distribution/storage/layerupload.go
Stephen J Day 68944ea9cf Clean up layer storage layout
Previously, discussions were still ongoing about different storage layouts that
could support various access models. This changeset removes a layer of
indirection that was in place due to earlier designs. Effectively, this both
associates a layer with a named repository and ensures that content cannot be
accessed across repositories. It also moves to rely on tarsum as a true
content-addressable identifier, removing a layer of indirection during blob
resolution.
2014-11-25 09:57:43 -08:00

449 lines
12 KiB
Go

package storage
import (
"encoding/json"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"code.google.com/p/go-uuid/uuid"
"github.com/docker/docker-registry/digest"
"github.com/docker/docker-registry/storagedriver"
"github.com/docker/docker/pkg/tarsum"
"io"
)
// LayerUploadState captures the state serializable state of the layer upload.
type LayerUploadState struct {
// name is the primary repository under which the layer will be linked.
Name string
// UUID identifies the upload.
UUID string
// offset contains the current progress of the upload.
Offset int64
}
// layerUploadController is used to control the various aspects of resumable
// layer upload. It implements the LayerUpload interface.
type layerUploadController struct {
LayerUploadState
layerStore *layerStore
uploadStore layerUploadStore
fp layerFile
err error // terminal error, if set, controller is closed
}
// layerFile documents the interface used while writing layer files, similar
// to *os.File. This is separate from layerReader, for now, because we want to
// store uploads on the local file system until we have write-through hashing
// support. They should be combined once this is worked out.
type layerFile interface {
io.WriteSeeker
io.Reader
io.Closer
// Sync commits the contents of the writer to storage.
Sync() (err error)
}
// layerUploadStore provides storage for temporary files and upload state of
// layers. This is be used by the LayerService to manage the state of ongoing
// uploads. This interface will definitely change and will most likely end up
// being exported to the app layer. Move the layer.go when it's ready to go.
type layerUploadStore interface {
New(name string) (LayerUploadState, error)
Open(uuid string) (layerFile, error)
GetState(uuid string) (LayerUploadState, error)
SaveState(lus LayerUploadState) error
DeleteState(uuid string) error
}
var _ LayerUpload = &layerUploadController{}
// Name of the repository under which the layer will be linked.
func (luc *layerUploadController) Name() string {
return luc.LayerUploadState.Name
}
// UUID returns the identifier for this upload.
func (luc *layerUploadController) UUID() string {
return luc.LayerUploadState.UUID
}
// Offset returns the position of the last byte written to this layer.
func (luc *layerUploadController) Offset() int64 {
return luc.LayerUploadState.Offset
}
// Finish marks the upload as completed, returning a valid handle to the
// uploaded layer. The final size and checksum are validated against the
// contents of the uploaded layer. The checksum should be provided in the
// format <algorithm>:<hex digest>.
func (luc *layerUploadController) Finish(size int64, digest digest.Digest) (Layer, error) {
// This section is going to be pretty ugly now. We will have to read the
// file twice. First, to get the tarsum and checksum. When those are
// available, and validated, we will upload it to the blob store and link
// it into the repository. In the future, we need to use resumable hash
// calculations for tarsum and checksum that can be calculated during the
// upload. This will allow us to cut the data directly into a temporary
// directory in the storage backend.
fp, err := luc.file()
if err != nil {
// Cleanup?
return nil, err
}
digest, err = luc.validateLayer(fp, size, digest)
if err != nil {
return nil, err
}
if err := luc.writeLayer(fp, size, digest); err != nil {
// Cleanup?
return nil, err
}
// Yes! We have written some layer data. Let's make it visible. Link the
// layer blob into the repository.
if err := luc.linkLayer(digest); err != nil {
return nil, err
}
// Ok, the upload has completed and finished. Delete the state.
if err := luc.uploadStore.DeleteState(luc.UUID()); err != nil {
// Can we ignore this error?
return nil, err
}
return luc.layerStore.Fetch(luc.Name(), digest)
}
// Cancel the layer upload process.
func (luc *layerUploadController) Cancel() error {
if err := luc.layerStore.uploadStore.DeleteState(luc.UUID()); err != nil {
return err
}
return luc.Close()
}
func (luc *layerUploadController) Write(p []byte) (int, error) {
wr, err := luc.file()
if err != nil {
return 0, err
}
n, err := wr.Write(p)
// Because we expect the reported offset to be consistent with the storage
// state, unfortunately, we need to Sync on every call to write.
if err := wr.Sync(); err != nil {
// Effectively, ignore the write state if the Sync fails. Report that
// no bytes were written and seek back to the starting offset.
offset, seekErr := wr.Seek(luc.Offset(), os.SEEK_SET)
if seekErr != nil {
// What do we do here? Quite disasterous.
luc.reset()
return 0, fmt.Errorf("multiple errors encounterd after Sync + Seek: %v then %v", err, seekErr)
}
if offset != luc.Offset() {
return 0, fmt.Errorf("unexpected offset after seek")
}
return 0, err
}
luc.LayerUploadState.Offset += int64(n)
if err := luc.uploadStore.SaveState(luc.LayerUploadState); err != nil {
// TODO(stevvooe): This failure case may require more thought.
return n, err
}
return n, err
}
func (luc *layerUploadController) Close() error {
if luc.err != nil {
return luc.err
}
if luc.fp != nil {
luc.err = luc.fp.Close()
}
return luc.err
}
func (luc *layerUploadController) file() (layerFile, error) {
if luc.fp != nil {
return luc.fp, nil
}
fp, err := luc.uploadStore.Open(luc.UUID())
if err != nil {
return nil, err
}
// TODO(stevvooe): We may need a more aggressive check here to ensure that
// the file length is equal to the current offset. We may want to sync the
// offset before return the layer upload to the client so it can be
// validated before proceeding with any writes.
// Seek to the current layer offset for good measure.
if _, err = fp.Seek(luc.Offset(), os.SEEK_SET); err != nil {
return nil, err
}
luc.fp = fp
return luc.fp, nil
}
// reset closes and drops the current writer.
func (luc *layerUploadController) reset() {
if luc.fp != nil {
luc.fp.Close()
luc.fp = nil
}
}
// validateLayer runs several checks on the layer file to ensure its validity.
// This is currently very expensive and relies on fast io and fast seek on the
// local host. If successful, the latest digest is returned, which should be
// used over the passed in value.
func (luc *layerUploadController) validateLayer(fp layerFile, size int64, dgst digest.Digest) (digest.Digest, error) {
// First, check the incoming tarsum version of the digest.
version, err := tarsum.GetVersionFromTarsum(dgst.String())
if err != nil {
return "", err
}
// TODO(stevvooe): Should we push this down into the digest type?
switch version {
case tarsum.Version1:
default:
// version 0 and dev, for now.
return "", ErrLayerTarSumVersionUnsupported
}
digestVerifier := digest.NewDigestVerifier(dgst)
lengthVerifier := digest.NewLengthVerifier(size)
// First, seek to the end of the file, checking the size is as expected.
end, err := fp.Seek(0, os.SEEK_END)
if err != nil {
return "", err
}
if end != size {
// Fast path length check.
return "", ErrLayerInvalidLength
}
// Now seek back to start and take care of the digest.
if _, err := fp.Seek(0, os.SEEK_SET); err != nil {
return "", err
}
tr := io.TeeReader(fp, lengthVerifier)
tr = io.TeeReader(tr, digestVerifier)
// TODO(stevvooe): This is one of the places we need a Digester write
// sink. Instead, its read driven. This migth be okay.
// Calculate an updated digest with the latest version.
dgst, err = digest.FromReader(tr)
if err != nil {
return "", err
}
if !lengthVerifier.Verified() {
return "", ErrLayerInvalidLength
}
if !digestVerifier.Verified() {
return "", ErrLayerInvalidDigest
}
return dgst, nil
}
// writeLayer actually writes the the layer file into its final destination.
// The layer should be validated before commencing the write.
func (luc *layerUploadController) writeLayer(fp layerFile, size int64, dgst digest.Digest) error {
blobPath, err := luc.layerStore.pathMapper.path(blobPathSpec{
digest: dgst,
})
if err != nil {
return err
}
// Check for existence
if _, err := luc.layerStore.driver.CurrentSize(blobPath); err != nil {
// TODO(stevvooe): This check is kind of problematic and very racy.
switch err := err.(type) {
case storagedriver.PathNotFoundError:
break // ensure that it doesn't exist.
default:
// TODO(stevvooe): This isn't actually an error: the blob store is
// content addressable and we should just use this to ensure we
// have it written. Although, we do need to verify that the
// content that is there is the correct length.
return err
}
}
// Seek our local layer file back now.
if _, err := fp.Seek(0, os.SEEK_SET); err != nil {
// Cleanup?
return err
}
// Okay: we can write the file to the blob store.
if err := luc.layerStore.driver.WriteStream(blobPath, 0, uint64(size), fp); err != nil {
return err
}
return nil
}
// linkLayer links a valid, written layer blob into the registry under the
// named repository for the upload controller.
func (luc *layerUploadController) linkLayer(digest digest.Digest) error {
layerLinkPath, err := luc.layerStore.pathMapper.path(layerLinkPathSpec{
name: luc.Name(),
digest: digest,
})
if err != nil {
return err
}
return luc.layerStore.driver.PutContent(layerLinkPath, []byte(digest))
}
// localFSLayerUploadStore implements a local layerUploadStore. There are some
// complexities around hashsums that make round tripping to the storage
// backend problematic, so we'll store and read locally for now. By GO-beta,
// this should be fully implemented on top of the backend storagedriver.
//
// For now, the directory layout is as follows:
//
// /<temp dir>/registry-layer-upload/
// <uuid>/
// -> state.json
// -> data
//
// Each upload, identified by uuid, has its own directory with a state file
// and a data file. The state file has a json representation of the current
// state. The data file is the in-progress upload data.
type localFSLayerUploadStore struct {
root string
}
func newTemporaryLocalFSLayerUploadStore() (layerUploadStore, error) {
path, err := ioutil.TempDir("", "registry-layer-upload")
if err != nil {
return nil, err
}
return &localFSLayerUploadStore{
root: path,
}, nil
}
func (llufs *localFSLayerUploadStore) New(name string) (LayerUploadState, error) {
lus := LayerUploadState{
Name: name,
UUID: uuid.New(),
}
if err := os.Mkdir(llufs.path(lus.UUID, ""), 0755); err != nil {
return lus, err
}
if err := llufs.SaveState(lus); err != nil {
return lus, err
}
return lus, nil
}
func (llufs *localFSLayerUploadStore) Open(uuid string) (layerFile, error) {
fp, err := os.OpenFile(llufs.path(uuid, "data"), os.O_CREATE|os.O_APPEND|os.O_RDWR, 0644)
if err != nil {
return nil, err
}
return fp, nil
}
func (llufs *localFSLayerUploadStore) GetState(uuid string) (LayerUploadState, error) {
// TODO(stevvoe): Storing this state on the local file system is an
// intermediate stop gap. This technique is unlikely to handle any kind of
// concurrency very well.
var lus LayerUploadState
fp, err := os.Open(llufs.path(uuid, "state.json"))
if err != nil {
if os.IsNotExist(err) {
return lus, ErrLayerUploadUnknown
}
return lus, err
}
defer fp.Close()
dec := json.NewDecoder(fp)
if err := dec.Decode(&lus); err != nil {
return lus, err
}
return lus, nil
}
func (llufs *localFSLayerUploadStore) SaveState(lus LayerUploadState) error {
p, err := json.Marshal(lus)
if err != nil {
return err
}
err = ioutil.WriteFile(llufs.path(lus.UUID, "state.json"), p, 0644)
if os.IsNotExist(err) {
return ErrLayerUploadUnknown
}
return err
}
func (llufs *localFSLayerUploadStore) DeleteState(uuid string) error {
if err := os.RemoveAll(llufs.path(uuid, "")); err != nil {
if os.IsNotExist(err) {
return ErrLayerUploadUnknown
}
return err
}
return nil
}
func (llufs *localFSLayerUploadStore) path(uuid, file string) string {
return filepath.Join(llufs.root, uuid, file)
}