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dephne compatibility of LocalCacheProxy

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This commit is contained in:
Laura Klünder 2025-04-17 23:25:51 +02:00
parent 80cf20d8f2
commit 2b3bb581bc
1 changed files with 16 additions and 11 deletions
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27
src/c3nav/mapdata/utils/cache/local.py vendored
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@ -1,4 +1,5 @@
from collections import OrderedDict from collections import OrderedDict
from contextvars import ContextVar
from django.core.cache import cache from django.core.cache import cache
from django.conf import settings from django.conf import settings
@ -10,42 +11,46 @@ class NoneFromCache:
class LocalCacheProxy: class LocalCacheProxy:
# django cache, buffered using a LRU cache # django cache, buffered using a LRU cache
# only usable for stuff that never changes, obviously # only usable for stuff that never needs to know about changes made by other cache clients, obviously
# todo: ensure thread-safety, compatible with async + daphne etc
def __init__(self, maxsize=128): def __init__(self, maxsize=128):
self._maxsize = maxsize self._maxsize = maxsize
self._mapupdate = None self._mapupdate = None
self._items = OrderedDict() self._items: ContextVar[OrderedDict] = ContextVar("cache items")
# do not use a default of a dict, this can lead to same instance in different contexts
# we don't particularly care about this for LocalCacheProxy,
# but we DEFINITELY care about this for the local request cache.
# Most importantly, this is why the clear function always sets a new dictionary to be extra sure.
self.clear()
def get(self, key, default=None): def get(self, key, default=None):
if self._mapupdate is None: if self._mapupdate is None:
self._check_mapupdate() self._check_mapupdate()
try: try:
# first check out cache # first check out cache
result = self._items[key] result = self._items.get()[key]
except KeyError: except KeyError:
# not in our cache # not in our cache
result = cache.get(key, default=NoneFromCache) result = cache.get(key, default=NoneFromCache)
if result is not NoneFromCache: if result is not NoneFromCache:
self._items[key] = result self._items.get()[key] = result
self._prune() self._prune()
else: else:
result = default result = default
else: else:
self._items.move_to_end(key, last=True) self._items.get().move_to_end(key, last=True)
return result return result
def _prune(self): def _prune(self):
# remove old items # remove old items
while len(self._items) > self._maxsize: while len(self._items.get()) > self._maxsize:
self._items.pop(next(iter(self._items.keys()))) self._items.get().pop(next(iter(self._items.get().keys())))
def _check_mapupdate(self): def _check_mapupdate(self):
# todo: thanks to enable_globally() we shouldn't need this any more # todo: thanks to enable_globally() we shouldn't need this any more
from c3nav.mapdata.models import MapUpdate from c3nav.mapdata.models import MapUpdate
mapupdate = MapUpdate.current_cache_key() mapupdate = MapUpdate.current_cache_key()
if self._mapupdate != mapupdate: if self._mapupdate != mapupdate:
self._items = OrderedDict() self.clear()
self._mapupdate = mapupdate self._mapupdate = mapupdate
enabled = False enabled = False
@ -61,11 +66,11 @@ class LocalCacheProxy:
self._check_mapupdate() self._check_mapupdate()
cache.set(key, value, expire) cache.set(key, value, expire)
if LocalCacheProxy.enabled: if LocalCacheProxy.enabled:
self._items[key] = value self._items.get()[key] = value
self._prune() self._prune()
def clear(self): def clear(self):
self._items.clear() self._items.set(OrderedDict())
class RequestLocalCacheProxy(LocalCacheProxy): class RequestLocalCacheProxy(LocalCacheProxy):