Function viewLogsJSONFileDirect

pkg/logging/json_logger.go:166–278

Loads JSON log entries directly from the provided JSON log file. If `LogViewOptions.Follow` is provided, it will refresh and re-read the file until it receives something through the stopChannel.

(lvopts LogViewOptions, jsonLogFilePath string, stdout, stderr io.Writer, stopChannel chan os.Signal)

// If `LogViewOptions.Follow` is provided, it will refresh and re-read the file until
// it receives something through the stopChannel.
func viewLogsJSONFileDirect(lvopts LogViewOptions, jsonLogFilePath string, stdout, stderr io.Writer, stopChannel chan os.Signal) error {
	fin, err := os.OpenFile(jsonLogFilePath, os.O_RDONLY, 0400)
	if err != nil {
		return err
	}
	defer func() { fin.Close() }()

	// Search start point based on tail line.
	start, err := tail.FindTailLineStartIndex(fin, lvopts.Tail)
	if err != nil {
		return fmt.Errorf("failed to tail %d lines of JSON logfile %q: %w", lvopts.Tail, jsonLogFilePath, err)
	}

	if _, err := fin.Seek(start, io.SeekStart); err != nil {
		return fmt.Errorf("failed to seek in log file %q from %d position: %w", jsonLogFilePath, start, err)
	}

	limitedMode := (lvopts.Tail > 0) && (!lvopts.Follow)
	limitedNum := lvopts.Tail
	var stop bool
	var watcher *fsnotify.Watcher
	baseName := filepath.Base(jsonLogFilePath)
	dir := filepath.Dir(jsonLogFilePath)
	retryTimes := 2
	backBytes := 0

	for {
		select {
		case <-stopChannel:
			log.L.Debug("received stop signal while re-reading JSON logfile, draining remaining logs and returning")
			// The stop signal is only sent after WaitForLogger has confirmed that the
			// logger finished writing (see pkg/cmd/container.Logs). However, the
			// watcher-driven read loop may not have consumed the final entries yet:
			// they may have been flushed to the file while we were blocked in
			// startTail, and the stop signal wins the next select iteration before
			// they are read. Do a final read so that we don't drop log content that
			// was written right before the container exited.
			// https://github.com/containerd/nerdctl/issues/5006
			if _, err := jsonfile.Decode(stdout, stderr, fin, lvopts.Timestamps, lvopts.Since, lvopts.Until); err != nil {
				log.L.WithError(err).Debugf("error draining remaining logs from JSON logfile %q", jsonLogFilePath)
			}
			return nil
		default:
			if stop || (limitedMode && limitedNum == 0) {
				log.L.Debugf("finished parsing log JSON filefile, path: %s", jsonLogFilePath)
				return nil
			}

			if line, err := jsonfile.Decode(stdout, stderr, fin, lvopts.Timestamps, lvopts.Since, lvopts.Until); err != nil {
				if len(line) > 0 {
					time.Sleep(5 * time.Millisecond)
					if retryTimes == 0 {
						log.L.Infof("finished parsing log JSON filefile, path: %s, line: %s", jsonLogFilePath, string(line))
						return fmt.Errorf("error occurred while doing read of JSON logfile %q: %w, retryTimes: %d", jsonLogFilePath, err, retryTimes)
					}
					retryTimes--
					backBytes = len(line)
				} else {