159 lines
3.9 KiB
Go
159 lines
3.9 KiB
Go
package client
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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"io/ioutil"
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"sync"
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"github.com/docker/docker-registry"
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"github.com/docker/docker-registry/digest"
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)
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var (
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// ErrLayerAlreadyExists is returned when attempting to create a layer with
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// a tarsum that is already in use.
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ErrLayerAlreadyExists = errors.New("Layer already exists")
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// ErrLayerLocked is returned when attempting to write to a layer which is
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// currently being written to.
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ErrLayerLocked = errors.New("Layer locked")
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)
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// ObjectStore is an interface which is designed to approximate the docker
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// engine storage. This interface is subject to change to conform to the
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// future requirements of the engine.
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type ObjectStore interface {
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// Manifest retrieves the image manifest stored at the given repository name
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// and tag
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Manifest(name, tag string) (*registry.ImageManifest, error)
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// WriteManifest stores an image manifest at the given repository name and
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// tag
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WriteManifest(name, tag string, manifest *registry.ImageManifest) error
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// Layer returns a handle to a layer for reading and writing
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Layer(dgst digest.Digest) (Layer, error)
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}
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// Layer is a generic image layer interface.
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// A Layer may only be written to once
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type Layer interface {
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// Reader returns an io.ReadCloser which reads the contents of the layer
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Reader() (io.ReadCloser, error)
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// Writer returns an io.WriteCloser which may write the contents of the
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// layer. This method may only be called once per Layer, and the contents
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// are made available on Close
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Writer() (io.WriteCloser, error)
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// Wait blocks until the Layer can be read from
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Wait() error
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}
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// memoryObjectStore is an in-memory implementation of the ObjectStore interface
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type memoryObjectStore struct {
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mutex *sync.Mutex
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manifestStorage map[string]*registry.ImageManifest
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layerStorage map[digest.Digest]Layer
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}
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func (objStore *memoryObjectStore) Manifest(name, tag string) (*registry.ImageManifest, error) {
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objStore.mutex.Lock()
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defer objStore.mutex.Unlock()
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manifest, ok := objStore.manifestStorage[name+":"+tag]
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if !ok {
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return nil, fmt.Errorf("No manifest found with Name: %q, Tag: %q", name, tag)
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}
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return manifest, nil
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}
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func (objStore *memoryObjectStore) WriteManifest(name, tag string, manifest *registry.ImageManifest) error {
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objStore.mutex.Lock()
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defer objStore.mutex.Unlock()
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objStore.manifestStorage[name+":"+tag] = manifest
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return nil
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}
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func (objStore *memoryObjectStore) Layer(dgst digest.Digest) (Layer, error) {
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objStore.mutex.Lock()
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defer objStore.mutex.Unlock()
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layer, ok := objStore.layerStorage[dgst]
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if !ok {
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layer = &memoryLayer{cond: sync.NewCond(new(sync.Mutex))}
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objStore.layerStorage[dgst] = layer
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}
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return layer, nil
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}
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type memoryLayer struct {
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cond *sync.Cond
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buffer *bytes.Buffer
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written bool
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}
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func (ml *memoryLayer) Writer() (io.WriteCloser, error) {
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ml.cond.L.Lock()
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defer ml.cond.L.Unlock()
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if ml.buffer != nil {
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if !ml.written {
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return nil, ErrLayerLocked
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}
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return nil, ErrLayerAlreadyExists
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}
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ml.buffer = new(bytes.Buffer)
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return &memoryLayerWriter{cond: ml.cond, buffer: ml.buffer, done: &ml.written}, nil
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}
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func (ml *memoryLayer) Reader() (io.ReadCloser, error) {
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ml.cond.L.Lock()
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defer ml.cond.L.Unlock()
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if ml.buffer == nil {
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return nil, fmt.Errorf("Layer has not been written to yet")
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}
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if !ml.written {
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return nil, ErrLayerLocked
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}
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return ioutil.NopCloser(bytes.NewReader(ml.buffer.Bytes())), nil
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}
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func (ml *memoryLayer) Wait() error {
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ml.cond.L.Lock()
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defer ml.cond.L.Unlock()
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if ml.buffer == nil {
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return fmt.Errorf("No writer to wait on")
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}
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for !ml.written {
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ml.cond.Wait()
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}
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return nil
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}
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type memoryLayerWriter struct {
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cond *sync.Cond
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buffer *bytes.Buffer
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done *bool
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}
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func (mlw *memoryLayerWriter) Write(p []byte) (int, error) {
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return mlw.buffer.Write(p)
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}
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func (mlw *memoryLayerWriter) Close() error {
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*mlw.done = true
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mlw.cond.Broadcast()
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return nil
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}
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