feat(storage): add a common blobstore to store all blobs (#3906)

Currently, zot uses one of the existing repos as the master copy for a blob to
achieve dedupe, which complicates dedupe tracking logic. Furthermore, we
have a global storage lock which is becoming a bottleneck. In order to
move to a per-repo lock, we first need to simplify this logic.

Now use a single hidden global repo (_blobstore/) as a blob store instead.

Signed-off-by: Ramkumar Chinchani <rchincha.dev@gmail.com>

pkg/extensions/sync/destination.go

@@ -90,6 +90,12 @@ func (registry *DestinationRegistry) GetImageReference(repo, reference string) (
 func (registry *DestinationRegistry) CommitAll(repo string, imageReference ref.Ref) error {
 	tempImageStore := getImageStoreFromImageReference(repo, imageReference, registry.log)
 
+	if tempImageStore == nil {
+		registry.log.Error().Str("repo", repo).Msg("failed to get temp image store for sync commit")
+
+		return zerr.ErrLocalImgStoreNotFound
+	}
+
 	defer os.RemoveAll(tempImageStore.RootDir())
 
 	repoDir := path.Join(tempImageStore.RootDir(), repo)

pkg/extensions/sync/sync_test.go

@@ -1720,7 +1720,16 @@ func TestDockerImagesAreSkipped(t *testing.T) {
 
 				// trigger config blob upstream error
 				// remove synced image
-				err = os.RemoveAll(path.Join(destDir, indexRepoName))
+				dstRepoPath := path.Join(destDir, indexRepoName)
+				for range 5 {
+					err = os.RemoveAll(dstRepoPath)
+					if err == nil {
+						break
+					}
+
+					time.Sleep(100 * time.Millisecond)
+				}
+
 				So(err, ShouldBeNil)
 
 				configBlobPath := path.Join(srcDir, indexRepoName, "blobs/sha256", configBlobDigest.Encoded())