Merge pull request #1006 from RichardScothern/proxy-serialize

Fix a race condition in pull through cache population

docs/proxy/proxyblobstore.go

@@ -22,15 +22,10 @@ type proxyBlobStore struct {
 	scheduler   *scheduler.TTLExpirationScheduler
 }
 
-var _ distribution.BlobStore = proxyBlobStore{}
+var _ distribution.BlobStore = &proxyBlobStore{}
-
-type inflightBlob struct {
-	refCount int
-	bw       distribution.BlobWriter
-}
 
 // inflight tracks currently downloading blobs
-var inflight = make(map[digest.Digest]*inflightBlob)
+var inflight = make(map[digest.Digest]struct{})
 
 // mu protects inflight
 var mu sync.Mutex
@@ -42,140 +37,113 @@ func setResponseHeaders(w http.ResponseWriter, length int64, mediaType string, d
 	w.Header().Set("Etag", digest.String())
 }
 
-func (pbs proxyBlobStore) ServeBlob(ctx context.Context, w http.ResponseWriter, r *http.Request, dgst digest.Digest) error {
+func (pbs *proxyBlobStore) copyContent(ctx context.Context, dgst digest.Digest, writer io.Writer) (distribution.Descriptor, error) {
-	desc, err := pbs.localStore.Stat(ctx, dgst)
+	desc, err := pbs.remoteStore.Stat(ctx, dgst)
-	if err != nil && err != distribution.ErrBlobUnknown {
-		return err
-	}
-
-	if err == nil {
-		proxyMetrics.BlobPush(uint64(desc.Size))
-		return pbs.localStore.ServeBlob(ctx, w, r, dgst)
-	}
-
-	desc, err = pbs.remoteStore.Stat(ctx, dgst)
 	if err != nil {
-		return err
+		return distribution.Descriptor{}, err
+	}
+
+	if w, ok := writer.(http.ResponseWriter); ok {
+		setResponseHeaders(w, desc.Size, desc.MediaType, dgst)
 	}
 
 	remoteReader, err := pbs.remoteStore.Open(ctx, dgst)
 	if err != nil {
-		return err
+		return distribution.Descriptor{}, err
 	}
 
-	bw, isNew, cleanup, err := getOrCreateBlobWriter(ctx, pbs.localStore, desc)
+	_, err = io.CopyN(writer, remoteReader, desc.Size)
 	if err != nil {
-		return err
+		return distribution.Descriptor{}, err
 	}
-	defer cleanup()
 
-	if isNew {
+	proxyMetrics.BlobPush(uint64(desc.Size))
-		go func() {
+
-			err := streamToStorage(ctx, remoteReader, desc, bw)
+	return desc, nil
+}
+
+func (pbs *proxyBlobStore) serveLocal(ctx context.Context, w http.ResponseWriter, r *http.Request, dgst digest.Digest) (bool, error) {
+	localDesc, err := pbs.localStore.Stat(ctx, dgst)
 	if err != nil {
-				context.GetLogger(ctx).Error(err)
+		// Stat can report a zero sized file here if it's checked between creation
+		// and population.  Return nil error, and continue
+		return false, nil
 	}
 
-			proxyMetrics.BlobPull(uint64(desc.Size))
+	if err == nil {
+		proxyMetrics.BlobPush(uint64(localDesc.Size))
+		return true, pbs.localStore.ServeBlob(ctx, w, r, dgst)
+	}
+
+	return false, nil
+
+}
+
+func (pbs *proxyBlobStore) storeLocal(ctx context.Context, dgst digest.Digest) error {
+	defer func() {
+		mu.Lock()
+		delete(inflight, dgst)
+		mu.Unlock()
 	}()
-		err := streamToClient(ctx, w, desc, bw)
-		if err != nil {
-			return err
-		}
-
-		proxyMetrics.BlobPush(uint64(desc.Size))
-		pbs.scheduler.AddBlob(dgst.String(), blobTTL)
-		return nil
-	}
-
-	err = streamToClient(ctx, w, desc, bw)
-	if err != nil {
-		return err
-	}
-	proxyMetrics.BlobPush(uint64(desc.Size))
-	return nil
-}
-
-type cleanupFunc func()
-
-// getOrCreateBlobWriter will track which blobs are currently being downloaded and enable client requesting
-// the same blob concurrently to read from the existing stream.
-func getOrCreateBlobWriter(ctx context.Context, blobs distribution.BlobService, desc distribution.Descriptor) (distribution.BlobWriter, bool, cleanupFunc, error) {
-	mu.Lock()
-	defer mu.Unlock()
-	dgst := desc.Digest
-
-	cleanup := func() {
-		mu.Lock()
-		defer mu.Unlock()
-		inflight[dgst].refCount--
-
-		if inflight[dgst].refCount == 0 {
-			defer delete(inflight, dgst)
-			_, err := inflight[dgst].bw.Commit(ctx, desc)
-			if err != nil {
-				// There is a narrow race here where Commit can be called while this blob's TTL is expiring
-				// and its being removed from storage.  In that case, the client stream will continue
-				// uninterruped and the blob will be pulled through on the next request, so just log it
-				context.GetLogger(ctx).Errorf("Error committing blob: %q", err)
-			}
-
-		}
-	}
 
+	var desc distribution.Descriptor
+	var err error
 	var bw distribution.BlobWriter
+
+	bw, err = pbs.localStore.Create(ctx)
+	if err != nil {
+		return err
+	}
+
+	desc, err = pbs.copyContent(ctx, dgst, bw)
+	if err != nil {
+		return err
+	}
+
+	_, err = bw.Commit(ctx, desc)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (pbs *proxyBlobStore) ServeBlob(ctx context.Context, w http.ResponseWriter, r *http.Request, dgst digest.Digest) error {
+	served, err := pbs.serveLocal(ctx, w, r, dgst)
+	if err != nil {
+		context.GetLogger(ctx).Errorf("Error serving blob from local storage: %s", err.Error())
+		return err
+	}
+
+	if served {
+		return nil
+	}
+
+	mu.Lock()
 	_, ok := inflight[dgst]
 	if ok {
-		bw = inflight[dgst].bw
+		mu.Unlock()
-		inflight[dgst].refCount++
+		_, err := pbs.copyContent(ctx, dgst, w)
-		return bw, false, cleanup, nil
+		return err
 	}
+	inflight[dgst] = struct{}{}
+	mu.Unlock()
 
-	var err error
+	go func(dgst digest.Digest) {
-	bw, err = blobs.Create(ctx)
+		if err := pbs.storeLocal(ctx, dgst); err != nil {
-	if err != nil {
+			context.GetLogger(ctx).Errorf("Error committing to storage: %s", err.Error())
-		return nil, false, nil, err
 		}
+		pbs.scheduler.AddBlob(dgst.String(), repositoryTTL)
+	}(dgst)
 
-	inflight[dgst] = &inflightBlob{refCount: 1, bw: bw}
+	_, err = pbs.copyContent(ctx, dgst, w)
-	return bw, true, cleanup, nil
-}
-
-func streamToStorage(ctx context.Context, remoteReader distribution.ReadSeekCloser, desc distribution.Descriptor, bw distribution.BlobWriter) error {
-	_, err := io.CopyN(bw, remoteReader, desc.Size)
 	if err != nil {
 		return err
 	}
-
 	return nil
 }
 
-func streamToClient(ctx context.Context, w http.ResponseWriter, desc distribution.Descriptor, bw distribution.BlobWriter) error {
+func (pbs *proxyBlobStore) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
-	setResponseHeaders(w, desc.Size, desc.MediaType, desc.Digest)
-
-	reader, err := bw.Reader()
-	if err != nil {
-		return err
-	}
-	defer reader.Close()
-	teeReader := io.TeeReader(reader, w)
-	buf := make([]byte, 32768, 32786)
-	var soFar int64
-	for {
-		rd, err := teeReader.Read(buf)
-		if err == nil || err == io.EOF {
-			soFar += int64(rd)
-			if soFar < desc.Size {
-				// buffer underflow, keep trying
-				continue
-			}
-			return nil
-		}
-		return err
-	}
-}
-
-func (pbs proxyBlobStore) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
 	desc, err := pbs.localStore.Stat(ctx, dgst)
 	if err == nil {
 		return desc, err
@@ -189,26 +157,26 @@ func (pbs proxyBlobStore) Stat(ctx context.Context, dgst digest.Digest) (distrib
 }
 
 // Unsupported functions
-func (pbs proxyBlobStore) Put(ctx context.Context, mediaType string, p []byte) (distribution.Descriptor, error) {
+func (pbs *proxyBlobStore) Put(ctx context.Context, mediaType string, p []byte) (distribution.Descriptor, error) {
 	return distribution.Descriptor{}, distribution.ErrUnsupported
 }
 
-func (pbs proxyBlobStore) Create(ctx context.Context) (distribution.BlobWriter, error) {
+func (pbs *proxyBlobStore) Create(ctx context.Context) (distribution.BlobWriter, error) {
 	return nil, distribution.ErrUnsupported
 }
 
-func (pbs proxyBlobStore) Resume(ctx context.Context, id string) (distribution.BlobWriter, error) {
+func (pbs *proxyBlobStore) Resume(ctx context.Context, id string) (distribution.BlobWriter, error) {
 	return nil, distribution.ErrUnsupported
 }
 
-func (pbs proxyBlobStore) Open(ctx context.Context, dgst digest.Digest) (distribution.ReadSeekCloser, error) {
+func (pbs *proxyBlobStore) Open(ctx context.Context, dgst digest.Digest) (distribution.ReadSeekCloser, error) {
 	return nil, distribution.ErrUnsupported
 }
 
-func (pbs proxyBlobStore) Get(ctx context.Context, dgst digest.Digest) ([]byte, error) {
+func (pbs *proxyBlobStore) Get(ctx context.Context, dgst digest.Digest) ([]byte, error) {
 	return nil, distribution.ErrUnsupported
 }
 
-func (pbs proxyBlobStore) Delete(ctx context.Context, dgst digest.Digest) error {
+func (pbs *proxyBlobStore) Delete(ctx context.Context, dgst digest.Digest) error {
 	return distribution.ErrUnsupported
 }

docs/proxy/proxyblobstore_test.go

@@ -1,10 +1,13 @@
 package proxy
 
 import (
-	"fmt"
+	"io/ioutil"
+	"math/rand"
 	"net/http"
 	"net/http/httptest"
+	"sync"
 	"testing"
+	"time"
 
 	"github.com/docker/distribution"
 	"github.com/docker/distribution/context"
@@ -12,75 +15,119 @@ import (
 	"github.com/docker/distribution/registry/proxy/scheduler"
 	"github.com/docker/distribution/registry/storage"
 	"github.com/docker/distribution/registry/storage/cache/memory"
+	"github.com/docker/distribution/registry/storage/driver/filesystem"
 	"github.com/docker/distribution/registry/storage/driver/inmemory"
 )
 
+var sbsMu sync.Mutex
+
 type statsBlobStore struct {
 	stats map[string]int
 	blobs distribution.BlobStore
 }
 
 func (sbs statsBlobStore) Put(ctx context.Context, mediaType string, p []byte) (distribution.Descriptor, error) {
+	sbsMu.Lock()
 	sbs.stats["put"]++
+	sbsMu.Unlock()
+
 	return sbs.blobs.Put(ctx, mediaType, p)
 }
 
 func (sbs statsBlobStore) Get(ctx context.Context, dgst digest.Digest) ([]byte, error) {
+	sbsMu.Lock()
 	sbs.stats["get"]++
+	sbsMu.Unlock()
+
 	return sbs.blobs.Get(ctx, dgst)
 }
 
 func (sbs statsBlobStore) Create(ctx context.Context) (distribution.BlobWriter, error) {
+	sbsMu.Lock()
 	sbs.stats["create"]++
+	sbsMu.Unlock()
+
 	return sbs.blobs.Create(ctx)
 }
 
 func (sbs statsBlobStore) Resume(ctx context.Context, id string) (distribution.BlobWriter, error) {
+	sbsMu.Lock()
 	sbs.stats["resume"]++
+	sbsMu.Unlock()
+
 	return sbs.blobs.Resume(ctx, id)
 }
 
 func (sbs statsBlobStore) Open(ctx context.Context, dgst digest.Digest) (distribution.ReadSeekCloser, error) {
+	sbsMu.Lock()
 	sbs.stats["open"]++
+	sbsMu.Unlock()
+
 	return sbs.blobs.Open(ctx, dgst)
 }
 
 func (sbs statsBlobStore) ServeBlob(ctx context.Context, w http.ResponseWriter, r *http.Request, dgst digest.Digest) error {
+	sbsMu.Lock()
 	sbs.stats["serveblob"]++
+	sbsMu.Unlock()
+
 	return sbs.blobs.ServeBlob(ctx, w, r, dgst)
 }
 
 func (sbs statsBlobStore) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
+
+	sbsMu.Lock()
 	sbs.stats["stat"]++
+	sbsMu.Unlock()
+
 	return sbs.blobs.Stat(ctx, dgst)
 }
 
 func (sbs statsBlobStore) Delete(ctx context.Context, dgst digest.Digest) error {
+	sbsMu.Lock()
 	sbs.stats["delete"]++
+	sbsMu.Unlock()
+
 	return sbs.blobs.Delete(ctx, dgst)
 }
 
 type testEnv struct {
+	numUnique int
 	inRemote  []distribution.Descriptor
 	store     proxyBlobStore
 	ctx       context.Context
 }
 
-func (te testEnv) LocalStats() *map[string]int {
+func (te *testEnv) LocalStats() *map[string]int {
+	sbsMu.Lock()
 	ls := te.store.localStore.(statsBlobStore).stats
+	sbsMu.Unlock()
 	return &ls
 }
 
-func (te testEnv) RemoteStats() *map[string]int {
+func (te *testEnv) RemoteStats() *map[string]int {
+	sbsMu.Lock()
 	rs := te.store.remoteStore.(statsBlobStore).stats
+	sbsMu.Unlock()
 	return &rs
 }
 
 // Populate remote store and record the digests
-func makeTestEnv(t *testing.T, name string) testEnv {
+func makeTestEnv(t *testing.T, name string) *testEnv {
 	ctx := context.Background()
 
-	localRegistry, err := storage.NewRegistry(ctx, inmemory.New(), storage.BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()), storage.EnableRedirect, storage.DisableDigestResumption)
+	truthDir, err := ioutil.TempDir("", "truth")
+	if err != nil {
+		t.Fatalf("unable to create tempdir: %s", err)
+	}
+
+	cacheDir, err := ioutil.TempDir("", "cache")
+	if err != nil {
+		t.Fatalf("unable to create tempdir: %s", err)
+	}
+
+	// todo: create a tempfile area here
+	localRegistry, err := storage.NewRegistry(ctx, filesystem.New(truthDir), storage.BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()), storage.EnableRedirect, storage.DisableDigestResumption)
 	if err != nil {
 		t.Fatalf("error creating registry: %v", err)
 	}
@@ -89,7 +136,7 @@ func makeTestEnv(t *testing.T, name string) testEnv {
 		t.Fatalf("unexpected error getting repo: %v", err)
 	}
 
-	truthRegistry, err := storage.NewRegistry(ctx, inmemory.New(), storage.BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()))
+	truthRegistry, err := storage.NewRegistry(ctx, filesystem.New(cacheDir), storage.BlobDescriptorCacheProvider(memory.NewInMemoryBlobDescriptorCacheProvider()))
 	if err != nil {
 		t.Fatalf("error creating registry: %v", err)
 	}
@@ -116,33 +163,59 @@ func makeTestEnv(t *testing.T, name string) testEnv {
 		scheduler:   s,
 	}
 
-	te := testEnv{
+	te := &testEnv{
 		store: proxyBlobStore,
 		ctx:   ctx,
 	}
 	return te
 }
 
-func populate(t *testing.T, te *testEnv, blobCount int) {
+func makeBlob(size int) []byte {
-	var inRemote []distribution.Descriptor
+	blob := make([]byte, size, size)
-	for i := 0; i < blobCount; i++ {
+	for i := 0; i < size; i++ {
-		bytes := []byte(fmt.Sprintf("blob%d", i))
+		blob[i] = byte('A' + rand.Int()%48)
+	}
+	return blob
+}
 
+func init() {
+	rand.Seed(42)
+}
+
+func perm(m []distribution.Descriptor) []distribution.Descriptor {
+	for i := 0; i < len(m); i++ {
+		j := rand.Intn(i + 1)
+		tmp := m[i]
+		m[i] = m[j]
+		m[j] = tmp
+	}
+	return m
+}
+
+func populate(t *testing.T, te *testEnv, blobCount, size, numUnique int) {
+	var inRemote []distribution.Descriptor
+
+	for i := 0; i < numUnique; i++ {
+		bytes := makeBlob(size)
+		for j := 0; j < blobCount/numUnique; j++ {
 			desc, err := te.store.remoteStore.Put(te.ctx, "", bytes)
 			if err != nil {
-			t.Errorf("Put in store")
+				t.Fatalf("Put in store")
 			}
+
 			inRemote = append(inRemote, desc)
 		}
+	}
 
 	te.inRemote = inRemote
-
+	te.numUnique = numUnique
 }
 
 func TestProxyStoreStat(t *testing.T) {
 	te := makeTestEnv(t, "foo/bar")
+
 	remoteBlobCount := 1
-	populate(t, &te, remoteBlobCount)
+	populate(t, te, remoteBlobCount, 10, 1)
 
 	localStats := te.LocalStats()
 	remoteStats := te.RemoteStats()
@@ -164,43 +237,91 @@ func TestProxyStoreStat(t *testing.T) {
 	}
 }
 
-func TestProxyStoreServe(t *testing.T) {
+func TestProxyStoreServeHighConcurrency(t *testing.T) {
 	te := makeTestEnv(t, "foo/bar")
-	remoteBlobCount := 1
+	blobSize := 200
-	populate(t, &te, remoteBlobCount)
+	blobCount := 10
+	numUnique := 1
+	populate(t, te, blobCount, blobSize, numUnique)
 
+	numClients := 16
+	testProxyStoreServe(t, te, numClients)
+}
+
+func TestProxyStoreServeMany(t *testing.T) {
+	te := makeTestEnv(t, "foo/bar")
+	blobSize := 200
+	blobCount := 10
+	numUnique := 4
+	populate(t, te, blobCount, blobSize, numUnique)
+
+	numClients := 4
+	testProxyStoreServe(t, te, numClients)
+}
+
+// todo(richardscothern): blobCount must be smaller than num clients
+func TestProxyStoreServeBig(t *testing.T) {
+	te := makeTestEnv(t, "foo/bar")
+
+	blobSize := 2 << 20
+	blobCount := 4
+	numUnique := 2
+	populate(t, te, blobCount, blobSize, numUnique)
+
+	numClients := 4
+	testProxyStoreServe(t, te, numClients)
+}
+
+// testProxyStoreServe will create clients to consume all blobs
+// populated in the truth store
+func testProxyStoreServe(t *testing.T, te *testEnv, numClients int) {
 	localStats := te.LocalStats()
 	remoteStats := te.RemoteStats()
 
+	var wg sync.WaitGroup
+
+	for i := 0; i < numClients; i++ {
 		// Serveblob - pulls through blobs
-	for _, dr := range te.inRemote {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for _, remoteBlob := range te.inRemote {
 				w := httptest.NewRecorder()
 				r, err := http.NewRequest("GET", "", nil)
 				if err != nil {
 					t.Fatal(err)
 				}
 
-		err = te.store.ServeBlob(te.ctx, w, r, dr.Digest)
+				err = te.store.ServeBlob(te.ctx, w, r, remoteBlob.Digest)
 				if err != nil {
 					t.Fatalf(err.Error())
 				}
 
-		dl, err := digest.FromBytes(w.Body.Bytes())
+				bodyBytes := w.Body.Bytes()
+				localDigest, err := digest.FromBytes(bodyBytes)
 				if err != nil {
 					t.Fatalf("Error making digest from blob")
 				}
-		if dl != dr.Digest {
+				if localDigest != remoteBlob.Digest {
-			t.Errorf("Mismatching blob fetch from proxy")
+					t.Fatalf("Mismatching blob fetch from proxy")
 				}
 			}
+		}()
+	}
 
-	if (*localStats)["stat"] != remoteBlobCount && (*localStats)["create"] != remoteBlobCount {
+	wg.Wait()
-		t.Fatalf("unexpected local stats")
+
-	}
+	remoteBlobCount := len(te.inRemote)
-	if (*remoteStats)["stat"] != remoteBlobCount && (*remoteStats)["open"] != remoteBlobCount {
+	if (*localStats)["stat"] != remoteBlobCount*numClients && (*localStats)["create"] != te.numUnique {
-		t.Fatalf("unexpected local stats")
+		t.Fatal("Expected: stat:", remoteBlobCount*numClients, "create:", remoteBlobCount)
 	}
 
+	// Wait for any async storage goroutines to finish
+	time.Sleep(3 * time.Second)
+
+	remoteStatCount := (*remoteStats)["stat"]
+	remoteOpenCount := (*remoteStats)["open"]
+
 	// Serveblob - blobs come from local
 	for _, dr := range te.inRemote {
 		w := httptest.NewRecorder()
@@ -223,15 +344,11 @@ func TestProxyStoreServe(t *testing.T) {
 		}
 	}
 
-	// Stat to find local, but no new blobs were created
+	localStats = te.LocalStats()
-	if (*localStats)["stat"] != remoteBlobCount*2 && (*localStats)["create"] != remoteBlobCount*2 {
+	remoteStats = te.RemoteStats()
-		t.Fatalf("unexpected local stats")
-	}
 
-	// Remote unchanged
+	// Ensure remote unchanged
-	if (*remoteStats)["stat"] != remoteBlobCount && (*remoteStats)["open"] != remoteBlobCount {
+	if (*remoteStats)["stat"] != remoteStatCount && (*remoteStats)["open"] != remoteOpenCount {
-		fmt.Printf("\tlocal=%#v, \n\tremote=%#v\n", localStats, remoteStats)
+		t.Fatalf("unexpected remote stats: %#v", remoteStats)
-		t.Fatalf("unexpected local stats")
 	}
-
 }

docs/proxy/proxyregistry.go

@@ -94,7 +94,7 @@ func (pr *proxyingRegistry) Repository(ctx context.Context, name string) (distri
 	}
 
 	return &proxiedRepository{
-		blobStore: proxyBlobStore{
+		blobStore: &proxyBlobStore{
 			localStore:  localRepo.Blobs(ctx),
 			remoteStore: remoteRepo.Blobs(ctx),
 			scheduler:   pr.scheduler,