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"""
Provides various throttling policies.
"""
from __future__ import unicode_literals
import time
from django.core.cache import cache as default_cache
from django.core.exceptions import ImproperlyConfigured
from rest_framework.settings import api_settings
class BaseThrottle(object):
"""
Rate throttling of requests.
"""
def allow_request(self, request, view):
"""
Return `True` if the request should be allowed, `False` otherwise.
"""
raise NotImplementedError('.allow_request() must be overridden')
def get_ident(self, request):
"""
Identify the machine making the request by parsing HTTP_X_FORWARDED_FOR
if present and number of proxies is > 0. If not use all of
HTTP_X_FORWARDED_FOR if it is available, if not use REMOTE_ADDR.
"""
xff = request.META.get('HTTP_X_FORWARDED_FOR')
remote_addr = request.META.get('REMOTE_ADDR')
num_proxies = api_settings.NUM_PROXIES
if num_proxies is not None:
if num_proxies == 0 or xff is None:
return remote_addr
addrs = xff.split(',')
client_addr = addrs[-min(num_proxies, len(addrs))]
return client_addr.strip()
return ''.join(xff.split()) if xff else remote_addr
def wait(self):
"""
Optionally, return a recommended number of seconds to wait before
the next request.
"""
return None
class SimpleRateThrottle(BaseThrottle):
"""
A simple cache implementation, that only requires `.get_cache_key()`
to be overridden.
The rate (requests / seconds) is set by a `rate` attribute on the View
class. The attribute is a string of the form 'number_of_requests/period'.
Period should be one of: ('s', 'sec', 'm', 'min', 'h', 'hour', 'd', 'day')
Previous request information used for throttling is stored in the cache.
"""
cache = default_cache
timer = time.time
cache_format = 'throttle_%(scope)s_%(ident)s'
scope = None
THROTTLE_RATES = api_settings.DEFAULT_THROTTLE_RATES
def __init__(self):
if not getattr(self, 'rate', None):
self.rate = self.get_rate()
self.num_requests, self.duration = self.parse_rate(self.rate)
def get_cache_key(self, request, view):
"""
Should return a unique cache-key which can be used for throttling.
Must be overridden.
May return `None` if the request should not be throttled.
"""
raise NotImplementedError('.get_cache_key() must be overridden')
def get_rate(self):
"""
Determine the string representation of the allowed request rate.
"""
if not getattr(self, 'scope', None):
msg = ("You must set either `.scope` or `.rate` for '%s' throttle" %
self.__class__.__name__)
raise ImproperlyConfigured(msg)
try:
return self.THROTTLE_RATES[self.scope]
except KeyError:
msg = "No default throttle rate set for '%s' scope" % self.scope
raise ImproperlyConfigured(msg)
def parse_rate(self, rate):
"""
Given the request rate string, return a two tuple of:
<allowed number of requests>, <period of time in seconds>
"""
if rate is None:
return (None, None)
num, period = rate.split('/')
num_requests = int(num)
duration = {'s': 1, 'm': 60, 'h': 3600, 'd': 86400}[period[0]]
return (num_requests, duration)
def allow_request(self, request, view):
"""
Implement the check to see if the request should be throttled.
On success calls `throttle_success`.
On failure calls `throttle_failure`.
"""
if self.rate is None:
return True
self.key = self.get_cache_key(request, view)
if self.key is None:
return True
self.history = self.cache.get(self.key, [])
self.now = self.timer()
# Drop any requests from the history which have now passed the
# throttle duration
while self.history and self.history[-1] <= self.now - self.duration:
self.history.pop()
if len(self.history) >= self.num_requests:
return self.throttle_failure()
return self.throttle_success()
def throttle_success(self):
"""
Inserts the current request's timestamp along with the key
into the cache.
"""
self.history.insert(0, self.now)
self.cache.set(self.key, self.history, self.duration)
return True
def throttle_failure(self):
"""
Called when a request to the API has failed due to throttling.
"""
return False
def wait(self):
"""
Returns the recommended next request time in seconds.
"""
if self.history:
remaining_duration = self.duration - (self.now - self.history[-1])
else:
remaining_duration = self.duration
available_requests = self.num_requests - len(self.history) + 1
if available_requests <= 0:
return None
return remaining_duration / float(available_requests)
class AnonRateThrottle(SimpleRateThrottle):
"""
Limits the rate of API calls that may be made by a anonymous users.
The IP address of the request will be used as the unique cache key.
"""
scope = 'anon'
def get_cache_key(self, request, view):
if request.user.is_authenticated:
return None # Only throttle unauthenticated requests.
return self.cache_format % {
'scope': self.scope,
'ident': self.get_ident(request)
}
class UserRateThrottle(SimpleRateThrottle):
"""
Limits the rate of API calls that may be made by a given user.
The user id will be used as a unique cache key if the user is
authenticated. For anonymous requests, the IP address of the request will
be used.
"""
scope = 'user'
def get_cache_key(self, request, view):
if request.user.is_authenticated:
ident = request.user.pk
else:
ident = self.get_ident(request)
return self.cache_format % {
'scope': self.scope,
'ident': ident
}
class ScopedRateThrottle(SimpleRateThrottle):
"""
Limits the rate of API calls by different amounts for various parts of
the API. Any view that has the `throttle_scope` property set will be
throttled. The unique cache key will be generated by concatenating the
user id of the request, and the scope of the view being accessed.
"""
scope_attr = 'throttle_scope'
def __init__(self):
# Override the usual SimpleRateThrottle, because we can't determine
# the rate until called by the view.
pass
def allow_request(self, request, view):
# We can only determine the scope once we're called by the view.
self.scope = getattr(view, self.scope_attr, None)
# If a view does not have a `throttle_scope` always allow the request
if not self.scope:
return True
# Determine the allowed request rate as we normally would during
# the `__init__` call.
self.rate = self.get_rate()
self.num_requests, self.duration = self.parse_rate(self.rate)
# We can now proceed as normal.
return super(ScopedRateThrottle, self).allow_request(request, view)
def get_cache_key(self, request, view):
"""
If `view.throttle_scope` is not set, don't apply this throttle.
Otherwise generate the unique cache key by concatenating the user id
with the '.throttle_scope` property of the view.
"""
if request.user.is_authenticated:
ident = request.user.pk
else:
ident = self.get_ident(request)
return self.cache_format % {
'scope': self.scope,
'ident': ident
}