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# Copyright 2014, 2015 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
class Ratelimiter(object):
"""
Ratelimit message sending by user.
"""
def __init__(self):
self.message_counts = collections.OrderedDict()
def send_message(self, user_id, time_now_s, msg_rate_hz, burst_count):
"""Can the user send a message?
Args:
user_id: The user sending a message.
time_now_s: The time now.
msg_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.
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.pop(
user_id, (0., time_now_s, None),
)
time_delta = time_now_s - time_start
sent_count = message_count - time_delta * msg_rate_hz
if sent_count < 0:
allowed = True
time_start = time_now_s
message_count = 1.
elif sent_count > burst_count - 1.:
allowed = False
else:
allowed = True
message_count += 1
self.message_counts[user_id] = (
message_count, time_start, msg_rate_hz
)
if msg_rate_hz > 0:
time_allowed = (
time_start + (message_count - burst_count + 1) / msg_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 user_id in self.message_counts.keys():
message_count, time_start, msg_rate_hz = (
self.message_counts[user_id]
)
time_delta = time_now_s - time_start
if message_count - time_delta * msg_rate_hz > 0:
break
else:
del self.message_counts[user_id]
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