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pull.go
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pull.go
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package pull
import (
"context"
"sync"
"github.com/containerd/containerd/content"
"github.com/containerd/containerd/images"
"github.com/containerd/containerd/platforms"
"github.com/containerd/containerd/reference"
"github.com/containerd/containerd/remotes"
"github.com/containerd/containerd/remotes/docker"
"github.com/containerd/containerd/remotes/docker/schema1"
"github.com/moby/buildkit/session"
"github.com/moby/buildkit/util/contentutil"
"github.com/moby/buildkit/util/flightcontrol"
"github.com/moby/buildkit/util/imageutil"
"github.com/moby/buildkit/util/progress/logs"
"github.com/moby/buildkit/util/pull/pullprogress"
"github.com/moby/buildkit/util/resolver"
"github.com/moby/buildkit/util/resolver/limited"
"github.com/moby/buildkit/util/resolver/retryhandler"
digest "github.com/opencontainers/go-digest"
ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/pkg/errors"
)
type Puller struct {
ContentStore content.Store
Resolver *resolver.Resolver
Src reference.Spec
Platform ocispecs.Platform
g flightcontrol.Group
resolveErr error
resolveDone bool
desc ocispecs.Descriptor
configDesc ocispecs.Descriptor
ref string
layers []ocispecs.Descriptor
nonlayers []ocispecs.Descriptor
}
var _ content.Provider = &provider{}
type PulledManifests struct {
Ref string
MainManifestDesc ocispecs.Descriptor
ConfigDesc ocispecs.Descriptor
Nonlayers []ocispecs.Descriptor
Descriptors []ocispecs.Descriptor
Provider func(session.Group) content.Provider
}
func (p *Puller) resolve(ctx context.Context, resolver remotes.Resolver) error {
_, err := p.g.Do(ctx, "", func(ctx context.Context) (_ interface{}, err error) {
if p.resolveErr != nil || p.resolveDone {
return nil, p.resolveErr
}
defer func() {
if !errors.Is(err, context.Canceled) {
p.resolveErr = err
}
}()
if p.tryLocalResolve(ctx) == nil {
return
}
ref, desc, err := resolver.Resolve(ctx, p.Src.String())
if err != nil {
return nil, err
}
p.desc = desc
p.ref = ref
p.resolveDone = true
return nil, nil
})
return err
}
func (p *Puller) tryLocalResolve(ctx context.Context) error {
desc := ocispecs.Descriptor{
Digest: p.Src.Digest(),
}
if desc.Digest == "" {
return errors.New("empty digest")
}
info, err := p.ContentStore.Info(ctx, desc.Digest)
if err != nil {
return err
}
desc.Size = info.Size
p.ref = p.Src.String()
ra, err := p.ContentStore.ReaderAt(ctx, desc)
if err != nil {
return err
}
mt, err := imageutil.DetectManifestMediaType(ra)
if err != nil {
return err
}
desc.MediaType = mt
p.desc = desc
return nil
}
func (p *Puller) PullManifests(ctx context.Context) (*PulledManifests, error) {
err := p.resolve(ctx, p.Resolver)
if err != nil {
return nil, err
}
platform := platforms.Only(p.Platform)
var mu sync.Mutex // images.Dispatch calls handlers in parallel
metadata := make(map[digest.Digest]ocispecs.Descriptor)
// TODO: need a wrapper snapshot interface that combines content
// and snapshots as 1) buildkit shouldn't have a dependency on contentstore
// or 2) cachemanager should manage the contentstore
var handlers []images.Handler
fetcher, err := p.Resolver.Fetcher(ctx, p.ref)
if err != nil {
return nil, err
}
var schema1Converter *schema1.Converter
if p.desc.MediaType == images.MediaTypeDockerSchema1Manifest {
// schema1 images are not lazy at this time, the converter will pull the whole image
// including layer blobs
schema1Converter = schema1.NewConverter(p.ContentStore, &pullprogress.FetcherWithProgress{
Fetcher: fetcher,
Manager: p.ContentStore,
})
handlers = append(handlers, schema1Converter)
} else {
// Get all the children for a descriptor
childrenHandler := images.ChildrenHandler(p.ContentStore)
// Filter the children by the platform
childrenHandler = images.FilterPlatforms(childrenHandler, platform)
// Limit manifests pulled to the best match in an index
childrenHandler = images.LimitManifests(childrenHandler, platform, 1)
dslHandler, err := docker.AppendDistributionSourceLabel(p.ContentStore, p.ref)
if err != nil {
return nil, err
}
handlers = append(handlers,
filterLayerBlobs(metadata, &mu),
retryhandler.New(limited.FetchHandler(p.ContentStore, fetcher, p.ref), logs.LoggerFromContext(ctx)),
childrenHandler,
dslHandler,
)
}
if err := images.Dispatch(ctx, images.Handlers(handlers...), nil, p.desc); err != nil {
return nil, err
}
if schema1Converter != nil {
p.desc, err = schema1Converter.Convert(ctx)
if err != nil {
return nil, err
}
// this just gathers metadata about the converted descriptors making up the image, does
// not fetch anything
if err := images.Dispatch(ctx, images.Handlers(
filterLayerBlobs(metadata, &mu),
images.FilterPlatforms(images.ChildrenHandler(p.ContentStore), platform),
), nil, p.desc); err != nil {
return nil, err
}
}
for _, desc := range metadata {
p.nonlayers = append(p.nonlayers, desc)
switch desc.MediaType {
case images.MediaTypeDockerSchema2Config, ocispecs.MediaTypeImageConfig:
p.configDesc = desc
}
}
// split all pulled data to layers and rest. layers remain roots and are deleted with snapshots. rest will be linked to layers.
p.layers, err = getLayers(ctx, p.ContentStore, p.desc, platform)
if err != nil {
return nil, err
}
return &PulledManifests{
Ref: p.ref,
MainManifestDesc: p.desc,
ConfigDesc: p.configDesc,
Nonlayers: p.nonlayers,
Descriptors: p.layers,
Provider: func(g session.Group) content.Provider {
return &provider{puller: p, resolver: p.Resolver.WithSession(g)}
},
}, nil
}
type provider struct {
puller *Puller
resolver remotes.Resolver
}
func (p *provider) ReaderAt(ctx context.Context, desc ocispecs.Descriptor) (content.ReaderAt, error) {
err := p.puller.resolve(ctx, p.resolver)
if err != nil {
return nil, err
}
fetcher, err := p.resolver.Fetcher(ctx, p.puller.ref)
if err != nil {
return nil, err
}
return contentutil.FromFetcher(fetcher).ReaderAt(ctx, desc)
}
// filterLayerBlobs causes layer blobs to be skipped for fetch, which is required to support lazy blobs.
// It also stores the non-layer blobs (metadata) it encounters in the provided map.
func filterLayerBlobs(metadata map[digest.Digest]ocispecs.Descriptor, mu sync.Locker) images.HandlerFunc {
return func(ctx context.Context, desc ocispecs.Descriptor) ([]ocispecs.Descriptor, error) {
switch desc.MediaType {
case ocispecs.MediaTypeImageLayer, images.MediaTypeDockerSchema2Layer, ocispecs.MediaTypeImageLayerGzip, images.MediaTypeDockerSchema2LayerGzip, images.MediaTypeDockerSchema2LayerForeign, images.MediaTypeDockerSchema2LayerForeignGzip:
return nil, images.ErrSkipDesc
default:
if metadata != nil {
mu.Lock()
metadata[desc.Digest] = desc
mu.Unlock()
}
}
return nil, nil
}
}
func getLayers(ctx context.Context, provider content.Provider, desc ocispecs.Descriptor, platform platforms.MatchComparer) ([]ocispecs.Descriptor, error) {
manifest, err := images.Manifest(ctx, provider, desc, platform)
if err != nil {
return nil, errors.WithStack(err)
}
image := images.Image{Target: desc}
diffIDs, err := image.RootFS(ctx, provider, platform)
if err != nil {
return nil, errors.Wrap(err, "failed to resolve rootfs")
}
if len(diffIDs) != len(manifest.Layers) {
return nil, errors.Errorf("mismatched image rootfs and manifest layers %+v %+v", diffIDs, manifest.Layers)
}
layers := make([]ocispecs.Descriptor, len(diffIDs))
for i := range diffIDs {
desc := manifest.Layers[i]
if desc.Annotations == nil {
desc.Annotations = map[string]string{}
}
desc.Annotations["containerd.io/uncompressed"] = diffIDs[i].String()
layers[i] = desc
}
return layers, nil
}