fs/multipart: Handle un-ordered creation of multiparts.

Fixes #1125

pkg/fs/fs-multipart.go

@@ -122,6 +122,9 @@ func doPartsMatch(parts []CompletePart, savedParts []PartMetadata) bool {
 	if parts == nil || savedParts == nil {
 		return false
 	}
+	if len(parts) != len(savedParts) {
+		return false
+	}
 	// Range of incoming parts and compare them with saved parts.
 	for i, part := range parts {
 		if strings.Trim(part.ETag, "\"") != savedParts[i].ETag {
@@ -245,6 +248,7 @@ func (fs Filesystem) NewMultipartUpload(bucket, object string) (string, *probe.E
 	mpartSession.ObjectName = object
 	mpartSession.UploadID = uploadID
 	mpartSession.Initiated = time.Now().UTC()
+	// Multipart has maximum of 10000 parts.
 	var parts []PartMetadata
 	mpartSession.Parts = parts
 
@@ -257,6 +261,26 @@ func (fs Filesystem) NewMultipartUpload(bucket, object string) (string, *probe.E
 	return uploadID, nil
 }
 
+// Remove all duplicated parts based on the latest time of their upload.
+func removeDuplicateParts(parts []PartMetadata) []PartMetadata {
+	length := len(parts) - 1
+	for i := 0; i < length; i++ {
+		for j := i + 1; j <= length; j++ {
+			if parts[i].PartNumber == parts[j].PartNumber {
+				if parts[i].LastModified.Sub(parts[j].LastModified) > 0 {
+					parts[i] = parts[length]
+				} else {
+					parts[j] = parts[length]
+				}
+				parts = parts[0:length]
+				length--
+				j--
+			}
+		}
+	}
+	return parts
+}
+
 // partNumber is a sortable interface for Part slice.
 type partNumber []PartMetadata
 
@@ -374,14 +398,14 @@ func (fs Filesystem) CreateObjectPart(bucket, object, uploadID, expectedMD5Sum s
 		return "", probe.NewError(InvalidUploadID{UploadID: uploadID})
 	}
 
-	// Append any pre-existing partNumber with new metadata, otherwise
-	// append to the list.
-	if len(deserializedMultipartSession.Parts) < partID {
+	// Add all incoming parts.
 	deserializedMultipartSession.Parts = append(deserializedMultipartSession.Parts, partMetadata)
-	} else {
-		deserializedMultipartSession.Parts[partID-1] = partMetadata
-	}
+
+	// Remove duplicate parts based on the most recent uploaded.
+	deserializedMultipartSession.Parts = removeDuplicateParts(deserializedMultipartSession.Parts)
+	// Save total parts uploaded.
 	deserializedMultipartSession.TotalParts = len(deserializedMultipartSession.Parts)
+
 	// Sort by part number before saving.
 	sort.Sort(partNumber(deserializedMultipartSession.Parts))