python日志增量抓取实现方法

import time
import pickle
import os
import re
class 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)