import time
from itertools import takewhile
import operator
from collections import OrderedDict
from abc import abstractmethod, ABC
[docs]class IStorage(ABC):
"""
Local storage for this node.
IStorage implementations of get must return the same type as put in by set
"""
[docs] @abstractmethod
def __setitem__(self, key, value):
"""
Set a key to the given value.
"""
[docs] @abstractmethod
def __getitem__(self, key):
"""
Get the given key. If item doesn't exist, raises C{KeyError}
"""
[docs] @abstractmethod
def get(self, key, default=None):
"""
Get given key. If not found, return default.
"""
[docs] @abstractmethod
def iter_older_than(self, seconds_old):
"""
Return the an iterator over (key, value) tuples for items older
than the given secondsOld.
"""
@abstractmethod
def __iter__(self):
"""
Get the iterator for this storage, should yield tuple of (key, value)
"""
[docs]class ForgetfulStorage(IStorage):
def __init__(self, ttl=604800):
"""
By default, max age is a week.
"""
self.data = OrderedDict()
self.ttl = ttl
[docs] def __setitem__(self, key, value):
if key in self.data:
del self.data[key]
self.data[key] = (time.monotonic(), value)
self.cull()
[docs] def cull(self):
for _, _ in self.iter_older_than(self.ttl):
self.data.popitem(last=False)
[docs] def get(self, key, default=None):
self.cull()
if key in self.data:
return self[key]
return default
[docs] def __getitem__(self, key):
self.cull()
return self.data[key][1]
def __repr__(self):
self.cull()
return repr(self.data)
[docs] def iter_older_than(self, seconds_old):
min_birthday = time.monotonic() - seconds_old
zipped = self._triple_iter()
matches = takewhile(lambda r: min_birthday >= r[1], zipped)
return list(map(operator.itemgetter(0, 2), matches))
def _triple_iter(self):
ikeys = self.data.keys()
ibirthday = map(operator.itemgetter(0), self.data.values())
ivalues = map(operator.itemgetter(1), self.data.values())
return zip(ikeys, ibirthday, ivalues)
def __iter__(self):
self.cull()
ikeys = self.data.keys()
ivalues = map(operator.itemgetter(1), self.data.values())
return zip(ikeys, ivalues)