distribution/client/objectstore.go

160 lines
3.9 KiB
Go
Raw Normal View History

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