diff options
Diffstat (limited to 'synapse/api/ratelimiting.py')
| -rw-r--r-- | synapse/api/ratelimiting.py | 154 |
1 files changed, 120 insertions, 34 deletions
diff --git a/synapse/api/ratelimiting.py b/synapse/api/ratelimiting.py index 172841f595..ec6b3a69a2 100644 --- a/synapse/api/ratelimiting.py +++ b/synapse/api/ratelimiting.py @@ -1,4 +1,5 @@ # Copyright 2014-2016 OpenMarket Ltd +# Copyright 2020 The Matrix.org Foundation C.I.C. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. @@ -12,76 +13,161 @@ # See the License for the specific language governing permissions and # limitations under the License. -import collections +from collections import OrderedDict +from typing import Any, Optional, Tuple from synapse.api.errors import LimitExceededError +from synapse.util import Clock class Ratelimiter(object): """ - Ratelimit message sending by user. + Ratelimit actions marked by arbitrary keys. + + Args: + clock: A homeserver clock, for retrieving the current time + rate_hz: The long term number of actions that can be performed in a second. + burst_count: How many actions that can be performed before being limited. """ - def __init__(self): - self.message_counts = collections.OrderedDict() + def __init__(self, clock: Clock, rate_hz: float, burst_count: int): + self.clock = clock + self.rate_hz = rate_hz + self.burst_count = burst_count + + # A ordered dictionary keeping track of actions, when they were last + # performed and how often. Each entry is a mapping from a key of arbitrary type + # to a tuple representing: + # * How many times an action has occurred since a point in time + # * The point in time + # * The rate_hz of this particular entry. This can vary per request + self.actions = OrderedDict() # type: OrderedDict[Any, Tuple[float, int, float]] - def can_do_action(self, key, time_now_s, rate_hz, burst_count, update=True): + def can_do_action( + self, + key: Any, + rate_hz: Optional[float] = None, + burst_count: Optional[int] = None, + update: bool = True, + _time_now_s: Optional[int] = None, + ) -> Tuple[bool, float]: """Can the entity (e.g. user or IP address) perform the action? + Args: key: The key we should use when rate limiting. Can be a user ID (when sending events), an IP address, etc. - time_now_s: The time now. - rate_hz: The long term number of messages a user can send in a - second. - burst_count: How many messages the user can send before being - limited. - update (bool): Whether to update the message rates or not. This is - useful to check if a message would be allowed to be sent before - its ready to be actually sent. + rate_hz: The long term number of actions that can be performed in a second. + Overrides the value set during instantiation if set. + burst_count: How many actions that can be performed before being limited. + Overrides the value set during instantiation if set. + update: Whether to count this check as performing the action + _time_now_s: The current time. Optional, defaults to the current time according + to self.clock. Only used by tests. + Returns: - A pair of a bool indicating if they can send a message now and a - time in seconds of when they can next send a message. + A tuple containing: + * A bool indicating if they can perform the action now + * The reactor timestamp for when the action can be performed next. + -1 if rate_hz is less than or equal to zero """ - self.prune_message_counts(time_now_s) - message_count, time_start, _ignored = self.message_counts.get( - key, (0.0, time_now_s, None) - ) + # Override default values if set + time_now_s = _time_now_s if _time_now_s is not None else self.clock.time() + rate_hz = rate_hz if rate_hz is not None else self.rate_hz + burst_count = burst_count if burst_count is not None else self.burst_count + + # Remove any expired entries + self._prune_message_counts(time_now_s) + + # Check if there is an existing count entry for this key + action_count, time_start, _ = self.actions.get(key, (0.0, time_now_s, 0.0)) + + # Check whether performing another action is allowed time_delta = time_now_s - time_start - sent_count = message_count - time_delta * rate_hz - if sent_count < 0: + performed_count = action_count - time_delta * rate_hz + if performed_count < 0: + # Allow, reset back to count 1 allowed = True time_start = time_now_s - message_count = 1.0 - elif sent_count > burst_count - 1.0: + action_count = 1.0 + elif performed_count > burst_count - 1.0: + # Deny, we have exceeded our burst count allowed = False else: + # We haven't reached our limit yet allowed = True - message_count += 1 + action_count += 1.0 if update: - self.message_counts[key] = (message_count, time_start, rate_hz) + self.actions[key] = (action_count, time_start, rate_hz) if rate_hz > 0: - time_allowed = time_start + (message_count - burst_count + 1) / rate_hz + # Find out when the count of existing actions expires + time_allowed = time_start + (action_count - burst_count + 1) / rate_hz + + # Don't give back a time in the past if time_allowed < time_now_s: time_allowed = time_now_s + else: + # XXX: Why is this -1? This seems to only be used in + # self.ratelimit. I guess so that clients get a time in the past and don't + # feel afraid to try again immediately time_allowed = -1 return allowed, time_allowed - def prune_message_counts(self, time_now_s): - for key in list(self.message_counts.keys()): - message_count, time_start, rate_hz = self.message_counts[key] + def _prune_message_counts(self, time_now_s: int): + """Remove message count entries that have not exceeded their defined + rate_hz limit + + Args: + time_now_s: The current time + """ + # We create a copy of the key list here as the dictionary is modified during + # the loop + for key in list(self.actions.keys()): + action_count, time_start, rate_hz = self.actions[key] + + # Rate limit = "seconds since we started limiting this action" * rate_hz + # If this limit has not been exceeded, wipe our record of this action time_delta = time_now_s - time_start - if message_count - time_delta * rate_hz > 0: - break + if action_count - time_delta * rate_hz > 0: + continue else: - del self.message_counts[key] + del self.actions[key] + + def ratelimit( + self, + key: Any, + rate_hz: Optional[float] = None, + burst_count: Optional[int] = None, + update: bool = True, + _time_now_s: Optional[int] = None, + ): + """Checks if an action can be performed. If not, raises a LimitExceededError + + Args: + key: An arbitrary key used to classify an action + rate_hz: The long term number of actions that can be performed in a second. + Overrides the value set during instantiation if set. + burst_count: How many actions that can be performed before being limited. + Overrides the value set during instantiation if set. + update: Whether to count this check as performing the action + _time_now_s: The current time. Optional, defaults to the current time according + to self.clock. Only used by tests. + + Raises: + LimitExceededError: If an action could not be performed, along with the time in + milliseconds until the action can be performed again + """ + time_now_s = _time_now_s if _time_now_s is not None else self.clock.time() - def ratelimit(self, key, time_now_s, rate_hz, burst_count, update=True): allowed, time_allowed = self.can_do_action( - key, time_now_s, rate_hz, burst_count, update + key, + rate_hz=rate_hz, + burst_count=burst_count, + update=update, + _time_now_s=time_now_s, ) if not allowed: |