91 lines
3.3 KiB
Python
91 lines
3.3 KiB
Python
# Copyright 2014-2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import collections
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from synapse.api.errors import LimitExceededError
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class Ratelimiter(object):
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"""
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Ratelimit message sending by user.
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"""
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def __init__(self):
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self.message_counts = collections.OrderedDict()
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def can_do_action(self, key, time_now_s, rate_hz, burst_count, update=True):
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"""Can the entity (e.g. user or IP address) perform the action?
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Args:
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key: The key we should use when rate limiting. Can be a user ID
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(when sending events), an IP address, etc.
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time_now_s: The time now.
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rate_hz: The long term number of messages a user can send in a
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second.
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burst_count: How many messages the user can send before being
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limited.
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update (bool): Whether to update the message rates or not. This is
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useful to check if a message would be allowed to be sent before
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its ready to be actually sent.
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Returns:
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A pair of a bool indicating if they can send a message now and a
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time in seconds of when they can next send a message.
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"""
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self.prune_message_counts(time_now_s)
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message_count, time_start, _ignored = self.message_counts.get(
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key, (0.0, time_now_s, None)
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)
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time_delta = time_now_s - time_start
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sent_count = message_count - time_delta * rate_hz
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if sent_count < 0:
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allowed = True
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time_start = time_now_s
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message_count = 1.0
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elif sent_count > burst_count - 1.0:
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allowed = False
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else:
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allowed = True
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message_count += 1
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if update:
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self.message_counts[key] = (message_count, time_start, rate_hz)
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if rate_hz > 0:
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time_allowed = time_start + (message_count - burst_count + 1) / rate_hz
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if time_allowed < time_now_s:
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time_allowed = time_now_s
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else:
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time_allowed = -1
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return allowed, time_allowed
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def prune_message_counts(self, time_now_s):
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for key in list(self.message_counts.keys()):
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message_count, time_start, rate_hz = self.message_counts[key]
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time_delta = time_now_s - time_start
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if message_count - time_delta * rate_hz > 0:
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break
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else:
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del self.message_counts[key]
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def ratelimit(self, key, time_now_s, rate_hz, burst_count, update=True):
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allowed, time_allowed = self.can_do_action(
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key, time_now_s, rate_hz, burst_count, update
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)
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if not allowed:
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raise LimitExceededError(
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retry_after_ms=int(1000 * (time_allowed - time_now_s))
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)
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