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writer.go
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writer.go
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package containerimage
import (
"bytes"
"context"
"encoding/json"
"fmt"
"time"
"github.com/containerd/containerd/content"
"github.com/containerd/containerd/diff"
"github.com/containerd/containerd/images"
"github.com/containerd/containerd/platforms"
"github.com/moby/buildkit/cache"
"github.com/moby/buildkit/cache/blobs"
"github.com/moby/buildkit/exporter"
"github.com/moby/buildkit/exporter/containerimage/exptypes"
"github.com/moby/buildkit/snapshot"
"github.com/moby/buildkit/util/progress"
"github.com/moby/buildkit/util/system"
digest "github.com/opencontainers/go-digest"
specs "github.com/opencontainers/image-spec/specs-go"
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"golang.org/x/sync/errgroup"
)
const (
emptyGZLayer = digest.Digest("sha256:4f4fb700ef54461cfa02571ae0db9a0dc1e0cdb5577484a6d75e68dc38e8acc1")
)
type WriterOpt struct {
Snapshotter snapshot.Snapshotter
ContentStore content.Store
Applier diff.Applier
Differ diff.Comparer
}
func NewImageWriter(opt WriterOpt) (*ImageWriter, error) {
return &ImageWriter{opt: opt}, nil
}
type ImageWriter struct {
opt WriterOpt
}
func (ic *ImageWriter) Commit(ctx context.Context, inp exporter.Source, oci bool, compression blobs.CompressionType) (*ocispec.Descriptor, error) {
platformsBytes, ok := inp.Metadata[exptypes.ExporterPlatformsKey]
if len(inp.Refs) > 0 && !ok {
return nil, errors.Errorf("unable to export multiple refs, missing platforms mapping")
}
if len(inp.Refs) == 0 {
layers, err := ic.exportLayers(ctx, compression, inp.Ref)
if err != nil {
return nil, err
}
return ic.commitDistributionManifest(ctx, inp.Ref, inp.Metadata[exptypes.ExporterImageConfigKey], layers[0], oci, inp.Metadata[exptypes.ExporterInlineCache])
}
var p exptypes.Platforms
if err := json.Unmarshal(platformsBytes, &p); err != nil {
return nil, errors.Wrapf(err, "failed to parse platforms passed to exporter")
}
if len(p.Platforms) != len(inp.Refs) {
return nil, errors.Errorf("number of platforms does not match references %d %d", len(p.Platforms), len(inp.Refs))
}
refs := make([]cache.ImmutableRef, 0, len(inp.Refs))
layersMap := make(map[string]int, len(inp.Refs))
for id, r := range inp.Refs {
layersMap[id] = len(refs)
refs = append(refs, r)
}
layers, err := ic.exportLayers(ctx, compression, refs...)
if err != nil {
return nil, err
}
idx := struct {
// MediaType is reserved in the OCI spec but
// excluded from go types.
MediaType string `json:"mediaType,omitempty"`
ocispec.Index
}{
MediaType: ocispec.MediaTypeImageIndex,
Index: ocispec.Index{
Versioned: specs.Versioned{
SchemaVersion: 2,
},
},
}
if !oci {
idx.MediaType = images.MediaTypeDockerSchema2ManifestList
}
labels := map[string]string{}
for i, p := range p.Platforms {
r, ok := inp.Refs[p.ID]
if !ok {
return nil, errors.Errorf("failed to find ref for ID %s", p.ID)
}
config := inp.Metadata[fmt.Sprintf("%s/%s", exptypes.ExporterImageConfigKey, p.ID)]
desc, err := ic.commitDistributionManifest(ctx, r, config, layers[layersMap[p.ID]], oci, inp.Metadata[fmt.Sprintf("%s/%s", exptypes.ExporterInlineCache, p.ID)])
if err != nil {
return nil, err
}
dp := p.Platform
desc.Platform = &dp
idx.Manifests = append(idx.Manifests, *desc)
labels[fmt.Sprintf("containerd.io/gc.ref.content.%d", i)] = desc.Digest.String()
}
idxBytes, err := json.MarshalIndent(idx, "", " ")
if err != nil {
return nil, errors.Wrap(err, "failed to marshal index")
}
idxDigest := digest.FromBytes(idxBytes)
idxDesc := ocispec.Descriptor{
Digest: idxDigest,
Size: int64(len(idxBytes)),
MediaType: idx.MediaType,
}
idxDone := oneOffProgress(ctx, "exporting manifest list "+idxDigest.String())
if err := content.WriteBlob(ctx, ic.opt.ContentStore, idxDigest.String(), bytes.NewReader(idxBytes), idxDesc, content.WithLabels(labels)); err != nil {
return nil, idxDone(errors.Wrapf(err, "error writing manifest list blob %s", idxDigest))
}
idxDone(nil)
return &idxDesc, nil
}
func (ic *ImageWriter) exportLayers(ctx context.Context, compression blobs.CompressionType, refs ...cache.ImmutableRef) ([][]blobs.DiffPair, error) {
eg, ctx := errgroup.WithContext(ctx)
layersDone := oneOffProgress(ctx, "exporting layers")
out := make([][]blobs.DiffPair, len(refs))
for i, ref := range refs {
func(i int, ref cache.ImmutableRef) {
eg.Go(func() error {
diffPairs, err := blobs.GetDiffPairs(ctx, ic.opt.ContentStore, ic.opt.Differ, ref, true, compression)
if err != nil {
return errors.Wrap(err, "failed calculating diff pairs for exported snapshot")
}
out[i] = diffPairs
return nil
})
}(i, ref)
}
if err := layersDone(eg.Wait()); err != nil {
return nil, err
}
return out, nil
}
func (ic *ImageWriter) commitDistributionManifest(ctx context.Context, ref cache.ImmutableRef, config []byte, layers []blobs.DiffPair, oci bool, cache []byte) (*ocispec.Descriptor, error) {
if len(config) == 0 {
var err error
config, err = emptyImageConfig()
if err != nil {
return nil, err
}
}
history, err := parseHistoryFromConfig(config)
if err != nil {
return nil, err
}
diffPairs, history := normalizeLayersAndHistory(layers, history, ref)
config, err = patchImageConfig(config, diffPairs, history, cache)
if err != nil {
return nil, err
}
var (
configDigest = digest.FromBytes(config)
manifestType = ocispec.MediaTypeImageManifest
configType = ocispec.MediaTypeImageConfig
)
// Use docker media types for older Docker versions and registries
if !oci {
manifestType = images.MediaTypeDockerSchema2Manifest
configType = images.MediaTypeDockerSchema2Config
}
mfst := struct {
// MediaType is reserved in the OCI spec but
// excluded from go types.
MediaType string `json:"mediaType,omitempty"`
ocispec.Manifest
}{
MediaType: manifestType,
Manifest: ocispec.Manifest{
Versioned: specs.Versioned{
SchemaVersion: 2,
},
Config: ocispec.Descriptor{
Digest: configDigest,
Size: int64(len(config)),
MediaType: configType,
},
},
}
labels := map[string]string{
"containerd.io/gc.ref.content.0": configDigest.String(),
}
layerMediaTypes := blobs.GetMediaTypeForLayers(diffPairs, ref)
cs := ic.opt.ContentStore
for i, dp := range diffPairs {
info, err := cs.Info(ctx, dp.Blobsum)
if err != nil {
return nil, errors.Wrapf(err, "could not find blob %s from contentstore", dp.Blobsum)
}
var layerType string
if len(layerMediaTypes) > i {
layerType = layerMediaTypes[i]
}
// NOTE: The media type might be missing for some migrated ones
// from before lease based storage. If so, we should detect
// the media type from blob data.
//
// Discussion: https://github.com/moby/buildkit/pull/1277#discussion_r352795429
if layerType == "" {
layerType, err = blobs.DetectLayerMediaType(ctx, cs, dp.Blobsum, oci)
if err != nil {
return nil, err
}
}
mfst.Layers = append(mfst.Layers, ocispec.Descriptor{
Digest: dp.Blobsum,
Size: info.Size,
MediaType: layerType,
})
labels[fmt.Sprintf("containerd.io/gc.ref.content.%d", i+1)] = dp.Blobsum.String()
}
mfstJSON, err := json.MarshalIndent(mfst, "", " ")
if err != nil {
return nil, errors.Wrap(err, "failed to marshal manifest")
}
mfstDigest := digest.FromBytes(mfstJSON)
mfstDesc := ocispec.Descriptor{
Digest: mfstDigest,
Size: int64(len(mfstJSON)),
}
mfstDone := oneOffProgress(ctx, "exporting manifest "+mfstDigest.String())
if err := content.WriteBlob(ctx, ic.opt.ContentStore, mfstDigest.String(), bytes.NewReader(mfstJSON), mfstDesc, content.WithLabels((labels))); err != nil {
return nil, mfstDone(errors.Wrapf(err, "error writing manifest blob %s", mfstDigest))
}
mfstDone(nil)
configDesc := ocispec.Descriptor{
Digest: configDigest,
Size: int64(len(config)),
MediaType: configType,
}
configDone := oneOffProgress(ctx, "exporting config "+configDigest.String())
if err := content.WriteBlob(ctx, ic.opt.ContentStore, configDigest.String(), bytes.NewReader(config), configDesc); err != nil {
return nil, configDone(errors.Wrap(err, "error writing config blob"))
}
configDone(nil)
return &ocispec.Descriptor{
Digest: mfstDigest,
Size: int64(len(mfstJSON)),
MediaType: manifestType,
}, nil
}
func (ic *ImageWriter) ContentStore() content.Store {
return ic.opt.ContentStore
}
func (ic *ImageWriter) Snapshotter() snapshot.Snapshotter {
return ic.opt.Snapshotter
}
func (ic *ImageWriter) Applier() diff.Applier {
return ic.opt.Applier
}
func emptyImageConfig() ([]byte, error) {
pl := platforms.Normalize(platforms.DefaultSpec())
type image struct {
ocispec.Image
// Variant defines platform variant. To be added to OCI.
Variant string `json:"variant,omitempty"`
}
img := image{
Image: ocispec.Image{
Architecture: pl.Architecture,
OS: pl.OS,
},
Variant: pl.Variant,
}
img.RootFS.Type = "layers"
img.Config.WorkingDir = "/"
img.Config.Env = []string{"PATH=" + system.DefaultPathEnv}
dt, err := json.Marshal(img)
return dt, errors.Wrap(err, "failed to create empty image config")
}
func parseHistoryFromConfig(dt []byte) ([]ocispec.History, error) {
var config struct {
History []ocispec.History
}
if err := json.Unmarshal(dt, &config); err != nil {
return nil, errors.Wrap(err, "failed to unmarshal history from config")
}
return config.History, nil
}
func patchImageConfig(dt []byte, dps []blobs.DiffPair, history []ocispec.History, cache []byte) ([]byte, error) {
m := map[string]json.RawMessage{}
if err := json.Unmarshal(dt, &m); err != nil {
return nil, errors.Wrap(err, "failed to parse image config for patch")
}
var rootFS ocispec.RootFS
rootFS.Type = "layers"
for _, dp := range dps {
rootFS.DiffIDs = append(rootFS.DiffIDs, dp.DiffID)
}
dt, err := json.Marshal(rootFS)
if err != nil {
return nil, errors.Wrap(err, "failed to marshal rootfs")
}
m["rootfs"] = dt
dt, err = json.Marshal(history)
if err != nil {
return nil, errors.Wrap(err, "failed to marshal history")
}
m["history"] = dt
if _, ok := m["created"]; !ok {
var tm *time.Time
for _, h := range history {
if h.Created != nil {
tm = h.Created
}
}
dt, err = json.Marshal(&tm)
if err != nil {
return nil, errors.Wrap(err, "failed to marshal creation time")
}
m["created"] = dt
}
if cache != nil {
dt, err := json.Marshal(cache)
if err != nil {
return nil, err
}
m["moby.buildkit.cache.v0"] = dt
}
dt, err = json.Marshal(m)
return dt, errors.Wrap(err, "failed to marshal config after patch")
}
func normalizeLayersAndHistory(diffs []blobs.DiffPair, history []ocispec.History, ref cache.ImmutableRef) ([]blobs.DiffPair, []ocispec.History) {
refMeta := getRefMetadata(ref, len(diffs))
var historyLayers int
for _, h := range history {
if !h.EmptyLayer {
historyLayers += 1
}
}
if historyLayers > len(diffs) {
// this case shouldn't happen but if it does force set history layers empty
// from the bottom
logrus.Warn("invalid image config with unaccounted layers")
historyCopy := make([]ocispec.History, 0, len(history))
var l int
for _, h := range history {
if l >= len(diffs) {
h.EmptyLayer = true
}
if !h.EmptyLayer {
l++
}
historyCopy = append(historyCopy, h)
}
history = historyCopy
}
if len(diffs) > historyLayers {
// some history items are missing. add them based on the ref metadata
for _, md := range refMeta[historyLayers:] {
history = append(history, ocispec.History{
Created: &md.createdAt,
CreatedBy: md.description,
Comment: "buildkit.exporter.image.v0",
})
}
}
var layerIndex int
for i, h := range history {
if !h.EmptyLayer {
if h.Created == nil {
h.Created = &refMeta[layerIndex].createdAt
}
if diffs[layerIndex].Blobsum == emptyGZLayer {
h.EmptyLayer = true
diffs = append(diffs[:layerIndex], diffs[layerIndex+1:]...)
} else {
layerIndex++
}
}
history[i] = h
}
// Find the first new layer time. Otherwise, the history item for a first
// metadata command would be the creation time of a base image layer.
// If there is no such then the last layer with timestamp.
var created *time.Time
var noCreatedTime bool
for _, h := range history {
if h.Created != nil {
created = h.Created
if noCreatedTime {
break
}
} else {
noCreatedTime = true
}
}
// Fill in created times for all history items to be either the first new
// layer time or the previous layer.
noCreatedTime = false
for i, h := range history {
if h.Created != nil {
if noCreatedTime {
created = h.Created
}
} else {
noCreatedTime = true
h.Created = created
}
history[i] = h
}
return diffs, history
}
type refMetadata struct {
description string
createdAt time.Time
}
func getRefMetadata(ref cache.ImmutableRef, limit int) []refMetadata {
if limit <= 0 {
return nil
}
meta := refMetadata{
description: "created by buildkit", // shouldn't be shown but don't fail build
createdAt: time.Now(),
}
if ref == nil {
return append(getRefMetadata(nil, limit-1), meta)
}
if descr := cache.GetDescription(ref.Metadata()); descr != "" {
meta.description = descr
}
meta.createdAt = cache.GetCreatedAt(ref.Metadata())
p := ref.Parent()
if p != nil {
defer p.Release(context.TODO())
}
return append(getRefMetadata(p, limit-1), meta)
}
func oneOffProgress(ctx context.Context, id string) func(err error) error {
pw, _, _ := progress.FromContext(ctx)
now := time.Now()
st := progress.Status{
Started: &now,
}
pw.Write(id, st)
return func(err error) error {
// TODO: set error on status
now := time.Now()
st.Completed = &now
pw.Write(id, st)
pw.Close()
return err
}
}