tinycache.py

# TinyCache
# simple object cache based on Durus (http://www.mems-exchange.org/software/durus/)
# provides multiple named cache pools; no expiration of entries

import logging
from cStringIO import StringIO

durus_log_file = StringIO()
durus_logger = logging.getLogger('durus')
durus_logger.addHandler(logging.StreamHandler(durus_log_file))
durus_logger.setLevel(logging.WARN)
cache_log = logging.getLogger('art17.scrape.cache')

from durus.file_storage import FileStorage
from durus.connection import Connection
from durus.persistent import Persistent
from durus.persistent_dict import PersistentDict

def open_db(cache_fname):
    db_connection = Connection(FileStorage(cache_fname))
    db_root = db_connection.get_root()
    return (db_connection, db_root)
db_connection, db_root = open_db('/TufaStuff/proiecte/edw-art17/data/cache.db')

class Cache():
    def __init__(self, data):
        self.data = data

    def put(self, key, data):
        cache_log.debug('saving "%s"' % key)
        self.data[key] = data
        db_connection.commit()

    def get(self, key):
        if key in self.data:
            cache_log.debug('cache hit "%s"' % key)
            return self.data[key]
        else:
            cache_log.debug('cache miss "%s"' % key)
            return None

def get_cache(name):
    if name not in db_root:
        db_root[name] = PersistentDict()
        db_connection.commit()
    return Cache(db_root[name])