Source Code for Module ZenUtils.ObjectCache

  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   
 14  """NcoProduct 
 15   
 16  Data connector for Micromuse Omnibus 
 17   
 18  $Id: ObjectCache.py,v 1.7 2003/04/14 21:08:25 edahl Exp $""" 
 19   
 20  __version__ = "$Revision: 1.7 $"[11:-2] 
 21   
 22  from Globals import Persistent 
 23  from Globals import DTMLFile 
 24  from AccessControl import ClassSecurityInfo 
 25  import time 
 26   
 27 -class ObjectCache(Persistent): 
 28      editCache = DTMLFile('dtml/editCache', globals()) 
 29      manage_options = ({'label':'Cache','action':'editCache'},) 
 30   
 31      security = ClassSecurityInfo() 
 32   
 33 -    def __init__(self, timeout=20, clearthresh=20): 
 34          self.timeout = timeout 
 35          self.clearthresh = clearthresh 
 36   
 37 -    def initCache(self): 
 38          """make sure that volitile attributes exist""" 
 39          if not hasattr(self, '_v_cache'): 
 40              self._v_cache = {} 
 41          if not hasattr(self, '_v_clearcount'): 
 42              self._v_clearcount = self.clearthresh 
 43   
 44 -    def checkCache(self, key): 
 45          """check to see if key is in cache return None if not""" 
 46          self.initCache() 
 47          if self._v_cache.has_key(key): 
 48              cobj = self._v_cache[key] 
 49              if cobj.checkTime():  
 50                  return cobj.getObj() 
 51              else: 
 52                  del self._v_cache[key] 
 53          return None 
 54   
 55   
 56 -    def addToCache(self, key, obj): 
 57          """add an object to the cache""" 
 58          self.initCache() 
 59          cobj = CacheObj(obj, self.timeout) 
 60          self._v_cache[key] = cobj 
 61   
 62   
 63 -    def clearCache(self, key=None): 
 64          """Clear the cache. 
 65          """ 
 66          if key is not None: 
 67              try: 
 68                  del self._v_cache[key] 
 69              except KeyError: 
 70                  pass 
 71          else: 
 72              self._v_cache = {} 
 73   
 74   
 75 -    def cleanCache(self, force=0): 
 76          """clean the cache if nessesary""" 
 77          self.initCache() 
 78          cleared = 0 
 79          if self._v_cache: 
 80              self._v_clearcount -= 1 
 81              if force or self._v_clearcount < self.clearthresh: 
 82                  for key, value in self._v_cache.items(): 
 83                      if not value.checkTime(): 
 84                          cleared = 1 
 85                          del self._v_cache[key] 
 86                  self._v_clearcount = self.clearthresh 
 87          return cleared 
 88           
 89 -    def getCache(self): 
 90          self.initCache() 
 91          return self._v_cache 
 92   
 93      security.declareProtected('View','getCacheTimeout') 
 94 -    def getCacheTimeout(self): 
 95          """return cache timeout""" 
 96          return self.timeout 
 97   
 98      security.declareProtected('View','getCacheClearthresh') 
 99 -    def getCacheClearthresh(self): 
100          """return cache clearthresh""" 
101          return self.clearthresh 
102   
103 -class CacheObj: 
104       
105 -    def __init__(self, obj, timeout): 
106          self._obj = obj 
107          self._timeout = timeout 
108          self._time = time.time() 
109   
110 -    def checkTime(self): 
111          if self._time + self._timeout < time.time(): 
112              return 0 
113          else: 
114              return 1   
115       
116 -    def getObj(self): 
117          return self._obj 
118   
119 -    def getTime(self): 
120          """Return the time at which this cache object was created""" 
121          return self._time 
122