fix offsets

segment.go

@@ -108,7 +108,7 @@ func removeCorruptedSegments(segmentNumbers []int, basePath string) ([]string, e
 
 // loadSegment loads segment info (file descriptor, name, size, etc) and index from segment file.
 func loadSegment(path string) (fd *os.File, checksumFd *os.File, lastOffset int64, index map[uint64]msg, err error) {
-	fd, err = os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0755)
+	fd, err = os.OpenFile(path, os.O_APPEND|os.O_CREATE, 0755)
 	if err != nil {
 		return nil, nil, 0, nil, errors.Wrap(err, "failed to open log segment file")
 	}
@@ -136,53 +136,23 @@ func loadSegment(path string) (fd *os.File, checksumFd *os.File, lastOffset int6
 }
 
 func calculateLastOffset(fd *os.File) (int64, error) {
-	var lastOffset int64
-
-	decoder := gob.NewDecoder(fd)
-	for {
-		var msg msg
-		offset, err := fd.Seek(0, io.SeekCurrent)
-		if err != nil {
-			return 0, errors.Wrap(err, "failed to get current offset")
-		}
-
-		if err = decoder.Decode(&msg); err != nil {
-			if err == io.EOF {
-				break
-			}
-
-			// set offset to the beginning of the file
-			if _, seekErr := fd.Seek(0, io.SeekStart); seekErr != nil {
-				return 0, errors.Wrap(seekErr, "failed to seek to the beginning of the file after error")
-			}
-
-			return lastOffset, nil
-		}
-
-		if _, err = fd.Seek(0, io.SeekStart); err != nil {
-			return 0, errors.Wrap(err, "failed to seek to the beginning of the file")
-		}
-
-		lastOffset = offset
-	}
-
-	// set offset to the beginning of the file
-	if _, err := fd.Seek(lastOffset, io.SeekStart); err != nil {
-		return 0, errors.Wrap(err, "failed to seek to the beginning of the file")
+	offset, err := fd.Seek(0, io.SeekCurrent)
+	if err != nil {
+		return 0, errors.Wrap(err, "failed to get current offset")
 	}
 
-	return lastOffset, nil
+	return offset, nil
 }
 
 // handleCorruptedSegment checks the checksum and removes the segment and checksum files if corrupted.
 func handleCorruptedSegment(segmentPath string) (bool, error) {
-	file, err := os.OpenFile(segmentPath, os.O_RDWR|os.O_CREATE, 0755)
+	file, err := os.OpenFile(segmentPath, os.O_RDWR, 0755)
 	if err != nil {
 		return false, errors.Wrap(err, "failed to open segment file")
 	}
 	defer file.Close()
 
-	checksumFile, err := os.OpenFile(segmentPath+checkSumPostfix, os.O_RDWR|os.O_CREATE, 0755)
+	checksumFile, err := os.OpenFile(segmentPath+checkSumPostfix, os.O_RDWR, 0755)
 	if err != nil {
 		return false, errors.Wrap(err, "failed to open checksum file")
 	}