fs: Fail createObject with appropriate message.

Fail createObject() if a file already exists and one attempts
to create a prefix/directory by same name.

Send an approriate error back to the client as 409 Conflict.

api-errors.go

@@ -74,6 +74,7 @@ const (
 	SignatureVersionNotSupported
 	BucketNotEmpty
 	RootPathFull
+	ObjectExistsAsPrefix
 )
 
 // APIError code to Error structure map
@@ -238,6 +239,11 @@ var errorCodeResponse = map[int]APIError{
 		Description:    "Root path has reached its minimum free disk threshold. Please delete few objects to proceed.",
 		HTTPStatusCode: http.StatusInternalServerError,
 	},
+	ObjectExistsAsPrefix: {
+		Code:           "ObjectExistsAsPrefix",
+		Description:    "An object already exists as your prefix, choose a different prefix to proceed.",
+		HTTPStatusCode: http.StatusConflict,
+	},
 }
 
 // errorCodeError provides errorCode to Error. It returns empty if the code provided is unknown

object-handlers.go

@@ -170,6 +170,8 @@ func (api CloudStorageAPI) PutObjectHandler(w http.ResponseWriter, req *http.Req
 			writeErrorResponse(w, req, EntityTooLarge, req.URL.Path)
 		case fs.InvalidDigest:
 			writeErrorResponse(w, req, InvalidDigest, req.URL.Path)
+		case fs.ObjectExistsAsPrefix:
+			writeErrorResponse(w, req, ObjectExistsAsPrefix, req.URL.Path)
 		default:
 			writeErrorResponse(w, req, InternalError, req.URL.Path)
 		}

pkg/fs/errors.go

@@ -102,6 +102,16 @@ func (e ObjectNotFound) Error() string {
 	return "Object not found: " + e.Bucket + "#" + e.Object
 }
 
+// ObjectExistsAsPrefix object already exists with a requested prefix.
+type ObjectExistsAsPrefix struct {
+	Bucket string
+	Prefix string
+}
+
+func (e ObjectExistsAsPrefix) Error() string {
+	return "Object exists on : " + e.Bucket + " as prefix " + e.Prefix
+}
+
 // ObjectCorrupted object found to be corrupted
 type ObjectCorrupted struct {
 	Object string

pkg/fs/fs-object.go

@@ -192,9 +192,9 @@ func (fs Filesystem) CreateObject(bucket, object, expectedMD5Sum string, size in
 	fs.lock.Lock()
 	defer fs.lock.Unlock()
 
-	di, err := disk.GetInfo(fs.path)
-	if err != nil {
-		return ObjectMetadata{}, probe.NewError(err)
+	di, e := disk.GetInfo(fs.path)
+	if e != nil {
+		return ObjectMetadata{}, probe.NewError(e)
 	}
 
 	// Remove 5% from total space for cumulative disk space used for journalling, inodes etc.
@@ -210,7 +210,7 @@ func (fs Filesystem) CreateObject(bucket, object, expectedMD5Sum string, size in
 
 	bucket = fs.denormalizeBucket(bucket)
 	bucketPath := filepath.Join(fs.path, bucket)
-	if _, e := os.Stat(bucketPath); e != nil {
+	if _, e = os.Stat(bucketPath); e != nil {
 		if os.IsNotExist(e) {
 			return ObjectMetadata{}, probe.NewError(BucketNotFound{Bucket: bucket})
 		}
@@ -225,8 +225,8 @@ func (fs Filesystem) CreateObject(bucket, object, expectedMD5Sum string, size in
 	objectPath := filepath.Join(bucketPath, object)
 	if strings.TrimSpace(expectedMD5Sum) != "" {
 		var expectedMD5SumBytes []byte
-		expectedMD5SumBytes, err = base64.StdEncoding.DecodeString(strings.TrimSpace(expectedMD5Sum))
-		if err != nil {
+		expectedMD5SumBytes, e = base64.StdEncoding.DecodeString(strings.TrimSpace(expectedMD5Sum))
+		if e != nil {
 			// pro-actively close the connection
 			return ObjectMetadata{}, probe.NewError(InvalidDigest{Md5: expectedMD5Sum})
 		}
@@ -234,9 +234,19 @@ func (fs Filesystem) CreateObject(bucket, object, expectedMD5Sum string, size in
 	}
 
 	// write object
-	file, err := atomic.FileCreateWithPrefix(objectPath, "")
-	if err != nil {
-		return ObjectMetadata{}, probe.NewError(err)
+	file, e := atomic.FileCreateWithPrefix(objectPath, "")
+	if e != nil {
+		switch e := e.(type) {
+		case *os.PathError:
+			if e.Op == "mkdir" {
+				if strings.Contains(e.Error(), "not a directory") {
+					return ObjectMetadata{}, probe.NewError(ObjectExistsAsPrefix{Bucket: bucket, Prefix: object})
+				}
+			}
+			return ObjectMetadata{}, probe.NewError(e)
+		default:
+			return ObjectMetadata{}, probe.NewError(e)
+		}
 	}
 
 	h := md5.New()
@@ -244,33 +254,33 @@ func (fs Filesystem) CreateObject(bucket, object, expectedMD5Sum string, size in
 	mw := io.MultiWriter(file, h, sh)
 
 	if size > 0 {
-		_, err = io.CopyN(mw, data, size)
-		if err != nil {
+		_, e = io.CopyN(mw, data, size)
+		if e != nil {
 			file.CloseAndPurge()
-			return ObjectMetadata{}, probe.NewError(err)
+			return ObjectMetadata{}, probe.NewError(e)
 		}
 	} else {
-		_, err = io.Copy(mw, data)
-		if err != nil {
+		_, e = io.Copy(mw, data)
+		if e != nil {
 			file.CloseAndPurge()
-			return ObjectMetadata{}, probe.NewError(err)
+			return ObjectMetadata{}, probe.NewError(e)
 		}
 	}
 
 	md5Sum := hex.EncodeToString(h.Sum(nil))
 	// 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 {
+		if e := isMD5SumEqual(strings.TrimSpace(expectedMD5Sum), md5Sum); e != nil {
 			file.CloseAndPurge()
 			return ObjectMetadata{}, probe.NewError(BadDigest{Md5: expectedMD5Sum, Bucket: bucket, Object: object})
 		}
 	}
 	sha256Sum := hex.EncodeToString(sh.Sum(nil))
 	if signature != nil {
-		ok, perr := signature.DoesSignatureMatch(sha256Sum)
-		if perr != nil {
+		ok, err := signature.DoesSignatureMatch(sha256Sum)
+		if err != nil {
 			file.CloseAndPurge()
-			return ObjectMetadata{}, perr.Trace()
+			return ObjectMetadata{}, err.Trace()
 		}
 		if !ok {
 			file.CloseAndPurge()
@@ -279,9 +289,9 @@ func (fs Filesystem) CreateObject(bucket, object, expectedMD5Sum string, size in
 	}
 	file.Close()
 
-	st, err := os.Stat(objectPath)
-	if err != nil {
-		return ObjectMetadata{}, probe.NewError(err)
+	st, e := os.Stat(objectPath)
+	if e != nil {
+		return ObjectMetadata{}, probe.NewError(e)
 	}
 	contentType := "application/octet-stream"
 	if objectExt := filepath.Ext(objectPath); objectExt != "" {
@@ -303,28 +313,28 @@ func deleteObjectPath(basePath, deletePath, bucket, object string) *probe.Error
 		return nil
 	}
 
-	fi, err := os.Stat(deletePath)
-	if err != nil {
-		if os.IsNotExist(err) {
+	fi, e := os.Stat(deletePath)
+	if e != nil {
+		if os.IsNotExist(e) {
 			return probe.NewError(ObjectNotFound{Bucket: bucket, Object: object})
 		}
-		return probe.NewError(err)
+		return probe.NewError(e)
 	}
 	if fi.IsDir() {
 		empty, err := isDirEmpty(deletePath)
 		if err != nil {
-			return err.Trace()
+			return err.Trace(deletePath)
 		}
 		if !empty {
 			return nil
 		}
 	}
 
-	if err := os.Remove(deletePath); err != nil {
-		return probe.NewError(err)
+	if e := os.Remove(deletePath); e != nil {
+		return probe.NewError(e)
 	}
 	if err := deleteObjectPath(basePath, filepath.Dir(deletePath), bucket, object); err != nil {
-		return err.Trace()
+		return err.Trace(basePath, deletePath, bucket, object)
 	}
 	return nil
 }
@@ -367,7 +377,7 @@ func (fs Filesystem) DeleteObject(bucket, object string) *probe.Error {
 		return probe.NewError(ObjectNotFound{Bucket: bucket, Object: object})
 	}
 	if err != nil {
-		return err.Trace()
+		return err.Trace(bucketPath, objectPath, bucket, object)
 	}
 	return nil
 }