Source code for CoreLayer.Cache

from AccessLayer import UtilityLayer
import logging as log
import collections
import sys

[docs]class Cache(object): """ Cache tiles and preloaded keywords Arguments ----------- _runtime: :class:`RUNTIME` Needed to make attributes for each instance Attributes ----------- _max_memory: int ``MAX`` from :data:`RUNTIME.CACHE`, and \ the max bytes of memory to be used. _cach_meta: str ``MAX`` from :data:`RUNTIME.CACHE`, and \ the key for the size of cached keywords _cache: Collections.OrderedDict A Least recently used ordered dictionary _now_memory: int The current bytes of memory used """ def __init__(self, _runtime): self._max_memory = _runtime.CACHE.MAX.VALUE self._cache_meta = _runtime.CACHE.META.NAME self._cache = collections.OrderedDict() self._now_memory = 0
[docs] def get(self, key): """ Get a value from the cache by key Arguments ---------- key: str The key from a :class:`Query` to access the cache Returns --------- anything The value stored in the cache, or an empty list """ try: # Get the value from the cache. Add to top. value = self._cache.pop(key) self._cache[key] = value return value except KeyError: return []
[docs] def set(self, key, value): """ Set a key in the cache to a value Arguments ---------- key: str The key from a :class:`Query` to access the cache value: anything The keywords or tile value to store in the cache Returns --------- int 0 if successful and -1 if value is too large """ value_memory = self.value_size(value) # Do not cache if value more than total memory if value_memory > self._max_memory: # Log Value over Max Cache msg = "Cannot cache {0}. {1} bytes is over max." log.warning(msg.format(key, value_memory)) return -1 # Add new item to cache memory count self._now_memory += value_memory try: self._cache.pop(key) except KeyError: while self._now_memory >= self._max_memory: # Remove old item from cache and memory count old_value = self._cache.popitem(last=False)[1] self._now_memory -= self.value_size(old_value) # Add new item to the cache self._cache[key] = value # Log successful add msg = "Add {0} to cache. Cache now {1} bytes.", self._now_memory)) return 0
[docs] def value_size(self, value): """ Get actual memory size of a value Arguments ---------- value: anything expected to be a dict or a numpy.ndarray Returns -------- int: the number of bytes used by the value """ if isinstance(value,dict): return int(value[self._cache_meta]) return sys.getsizeof(value)