := l.rs.Get(namedRef)
if err != nil {
return nil, err
}
if err := addAssoc(image.IDFromDigest(id), namedRef); err != nil {
return nil, err
}
}
return imgDescr, nil
}
// takeLayerReference will take/Get the image top layer reference
func (l *tarexporter) takeLayerReference(id image.ID, imgDescr *imageDescriptor) error {
img, err := l.is.Get(id)
if err != nil {
return err
}
if os := img.OperatingSystem(); !system.IsOSSupported(os) {
return fmt.Errorf("os %q is not supported", os)
}
imgDescr.image = img
topLayerID := img.RootFS.ChainID()
if topLayerID == "" {
return nil
}
layer, err := l.lss.Get(topLayerID)
if err != nil {
return err
}
imgDescr.layerRef = layer
return nil
}
// releaseLayerReferences will release all the image top layer references
func (l *tarexporter) releaseLayerReferences(imgDescr map[image.ID]*imageDescriptor) error {
for _, descr := range imgDescr {
if descr.layerRef != nil {
l.lss.Release(descr.layerRef)
}
}
return nil
}
func (s *saveSession) save(outStream io.Writer) error {
s.savedLayers = make(map[string]struct{})
s.diffIDPaths = make(map[layer.DiffID]string)
// get image json
tempDir, err := os.MkdirTemp("", "docker-export-")
if err != nil {
return err
}
defer os.RemoveAll(tempDir)
s.outDir = tempDir
reposLegacy := make(map[string]map[string]string)
var manifest []manifestItem
var parentLinks []parentLink
for id, imageDescr := range s.images {
foreignSrcs, err := s.saveImage(id)
if err != nil {
return err
}
var repoTags []string
var layers []string
for _, ref := range imageDescr.refs {
familiarName := reference.FamiliarName(ref)
if _, ok := reposLegacy[familiarName]; !ok {
reposLegacy[familiarName] = make(map[string]string)
}
reposLegacy[familiarName][ref.Tag()] = imageDescr.layers[len(imageDescr.layers)-1]
repoTags = append(repoTags, reference.FamiliarString(ref))
}
for _, l := range imageDescr.layers {
// IMPORTANT: We use path, not filepath here to ensure the layers
// in the manifest use Unix-style forward-slashes.
layers = append(layers, path.Join(l, legacyLayerFileName))
}
manifest = append(manifest, manifestItem{
Config: id.Digest().Hex() + ".json",
RepoTags: repoTags,
Layers: layers,
LayerSources: foreignSrcs,
})
parentID, _ := s.is.GetParent(id)
parentLinks = append(parentLinks, parentLink{id, parentID})
s.tarexporter.loggerImgEvent.LogImageEvent(id.String(), id.String(), "save")
}
for i, p := range validatedParentLinks(parentLinks) {
if p.parentID != "" {
manifest[i].Parent = p.parentID
}
}
if len(reposLegacy) > 0 {
reposFile := filepath.Join(tempDir, legacyRepositoriesFileName)
rf, err := os.OpenFile(reposFile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
if err != nil {
return err
}
if err := json.NewEncoder(rf).Encode(reposLegacy); err != nil {
rf.Close()
return err
}
rf.Close()
if err := system.Chtimes(reposFile, time.Unix(0, 0), time.Unix(0, 0)); err != nil {
return err
}
}
manifestFileName := filepath.Join(tempDir, manifestFileName)
f, err := os.OpenFile(manifestFileName, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
if err != nil {
return err
}
if err := json.NewEncoder(f).Encode(manifest); err != nil {
f.Close()
return err
}
f.Close()
if err := system.Chtimes(manifestFileName, time.Unix(0, 0), time.Unix(0, 0)); err != nil {
return err
}
fs, err := archive.Tar(tempDir, archive.Uncompressed)
if err != nil {
return err
}
defer fs.Close()
_, err = io.Copy(outStream, fs)
return err
}
func (s *saveSession) saveImage(id image.ID) (map[layer.DiffID]distribution.Descriptor, error) {
img := s.images[id].image
if len(img.RootFS.DiffIDs) == 0 {
return nil, fmt.Errorf("empty export - not implemented")
}
var parent digest.Digest
var layers []string
var foreignSrcs map[layer.DiffID]distribution.Descriptor
for i := range img.RootFS.DiffIDs {
v1Img := image.V1Image{
// This is for backward compatibility used for
// pre v1.9 docker.
Created: time.Unix(0, 0),
}
if i == len(img.RootFS.DiffIDs)-1 {
v1Img = img.V1Image
}
rootFS := *img.RootFS
rootFS.DiffIDs = rootFS.DiffIDs[:i+1]
v1ID, err := v1.CreateID(v1Img, rootFS.ChainID(), parent)
if err != nil {
return nil, err
}
v1Img.ID = v1ID.Hex()
if parent != "" {
v1Img.Parent = parent.Hex()
}
v1Img.OS = img.OS
src, err := s.saveLayer(rootFS.ChainID(), v1Img, img.Created)
if err != nil {
return nil, err
}
layers = append(layers, v1Img.ID)
parent = v1ID
if src.Digest != "" {
if foreignSrcs == nil {
foreignSrcs = make(map[layer.DiffID]distribution.Descriptor)
}
foreignSrcs[img.RootFS.DiffIDs[i]] = src
}
}
configFile := filepath.Join(s.outDir, id.Digest().Hex()+".json")
if err := os.WriteFile(configFile, img.RawJSON(), 0644); err != nil {
return nil, err
}
if err := system.Chtimes(configFile, img.Created, img.Created); err != nil {
return nil, err
}
s.images[id].layers = layers
return foreignSrcs, nil
}
func (s *saveSession) saveLayer(id layer.ChainID, legacyImg image.V1Image, createdTime time.Time) (distribution.Descriptor, error) {
if _, exists := s.savedLayers[legacyImg.ID]; exists {
return distribution.Descriptor{}, nil
}
outDir := filepath.Join(s.outDir, legacyImg.ID)
if err := os.Mkdir(outDir, 0755); err != nil {
return distribution.Descriptor{}, err
}
// todo: why is this version file here?
if err := os.WriteFile(filepath.Join(outDir, legacyVersionFileName), []byte("1.0"), 0644); err != nil {
return distribution.Descriptor{}, err
}
imageConfig, err := json.Marshal(legacyImg)
if err != nil {
return distribution.Descriptor{}, err
}
if err := os.WriteFile(filepath.Join(outDir, legacyConfigFileName), imageConfig, 0644); err != nil {
return distribution.Descriptor{}, err
}
// serialize filesystem
layerPath := filepath.Join(outDir, legacyLayerFileName)
l, err := s.lss.Get(id)
if err != nil {
return distribution.Descriptor{}, err
}
defer layer.ReleaseAndLog(s.lss, l)
if oldPath, exists := s.diffIDPaths[l.DiffID()]; exists {
relPath, err := filepath.Rel(outDir, oldPath)
if err != nil {
return distribution.Descriptor{}, err
}
if err := os.Symlink(relPath, layerPath); err != nil {
return distribution.Descriptor{}, errors.Wrap(err, "error creating symlink while saving layer")
}
} else {
// Use system.CreateSequential rather than os.Create. This ensures sequential
// file access on Windows to avoid eating into MM standby list.
// On Linux, this equates to a regular os.Create.
tarFile, err := system.CreateSequential(layerPath)
if err != nil {
return distribution.Descriptor{}, err
}
defer tarFile.Close()
arch, err := l.TarStream()
if err != nil {
return distribution.Descriptor{}, err
}
defer arch.Close()
if _, err := io.Copy(tarFile, arch); err != nil {
return distribution.Descriptor{}, err
}
for _, fname := range []string{"", legacyVersionFileName, legacyConfigFileName, legacyLayerFileName} {
// todo: maybe save layer created timestamp?
if err := system.Chtimes(filepath.Join(outDir, fname), createdTime, createdTime); err != nil {
return distribution.Descriptor{}, err
}
}
s.diffIDPaths[l.DiffID()] = layerPath
}
s.savedLayers[legacyImg.ID] = struct{}{}
var src distribution.Descriptor
if fs, ok := l.(distribution.Describable); ok {
src = fs.Descriptor()
}
return src, nil
}