mirror of https://github.com/zulip/zulip.git
355 lines
13 KiB
Python
355 lines
13 KiB
Python
import os
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from abc import ABC, abstractmethod
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from typing import Dict, List, Optional, Tuple
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from django.conf import settings
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from django.http import HttpRequest
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from zerver.lib.exceptions import RateLimited
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from zerver.lib.redis_utils import get_redis_client
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from zerver.lib.utils import statsd
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from zerver.models import UserProfile
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import logging
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import redis
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import time
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# Implement a rate-limiting scheme inspired by the one described here, but heavily modified
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# https://www.domaintools.com/resources/blog/rate-limiting-with-redis
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client = get_redis_client()
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rules = settings.RATE_LIMITING_RULES # type: Dict[str, List[Tuple[int, int]]]
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KEY_PREFIX = ''
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logger = logging.getLogger(__name__)
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class RateLimiterLockingException(Exception):
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pass
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class RateLimitedObject(ABC):
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def __init__(self) -> None:
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self.backend = RedisRateLimiterBackend
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def rate_limit(self) -> Tuple[bool, float]:
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# Returns (ratelimited, secs_to_freedom)
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return self.backend.rate_limit_entity(self.key(), self.rules(),
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self.max_api_calls(),
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self.max_api_window())
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def rate_limit_request(self, request: HttpRequest) -> None:
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ratelimited, time = self.rate_limit()
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entity_type = type(self).__name__
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if not hasattr(request, '_ratelimit'):
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request._ratelimit = {}
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request._ratelimit[entity_type] = RateLimitResult(
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entity=self,
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secs_to_freedom=time,
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over_limit=ratelimited
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)
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# Abort this request if the user is over their rate limits
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if ratelimited:
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# Pass information about what kind of entity got limited in the exception:
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raise RateLimited(entity_type)
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calls_remaining, time_reset = self.api_calls_left()
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request._ratelimit[entity_type].remaining = calls_remaining
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request._ratelimit[entity_type].secs_to_freedom = time_reset
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def block_access(self, seconds: int) -> None:
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"Manually blocks an entity for the desired number of seconds"
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self.backend.block_access(self.key(), seconds)
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def unblock_access(self) -> None:
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self.backend.unblock_access(self.key())
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def clear_history(self) -> None:
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self.backend.clear_history(self.key())
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def max_api_calls(self) -> int:
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"Returns the API rate limit for the highest limit"
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return self.rules()[-1][1]
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def max_api_window(self) -> int:
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"Returns the API time window for the highest limit"
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return self.rules()[-1][0]
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def api_calls_left(self) -> Tuple[int, float]:
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"""Returns how many API calls in this range this client has, as well as when
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the rate-limit will be reset to 0"""
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max_window = self.max_api_window()
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max_calls = self.max_api_calls()
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return self.backend.get_api_calls_left(self.key(), max_window, max_calls)
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@abstractmethod
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def key(self) -> str:
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pass
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@abstractmethod
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def rules(self) -> List[Tuple[int, int]]:
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pass
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class RateLimitedUser(RateLimitedObject):
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def __init__(self, user: UserProfile, domain: str='api_by_user') -> None:
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self.user = user
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self.domain = domain
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super().__init__()
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def key(self) -> str:
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return "{}:{}:{}".format(type(self).__name__, self.user.id, self.domain)
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def rules(self) -> List[Tuple[int, int]]:
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# user.rate_limits are general limits, applicable to the domain 'api_by_user'
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if self.user.rate_limits != "" and self.domain == 'api_by_user':
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result = [] # type: List[Tuple[int, int]]
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for limit in self.user.rate_limits.split(','):
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(seconds, requests) = limit.split(':', 2)
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result.append((int(seconds), int(requests)))
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return result
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return rules[self.domain]
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def bounce_redis_key_prefix_for_testing(test_name: str) -> None:
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global KEY_PREFIX
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KEY_PREFIX = test_name + ':' + str(os.getpid()) + ':'
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def add_ratelimit_rule(range_seconds: int, num_requests: int, domain: str='api_by_user') -> None:
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"Add a rate-limiting rule to the ratelimiter"
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global rules
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if domain not in rules:
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# If we don't have any rules for domain yet, the domain key needs to be
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# added to the rules dictionary.
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rules[domain] = []
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rules[domain].append((range_seconds, num_requests))
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rules[domain].sort(key=lambda x: x[0])
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def remove_ratelimit_rule(range_seconds: int, num_requests: int, domain: str='api_by_user') -> None:
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global rules
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rules[domain] = [x for x in rules[domain] if x[0] != range_seconds and x[1] != num_requests]
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class RateLimiterBackend(ABC):
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@classmethod
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@abstractmethod
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def block_access(cls, entity_key: str, seconds: int) -> None:
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"Manually blocks an entity for the desired number of seconds"
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@classmethod
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@abstractmethod
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def unblock_access(cls, entity_key: str) -> None:
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pass
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@classmethod
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@abstractmethod
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def clear_history(cls, entity_key: str) -> None:
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pass
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@classmethod
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@abstractmethod
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def get_api_calls_left(cls, entity_key: str, range_seconds: int,
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max_calls: int) -> Tuple[int, float]:
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pass
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@classmethod
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@abstractmethod
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def rate_limit_entity(cls, entity_key: str, rules: List[Tuple[int, int]],
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max_api_calls: int, max_api_window: int) -> Tuple[bool, float]:
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# Returns (ratelimited, secs_to_freedom)
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pass
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class RedisRateLimiterBackend(RateLimiterBackend):
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@classmethod
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def get_keys(cls, entity_key: str) -> List[str]:
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return ["{}ratelimit:{}:{}".format(KEY_PREFIX, entity_key, keytype)
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for keytype in ['list', 'zset', 'block']]
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@classmethod
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def block_access(cls, entity_key: str, seconds: int) -> None:
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"Manually blocks an entity for the desired number of seconds"
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_, _, blocking_key = cls.get_keys(entity_key)
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with client.pipeline() as pipe:
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pipe.set(blocking_key, 1)
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pipe.expire(blocking_key, seconds)
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pipe.execute()
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@classmethod
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def unblock_access(cls, entity_key: str) -> None:
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_, _, blocking_key = cls.get_keys(entity_key)
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client.delete(blocking_key)
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@classmethod
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def clear_history(cls, entity_key: str) -> None:
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for key in cls.get_keys(entity_key):
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client.delete(key)
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@classmethod
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def get_api_calls_left(cls, entity_key: str, range_seconds: int,
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max_calls: int) -> Tuple[int, float]:
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list_key, set_key, _ = cls.get_keys(entity_key)
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# Count the number of values in our sorted set
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# that are between now and the cutoff
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now = time.time()
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boundary = now - range_seconds
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with client.pipeline() as pipe:
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# Count how many API calls in our range have already been made
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pipe.zcount(set_key, boundary, now)
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# Get the newest call so we can calculate when the ratelimit
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# will reset to 0
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pipe.lindex(list_key, 0)
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results = pipe.execute()
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count = results[0] # type: int
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newest_call = results[1] # type: Optional[bytes]
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calls_left = max_calls - count
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if newest_call is not None:
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time_reset = now + (range_seconds - (now - float(newest_call)))
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else:
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time_reset = now
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return calls_left, time_reset
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@classmethod
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def is_ratelimited(cls, entity_key: str, rules: List[Tuple[int, int]]) -> Tuple[bool, float]:
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"Returns a tuple of (rate_limited, time_till_free)"
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list_key, set_key, blocking_key = cls.get_keys(entity_key)
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if len(rules) == 0:
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return False, 0.0
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# Go through the rules from shortest to longest,
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# seeing if this user has violated any of them. First
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# get the timestamps for each nth items
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with client.pipeline() as pipe:
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for _, request_count in rules:
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pipe.lindex(list_key, request_count - 1) # 0-indexed list
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# Get blocking info
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pipe.get(blocking_key)
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pipe.ttl(blocking_key)
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rule_timestamps = pipe.execute() # type: List[Optional[bytes]]
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# Check if there is a manual block on this API key
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blocking_ttl_b = rule_timestamps.pop()
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key_blocked = rule_timestamps.pop()
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if key_blocked is not None:
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# We are manually blocked. Report for how much longer we will be
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if blocking_ttl_b is None:
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blocking_ttl = 0.5
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else:
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blocking_ttl = int(blocking_ttl_b)
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return True, blocking_ttl
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now = time.time()
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for timestamp, (range_seconds, num_requests) in zip(rule_timestamps, rules):
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# Check if the nth timestamp is newer than the associated rule. If so,
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# it means we've hit our limit for this rule
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if timestamp is None:
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continue
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boundary = float(timestamp) + range_seconds
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if boundary > now:
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free = boundary - now
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return True, free
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# No api calls recorded yet
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return False, 0.0
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@classmethod
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def incr_ratelimit(cls, entity_key: str, rules: List[Tuple[int, int]],
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max_api_calls: int, max_api_window: int) -> None:
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"""Increases the rate-limit for the specified entity"""
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list_key, set_key, _ = cls.get_keys(entity_key)
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now = time.time()
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# If we have no rules, we don't store anything
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if len(rules) == 0:
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return
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# Start redis transaction
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with client.pipeline() as pipe:
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count = 0
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while True:
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try:
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# To avoid a race condition between getting the element we might trim from our list
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# and removing it from our associated set, we abort this whole transaction if
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# another agent manages to change our list out from under us
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# When watching a value, the pipeline is set to Immediate mode
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pipe.watch(list_key)
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# Get the last elem that we'll trim (so we can remove it from our sorted set)
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last_val = pipe.lindex(list_key, max_api_calls - 1)
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# Restart buffered execution
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pipe.multi()
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# Add this timestamp to our list
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pipe.lpush(list_key, now)
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# Trim our list to the oldest rule we have
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pipe.ltrim(list_key, 0, max_api_calls - 1)
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# Add our new value to the sorted set that we keep
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# We need to put the score and val both as timestamp,
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# as we sort by score but remove by value
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pipe.zadd(set_key, {str(now): now})
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# Remove the trimmed value from our sorted set, if there was one
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if last_val is not None:
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pipe.zrem(set_key, last_val)
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# Set the TTL for our keys as well
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api_window = max_api_window
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pipe.expire(list_key, api_window)
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pipe.expire(set_key, api_window)
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pipe.execute()
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# If no exception was raised in the execution, there were no transaction conflicts
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break
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except redis.WatchError:
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if count > 10:
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raise RateLimiterLockingException()
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count += 1
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continue
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@classmethod
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def rate_limit_entity(cls, entity_key: str, rules: List[Tuple[int, int]],
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max_api_calls: int, max_api_window: int) -> Tuple[bool, float]:
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ratelimited, time = cls.is_ratelimited(entity_key, rules)
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if ratelimited:
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statsd.incr("ratelimiter.limited.%s" % (entity_key,))
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else:
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try:
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cls.incr_ratelimit(entity_key, rules, max_api_calls, max_api_window)
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except RateLimiterLockingException:
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logger.warning("Deadlock trying to incr_ratelimit for %s" % (entity_key,))
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# rate-limit users who are hitting the API so hard we can't update our stats.
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ratelimited = True
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return ratelimited, time
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class RateLimitResult:
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def __init__(self, entity: RateLimitedObject, secs_to_freedom: float, over_limit: bool,
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remaining: Optional[int]=None) -> None:
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if over_limit:
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assert not remaining
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self.entity = entity
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self.secs_to_freedom = secs_to_freedom
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self.over_limit = over_limit
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self.remaining = remaining
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def get_rate_limit_result_from_request(request: HttpRequest, entity_type: str) -> RateLimitResult:
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return request._ratelimit[entity_type]
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