This change refactors the storage backend to use the new path layout. To facilitate this, manifest storage has been separated into a revision store and tag store, supported by a more general blob store. The blob store is a hybrid object, effectively providing both small object access, keyed by content address, as well as methods that can be used to manage and traverse links to underlying blobs. This covers common operations used in the revision store and tag store, such as linking and traversal. The blob store can also be updated to better support layer reading but this refactoring has been left for another day. The revision store and tag store support the manifest store's compound view of data. These underlying stores provide facilities for richer access models, such as content-addressable access and a richer tagging model. The highlight of this change is the ability to sign a manifest from different hosts and have the registry merge and serve those signatures as part of the manifest package. Various other items, such as the delegate layer handler, were updated to more directly use the blob store or other mechanism to fit with the changes. Signed-off-by: Stephen J Day <stephen.day@docker.com>
159 lines
3.9 KiB
Go
159 lines
3.9 KiB
Go
package storage
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import (
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"fmt"
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"github.com/Sirupsen/logrus"
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"github.com/docker/distribution/digest"
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"github.com/docker/distribution/storagedriver"
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)
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// TODO(stevvooe): Currently, the blobStore implementation used by the
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// manifest store. The layer store should be refactored to better leverage the
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// blobStore, reducing duplicated code.
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// blobStore implements a generalized blob store over a driver, supporting the
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// read side and link management. This object is intentionally a leaky
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// abstraction, providing utility methods that support creating and traversing
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// backend links.
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type blobStore struct {
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driver storagedriver.StorageDriver
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pm *pathMapper
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}
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// exists reports whether or not the path exists. If the driver returns error
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// other than storagedriver.PathNotFound, an error may be returned.
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func (bs *blobStore) exists(dgst digest.Digest) (bool, error) {
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path, err := bs.path(dgst)
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if err != nil {
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return false, err
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}
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ok, err := exists(bs.driver, path)
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if err != nil {
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return false, err
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}
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return ok, nil
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}
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// get retrieves the blob by digest, returning it a byte slice. This should
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// only be used for small objects.
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func (bs *blobStore) get(dgst digest.Digest) ([]byte, error) {
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bp, err := bs.path(dgst)
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if err != nil {
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return nil, err
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}
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return bs.driver.GetContent(bp)
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}
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// link links the path to the provided digest by writing the digest into the
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// target file.
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func (bs *blobStore) link(path string, dgst digest.Digest) error {
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if exists, err := bs.exists(dgst); err != nil {
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return err
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} else if !exists {
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return fmt.Errorf("cannot link non-existent blob")
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}
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// The contents of the "link" file are the exact string contents of the
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// digest, which is specified in that package.
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return bs.driver.PutContent(path, []byte(dgst))
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}
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// linked reads the link at path and returns the content.
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func (bs *blobStore) linked(path string) ([]byte, error) {
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linked, err := bs.readlink(path)
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if err != nil {
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return nil, err
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}
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return bs.get(linked)
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}
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// readlink returns the linked digest at path.
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func (bs *blobStore) readlink(path string) (digest.Digest, error) {
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content, err := bs.driver.GetContent(path)
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if err != nil {
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return "", err
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}
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linked, err := digest.ParseDigest(string(content))
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if err != nil {
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return "", err
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}
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if exists, err := bs.exists(linked); err != nil {
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return "", err
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} else if !exists {
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return "", fmt.Errorf("link %q invalid: blob %s does not exist", path, linked)
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}
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return linked, nil
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}
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// resolve reads the digest link at path and returns the blob store link.
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func (bs *blobStore) resolve(path string) (string, error) {
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dgst, err := bs.readlink(path)
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if err != nil {
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return "", err
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}
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return bs.path(dgst)
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}
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// put stores the content p in the blob store, calculating the digest. If the
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// content is already present, only the digest will be returned. This should
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// only be used for small objects, such as manifests.
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func (bs *blobStore) put(p []byte) (digest.Digest, error) {
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dgst, err := digest.FromBytes(p)
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if err != nil {
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logrus.Errorf("error digesting content: %v, %s", err, string(p))
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return "", err
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}
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bp, err := bs.path(dgst)
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if err != nil {
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return "", err
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}
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// If the content already exists, just return the digest.
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if exists, err := bs.exists(dgst); err != nil {
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return "", err
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} else if exists {
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return dgst, nil
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}
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return dgst, bs.driver.PutContent(bp, p)
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}
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// path returns the canonical path for the blob identified by digest. The blob
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// may or may not exist.
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func (bs *blobStore) path(dgst digest.Digest) (string, error) {
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bp, err := bs.pm.path(blobDataPathSpec{
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digest: dgst,
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})
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if err != nil {
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return "", err
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}
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return bp, nil
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}
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// exists provides a utility method to test whether or not
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func exists(driver storagedriver.StorageDriver, path string) (bool, error) {
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if _, err := driver.Stat(path); err != nil {
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switch err := err.(type) {
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case storagedriver.PathNotFoundError:
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return false, nil
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default:
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return false, err
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}
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}
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return true, nil
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}
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