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