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rate_limiter.py
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rate_limiter.py
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import datetime
import user_util
from google.appengine.api import memcache
class RateLimiter:
def __init__(self, user_data, hourly_limit, desc):
self.hourly_limit = hourly_limit
self.desc = desc
self.user_data = user_data
def is_allowed(self):
return len(self.purge()) < self.hourly_limit or \
user_util.is_current_user_developer() or \
self.user_data.moderator
def increment(self):
if not self.is_allowed():
return False
self.add_new()
return True
def get_key(self):
return "rate_limiter_%s_%s" % (self.__class__.__name__,
self.user_data.key_email)
def add_new(self):
key = self.get_key()
dates = memcache.get(key)
if not dates:
dates = []
dates.append(datetime.datetime.now())
memcache.set(key, dates)
def purge(self):
key = self.get_key()
dates = memcache.get(key)
if not dates:
return []
date_now = datetime.datetime.now()
modified = False
for date in dates:
if (date_now - date) > datetime.timedelta(seconds=3600):
modified = True
dates.remove(date)
if modified:
memcache.set(key, dates)
return dates
def denied_desc(self):
return self.desc % self.hourly_limit
class VoteRateLimiter(RateLimiter):
def __init__(self, user_data):
RateLimiter.__init__(self, user_data, 10,
"You can only vote %s times every hour.")
class FlagRateLimiter(RateLimiter):
def __init__(self, user_data):
RateLimiter.__init__(self, user_data, 10,
"You can only flag %s times every hour.")