利用MongoDB中oplog机制实现准实时数据的操作监控

"ts" : Timestamp(6417682881216249, 1), 时间戳
"h" : NumberLong(0), 长度
"v" : 2, 
"op" : "n", 操作类型
"ns" : "", 操作的库和集合
"o2" : "_id" update条件
"o" : {} 操作值，即document

insert，'i'
update, 'u'
remove(delete), 'd'
cmd, 'c'
noop, 'n' 空操作

#!/usr/bin/python
import pymongo
import re
import time
from pprint import pprint # pretty printer
from pymongo.errors import AutoReconnect

class OplogWatcher(object):
  def __init__(self, db=None, collection=None, poll_time=1.0, connection=None, start_now=True):
    if collection is not None:
      if db is None:
        raise ValueError('must specify db if you specify a collection')
      self._ns_filter = db + '.' + collection
    elif db is not None:
      self._ns_filter = re.compile(r'^%s\.' % db)
    else:
      self._ns_filter = None

    self.poll_time = poll_time
    self.connection = connection or pymongo.Connection()

    if start_now:
      self.start()

  @staticmethod
  def __get_id(op):
    id = None
    o2 = op.get('o2')
    if o2 is not None:
      id = o2.get('_id')

    if id is None:
      id = op['o'].get('_id')

    return id

  def start(self):
    oplog = self.connection.local['oplog.$main']
    ts = oplog.find().sort('$natural', -1)[0]['ts']
    while True:
      if self._ns_filter is None: 
        filter = {}
      else:
        filter = {'ns': self._ns_filter}
      filter['ts'] = {'$gt': ts}
      try:
        cursor = oplog.find(filter, tailable=True)
        while True:
          for op in cursor:
            ts = op['ts']
            id = self.__get_id(op)
            self.all_with_noop(ns=op['ns'], ts=ts, op=op['op'], id=id, raw=op)
          time.sleep(self.poll_time)
          if not cursor.alive:
            break
      except AutoReconnect:
        time.sleep(self.poll_time)

  def all_with_noop(self, ns, ts, op, id, raw):
    if op == 'n':
      self.noop(ts=ts)
    else:
      self.all(ns=ns, ts=ts, op=op, id=id, raw=raw)

  def all(self, ns, ts, op, id, raw):
    if op == 'i':
      self.insert(ns=ns, ts=ts, id=id, obj=raw['o'], raw=raw)
    elif op == 'u':
      self.update(ns=ns, ts=ts, id=id, mod=raw['o'], raw=raw)
    elif op == 'd':
      self.delete(ns=ns, ts=ts, id=id, raw=raw)
    elif op == 'c':
      self.command(ns=ns, ts=ts, cmd=raw['o'], raw=raw)
    elif op == 'db':
      self.db_declare(ns=ns, ts=ts, raw=raw)

  def noop(self, ts):
    pass

  def insert(self, ns, ts, id, obj, raw, **kw):
    pass

  def update(self, ns, ts, id, mod, raw, **kw):
    pass

  def delete(self, ns, ts, id, raw, **kw):
    pass

  def command(self, ns, ts, cmd, raw, **kw):
    pass

  def db_declare(self, ns, ts, **kw):
    pass

class OplogPrinter(OplogWatcher):
  def all(self, **kw):
    pprint (kw)
    print #newline

if __name__ == '__main__':
  OplogPrinter()

self.poll_time = poll_time
self.connection = connection or pymongo.MongoClient()

def start(self):
 oplog = self.connection.local['oplog.$main']
 #读取之前提到的库
 ts = oplog.find().sort('$natural', -1)[0]['ts']
 #获取一个时间边际
 while True:
 if self._ns_filter is None:
  filter = {}
 else:
  filter = {'ns': self._ns_filter}
 filter['ts'] = {'$gt': ts}
 try:
  cursor = oplog.find(filter)
  #对此时间之后的进行处理
  while True:
  for op in cursor:
   ts = op['ts']
   id = self.__get_id(op)
   self.all_with_noop(ns=op['ns'], ts=ts, op=op['op'], id=id, raw=op)
   #可以指定处理插入监控，更新监控或者删除监控等
  time.sleep(self.poll_time)
  if not cursor.alive:
   break
 except AutoReconnect:
  time.sleep(self.poll_time)