Add Append() method to trove cache for appending data to an existing key

This largely avoids a large buffer copy which would accumulate inside proxyReader{}

This patch also implements "initialize()" function to init and populate data
on all the existing buckets, avoiding the redundant ListBuckets() invoked by
every API call.

pkg/storage/drivers/donut/donut.go

@@ -69,29 +69,23 @@ type donutDriver struct {
 }
 
 // This is a dummy nodeDiskMap which is going to be deprecated soon
-// once the Management API is standardized, this map is useful for now
-// to show multi disk API correctness and parity calculation
-//
-// Ideally this should be obtained from per node configuration file
-func createNodeDiskMap(p string) map[string][]string {
-	nodes := make(map[string][]string)
-	nodes["localhost"] = make([]string, 16)
-	for i := 0; i < len(nodes["localhost"]); i++ {
-		diskPath := filepath.Join(p, strconv.Itoa(i))
-		if _, err := os.Stat(diskPath); err != nil {
-			if os.IsNotExist(err) {
-				os.MkdirAll(diskPath, 0700)
+// once the Management API is standardized, and we have way of adding
+// and removing disks. This is useful for now to take inputs from CLI
+func createNodeDiskMap(paths []string) map[string][]string {
+	if len(paths) == 1 {
+		nodes := make(map[string][]string)
+		nodes["localhost"] = make([]string, 16)
+		for i := 0; i < len(nodes["localhost"]); i++ {
+			diskPath := filepath.Join(paths[0], strconv.Itoa(i))
+			if _, err := os.Stat(diskPath); err != nil {
+				if os.IsNotExist(err) {
+					os.MkdirAll(diskPath, 0700)
+				}
 			}
+			nodes["localhost"][i] = diskPath
 		}
-		nodes["localhost"][i] = diskPath
+		return nodes
 	}
-	return nodes
-}
-
-// This is a dummy nodeDiskMap which is going to be deprecated soon
-// once the Management API is standardized, and we have way of adding
-// and removing disks. This is useful for now to take inputs from CLI
-func createNodeDiskMapFromSlice(paths []string) map[string][]string {
 	diskPaths := make([]string, len(paths))
 	nodes := make(map[string][]string)
 	for i, p := range paths {
@@ -107,6 +101,43 @@ func createNodeDiskMapFromSlice(paths []string) map[string][]string {
 	return nodes
 }
 
+func initialize(d *donutDriver) {
+	// Soon to be user configurable, when Management API is available
+	// we should remove "default" to something which is passed down
+	// from configuration paramters
+	var err error
+	d.donut, err = donut.NewDonut("default", createNodeDiskMap(d.paths))
+	if err != nil {
+		panic(iodine.New(err, nil))
+	}
+	buckets, err := d.donut.ListBuckets()
+	if err != nil {
+		panic(iodine.New(err, nil))
+	}
+	for bucketName, metadata := range buckets {
+		d.lock.RLock()
+		storedBucket := d.storedBuckets[bucketName]
+		d.lock.RUnlock()
+		if len(storedBucket.multiPartSession) == 0 {
+			storedBucket.multiPartSession = make(map[string]multiPartSession)
+		}
+		if len(storedBucket.objectMetadata) == 0 {
+			storedBucket.objectMetadata = make(map[string]drivers.ObjectMetadata)
+		}
+		if len(storedBucket.partMetadata) == 0 {
+			storedBucket.partMetadata = make(map[string]drivers.PartMetadata)
+		}
+		storedBucket.bucketMetadata = drivers.BucketMetadata{
+			Name:    metadata.Name,
+			Created: metadata.Created,
+			ACL:     drivers.BucketACL(metadata.ACL),
+		}
+		d.lock.Lock()
+		d.storedBuckets[bucketName] = storedBucket
+		d.lock.Unlock()
+	}
+}
+
 // Start a single disk subsystem
 func Start(paths []string, maxSize uint64, expiration time.Duration) (chan<- string, <-chan error, drivers.Driver) {
 	ctrlChannel := make(chan string)
@@ -126,34 +157,17 @@ func Start(paths []string, maxSize uint64, expiration time.Duration) (chan<- str
 	// set up memory expiration
 	driver.objects.ExpireObjects(time.Second * 5)
 
-	// Soon to be user configurable, when Management API is available
-	// we should remove "default" to something which is passed down
-	// from configuration paramters
-	switch {
-	case len(paths) == 1:
-		d, err := donut.NewDonut("default", createNodeDiskMap(paths[0]))
-		if err != nil {
-			err = iodine.New(err, nil)
-			log.Error.Println(err)
-		}
-		driver.donut = d
-	default:
-		d, err := donut.NewDonut("default", createNodeDiskMapFromSlice(paths))
-		if err != nil {
-			err = iodine.New(err, nil)
-			log.Error.Println(err)
-		}
-		driver.donut = d
-	}
 	driver.paths = paths
 	driver.lock = new(sync.RWMutex)
 
+	initialize(driver)
+
 	go start(ctrlChannel, errorChannel, driver)
 	return ctrlChannel, errorChannel, driver
 }
 
 func start(ctrlChannel <-chan string, errorChannel chan<- error, driver *donutDriver) {
-	close(errorChannel)
+	defer close(errorChannel)
 }
 
 func (d donutDriver) expiredObject(a ...interface{}) {
@@ -186,31 +200,8 @@ func (d donutDriver) ListBuckets() (results []drivers.BucketMetadata, err error)
 	if d.donut == nil {
 		return nil, iodine.New(drivers.InternalError{}, nil)
 	}
-	buckets, err := d.donut.ListBuckets()
-	if err != nil {
-		return nil, iodine.New(err, nil)
-	}
-	for bucketName, metadata := range buckets {
-		result := drivers.BucketMetadata{
-			Name:    metadata.Name,
-			Created: metadata.Created,
-			ACL:     drivers.BucketACL(metadata.ACL),
-		}
-		d.lock.Lock()
-		storedBucket := d.storedBuckets[bucketName]
-		if len(storedBucket.multiPartSession) == 0 {
-			storedBucket.multiPartSession = make(map[string]multiPartSession)
-		}
-		if len(storedBucket.objectMetadata) == 0 {
-			storedBucket.objectMetadata = make(map[string]drivers.ObjectMetadata)
-		}
-		if len(storedBucket.partMetadata) == 0 {
-			storedBucket.partMetadata = make(map[string]drivers.PartMetadata)
-		}
-		storedBucket.bucketMetadata = result
-		d.storedBuckets[bucketName] = storedBucket
-		d.lock.Unlock()
-		results = append(results, result)
+	for _, storedBucket := range d.storedBuckets {
+		results = append(results, storedBucket.bucketMetadata)
 	}
 	sort.Sort(byBucketName(results))
 	return results, nil
@@ -229,7 +220,7 @@ func (d donutDriver) CreateBucket(bucketName, acl string) error {
 	if !drivers.IsValidBucketACL(acl) {
 		return iodine.New(drivers.InvalidACL{ACL: acl}, nil)
 	}
-	if drivers.IsValidBucket(bucketName) && !strings.Contains(bucketName, ".") {
+	if drivers.IsValidBucket(bucketName) {
 		if strings.TrimSpace(acl) == "" {
 			acl = "private"
 		}
@@ -244,6 +235,15 @@ func (d donutDriver) CreateBucket(bucketName, acl string) error {
 		newBucket.objectMetadata = make(map[string]drivers.ObjectMetadata)
 		newBucket.multiPartSession = make(map[string]multiPartSession)
 		newBucket.partMetadata = make(map[string]drivers.PartMetadata)
+		metadata, err := d.donut.GetBucketMetadata(bucketName)
+		if err != nil {
+			return iodine.New(err, nil)
+		}
+		newBucket.bucketMetadata = drivers.BucketMetadata{
+			Name:    metadata.Name,
+			Created: metadata.Created,
+			ACL:     drivers.BucketACL(metadata.ACL),
+		}
 		d.storedBuckets[bucketName] = newBucket
 		return nil
 	}
@@ -268,7 +268,7 @@ func (d donutDriver) GetBucketMetadata(bucketName string) (drivers.BucketMetadat
 		return drivers.BucketMetadata{}, iodine.New(drivers.BucketNotFound{Bucket: bucketName}, nil)
 	}
 	bucketMetadata := drivers.BucketMetadata{
-		Name:    bucketName,
+		Name:    metadata.Name,
 		Created: metadata.Created,
 		ACL:     drivers.BucketACL(metadata.ACL),
 	}
@@ -302,8 +302,6 @@ func (d donutDriver) SetBucketMetadata(bucketName, acl string) error {
 
 // GetObject retrieves an object and writes it to a writer
 func (d donutDriver) GetObject(w io.Writer, bucketName, objectName string) (int64, error) {
-	d.lock.RLock()
-	defer d.lock.RUnlock()
 	if d.donut == nil {
 		return 0, iodine.New(drivers.InternalError{}, nil)
 	}
@@ -316,15 +314,24 @@ func (d donutDriver) GetObject(w io.Writer, bucketName, objectName string) (int6
 	if _, ok := d.storedBuckets[bucketName]; ok == false {
 		return 0, iodine.New(drivers.BucketNotFound{Bucket: bucketName}, nil)
 	}
+	d.lock.RLock()
+	defer d.lock.RUnlock()
 	objectKey := bucketName + "/" + objectName
 	data, ok := d.objects.Get(objectKey)
 	if !ok {
 		reader, size, err := d.donut.GetObject(bucketName, objectName)
 		if err != nil {
-			return 0, iodine.New(drivers.ObjectNotFound{
-				Bucket: bucketName,
-				Object: objectName,
-			}, nil)
+			switch iodine.ToError(err).(type) {
+			case donut.BucketNotFound:
+				return 0, iodine.New(drivers.BucketNotFound{Bucket: bucketName}, nil)
+			case donut.ObjectNotFound:
+				return 0, iodine.New(drivers.ObjectNotFound{
+					Bucket: bucketName,
+					Object: objectName,
+				}, nil)
+			default:
+				return 0, iodine.New(drivers.InternalError{}, nil)
+			}
 		}
 		n, err := io.CopyN(w, reader, size)
 		if err != nil {
@@ -372,10 +379,17 @@ func (d donutDriver) GetPartialObject(w io.Writer, bucketName, objectName string
 	if !ok {
 		reader, size, err := d.donut.GetObject(bucketName, objectName)
 		if err != nil {
-			return 0, iodine.New(drivers.ObjectNotFound{
-				Bucket: bucketName,
-				Object: objectName,
-			}, nil)
+			switch iodine.ToError(err).(type) {
+			case donut.BucketNotFound:
+				return 0, iodine.New(drivers.BucketNotFound{Bucket: bucketName}, nil)
+			case donut.ObjectNotFound:
+				return 0, iodine.New(drivers.ObjectNotFound{
+					Bucket: bucketName,
+					Object: objectName,
+				}, nil)
+			default:
+				return 0, iodine.New(drivers.InternalError{}, nil)
+			}
 		}
 		defer reader.Close()
 		if start > size || (start+length-1) > size {
@@ -486,25 +500,32 @@ func (d donutDriver) ListObjects(bucketName string, resources drivers.BucketReso
 }
 
 type proxyReader struct {
-	io.Reader
-	readBytes []byte
+	reader io.Reader
+	driver donutDriver
+	object string
 }
 
 func (r *proxyReader) Read(p []byte) (n int, err error) {
-	n, err = r.Reader.Read(p)
+	n, err = r.reader.Read(p)
 	if err == io.EOF || err == io.ErrUnexpectedEOF {
-		r.readBytes = append(r.readBytes, p[0:n]...)
+		ok := r.driver.objects.Append(r.object, p[0:n])
+		if !ok {
+			return n, io.ErrShortBuffer
+		}
 		return
 	}
 	if err != nil {
 		return
 	}
-	r.readBytes = append(r.readBytes, p[0:n]...)
+	ok := r.driver.objects.Append(r.object, p[0:n])
+	if !ok {
+		return n, io.ErrShortBuffer
+	}
 	return
 }
 
-func newProxyReader(r io.Reader) *proxyReader {
-	return &proxyReader{r, nil}
+func newProxyReader(r io.Reader, d donutDriver, k string) *proxyReader {
+	return &proxyReader{reader: r, driver: d, object: k}
 }
 
 // CreateObject creates a new object
@@ -552,7 +573,7 @@ func (d donutDriver) CreateObject(bucketName, objectName, contentType, expectedM
 		}
 		expectedMD5Sum = hex.EncodeToString(expectedMD5SumBytes)
 	}
-	newReader := newProxyReader(reader)
+	newReader := newProxyReader(reader, d, objectKey)
 	calculatedMD5Sum, err := d.donut.PutObject(bucketName, objectName, expectedMD5Sum, newReader, metadata)
 	if err != nil {
 		switch iodine.ToError(err).(type) {
@@ -561,14 +582,9 @@ func (d donutDriver) CreateObject(bucketName, objectName, contentType, expectedM
 		}
 		return "", iodine.New(err, errParams)
 	}
-	// get object key
-	ok := d.objects.Set(objectKey, newReader.readBytes)
-	// setting up for de-allocation
-	newReader.readBytes = nil
+	// free up
 	go debug.FreeOSMemory()
-	if !ok {
-		return "", iodine.New(drivers.InternalError{}, nil)
-	}
+
 	objectMetadata, err := d.donut.GetObjectMetadata(bucketName, objectName)
 	if err != nil {
 		return "", iodine.New(err, nil)

pkg/storage/drivers/donut/multipart.go

@@ -64,33 +64,6 @@ func (d donutDriver) NewMultipartUpload(bucketName, objectName, contentType stri
 		d.lock.RUnlock()
 		return "", iodine.New(drivers.ObjectNameInvalid{Object: objectName}, nil)
 	}
-	d.lock.RUnlock()
-	buckets, err := d.donut.ListBuckets()
-	if err != nil {
-		return "", iodine.New(err, nil)
-	}
-	for bucketName, metadata := range buckets {
-		result := drivers.BucketMetadata{
-			Name:    metadata.Name,
-			Created: metadata.Created,
-			ACL:     drivers.BucketACL(metadata.ACL),
-		}
-		d.lock.Lock()
-		storedBucket := d.storedBuckets[bucketName]
-		storedBucket.bucketMetadata = result
-		if len(storedBucket.multiPartSession) == 0 {
-			storedBucket.multiPartSession = make(map[string]multiPartSession)
-		}
-		if len(storedBucket.objectMetadata) == 0 {
-			storedBucket.objectMetadata = make(map[string]drivers.ObjectMetadata)
-		}
-		if len(storedBucket.partMetadata) == 0 {
-			storedBucket.partMetadata = make(map[string]drivers.PartMetadata)
-		}
-		d.storedBuckets[bucketName] = storedBucket
-		d.lock.Unlock()
-	}
-	d.lock.RLock()
 	if _, ok := d.storedBuckets[bucketName]; ok == false {
 		d.lock.RUnlock()
 		return "", iodine.New(drivers.BucketNotFound{Bucket: bucketName}, nil)
@@ -117,17 +90,17 @@ func (d donutDriver) NewMultipartUpload(bucketName, objectName, contentType stri
 	return uploadID, nil
 }
 
-func (d donutDriver) AbortMultipartUpload(bucket, key, uploadID string) error {
+func (d donutDriver) AbortMultipartUpload(bucketName, objectName, uploadID string) error {
 	d.lock.RLock()
-	storedBucket := d.storedBuckets[bucket]
-	if storedBucket.multiPartSession[key].uploadID != uploadID {
+	storedBucket := d.storedBuckets[bucketName]
+	if storedBucket.multiPartSession[objectName].uploadID != uploadID {
 		d.lock.RUnlock()
 		return iodine.New(drivers.InvalidUploadID{UploadID: uploadID}, nil)
 	}
 	d.lock.RUnlock()
 
-	d.cleanupMultiparts(bucket, key, uploadID)
-	d.cleanupMultipartSession(bucket, key, uploadID)
+	d.cleanupMultiparts(bucketName, objectName, uploadID)
+	d.cleanupMultipartSession(bucketName, objectName, uploadID)
 	return nil
 }
 
@@ -135,17 +108,17 @@ func getMultipartKey(key string, uploadID string, partNumber int) string {
 	return key + "?uploadId=" + uploadID + "&partNumber=" + strconv.Itoa(partNumber)
 }
 
-func (d donutDriver) CreateObjectPart(bucket, key, uploadID string, partID int, contentType, expectedMD5Sum string, size int64, data io.Reader) (string, error) {
+func (d donutDriver) CreateObjectPart(bucketName, objectName, uploadID string, partID int, contentType, expectedMD5Sum string, size int64, data io.Reader) (string, error) {
 	// Verify upload id
 	d.lock.RLock()
-	storedBucket := d.storedBuckets[bucket]
-	if storedBucket.multiPartSession[key].uploadID != uploadID {
+	storedBucket := d.storedBuckets[bucketName]
+	if storedBucket.multiPartSession[objectName].uploadID != uploadID {
 		d.lock.RUnlock()
 		return "", iodine.New(drivers.InvalidUploadID{UploadID: uploadID}, nil)
 	}
 	d.lock.RUnlock()
 
-	etag, err := d.createObjectPart(bucket, key, uploadID, partID, "", expectedMD5Sum, size, data)
+	etag, err := d.createObjectPart(bucketName, objectName, uploadID, partID, "", expectedMD5Sum, size, data)
 	if err != nil {
 		return "", iodine.New(err, nil)
 	}
@@ -155,23 +128,23 @@ func (d donutDriver) CreateObjectPart(bucket, key, uploadID string, partID int,
 }
 
 // createObject - PUT object to memory buffer
-func (d donutDriver) createObjectPart(bucket, key, uploadID string, partID int, contentType, expectedMD5Sum string, size int64, data io.Reader) (string, error) {
+func (d donutDriver) createObjectPart(bucketName, objectName, uploadID string, partID int, contentType, expectedMD5Sum string, size int64, data io.Reader) (string, error) {
 	d.lock.RLock()
-	if !drivers.IsValidBucket(bucket) {
+	if !drivers.IsValidBucket(bucketName) {
 		d.lock.RUnlock()
-		return "", iodine.New(drivers.BucketNameInvalid{Bucket: bucket}, nil)
+		return "", iodine.New(drivers.BucketNameInvalid{Bucket: bucketName}, nil)
 	}
-	if !drivers.IsValidObjectName(key) {
+	if !drivers.IsValidObjectName(objectName) {
 		d.lock.RUnlock()
-		return "", iodine.New(drivers.ObjectNameInvalid{Object: key}, nil)
+		return "", iodine.New(drivers.ObjectNameInvalid{Object: objectName}, nil)
 	}
-	if _, ok := d.storedBuckets[bucket]; ok == false {
+	if _, ok := d.storedBuckets[bucketName]; ok == false {
 		d.lock.RUnlock()
-		return "", iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
+		return "", iodine.New(drivers.BucketNotFound{Bucket: bucketName}, nil)
 	}
-	storedBucket := d.storedBuckets[bucket]
+	storedBucket := d.storedBuckets[bucketName]
 	// get object key
-	partKey := bucket + "/" + getMultipartKey(key, uploadID, partID)
+	partKey := bucketName + "/" + getMultipartKey(objectName, uploadID, partID)
 	if _, ok := storedBucket.partMetadata[partKey]; ok == true {
 		d.lock.RUnlock()
 		return storedBucket.partMetadata[partKey].ETag, nil
@@ -225,7 +198,11 @@ func (d donutDriver) createObjectPart(bucket, key, uploadID string, partID int,
 	// Verify if the written object is equal to what is expected, only if it is requested as such
 	if strings.TrimSpace(expectedMD5Sum) != "" {
 		if err := isMD5SumEqual(strings.TrimSpace(expectedMD5Sum), md5Sum); err != nil {
-			return "", iodine.New(drivers.BadDigest{Md5: expectedMD5Sum, Bucket: bucket, Key: key}, nil)
+			return "", iodine.New(drivers.BadDigest{
+				Md5:    expectedMD5Sum,
+				Bucket: bucketName,
+				Key:    objectName,
+			}, nil)
 		}
 	}
 	newPart := drivers.PartMetadata{
@@ -237,43 +214,43 @@ func (d donutDriver) createObjectPart(bucket, key, uploadID string, partID int,
 
 	d.lock.Lock()
 	storedBucket.partMetadata[partKey] = newPart
-	multiPartSession := storedBucket.multiPartSession[key]
+	multiPartSession := storedBucket.multiPartSession[objectName]
 	multiPartSession.totalParts++
-	storedBucket.multiPartSession[key] = multiPartSession
-	d.storedBuckets[bucket] = storedBucket
+	storedBucket.multiPartSession[objectName] = multiPartSession
+	d.storedBuckets[bucketName] = storedBucket
 	d.lock.Unlock()
 
 	return md5Sum, nil
 }
 
-func (d donutDriver) cleanupMultipartSession(bucket, key, uploadID string) {
+func (d donutDriver) cleanupMultipartSession(bucketName, objectName, uploadID string) {
 	d.lock.Lock()
 	defer d.lock.Unlock()
-	delete(d.storedBuckets[bucket].multiPartSession, key)
+	delete(d.storedBuckets[bucketName].multiPartSession, objectName)
 }
 
-func (d donutDriver) cleanupMultiparts(bucket, key, uploadID string) {
-	for i := 1; i <= d.storedBuckets[bucket].multiPartSession[key].totalParts; i++ {
-		objectKey := bucket + "/" + getMultipartKey(key, uploadID, i)
+func (d donutDriver) cleanupMultiparts(bucketName, objectName, uploadID string) {
+	for i := 1; i <= d.storedBuckets[bucketName].multiPartSession[objectName].totalParts; i++ {
+		objectKey := bucketName + "/" + getMultipartKey(objectName, uploadID, i)
 		d.multiPartObjects.Delete(objectKey)
 	}
 }
 
-func (d donutDriver) CompleteMultipartUpload(bucket, key, uploadID string, parts map[int]string) (string, error) {
-	if !drivers.IsValidBucket(bucket) {
-		return "", iodine.New(drivers.BucketNameInvalid{Bucket: bucket}, nil)
+func (d donutDriver) CompleteMultipartUpload(bucketName, objectName, uploadID string, parts map[int]string) (string, error) {
+	if !drivers.IsValidBucket(bucketName) {
+		return "", iodine.New(drivers.BucketNameInvalid{Bucket: bucketName}, nil)
 	}
-	if !drivers.IsValidObjectName(key) {
-		return "", iodine.New(drivers.ObjectNameInvalid{Object: key}, nil)
+	if !drivers.IsValidObjectName(objectName) {
+		return "", iodine.New(drivers.ObjectNameInvalid{Object: objectName}, nil)
 	}
 	// Verify upload id
 	d.lock.RLock()
-	if _, ok := d.storedBuckets[bucket]; ok == false {
+	if _, ok := d.storedBuckets[bucketName]; ok == false {
 		d.lock.RUnlock()
-		return "", iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
+		return "", iodine.New(drivers.BucketNotFound{Bucket: bucketName}, nil)
 	}
-	storedBucket := d.storedBuckets[bucket]
-	if storedBucket.multiPartSession[key].uploadID != uploadID {
+	storedBucket := d.storedBuckets[bucketName]
+	if storedBucket.multiPartSession[objectName].uploadID != uploadID {
 		d.lock.RUnlock()
 		return "", iodine.New(drivers.InvalidUploadID{UploadID: uploadID}, nil)
 	}
@@ -284,7 +261,7 @@ func (d donutDriver) CompleteMultipartUpload(bucket, key, uploadID string, parts
 	var fullObject bytes.Buffer
 	for i := 1; i <= len(parts); i++ {
 		recvMD5 := parts[i]
-		object, ok := d.multiPartObjects.Get(bucket + "/" + getMultipartKey(key, uploadID, i))
+		object, ok := d.multiPartObjects.Get(bucketName + "/" + getMultipartKey(objectName, uploadID, i))
 		if ok == false {
 			d.lock.Unlock()
 			return "", iodine.New(errors.New("missing part: "+strconv.Itoa(i)), nil)
@@ -297,7 +274,11 @@ func (d donutDriver) CompleteMultipartUpload(bucket, key, uploadID string, parts
 			return "", iodine.New(drivers.InvalidDigest{Md5: recvMD5}, nil)
 		}
 		if !bytes.Equal(recvMD5Bytes, calcMD5Bytes[:]) {
-			return "", iodine.New(drivers.BadDigest{Md5: recvMD5, Bucket: bucket, Key: getMultipartKey(key, uploadID, i)}, nil)
+			return "", iodine.New(drivers.BadDigest{
+				Md5:    recvMD5,
+				Bucket: bucketName,
+				Key:    getMultipartKey(objectName, uploadID, i),
+			}, nil)
 		}
 		_, err = io.Copy(&fullObject, bytes.NewBuffer(object))
 		if err != nil {
@@ -311,15 +292,15 @@ func (d donutDriver) CompleteMultipartUpload(bucket, key, uploadID string, parts
 	md5sumSlice := md5.Sum(fullObject.Bytes())
 	// this is needed for final verification inside CreateObject, do not convert this to hex
 	md5sum := base64.StdEncoding.EncodeToString(md5sumSlice[:])
-	etag, err := d.CreateObject(bucket, key, "", md5sum, size, &fullObject)
+	etag, err := d.CreateObject(bucketName, objectName, "", md5sum, size, &fullObject)
 	if err != nil {
 		// No need to call internal cleanup functions here, caller will call AbortMultipartUpload()
 		// which would in-turn cleanup properly in accordance with S3 Spec
 		return "", iodine.New(err, nil)
 	}
 	fullObject.Reset()
-	d.cleanupMultiparts(bucket, key, uploadID)
-	d.cleanupMultipartSession(bucket, key, uploadID)
+	d.cleanupMultiparts(bucketName, objectName, uploadID)
+	d.cleanupMultipartSession(bucketName, objectName, uploadID)
 	return etag, nil
 }
 
@@ -330,14 +311,13 @@ func (a byKey) Len() int           { return len(a) }
 func (a byKey) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
 func (a byKey) Less(i, j int) bool { return a[i].Key < a[j].Key }
 
-func (d donutDriver) ListMultipartUploads(bucket string, resources drivers.BucketMultipartResourcesMetadata) (drivers.BucketMultipartResourcesMetadata, error) {
-	// TODO handle delimiter
+func (d donutDriver) ListMultipartUploads(bucketName string, resources drivers.BucketMultipartResourcesMetadata) (drivers.BucketMultipartResourcesMetadata, error) {
 	d.lock.RLock()
 	defer d.lock.RUnlock()
-	if _, ok := d.storedBuckets[bucket]; ok == false {
-		return drivers.BucketMultipartResourcesMetadata{}, iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
+	if _, ok := d.storedBuckets[bucketName]; ok == false {
+		return drivers.BucketMultipartResourcesMetadata{}, iodine.New(drivers.BucketNotFound{Bucket: bucketName}, nil)
 	}
-	storedBucket := d.storedBuckets[bucket]
+	storedBucket := d.storedBuckets[bucketName]
 	var uploads []*drivers.UploadMetadata
 
 	for key, session := range storedBucket.multiPartSession {
@@ -391,23 +371,23 @@ func (a partNumber) Len() int           { return len(a) }
 func (a partNumber) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
 func (a partNumber) Less(i, j int) bool { return a[i].PartNumber < a[j].PartNumber }
 
-func (d donutDriver) ListObjectParts(bucket, key string, resources drivers.ObjectResourcesMetadata) (drivers.ObjectResourcesMetadata, error) {
+func (d donutDriver) ListObjectParts(bucketName, objectName string, resources drivers.ObjectResourcesMetadata) (drivers.ObjectResourcesMetadata, error) {
 	// Verify upload id
 	d.lock.RLock()
 	defer d.lock.RUnlock()
-	if _, ok := d.storedBuckets[bucket]; ok == false {
-		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.BucketNotFound{Bucket: bucket}, nil)
+	if _, ok := d.storedBuckets[bucketName]; ok == false {
+		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.BucketNotFound{Bucket: bucketName}, nil)
 	}
-	storedBucket := d.storedBuckets[bucket]
-	if _, ok := storedBucket.multiPartSession[key]; ok == false {
-		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.ObjectNotFound{Bucket: bucket, Object: key}, nil)
+	storedBucket := d.storedBuckets[bucketName]
+	if _, ok := storedBucket.multiPartSession[objectName]; ok == false {
+		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.ObjectNotFound{Bucket: bucketName, Object: objectName}, nil)
 	}
-	if storedBucket.multiPartSession[key].uploadID != resources.UploadID {
+	if storedBucket.multiPartSession[objectName].uploadID != resources.UploadID {
 		return drivers.ObjectResourcesMetadata{}, iodine.New(drivers.InvalidUploadID{UploadID: resources.UploadID}, nil)
 	}
 	objectResourcesMetadata := resources
-	objectResourcesMetadata.Bucket = bucket
-	objectResourcesMetadata.Key = key
+	objectResourcesMetadata.Bucket = bucketName
+	objectResourcesMetadata.Key = objectName
 	var parts []*drivers.PartMetadata
 	var startPartNumber int
 	switch {
@@ -416,7 +396,7 @@ func (d donutDriver) ListObjectParts(bucket, key string, resources drivers.Objec
 	default:
 		startPartNumber = objectResourcesMetadata.PartNumberMarker
 	}
-	for i := startPartNumber; i <= storedBucket.multiPartSession[key].totalParts; i++ {
+	for i := startPartNumber; i <= storedBucket.multiPartSession[objectName].totalParts; i++ {
 		if len(parts) > objectResourcesMetadata.MaxParts {
 			sort.Sort(partNumber(parts))
 			objectResourcesMetadata.IsTruncated = true
@@ -424,7 +404,7 @@ func (d donutDriver) ListObjectParts(bucket, key string, resources drivers.Objec
 			objectResourcesMetadata.NextPartNumberMarker = i
 			return objectResourcesMetadata, nil
 		}
-		part, ok := storedBucket.partMetadata[bucket+"/"+getMultipartKey(key, resources.UploadID, i)]
+		part, ok := storedBucket.partMetadata[bucketName+"/"+getMultipartKey(objectName, resources.UploadID, i)]
 		if !ok {
 			return drivers.ObjectResourcesMetadata{}, iodine.New(errors.New("missing part: "+strconv.Itoa(i)), nil)
 		}

pkg/storage/trove/trove.go

@@ -115,6 +115,39 @@ func (r *Cache) Get(key string) ([]byte, bool) {
 	return value, true
 }
 
+// Append will append new data to an existing key,
+// if key doesn't exist it behaves like Set()
+func (r *Cache) Append(key string, value []byte) bool {
+	r.Lock()
+	defer r.Unlock()
+	valueLen := uint64(len(value))
+	if r.maxSize > 0 {
+		// check if the size of the object is not bigger than the
+		// capacity of the cache
+		if valueLen > r.maxSize {
+			return false
+		}
+		// remove random key if only we reach the maxSize threshold
+		for (r.currentSize + valueLen) > r.maxSize {
+			for randomKey := range r.items {
+				r.doDelete(randomKey)
+				break
+			}
+		}
+	}
+	_, ok := r.items[key]
+	if !ok {
+		r.items[key] = value
+		r.currentSize += valueLen
+		r.updatedAt[key] = time.Now()
+		return true
+	}
+	r.items[key] = append(r.items[key], value...)
+	r.currentSize += valueLen
+	r.updatedAt[key] = time.Now()
+	return true
+}
+
 // Set will persist a value to the cache
 func (r *Cache) Set(key string, value []byte) bool {
 	r.Lock()
@@ -128,8 +161,8 @@ func (r *Cache) Set(key string, value []byte) bool {
 		}
 		// remove random key if only we reach the maxSize threshold
 		for (r.currentSize + valueLen) > r.maxSize {
-			for key := range r.items {
-				r.doDelete(key)
+			for randomKey := range r.items {
+				r.doDelete(randomKey)
 				break
 			}
 		}