Cache Manager

cache.py

import threading
import collections
import logging

class CacheManager(object):
  _lock = threading.RLock()
  _cache = dict()
  _cache_lock = collections.defaultdict(threading.Lock)

  @staticmethod
  def get(function, *args, **kwargs):
    cache_hash = "%s_%s_%s" % (function, args, kwargs)
    cache_lock = None
    with CacheManager._lock:
      cache_lock = CacheManager._cache_lock[cache_hash]

    with cache_lock:
      if cache_hash not in CacheManager._cache:
        try:
          result = function(*args, **kwargs)
          CacheManager._cache[cache_hash] = result
        except:
          logging.exception("Exception in running %s(%s, %s)", function, args, kwargs)
          raise
      return CacheManager._cache[cache_hash]

def test():
  func = lambda x: x
  def bad_func(msg, no_raise=False):
    if not no_raise:
      raise StandardError(msg)
    return msg
  print CacheManager.get(func, 2)

  print CacheManager.get(bad_func, msg="OK", no_raise=True)
  print CacheManager.get(bad_func, msg="NO!")

if __name__ == '__main__':
  test()