272 lines
9.3 KiB
Go
272 lines
9.3 KiB
Go
/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package source
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import (
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"context"
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"fmt"
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"strings"
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"github.com/containerd/containerd/v2/core/images"
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"github.com/containerd/containerd/v2/core/remotes/docker"
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"github.com/containerd/containerd/v2/pkg/labels"
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"github.com/containerd/containerd/v2/pkg/reference"
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"github.com/containerd/stargz-snapshotter/fs/config"
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digest "github.com/opencontainers/go-digest"
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ocispec "github.com/opencontainers/image-spec/specs-go/v1"
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)
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// GetSources is a function for converting snapshot labels into typed blob sources
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// information. This package defines a default converter which provides source
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// information based on some labels but implementations aren't required to use labels.
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// Implementations are allowed to return several sources (registry config + image refs)
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// about the blob.
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type GetSources func(labels map[string]string) (source []Source, err error)
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// RegistryHosts returns a list of registries that provides the specified image.
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type RegistryHosts func(reference.Spec) ([]docker.RegistryHost, error)
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// Source is a typed blob source information. This contains information about
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// a blob stored in registries and some contexts of the blob.
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type Source struct {
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// Hosts is a registry configuration where this blob is stored.
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Hosts RegistryHosts
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// Name is an image reference which contains this blob.
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Name reference.Spec
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// Target is a descriptor of this blob.
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Target ocispec.Descriptor
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// Manifest is an image manifest which contains the blob. This will
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// be used by the filesystem to pre-resolve some layers contained in
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// the manifest.
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// Currently, only layer digests (Manifest.Layers.Digest) will be used.
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Manifest ocispec.Manifest
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}
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const (
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// targetRefLabel is a label which contains image reference.
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targetRefLabel = "containerd.io/snapshot/remote/stargz.reference"
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// targetDigestLabel is a label which contains layer digest.
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targetDigestLabel = "containerd.io/snapshot/remote/stargz.digest"
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// targetImageLayersLabel is a label which contains layer digests contained in
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// the target image.
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targetImageLayersLabel = "containerd.io/snapshot/remote/stargz.layers"
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// targetImageURLsLabelPrefix is a label prefix which constructs a map from the layer index to
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// urls of the layer descriptor.
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targetImageURLsLabelPrefix = "containerd.io/snapshot/remote/urls."
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// targetURsLLabel is a label which contains layer URL. This is only used to pass URL from containerd
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// to snapshotter.
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targetURLsLabel = "containerd.io/snapshot/remote/urls"
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)
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// FromDefaultLabels returns a function for converting snapshot labels to
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// source information based on labels.
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func FromDefaultLabels(hosts RegistryHosts) GetSources {
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return func(labels map[string]string) ([]Source, error) {
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refStr, ok := labels[targetRefLabel]
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if !ok {
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return nil, fmt.Errorf("reference hasn't been passed")
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}
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refspec, err := reference.Parse(refStr)
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if err != nil {
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return nil, err
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}
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digestStr, ok := labels[targetDigestLabel]
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if !ok {
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return nil, fmt.Errorf("digest hasn't been passed")
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}
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target, err := digest.Parse(digestStr)
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if err != nil {
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return nil, err
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}
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var neighboringLayers []ocispec.Descriptor
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if l, ok := labels[targetImageLayersLabel]; ok {
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layersStr := strings.Split(l, ",")
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for i, l := range layersStr {
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d, err := digest.Parse(l)
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if err != nil {
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return nil, err
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}
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if d.String() != target.String() {
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desc := ocispec.Descriptor{Digest: d}
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if urls, ok := labels[targetImageURLsLabelPrefix+fmt.Sprintf("%d", i)]; ok {
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desc.URLs = strings.Split(urls, ",")
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}
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neighboringLayers = append(neighboringLayers, desc)
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}
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}
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}
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targetDesc := ocispec.Descriptor{
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Digest: target,
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Annotations: labels,
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}
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if targetURLs, ok := labels[targetURLsLabel]; ok {
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targetDesc.URLs = append(targetDesc.URLs, strings.Split(targetURLs, ",")...)
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}
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return []Source{
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{
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Hosts: hosts,
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Name: refspec,
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Target: targetDesc,
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Manifest: ocispec.Manifest{Layers: append([]ocispec.Descriptor{targetDesc}, neighboringLayers...)},
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},
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}, nil
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}
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}
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// AppendDefaultLabelsHandlerWrapper makes a handler which appends image's basic
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// information to each layer descriptor as annotations during unpack. These
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// annotations will be passed to this remote snapshotter as labels and used to
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// construct source information.
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func AppendDefaultLabelsHandlerWrapper(ref string, prefetchSize int64) func(f images.Handler) images.Handler {
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return func(f images.Handler) images.Handler {
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return images.HandlerFunc(func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
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children, err := f.Handle(ctx, desc)
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if err != nil {
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return nil, err
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}
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switch desc.MediaType {
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case ocispec.MediaTypeImageManifest, images.MediaTypeDockerSchema2Manifest:
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for i := range children {
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c := &children[i]
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if images.IsLayerType(c.MediaType) {
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if c.Annotations == nil {
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c.Annotations = make(map[string]string)
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}
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c.Annotations[targetRefLabel] = ref
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c.Annotations[targetDigestLabel] = c.Digest.String()
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var layers string
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for i, l := range children[i:] {
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if images.IsLayerType(l.MediaType) {
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ls := fmt.Sprintf("%s,", l.Digest.String())
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// This avoids the label hits the size limitation.
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// Skipping layers is allowed here and only affects performance.
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if err := labels.Validate(targetImageLayersLabel, layers+ls); err != nil {
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break
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}
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layers += ls
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// Store URLs of the neighbouring layer as well.
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urlsKey := targetImageURLsLabelPrefix + fmt.Sprintf("%d", i)
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c.Annotations[urlsKey] = appendWithValidation(urlsKey, l.URLs)
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}
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}
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c.Annotations[targetImageLayersLabel] = strings.TrimSuffix(layers, ",")
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c.Annotations[config.TargetPrefetchSizeLabel] = fmt.Sprintf("%d", prefetchSize)
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// store URL in annotation to let containerd to pass it to the snapshotter
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c.Annotations[targetURLsLabel] = appendWithValidation(targetURLsLabel, c.URLs)
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}
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}
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}
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return children, nil
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})
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}
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}
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func appendWithValidation(key string, values []string) string {
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var v string
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for _, u := range values {
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s := fmt.Sprintf("%s,", u)
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if err := labels.Validate(key, v+s); err != nil {
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break
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}
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v += s
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}
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return strings.TrimSuffix(v, ",")
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}
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// TODO: switch to "github.com/containerd/containerd/pkg/snapshotters" once all tools using
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//
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// stargz-snapshotter (e.g. k3s) move to containerd version where that pkg is available.
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const (
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// targetImageLayersLabel is a label which contains layer digests contained in
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// the target image and will be passed to snapshotters for preparing layers in
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// parallel. Skipping some layers is allowed and only affects performance.
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targetImageLayersLabelContainerd = "containerd.io/snapshot/cri.image-layers"
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)
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// AppendExtraLabelsHandler adds optional labels that aren't provided by
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// "github.com/containerd/containerd/pkg/snapshotters" but can be used for stargz snapshotter's extra functionalities.
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func AppendExtraLabelsHandler(prefetchSize int64, wrapper func(images.Handler) images.Handler) func(images.Handler) images.Handler {
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return func(f images.Handler) images.Handler {
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return images.HandlerFunc(func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
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children, err := wrapper(f).Handle(ctx, desc)
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if err != nil {
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return nil, err
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}
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switch desc.MediaType {
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case ocispec.MediaTypeImageManifest, images.MediaTypeDockerSchema2Manifest:
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for i := range children {
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c := &children[i]
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if !images.IsLayerType(c.MediaType) {
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continue
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}
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if _, ok := c.Annotations[targetURLsLabel]; !ok { // nop if this key is already set
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c.Annotations[targetURLsLabel] = appendWithValidation(targetURLsLabel, c.URLs)
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}
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if _, ok := c.Annotations[config.TargetPrefetchSizeLabel]; !ok { // nop if this key is already set
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c.Annotations[config.TargetPrefetchSizeLabel] = fmt.Sprintf("%d", prefetchSize)
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}
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// Store URLs of the neighbouring layer as well.
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nlayers, ok := c.Annotations[targetImageLayersLabelContainerd]
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if !ok {
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continue
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}
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for j, dstr := range strings.Split(nlayers, ",") {
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d, err := digest.Parse(dstr)
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if err != nil {
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return nil, err
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}
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l, ok := layerFromDigest(children, d)
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if !ok {
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continue
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}
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urlsKey := targetImageURLsLabelPrefix + fmt.Sprintf("%d", j)
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if _, ok := c.Annotations[urlsKey]; !ok { // nop if this key is already set
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c.Annotations[urlsKey] = appendWithValidation(urlsKey, l.URLs)
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}
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}
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}
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}
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return children, nil
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})
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}
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}
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func layerFromDigest(layers []ocispec.Descriptor, target digest.Digest) (ocispec.Descriptor, bool) {
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for _, l := range layers {
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if l.Digest == target {
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return l, images.IsLayerType(l.MediaType)
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}
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}
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return ocispec.Descriptor{}, false
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}
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