cacheable

Table of Content

• Name
• Status
• Synopsis
• Description
• Classes
  • cacheable.LRU
  • cacheable.Cacheable
• Methods
  • LRU[key]
  • cacheable.cache
• Author
• Copyright and License

Name

cacheable

Status

The library is considered production ready.

Synopsis

from pykit import cacheable

# create a `LRU`, capacity:10 timeout:60
c = cacheable.LRU(10, 60)

# set value like the `dict`
c['key'] = 'val'

# get value like the `dict`
# if item timeout, delete it and raise `KeyError`
# if item not exist, raise `KeyError`
try:
    val = c['key']
except KeyError:
    print('key error')

from pykit import cacheable

cache_data = {
    'key1': 'val_1',
    'key2': 'val_2',
}

# define the function with a decorator
@cacheable.cache('cache_name', capacity=100, timeout=60,
                    is_deepcopy=False, mutex_update=False)
def get_data(param):
    return cache_data.get(param, '')

# call `get_data`, if item has not been cached, cache the return value
data = get_data('key1')

# call `get_data` use the same param, data will be got from cache
time.sleep(30)
data = get_data('key1')

# if item timeout, when call `get_data`, cache again
time.sleep(70)
data = get_data('key1')

# define a method with a decorator
class MethodCache(object):

    @cacheable.cache('method_cache_name', capacity=100, timeout=60,
                        is_deepcopy=False, mutex_update=False)
    def get_data(self, param):
        return cache_data.get(param, '')

mm = MethodCache()
data = mm.get_data('key2')

Description

Cache data which access frequently.

Classes

cacheable.LRU

syntax: cacheable.LRU(capacity, timeout=60)

Least Recently Used Cache.

arguments:

• capacity: capacity of LRU, when the size of LRU is greater than capacity * 1.5, clean old items until the size is equal to capacity

• timeout: max cache time of item, unit is second, default is 60

cacheable.Cacheable

syntax: cacheable.Cacheable(capacity=1024 * 4, timeout=60, is_deepcopy=True, is_pack=False, mutex_update=False)

Create a LRU object, all items will be cached in it.

arguments:

• capacity: for create LRU object, default is 1024 * 4

• timeout: for create LRU object, default is 60, unit is second

• is_deepcopy: cacheable.cache return a decorator that use is_deepcopy to return deepcopy or reference of cached item.

  • True: return deepcopy of cached item

  • False: return reference of cached item

• is_pack: cacheable.cache return a decorator that use is_pack to return msgpack.pack item.

  • True: return msgpack.pack of cached item

  • False: return reference of cached item

• mutex_update: allows only one thread to update the cache item. Default is False.

  • True: mutex update

  • False: concurrently update

Methods

LRU[key]

LRU contain __getitem__ and __setitem__, so can get value and set value like dict

• LRU[key]: return the item of LRU with key.

  If item exist, move it to the tail to avoid to be cleaned.

  Raise a KeyError if key is not in LRU or has been timeout.

  from pykit import cacheable
  # create `LRU`, capacity:10, timeout:60
  lru = cacheable.LRU(10, 60)
  
  # set `lru['a']` to 'val_a'
  lru['a'] = 'val_a'
  
  sleep_time = 30
  try:
      time.sleep(sleep_time)
      val = lru['a']
      # if sleep_time <= timeout of LRU, return the value
      # if sleep_time > timeout of LRU, delete it and raise a `KeyError`
  except KeyError as e:
      print('key not in lru')
  
  try:
      val = lru['b']
      # if item not in lru, raise a `KeyError`
  except KeyError as e:
      print('key not in lru')

• LRU[key] = value: set LRU[key] to value and move it to tail of LRU to avoid to be cleaned.

  If size of LRU is greater than capacity * 1.5, clean items from head until size is equal to capacity.

  from pykit import cacheable
  # create a `LRU`, capacity:2 timeout:60
  c = cacheable.LRU(2, 60)
  
  # insert new item to the tail of `LRU`
  c['a'] = 'val_a'
  c['b'] = 'val_b'
  c['c'] = 'val_c'
  
  # after insert `d`, `a` and `b` will be cleaned
  c['d'] = 'val_d'

cacheable.cache

syntax: cacheable.cache(name, capacity=1024 * 4, timeout=60, is_deepcopy=True, is_pack=False, mutex_update=False)

If not exist, create a cacheable.Cacheable and save it, else use exist one.

from pykit import cacheable

need_cache_data_aa = {'key': 'val_aa'}
need_cache_data_bb = {'key': 'val_bb'}

#use different `name` create two objects, they don't have any relation.
@cacheable.cache('name_aa', capacity=100, timeout=60, is_deepcopy=False, mutex_update=False)
def cache_aa(param):
    return need_cache_data_aa.get(param, '')

@cacheable.cache('name_bb', capacity=100, timeout=60, is_deepcopy=False, mutex_update=False)
def cache_bb(param):
    return need_cache_data_bb.get(param, '')

arguments:

• name: for distinguishing different cacheable.Cacheable

• capacity: used as capacity of cacheable.Cacheable

• timeout: used as timeout of cacheable.Cacheable

• is_deepcopy: used as is_deepcopy of cacheable.Cacheable

• mutex_update: used as mutex_update of cacheable.Cacheable

return: A decorator function that it checks whether the data has been cached, if not or has been timeout, cache and return the data.

from pykit import cacheable

need_cache_data = {
    'key1': 'val_1',
    'key2': 'val_2',
}

@cacheable.cache('cache', capacity=100, timeout=60, is_deepcopy=False, mutex_update=False)
def get_data(key):
    return need_cache_data.get(key, '')

# params of `get_data` are used to generate key of LRU
# if params are different, cache them as different items
get_data('key1')
get_data('key2')

Author

Baohai Liu(刘保海) baohai.liu@baishancloud.com

Copyright and License

The MIT License (MIT)

Copyright (c) 2017 Baohai Liu(刘保海) baohai.liu@baishancloud.com