Source Code for Module ZenEvents.DbConnectionPool

  1  ########################################################################### 
  2  # 
  3  # This program is part of Zenoss Core, an open source monitoring platform. 
  4  # Copyright (C) 2007, Zenoss Inc. 
  5  # 
  6  # This program is free software; you can redistribute it and/or modify it 
  7  # under the terms of the GNU General Public License version 2 as published by 
  8  # the Free Software Foundation. 
  9  # 
 10  # For complete information please visit: http://www.zenoss.com/oss/ 
 11  # 
 12  ########################################################################### 
 13  from Exceptions import MySQLConnectionError 
 14   
 15  import time 
 16  import DateTime 
 17   
 18  from Queue import Queue, Empty, Full 
 19   
 20  import logging 
 21  log = logging.getLogger("zen.DbConnectionPool") 
 22   
 23  POOL_SIZE = 5 
 24  KEEP_ALIVE = 28800 
 25   
 26 -class DbConnectionPool: 
 27   
 28 -    def __new__(self):                  # self is a type 
 29          if not '_the_instance' in self.__dict__: 
 30              self._the_instance = object.__new__(self) 
 31          return self._the_instance 
 32           
 33      ''' 
 34      instance = None 
 35      def __new__(cls, *args, **kargs):  
 36          if cls.instance is None: 
 37              cls.instance = object.__new__(cls, *args, **kargs) 
 38          log.debug('Returning single instance of DbConnectionPool') 
 39          return cls.instance 
 40      ''' 
 41           
 42 -    def __init__(self): 
 43          self.q = Queue(POOL_SIZE) 
 44   
 45 -    def qsize(self): 
 46          return self.q.qsize() 
 47   
 48 -    def get(self, host=None, port=None, username=None,  
 49              password=None, database=None, block=0): 
 50          try: 
 51              putstamp,obj = self.q.get(block) 
 52   
 53              if time.time() - putstamp >= KEEP_ALIVE: 
 54                  log.debug('Retrieved a stale connection; Pool size: %s' % self.qsize()) 
 55                  obj.close() 
 56                  return self._createConnection(host=host, port=port,  
 57                                              username=username,  
 58                                              password=password, 
 59                                              database=database) 
 60              else: 
 61                  log.debug('Retrieved a connection; Pool size: %s' % self.qsize()) 
 62                  if hasattr(obj, 'ping'): 
 63                      # maybe the connection timed out: reconnect if necessary 
 64                      obj.ping() 
 65                  return obj 
 66   
 67          except Empty: 
 68              return self._createConnection(host=host, port=port,  
 69                                          username=username,  
 70                                          password=password, 
 71                                          database=database) 
 72   
 73 -    def put(self, obj, block=0): 
 74          try: 
 75              self.q.put((time.time(),obj), block) 
 76              log.debug('Returned a connection; Pool size: %s' % self.qsize()) 
 77          except Full: 
 78              pass 
 79   
 80 -    def _createConnection(self, host=None, port=None,  
 81                          username=None, password=None, database=None): 
 82          # These MySQLdb imports were moved from the top of the file to 
 83          # here to avoid importing MySQLdb libs at startup.  This is 
 84          # desirable for DistributedCollector where we are usually 
 85          # executing on a remote box that may not have mysql libs around. 
 86          import MySQLdb 
 87          import MySQLdb.converters 
 88          from MySQLdb.constants import FIELD_TYPE 
 89          log.debug('Creating a new connection; Pool size: %s' % self.qsize()) 
 90          conn = None 
 91          mysqlconv = MySQLdb.converters.conversions.copy() 
 92          mysqlconv[FIELD_TYPE.DATETIME] = DateTime.DateTime 
 93          mysqlconv[FIELD_TYPE.TIMESTAMP] = DateTime.DateTime 
 94          # FIXME for some reason it thinks my int is a long -EAD 
 95          mysqlconv[FIELD_TYPE.LONG] = int 
 96          if not host: 
 97              host, database = database, 'events' 
 98          if port: 
 99              port = int(port) 
100          try: 
101              conn = MySQLdb.connect(host=host, user=username, 
102                                     port=port, passwd=password,  
103                                     db=database, conv=mysqlconv, reconnect=1) 
104              conn.autocommit(1) 
105              return conn 
106          except Exception, e: 
107              raise MySQLConnectionError(str(e)) 
108