remotes/docker: Add MountedFrom and Exists push status

This makes it possible to check whether content didn't actually need to
be pushed to the remote registry and was cross-repo mounted or already
existed.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

remotes/docker/pusher_test.go

@@ -31,6 +31,7 @@ import (
 
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/errdefs"
+	"github.com/containerd/containerd/reference"
 	"github.com/containerd/containerd/remotes"
 	"github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
@@ -69,7 +70,7 @@ func TestGetManifestPath(t *testing.T) {
 func TestPusherErrClosedRetry(t *testing.T) {
 	ctx := context.Background()
 
-	p, reg, done := samplePusher(t)
+	p, reg, _, done := samplePusher(t)
 	defer done()
 
 	layerContent := []byte("test")
@@ -88,7 +89,7 @@ func TestPusherErrClosedRetry(t *testing.T) {
 // TestPusherErrReset tests the push method if the request needs to be retried
 // i.e when ErrReset occurs
 func TestPusherErrReset(t *testing.T) {
-	p, reg, done := samplePusher(t)
+	p, reg, _, done := samplePusher(t)
 	defer done()
 
 	p.object = "latest@sha256:55d31f3af94c797b65b310569803cacc1c9f4a34bf61afcdc8138f89345c8308"
@@ -149,7 +150,7 @@ func tryUpload(ctx context.Context, t *testing.T, p dockerPusher, layerContent [
 	return cw.Commit(ctx, 0, "")
 }
 
-func samplePusher(t *testing.T) (dockerPusher, *uploadableMockRegistry, func()) {
+func samplePusher(t *testing.T) (dockerPusher, *uploadableMockRegistry, StatusTrackLocker, func()) {
 	reg := &uploadableMockRegistry{
 		availableContents: make([]string, 0),
 	}
@@ -158,8 +159,12 @@ func samplePusher(t *testing.T) (dockerPusher, *uploadableMockRegistry, func())
 	if err != nil {
 		t.Fatal(err)
 	}
+	tracker := NewInMemoryTracker()
 	return dockerPusher{
 		dockerBase: &dockerBase{
+			refspec: reference.Spec{
+				Locator: "sample",
+			},
 			repository: "sample",
 			hosts: []RegistryHost{
 				{
@@ -172,8 +177,8 @@ func samplePusher(t *testing.T) (dockerPusher, *uploadableMockRegistry, func())
 			},
 		},
 		object:  "sample",
-		tracker: NewInMemoryTracker(),
-	}, reg, s.Close
+		tracker: tracker,
+	}, reg, tracker, s.Close
 }
 
 var manifestRegexp = regexp.MustCompile(`/([a-z0-9]+)/manifests/(.*)`)
@@ -204,11 +209,21 @@ func (u *uploadableMockRegistry) defaultHandler(w http.ResponseWriter, r *http.R
 			} else {
 				w.Header().Set("Location", "/cannotupload")
 			}
+
 			dgstr := digest.Canonical.Digester()
+
 			if _, err := io.Copy(dgstr.Hash(), r.Body); err != nil {
 				w.WriteHeader(http.StatusInternalServerError)
 				return
 			}
+
+			query := r.URL.Query()
+			if query.Has("mount") && query.Get("from") == "always-mount" {
+				w.Header().Set("Docker-Content-Digest", dgstr.Digest().String())
+				w.WriteHeader(http.StatusCreated)
+				return
+			}
+
 			u.availableContents = append(u.availableContents, dgstr.Digest().String())
 			w.WriteHeader(http.StatusAccepted)
 			return
@@ -262,7 +277,7 @@ func (u *uploadableMockRegistry) isContentAlreadyExist(c string) bool {
 
 func Test_dockerPusher_push(t *testing.T) {
 
-	p, reg, done := samplePusher(t)
+	p, reg, tracker, done := samplePusher(t)
 	defer done()
 
 	reg.uploadable = true
@@ -280,6 +295,7 @@ func Test_dockerPusher_push(t *testing.T) {
 		mediatype         string
 		ref               string
 		unavailableOnFail bool
+		annotations       map[string]string
 	}
 	tests := []struct {
 		name             string
@@ -288,6 +304,7 @@ func Test_dockerPusher_push(t *testing.T) {
 		args             args
 		checkerFunc      func(writer *pushWriter) bool
 		wantErr          error
+		wantStatus       *PushStatus
 	}{
 		{
 			name:             "when a manifest is pushed",
@@ -321,6 +338,68 @@ func Test_dockerPusher_push(t *testing.T) {
 				unavailableOnFail: false,
 			},
 			wantErr: fmt.Errorf("content %v on remote: %w", digest.FromBytes(manifestContent), errdefs.ErrAlreadyExists),
+			wantStatus: &PushStatus{
+				Exists:      true,
+				MountedFrom: "",
+			},
+		},
+		{
+			name: "success cross-repo mount a blob layer",
+			dp:   p,
+			// Not needed to set the base object as it is used to generate path only in case of manifests
+			// dockerBaseObject:
+			args: args{
+				content:           layerContent,
+				mediatype:         ocispec.MediaTypeImageLayer,
+				ref:               fmt.Sprintf("layer2-%s", layerContentDigest.String()),
+				unavailableOnFail: false,
+				annotations: map[string]string{
+					distributionSourceLabelKey("sample"): "always-mount",
+				},
+			},
+			checkerFunc: func(writer *pushWriter) bool {
+				select {
+				case resp := <-writer.respC:
+					// 201 should be the response code when uploading a new blob
+					return resp.StatusCode == http.StatusCreated
+				case <-writer.errC:
+					return false
+				}
+			},
+			wantErr: fmt.Errorf("content %v on remote: %w", digest.FromBytes(layerContent), errdefs.ErrAlreadyExists),
+			wantStatus: &PushStatus{
+				MountedFrom: "sample/always-mount",
+				Exists:      false,
+			},
+		},
+		{
+			name: "failed to cross-repo mount a blob layer",
+			dp:   p,
+			// Not needed to set the base object as it is used to generate path only in case of manifests
+			// dockerBaseObject:
+			args: args{
+				content:           layerContent,
+				mediatype:         ocispec.MediaTypeImageLayer,
+				ref:               fmt.Sprintf("layer3-%s", layerContentDigest.String()),
+				unavailableOnFail: false,
+				annotations: map[string]string{
+					distributionSourceLabelKey("sample"): "never-mount",
+				},
+			},
+			checkerFunc: func(writer *pushWriter) bool {
+				select {
+				case resp := <-writer.respC:
+					// 201 should be the response code when uploading a new blob
+					return resp.StatusCode == http.StatusCreated
+				case <-writer.errC:
+					return false
+				}
+			},
+			wantErr: nil,
+			wantStatus: &PushStatus{
+				MountedFrom: "",
+				Exists:      false,
+			},
 		},
 		{
 			name: "trying to push a blob layer",
@@ -343,14 +422,20 @@ func Test_dockerPusher_push(t *testing.T) {
 				}
 			},
 			wantErr: nil,
+			wantStatus: &PushStatus{
+				MountedFrom: "",
+				Exists:      false,
+			},
 		},
 	}
 	for _, test := range tests {
+		test := test
 		t.Run(test.name, func(t *testing.T) {
 			desc := ocispec.Descriptor{
-				MediaType: test.args.mediatype,
-				Digest:    digest.FromBytes(test.args.content),
-				Size:      int64(len(test.args.content)),
+				MediaType:   test.args.mediatype,
+				Digest:      digest.FromBytes(test.args.content),
+				Size:        int64(len(test.args.content)),
+				Annotations: test.args.annotations,
 			}
 
 			test.dp.object = test.dockerBaseObject
@@ -358,6 +443,13 @@ func Test_dockerPusher_push(t *testing.T) {
 			got, err := test.dp.push(context.Background(), desc, test.args.ref, test.args.unavailableOnFail)
 
 			assert.Equal(t, test.wantErr, err)
+
+			if test.wantStatus != nil {
+				status, err := tracker.GetStatus(test.args.ref)
+				assert.NoError(t, err)
+				assert.Equal(t, *test.wantStatus, status.PushStatus)
+			}
+
 			// if an error is expected, further comparisons are not required.
 			if test.wantErr != nil {
 				return