add concurrency limits for tag lookup and untag

Harbor is using the distribution for it's (harbor-registry) registry component.
The harbor GC will call into the registry to delete the manifest, which in turn
then does a lookup for all tags that reference the deleted manifest.
To find the tag references, the registry will iterate every tag in the repository
and read it's link file to check if it matches the deleted manifest (i.e. to see
if uses the same sha256 digest). So, the more tags in repository, the worse the
performance will be (as there will be more s3 API calls occurring for the tag
directory lookups and tag file reads).

Therefore, we can use concurrent lookup and untag to optimize performance as described in https://github.com/goharbor/harbor/issues/12948.

P.S. This optimization was originally contributed by @Antiarchitect, now I would like to take it over.
Thanks @Antiarchitect's efforts with PR https://github.com/distribution/distribution/pull/3890.

Signed-off-by: Liang Zheng <zhengliang0901@gmail.com>

cmd/registry/config-cache.yml

@@ -12,6 +12,8 @@ storage:
     maintenance:
         uploadpurging:
             enabled: false
+    tag:
+      concurrencylimit: 8
 http:
     addr: :5000
     secret: asecretforlocaldevelopment

cmd/registry/config-dev.yml

@@ -14,6 +14,8 @@ storage:
     maintenance:
         uploadpurging:
             enabled: false
+    tag:
+      concurrencylimit: 8
 http:
     addr: :5000
     debug:

cmd/registry/config-example.yml

@@ -7,6 +7,8 @@ storage:
     blobdescriptor: inmemory
   filesystem:
     rootdirectory: /var/lib/registry
+  tag:
+    concurrencylimit: 8
 http:
   addr: :5000
   headers:

configuration/configuration.go

@@ -441,6 +441,8 @@ func (storage Storage) Type() string {
 			// allow configuration of delete
 		case "redirect":
 			// allow configuration of redirect
+		case "tag":
+			// allow configuration of tag
 		default:
 			storageType = append(storageType, k)
 		}
@@ -454,6 +456,19 @@ func (storage Storage) Type() string {
 	return ""
 }
 
+// TagParameters returns the Parameters map for a Storage tag configuration
+func (storage Storage) TagParameters() Parameters {
+	return storage["tag"]
+}
+
+// setTagParameter changes the parameter at the provided key to the new value
+func (storage Storage) setTagParameter(key string, value interface{}) {
+	if _, ok := storage["tag"]; !ok {
+		storage["tag"] = make(Parameters)
+	}
+	storage["tag"][key] = value
+}
+
 // Parameters returns the Parameters map for a Storage configuration
 func (storage Storage) Parameters() Parameters {
 	return storage[storage.Type()]
@@ -482,6 +497,8 @@ func (storage *Storage) UnmarshalYAML(unmarshal func(interface{}) error) error {
 					// allow configuration of delete
 				case "redirect":
 					// allow configuration of redirect
+				case "tag":
+					// allow configuration of tag
 				default:
 					types = append(types, k)
 				}

configuration/configuration_test.go

@@ -39,6 +39,9 @@ var configStruct = Configuration{
 			"url1":    "https://foo.example.com",
 			"path1":   "/some-path",
 		},
+		"tag": Parameters{
+			"concurrencylimit": 10,
+		},
 	},
 	Auth: Auth{
 		"silly": Parameters{
@@ -167,6 +170,8 @@ storage:
     int1: 42
     url1: "https://foo.example.com"
     path1: "/some-path"
+  tag:
+    concurrencylimit: 10
 auth:
   silly:
     realm: silly
@@ -542,6 +547,9 @@ func copyConfig(config Configuration) *Configuration {
 	for k, v := range config.Storage.Parameters() {
 		configCopy.Storage.setParameter(k, v)
 	}
+	for k, v := range config.Storage.TagParameters() {
+		configCopy.Storage.setTagParameter(k, v)
+	}
 
 	configCopy.Auth = Auth{config.Auth.Type(): Parameters{}}
 	for k, v := range config.Auth.Parameters() {

docs/content/about/configuration.md

@@ -141,6 +141,8 @@ storage:
     usedualstack: false
     loglevel: debug
   inmemory:  # This driver takes no parameters
+  tag:
+    concurrencylimit: 8
   delete:
     enabled: false
   redirect:
@@ -521,6 +523,26 @@ parameter sets a limit on the number of descriptors to store in the cache.
 The default value is 10000. If this parameter is set to 0, the cache is allowed
 to grow with no size limit.
 
+### `tag`
+
+The `tag` subsection provides configuration to set concurrency limit for tag lookup.
+When user calls into the registry to delete the manifest, which in turn then does a
+lookup for all tags that reference the deleted manifest. To find the tag references,
+the registry will iterate every tag in the repository and read it's link file to check
+if it matches the deleted manifest (i.e. to see if uses the same sha256 digest).
+So, the more tags in repository, the worse the performance will be (as there will
+be more S3 API calls occurring for the tag directory lookups and tag file reads if
+using S3 storage driver).
+
+Therefore, add a single flag `concurrencylimit` to set concurrency limit to optimize tag
+lookup performance under the `tag` section. When a value is not provided or equal to 0,
+`GOMAXPROCS` will be used.
+
+```yaml
+tag:
+  concurrencylimit: 8
+```
+
 ### `redirect`
 
 The `redirect` subsection provides configuration for managing redirects from

registry/handlers/app.go

@@ -188,6 +188,21 @@ func NewApp(ctx context.Context, config *configuration.Configuration) *App {
 		}
 	}
 
+	// configure tag lookup concurrency limit
+	if p := config.Storage.TagParameters(); p != nil {
+		l, ok := p["concurrencylimit"]
+		if ok {
+			limit, ok := l.(int)
+			if !ok {
+				panic("tag lookup concurrency limit config key must have a integer value")
+			}
+			if limit < 0 {
+				panic("tag lookup concurrency limit should be a non-negative integer value")
+			}
+			options = append(options, storage.TagLookupConcurrencyLimit(limit))
+		}
+	}
+
 	// configure redirects
 	var redirectDisabled bool
 	if redirectConfig, ok := config.Storage["redirect"]; ok {

registry/handlers/manifests.go

@@ -6,6 +6,7 @@ import (
 	"mime"
 	"net/http"
 	"strings"
+	"sync"
 
 	"github.com/distribution/distribution/v3"
 	"github.com/distribution/distribution/v3/internal/dcontext"
@@ -13,11 +14,13 @@ import (
 	"github.com/distribution/distribution/v3/manifest/ocischema"
 	"github.com/distribution/distribution/v3/manifest/schema2"
 	"github.com/distribution/distribution/v3/registry/api/errcode"
+	"github.com/distribution/distribution/v3/registry/storage"
 	"github.com/distribution/distribution/v3/registry/storage/driver"
 	"github.com/distribution/reference"
 	"github.com/gorilla/handlers"
 	"github.com/opencontainers/go-digest"
 	v1 "github.com/opencontainers/image-spec/specs-go/v1"
+	"golang.org/x/sync/errgroup"
 )
 
 const (
@@ -481,12 +484,26 @@ func (imh *manifestHandler) DeleteManifest(w http.ResponseWriter, r *http.Reques
 		return
 	}
 
+	var (
+		errs []error
+		mu   sync.Mutex
+	)
+	g := errgroup.Group{}
+	g.SetLimit(storage.DefaultConcurrencyLimit)
 	for _, tag := range referencedTags {
-		if err := tagService.Untag(imh, tag); err != nil {
+		tag := tag
-			imh.Errors = append(imh.Errors, err)
+
-			return
+		g.Go(func() error {
-		}
+			if err := tagService.Untag(imh, tag); err != nil {
+				mu.Lock()
+				errs = append(errs, err)
+				mu.Unlock()
+			}
+			return nil
+		})
 	}
+	_ = g.Wait() // imh will record all errors, so ignore the error of Wait()
+	imh.Errors = errs
 
 	w.WriteHeader(http.StatusAccepted)
 }

registry/storage/registry.go

@@ -3,6 +3,7 @@ package storage
 import (
 	"context"
 	"regexp"
+	"runtime"
 
 	"github.com/distribution/distribution/v3"
 	"github.com/distribution/distribution/v3/registry/storage/cache"
@@ -10,6 +11,10 @@ import (
 	"github.com/distribution/reference"
 )
 
+var (
+	DefaultConcurrencyLimit = runtime.GOMAXPROCS(0)
+)
+
 // registry is the top-level implementation of Registry for use in the storage
 // package. All instances should descend from this object.
 type registry struct {
@@ -18,6 +23,7 @@ type registry struct {
 	statter                      *blobStatter // global statter service.
 	blobDescriptorCacheProvider  cache.BlobDescriptorCacheProvider
 	deleteEnabled                bool
+	tagLookupConcurrencyLimit    int
 	resumableDigestEnabled       bool
 	blobDescriptorServiceFactory distribution.BlobDescriptorServiceFactory
 	manifestURLs                 manifestURLs
@@ -40,6 +46,13 @@ func EnableRedirect(registry *registry) error {
 	return nil
 }
 
+func TagLookupConcurrencyLimit(concurrencyLimit int) RegistryOption {
+	return func(registry *registry) error {
+		registry.tagLookupConcurrencyLimit = concurrencyLimit
+		return nil
+	}
+}
+
 // EnableDelete is a functional option for NewRegistry. It enables deletion on
 // the registry.
 func EnableDelete(registry *registry) error {
@@ -184,9 +197,14 @@ func (repo *repository) Named() reference.Named {
 }
 
 func (repo *repository) Tags(ctx context.Context) distribution.TagService {
+	limit := DefaultConcurrencyLimit
+	if repo.tagLookupConcurrencyLimit > 0 {
+		limit = repo.tagLookupConcurrencyLimit
+	}
 	tags := &tagStore{
-		repository: repo,
+		repository:       repo,
-		blobStore:  repo.registry.blobStore,
+		blobStore:        repo.registry.blobStore,
+		concurrencyLimit: limit,
 	}
 
 	return tags

registry/storage/tagstore.go

@@ -4,10 +4,13 @@ import (
 	"context"
 	"path"
 	"sort"
+	"sync"
+
+	"github.com/opencontainers/go-digest"
+	"golang.org/x/sync/errgroup"
 
 	"github.com/distribution/distribution/v3"
 	storagedriver "github.com/distribution/distribution/v3/registry/storage/driver"
-	"github.com/opencontainers/go-digest"
 )
 
 var _ distribution.TagService = &tagStore{}
@@ -18,8 +21,9 @@ var _ distribution.TagService = &tagStore{}
 // which only makes use of the Digest field of the returned distribution.Descriptor
 // but does not enable full roundtripping of Descriptor objects
 type tagStore struct {
-	repository *repository
+	repository       *repository
-	blobStore  *blobStore
+	blobStore        *blobStore
+	concurrencyLimit int
 }
 
 // All returns all tags
@@ -145,26 +149,48 @@ func (ts *tagStore) Lookup(ctx context.Context, desc distribution.Descriptor) ([
 		return nil, err
 	}
 
-	var tags []string
+	g, ctx := errgroup.WithContext(ctx)
+	g.SetLimit(ts.concurrencyLimit)
+
+	var (
+		tags []string
+		mu   sync.Mutex
+	)
 	for _, tag := range allTags {
-		tagLinkPathSpec := manifestTagCurrentPathSpec{
+		if ctx.Err() != nil {
-			name: ts.repository.Named().Name(),
+			break
-			tag:  tag,
 		}
+		tag := tag
 
-		tagLinkPath, _ := pathFor(tagLinkPathSpec)
+		g.Go(func() error {
-		tagDigest, err := ts.blobStore.readlink(ctx, tagLinkPath)
+			tagLinkPathSpec := manifestTagCurrentPathSpec{
-		if err != nil {
+				name: ts.repository.Named().Name(),
-			switch err.(type) {
+				tag:  tag,
-			case storagedriver.PathNotFoundError:
-				continue
 			}
-			return nil, err
-		}
 
-		if tagDigest == desc.Digest {
+			tagLinkPath, _ := pathFor(tagLinkPathSpec)
-			tags = append(tags, tag)
+			tagDigest, err := ts.blobStore.readlink(ctx, tagLinkPath)
-		}
+			if err != nil {
+				switch err.(type) {
+				case storagedriver.PathNotFoundError:
+					return nil
+				}
+				return err
+			}
+
+			if tagDigest == desc.Digest {
+				mu.Lock()
+				tags = append(tags, tag)
+				mu.Unlock()
+			}
+
+			return nil
+		})
+	}
+
+	err = g.Wait()
+	if err != nil {
+		return nil, err
 	}
 
 	return tags, nil