python 日志增量抓取实现方法

import timeimport pickleimport osimport reclass LogIncScaner(object):  def __init__(self,log_file, reg_ex,seek_file='/tmp/log-inc-scan.seek.temp'):    self.log_file = log_file    self.reg_ex = reg_ex    self.seek_file = seek_file  def scan(self):    seek = self._get_seek()    file_mtime = os.path.getmtime(self.log_file)    if file_mtime <= seek['time']:      print 'file mtime not change since last scan'      seek['time'] = file_mtime      self._dump_seek(seek)      return []    file_size = os.path.getsize(self.log_file)    if file_size <= seek['position']:      print 'file size not change since last scan'      seek['position'] = file_size      self._dump_seek(seek)      return []    print 'file changed,start to scan'    matchs = []    with open(self.log_file, 'rb') as logfd:      logfd.seek(seek['position'],os.SEEK_SET)      for match in re.finditer(self.reg_ex, logfd.read()):        matchs.append(match)      seek = {'time':time.time(),'position': logfd.tell()}      print seek      self._dump_seek(seek)    return matchs  def _get_seek(self):    seek = {'time':time.time(),'position':0}    if os.path.exists(self.seek_file):      with open(self.seek_file,'rb') as seekfd:          try:            seek = pickle.load(seekfd)          except:            pass    print seek    return seek  def _dump_seek(self, seek):    with open(self.seek_file,'wb') as seekfd:      pickle.dump(seek,seekfd)  def reset_seek(self):    self._dump_seek({'time':time.time(),'position':0})if __name__ == "__main__":  scaner = LogIncScaner('/var/log/messages',r'(/w+ /d+ /d+:/d+:/d+) .+?exception')  scaner.reset_seek()  while True:    matchs = scaner.scan()    for match in matchs:      print 'fond at:' + match.group(1) + ' content:' + match.group(0)    time.sleep(5)