introducing LocalCacheProxy to skip pickling stuff

src/c3nav/mapdata/utils/cache/local.py

@@ -0,0 +1,42 @@
+from collections import OrderedDict
+
+from django.core.cache import cache
+
+
+class NoneFromCache:
+    pass
+
+
+class LocalCacheProxy:
+    # django cache, buffered using a LRU cache
+    # only usable for stuff that never changes, obviously
+    def __init__(self, maxsize=128):
+        self._maxsize = maxsize
+        self._items = OrderedDict()
+
+    def get(self, key, default=None):
+        print('get')
+        try:
+            # first check out cache
+            result = self._items[key]
+        except KeyError:
+            # not in our cache
+            result = cache.get(key, default=NoneFromCache)
+            if result is not NoneFromCache:
+                self._items[key] = result
+                self._prune()
+            else:
+                result = default
+        else:
+            self._items.move_to_end(key, last=True)
+        return result
+
+    def _prune(self):
+        # remove old items
+        while len(self._items) > self._maxsize:
+            self._items.pop(next(iter(self._items.keys())))
+
+    def set(self, key, value, expire):
+        cache.set(key, value, expire)
+        self._items[key] = value
+        self._prune()