[Zope-dev] RAMCacheManager and object size

[Dieter Maurer]

Florent Guillaume wrote at 2005-7-8 20:36 +0200:
>The RAMCacheManager does a costly pseudo-pickling of the objects it  
>stores to compute their size, but that information is only used in  
>the statistics screen.

I replaced it by the following code:


try: from cPickle import Pickler, HIGHEST_PROTOCOL
except: from pickle import Pickler, HIGHEST_PROTOCOL
...

class CacheEntry:
    '''
    Represents a cached value.
    '''

    def __init__(self, index, data, view_name):
        try:
            # This is a protective barrier that hopefully prevents
            # us from caching something that might result in memory
            # leaks.  It's also convenient for determining the
            # approximate memory usage of the cache entry.
            # DM 2004-11-29: this code causes excessive time.
            #   Note also that it does not prevent us from
            #   caching objects with references to persistent objects
            #   When we do, nasty persistency errors are likely
            #   to occur ("shouldn't load data while connection is closed").
            #self.size = len(dumps(index)) + len(dumps(data))
            sizer = _ByteCounter()
            pickler = Pickler(sizer, HIGHEST_PROTOCOL)
            pickler.dump(index)
            pickler.dump(data)
            self.size = sizer.getCount()
....

class _ByteCounter:
    '''auxiliary file like class which just counts the bytes written.'''
    _count = 0

    def write(self, bytes):
        self._count += len(bytes)

    def getCount(self):
        return self._count



-- 
Dieter