code: def _reduce_file_size_if_necessary(fileName, maxSize):
      
      fileSize = os.path.getsize(fileName)
  
      if maxSize is None:
          logging.debug("Size of logfile '%s' is %s bytes, size limit disabled.", fileName, fileSize)
          return # disabled, nothing to do
  
      if fileSize < (maxSize + 500):
          logging.debug("Size of logfile '%s' is %s bytes, nothing to do.", fileName, fileSize)
          return
  
      logging.warning("Logfile '%s' is too big (size %s bytes). Removing lines.", fileName, fileSize)
      util.shrink_text_file(fileName, maxSize, _LOG_SHRINK_MARKER)
docs: This function shrinks a file.
      We remove only the middle part of a file,
      the file-start and the file-end remain unchanged.