+def purge_cache(obj, age=4):
+ """purge old entries in http client cache
+ """
+ now = datetime.utcnow()
+ if now.hour == obj.timestamp.hour:
+ return
+ obj.timestamp = datetime.utcnow()
+ cache = obj.cache
+ delta = timedelta(hours=age)
+ for url in list(cache.keys()):
+ timestamp = cache.get(url).created()
+ if now - timestamp > delta:
+ cache.pop(url)
+
+