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- # Copyright 2014-2016 OpenMarket Ltd
- #
- # Licensed under the Apache License, Version 2.0 (the "License");
- # you may not use this file except in compliance with the License.
- # You may obtain a copy of the License at
- #
- # http://www.apache.org/licenses/LICENSE-2.0
- #
- # Unless required by applicable law or agreed to in writing, software
- # distributed under the License is distributed on an "AS IS" BASIS,
- # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- # See the License for the specific language governing permissions and
- # limitations under the License.
- import collections
- from synapse.api.errors import LimitExceededError
- class Ratelimiter(object):
- """
- Ratelimit message sending by user.
- """
- def __init__(self):
- self.message_counts = collections.OrderedDict()
- def can_do_action(self, key, time_now_s, rate_hz, burst_count, update=True):
- """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.
- 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.
- """
- self.prune_message_counts(time_now_s)
- message_count, time_start, _ignored = self.message_counts.get(
- key, (0.0, time_now_s, None)
- )
- time_delta = time_now_s - time_start
- sent_count = message_count - time_delta * rate_hz
- if sent_count < 0:
- allowed = True
- time_start = time_now_s
- message_count = 1.0
- elif sent_count > burst_count - 1.0:
- allowed = False
- else:
- allowed = True
- message_count += 1
- if update:
- self.message_counts[key] = (message_count, time_start, rate_hz)
- if rate_hz > 0:
- time_allowed = time_start + (message_count - burst_count + 1) / rate_hz
- if time_allowed < time_now_s:
- time_allowed = time_now_s
- else:
- 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]
- time_delta = time_now_s - time_start
- if message_count - time_delta * rate_hz > 0:
- break
- else:
- del self.message_counts[key]
- 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
- )
- if not allowed:
- raise LimitExceededError(
- retry_after_ms=int(1000 * (time_allowed - time_now_s))
- )
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