Avoid frivolous GetObjectMetadata() calls at driver level, return back all the information in donut ListObjects()

pkg/storage/donut/bucket.go

@@ -84,28 +84,6 @@ func newBucket(bucketName, aclType, donutName string, nodes map[string]node) (bu
 func (b bucket) getBucketName() string {
 	return b.name
 }
-
-func (b bucket) GetObjectMetadata(objectName string) (ObjectMetadata, error) {
-	b.lock.RLock()
-	defer b.lock.RUnlock()
-	metadataReaders, err := b.getDiskReaders(normalizeObjectName(objectName), objectMetadataConfig)
-	if err != nil {
-		return ObjectMetadata{}, iodine.New(err, nil)
-	}
-	for _, metadataReader := range metadataReaders {
-		defer metadataReader.Close()
-	}
-	objMetadata := ObjectMetadata{}
-	for _, metadataReader := range metadataReaders {
-		jdec := json.NewDecoder(metadataReader)
-		if err := jdec.Decode(&objMetadata); err != nil {
-			return ObjectMetadata{}, iodine.New(err, nil)
-		}
-		return objMetadata, nil
-	}
-	return ObjectMetadata{}, iodine.New(InvalidArgument{}, nil)
-}
-
 func (b bucket) getBucketMetadataReaders() ([]io.ReadCloser, error) {
 	var readers []io.ReadCloser
 	for _, node := range b.nodes {
@@ -144,6 +122,13 @@ func (b bucket) getBucketMetadata() (*AllBuckets, error) {
 	return nil, iodine.New(InvalidArgument{}, nil)
 }
 
+// GetObjectMetadata - get metadata for an object
+func (b bucket) GetObjectMetadata(objectName string) (ObjectMetadata, error) {
+	b.lock.RLock()
+	defer b.lock.RUnlock()
+	return b.readObjectMetadata(objectName)
+}
+
 // ListObjects - list all objects
 func (b bucket) ListObjects(prefix, marker, delimiter string, maxkeys int) (ListObjects, error) {
 	b.lock.RLock()
@@ -191,13 +176,20 @@ func (b bucket) ListObjects(prefix, marker, delimiter string, maxkeys int) (List
 		}
 		results = AppendU(results, prefix+objectName)
 	}
-	sort.Strings(results)
 	sort.Strings(commonPrefixes)
 
 	listObjects := ListObjects{}
-	listObjects.Objects = results
+	listObjects.Objects = make(map[string]ObjectMetadata)
 	listObjects.CommonPrefixes = commonPrefixes
 	listObjects.IsTruncated = isTruncated
+
+	for _, objectName := range results {
+		objMetadata, err := b.readObjectMetadata(normalizeObjectName(objectName))
+		if err != nil {
+			return ListObjects{}, iodine.New(err, nil)
+		}
+		listObjects.Objects[objectName] = objMetadata
+	}
 	return listObjects, nil
 }
 
@@ -215,21 +207,10 @@ func (b bucket) ReadObject(objectName string) (reader io.ReadCloser, size int64,
 	if _, ok := bucketMetadata.Buckets[b.getBucketName()].BucketObjects[objectName]; !ok {
 		return nil, 0, iodine.New(ObjectNotFound{Object: objectName}, nil)
 	}
-	objMetadata := ObjectMetadata{}
-	metadataReaders, err := b.getDiskReaders(normalizeObjectName(objectName), objectMetadataConfig)
+	objMetadata, err := b.readObjectMetadata(normalizeObjectName(objectName))
 	if err != nil {
 		return nil, 0, iodine.New(err, nil)
 	}
-	for _, metadataReader := range metadataReaders {
-		defer metadataReader.Close()
-	}
-	for _, metadataReader := range metadataReaders {
-		jdec := json.NewDecoder(metadataReader)
-		if err := jdec.Decode(&objMetadata); err != nil {
-			return nil, 0, iodine.New(err, nil)
-		}
-		break
-	}
 	// read and reply back to GetObject() request in a go-routine
 	go b.readEncodedData(normalizeObjectName(objectName), writer, objMetadata)
 	return reader, objMetadata.Size, nil
@@ -346,6 +327,29 @@ func (b bucket) writeObjectMetadata(objectName string, objMetadata *ObjectMetada
 	return nil
 }
 
+// readObjectMetadata - read object metadata
+func (b bucket) readObjectMetadata(objectName string) (ObjectMetadata, error) {
+	objMetadata := ObjectMetadata{}
+	if objectName == "" {
+		return ObjectMetadata{}, iodine.New(InvalidArgument{}, nil)
+	}
+	objMetadataReaders, err := b.getDiskReaders(objectName, objectMetadataConfig)
+	if err != nil {
+		return ObjectMetadata{}, iodine.New(err, nil)
+	}
+	for _, objMetadataReader := range objMetadataReaders {
+		defer objMetadataReader.Close()
+	}
+	for _, objMetadataReader := range objMetadataReaders {
+		jdec := json.NewDecoder(objMetadataReader)
+		if err := jdec.Decode(&objMetadata); err != nil {
+			return ObjectMetadata{}, iodine.New(err, nil)
+		}
+		break
+	}
+	return objMetadata, nil
+}
+
 // TODO - This a temporary normalization of objectNames, need to find a better way
 //
 // normalizedObjectName - all objectNames with "/" get normalized to a simple objectName

pkg/storage/donut/definitions.go

@@ -67,7 +67,7 @@ type BucketMetadata struct {
 
 // ListObjects container for list objects response
 type ListObjects struct {
-	Objects        []string `json:"objects"`
-	CommonPrefixes []string `json:"commonPrefixes"`
-	IsTruncated    bool     `json:"isTruncated"`
+	Objects        map[string]ObjectMetadata `json:"objects"`
+	CommonPrefixes []string                  `json:"commonPrefixes"`
+	IsTruncated    bool                      `json:"isTruncated"`
 }

pkg/storage/donut/donut_test.go

@@ -93,7 +93,7 @@ func (s *MySuite) TestEmptyBucket(c *C) {
 	// check if bucket is empty
 	listObjects, err := donut.ListObjects("foo", "", "", "", 1)
 	c.Assert(err, IsNil)
-	c.Assert(listObjects.Objects, IsNil)
+	c.Assert(len(listObjects.Objects), Equals, 0)
 	c.Assert(listObjects.CommonPrefixes, IsNil)
 	c.Assert(listObjects.IsTruncated, Equals, false)
 }
@@ -312,7 +312,8 @@ func (s *MySuite) TestMultipleNewObjects(c *C) {
 	// test list objects with only delimiter
 	listObjects, err = donut.ListObjects("foo", "", "", "1", 10)
 	c.Assert(err, IsNil)
-	c.Assert(listObjects.Objects[0], Equals, "obj2")
+	_, ok := listObjects.Objects["obj2"]
+	c.Assert(ok, Equals, true)
 	c.Assert(listObjects.IsTruncated, Equals, false)
 	c.Assert(listObjects.CommonPrefixes[0], Equals, "obj1")
 
@@ -320,7 +321,10 @@ func (s *MySuite) TestMultipleNewObjects(c *C) {
 	listObjects, err = donut.ListObjects("foo", "o", "", "", 10)
 	c.Assert(err, IsNil)
 	c.Assert(listObjects.IsTruncated, Equals, false)
-	c.Assert(listObjects.Objects, DeepEquals, []string{"obj1", "obj2"})
+	_, ok1 := listObjects.Objects["obj1"]
+	_, ok2 := listObjects.Objects["obj2"]
+	c.Assert(ok1, Equals, true)
+	c.Assert(ok2, Equals, true)
 
 	three := ioutil.NopCloser(bytes.NewReader([]byte("three")))
 	metadata["contentLength"] = strconv.Itoa(len("three"))

pkg/storage/drivers/donut/donut.go

@@ -448,6 +448,12 @@ func (d donutDriver) GetObjectMetadata(bucketName, objectName string) (drivers.O
 	return objectMetadata, nil
 }
 
+type byObjectName []drivers.ObjectMetadata
+
+func (b byObjectName) Len() int           { return len(b) }
+func (b byObjectName) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
+func (b byObjectName) Less(i, j int) bool { return b[i].Key < b[j].Key }
+
 // ListObjects - returns list of objects
 func (d donutDriver) ListObjects(bucketName string, resources drivers.BucketResourcesMetadata) ([]drivers.ObjectMetadata, drivers.BucketResourcesMetadata, error) {
 	d.lock.RLock()
@@ -470,23 +476,18 @@ func (d donutDriver) ListObjects(bucketName string, resources drivers.BucketReso
 	}
 	resources.CommonPrefixes = listObjects.CommonPrefixes
 	resources.IsTruncated = listObjects.IsTruncated
-	if resources.IsTruncated && resources.IsDelimiterSet() {
-		resources.NextMarker = listObjects.Objects[len(listObjects.Objects)-1]
-	}
-	// make sure to keep the lexical order same as returned by donut
-	// we do not have to sort here again
-	results := make([]drivers.ObjectMetadata, len(listObjects.Objects))
-	for i, objectName := range listObjects.Objects {
-		objectMetadata, err := d.donut.GetObjectMetadata(bucketName, objectName)
-		if err != nil {
-			return nil, drivers.BucketResourcesMetadata{}, iodine.New(err, errParams)
-		}
+	var results []drivers.ObjectMetadata
+	for _, objMetadata := range listObjects.Objects {
 		metadata := drivers.ObjectMetadata{
-			Key:     objectMetadata.Object,
-			Created: objectMetadata.Created,
-			Size:    objectMetadata.Size,
+			Key:     objMetadata.Object,
+			Created: objMetadata.Created,
+			Size:    objMetadata.Size,
 		}
-		results[i] = metadata
+		results = append(results, metadata)
+	}
+	sort.Sort(byObjectName(results))
+	if resources.IsTruncated && resources.IsDelimiterSet() {
+		resources.NextMarker = results[len(results)-1].Key
 	}
 	return results, resources, nil
 }