Add shared content label to namespaces

Adds shared content labels to namespaces allowing content to be shared
between namespaces if that namespace is specifically tagged as being
sharable by adding the `containerd.io/namespace/sharable` label to the
namespace.

Signed-off-by: Cody Roseborough <cdr@amazon.com>

metadata/buckets_test.go

@@ -0,0 +1,171 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package metadata
+
+import (
+	"io/ioutil"
+	"path/filepath"
+	"testing"
+
+	"github.com/containerd/containerd/labels"
+	digest "github.com/opencontainers/go-digest"
+	"github.com/pkg/errors"
+	bolt "go.etcd.io/bbolt"
+)
+
+func TestHasSharedLabel(t *testing.T) {
+	tmpdir, err := ioutil.TempDir("", "bucket-testing-")
+	if err != nil {
+		t.Error(err)
+	}
+
+	db, err := bolt.Open(filepath.Join(tmpdir, "metadata.db"), 0660, nil)
+	if err != nil {
+		t.Error(err)
+	}
+
+	err = createNamespaceLabelsBucket(db, "testing-with-shareable", true)
+	if err != nil {
+		t.Error(err)
+	}
+
+	err = createNamespaceLabelsBucket(db, "testing-without-shareable", false)
+	if err != nil {
+		t.Error(err)
+	}
+
+	err = db.View(func(tx *bolt.Tx) error {
+		if !hasSharedLabel(tx, "testing-with-shareable") {
+			return errors.New("hasSharedLabel should return true when label is set")
+		}
+		if hasSharedLabel(tx, "testing-without-shareable") {
+			return errors.New("hasSharedLabel should return false when label is not set")
+		}
+		return nil
+	})
+
+	if err != nil {
+		t.Error(err)
+	}
+}
+
+func TestGetShareableBucket(t *testing.T) {
+	tmpdir, err := ioutil.TempDir("", "bucket-testing-")
+	if err != nil {
+		t.Error(err)
+	}
+
+	db, err := bolt.Open(filepath.Join(tmpdir, "metadata.db"), 0660, nil)
+	if err != nil {
+		t.Error(err)
+	}
+
+	goodDigest := digest.FromString("gooddigest")
+	imagePresentNS := "has-image-is-shareable"
+	imageAbsentNS := "image-absent"
+
+	// Create two namespaces, empty for now
+	err = db.Update(func(tx *bolt.Tx) error {
+		_, err := createImagesBucket(tx, imagePresentNS)
+		if err != nil {
+			return err
+		}
+
+		_, err = createImagesBucket(tx, imageAbsentNS)
+		if err != nil {
+			return err
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Test that getShareableBucket is correctly returning nothing when a
+	// a bucket with that digest is not present in any namespace.
+	err = db.View(func(tx *bolt.Tx) error {
+		if bkt := getShareableBucket(tx, goodDigest); bkt != nil {
+			return errors.New("getShareableBucket should return nil if digest is not present")
+		}
+		return nil
+	})
+
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Create a blob bucket in one of the namespaces with a well-known digest
+	err = db.Update(func(tx *bolt.Tx) error {
+		_, err = createBlobBucket(tx, imagePresentNS, goodDigest)
+		if err != nil {
+			return err
+		}
+		return nil
+	})
+
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Verify that it is still not retrievable if the shareable label is not present
+	err = db.View(func(tx *bolt.Tx) error {
+		if bkt := getShareableBucket(tx, goodDigest); bkt != nil {
+			return errors.New("getShareableBucket should return nil if digest is present but doesn't have shareable label")
+		}
+		return nil
+	})
+
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Create the namespace labels bucket and mark it as shareable
+	err = createNamespaceLabelsBucket(db, imagePresentNS, true)
+	if err != nil {
+		t.Error(err)
+	}
+
+	// Verify that this digest is retrievable from getShareableBucket
+	err = db.View(func(tx *bolt.Tx) error {
+		if bkt := getShareableBucket(tx, goodDigest); bkt == nil {
+			return errors.New("getShareableBucket should not return nil if digest is present")
+		}
+		return nil
+	})
+
+	if err != nil {
+		t.Error(err)
+	}
+}
+
+func createNamespaceLabelsBucket(db transactor, ns string, shareable bool) error {
+	err := db.Update(func(tx *bolt.Tx) error {
+		err := withNamespacesLabelsBucket(tx, ns, func(bkt *bolt.Bucket) error {
+			if shareable {
+				err := bkt.Put([]byte(labels.LabelSharedNamespace), []byte("true"))
+				if err != nil {
+					return err
+				}
+			}
+			return nil
+		})
+		return err
+	})
+	return err
+}