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// Copyright 2021 Google LLC All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package cache provides methods to cache layers.
package cache
import (
"errors"
"io"
"github.com/google/go-containerregistry/pkg/logs"
v1 "github.com/google/go-containerregistry/pkg/v1"
"github.com/google/go-containerregistry/pkg/v1/types"
)
// Cache encapsulates methods to interact with cached layers.
type Cache interface {
// Put writes the Layer to the Cache.
//
// The returned Layer should be used for future operations, since lazy
// cachers might only populate the cache when the layer is actually
// consumed.
//
// The returned layer can be consumed, and the cache entry populated,
// by calling either Compressed or Uncompressed and consuming the
// returned io.ReadCloser.
Put(v1.Layer) (v1.Layer, error)
// Get returns the Layer cached by the given Hash, or ErrNotFound if no
// such layer was found.
Get(v1.Hash) (v1.Layer, error)
// Delete removes the Layer with the given Hash from the Cache.
Delete(v1.Hash) error
}
// ErrNotFound is returned by Get when no layer with the given Hash is found.
var ErrNotFound = errors.New("layer was not found")
// Image returns a new Image which wraps the given Image, whose layers will be
// pulled from the Cache if they are found, and written to the Cache as they
// are read from the underlying Image.
func Image(i v1.Image, c Cache) v1.Image {
return &image{
Image: i,
c: c,
}
}
type image struct {
v1.Image
c Cache
}
func (i *image) Layers() ([]v1.Layer, error) {
ls, err := i.Image.Layers()
if err != nil {
return nil, err
}
out := make([]v1.Layer, len(ls))
for idx, l := range ls {
out[idx] = &lazyLayer{inner: l, c: i.c}
}
return out, nil
}
type lazyLayer struct {
inner v1.Layer
c Cache
}
func (l *lazyLayer) Compressed() (io.ReadCloser, error) {
digest, err := l.inner.Digest()
if err != nil {
return nil, err
}
if cl, err := l.c.Get(digest); err == nil {
// Layer found in the cache.
logs.Progress.Printf("Layer %s found (compressed) in cache", digest)
return cl.Compressed()
} else if !errors.Is(err, ErrNotFound) {
return nil, err
}
// Not cached, pull and return the real layer.
logs.Progress.Printf("Layer %s not found (compressed) in cache, getting", digest)
rl, err := l.c.Put(l.inner)
if err != nil {
return nil, err
}
return rl.Compressed()
}
func (l *lazyLayer) Uncompressed() (io.ReadCloser, error) {
diffID, err := l.inner.DiffID()
if err != nil {
return nil, err
}
if cl, err := l.c.Get(diffID); err == nil {
// Layer found in the cache.
logs.Progress.Printf("Layer %s found (uncompressed) in cache", diffID)
return cl.Uncompressed()
} else if !errors.Is(err, ErrNotFound) {
return nil, err
}
// Not cached, pull and return the real layer.
logs.Progress.Printf("Layer %s not found (uncompressed) in cache, getting", diffID)
rl, err := l.c.Put(l.inner)
if err != nil {
return nil, err
}
return rl.Uncompressed()
}
func (l *lazyLayer) Size() (int64, error) { return l.inner.Size() }
func (l *lazyLayer) DiffID() (v1.Hash, error) { return l.inner.DiffID() }
func (l *lazyLayer) Digest() (v1.Hash, error) { return l.inner.Digest() }
func (l *lazyLayer) MediaType() (types.MediaType, error) { return l.inner.MediaType() }
func (i *image) LayerByDigest(h v1.Hash) (v1.Layer, error) {
l, err := i.c.Get(h)
if errors.Is(err, ErrNotFound) {
// Not cached, get it and write it.
l, err := i.Image.LayerByDigest(h)
if err != nil {
return nil, err
}
return i.c.Put(l)
}
return l, err
}
func (i *image) LayerByDiffID(h v1.Hash) (v1.Layer, error) {
l, err := i.c.Get(h)
if errors.Is(err, ErrNotFound) {
// Not cached, get it and write it.
l, err := i.Image.LayerByDiffID(h)
if err != nil {
return nil, err
}
return i.c.Put(l)
}
return l, err
}
// ImageIndex returns a new ImageIndex which wraps the given ImageIndex's
// children with either Image(child, c) or ImageIndex(child, c) depending on type.
func ImageIndex(ii v1.ImageIndex, c Cache) v1.ImageIndex {
return &imageIndex{
inner: ii,
c: c,
}
}
type imageIndex struct {
inner v1.ImageIndex
c Cache
}
func (ii *imageIndex) MediaType() (types.MediaType, error) { return ii.inner.MediaType() }
func (ii *imageIndex) Digest() (v1.Hash, error) { return ii.inner.Digest() }
func (ii *imageIndex) Size() (int64, error) { return ii.inner.Size() }
func (ii *imageIndex) IndexManifest() (*v1.IndexManifest, error) { return ii.inner.IndexManifest() }
func (ii *imageIndex) RawManifest() ([]byte, error) { return ii.inner.RawManifest() }
func (ii *imageIndex) Image(h v1.Hash) (v1.Image, error) {
i, err := ii.inner.Image(h)
if err != nil {
return nil, err
}
return Image(i, ii.c), nil
}
func (ii *imageIndex) ImageIndex(h v1.Hash) (v1.ImageIndex, error) {
idx, err := ii.inner.ImageIndex(h)
if err != nil {
return nil, err
}
return ImageIndex(idx, ii.c), nil
}
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