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# -*- coding: utf-8 -*-
# Copyright 2015, 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.
from twisted.internet import defer
from synapse.api.errors import LimitExceededError
from synapse.util.async import sleep
import collections
import contextlib
import logging
logger = logging.getLogger(__name__)
class FederationRateLimiter(object):
def __init__(self, clock, window_size, sleep_limit, sleep_msec,
reject_limit, concurrent_requests):
"""
Args:
clock (Clock)
window_size (int): The window size in milliseconds.
sleep_limit (int): The number of requests received in the last
`window_size` milliseconds before we artificially start
delaying processing of requests.
sleep_msec (int): The number of milliseconds to delay processing
of incoming requests by.
reject_limit (int): The maximum number of requests that are can be
queued for processing before we start rejecting requests with
a 429 Too Many Requests response.
concurrent_requests (int): The number of concurrent requests to
process.
"""
self.clock = clock
self.window_size = window_size
self.sleep_limit = sleep_limit
self.sleep_msec = sleep_msec
self.reject_limit = reject_limit
self.concurrent_requests = concurrent_requests
self.ratelimiters = {}
def ratelimit(self, host):
"""Used to ratelimit an incoming request from given host
Example usage:
with rate_limiter.ratelimit(origin) as wait_deferred:
yield wait_deferred
# Handle request ...
Args:
host (str): Origin of incoming request.
Returns:
_PerHostRatelimiter
"""
return self.ratelimiters.setdefault(
host,
_PerHostRatelimiter(
clock=self.clock,
window_size=self.window_size,
sleep_limit=self.sleep_limit,
sleep_msec=self.sleep_msec,
reject_limit=self.reject_limit,
concurrent_requests=self.concurrent_requests,
)
).ratelimit()
class _PerHostRatelimiter(object):
def __init__(self, clock, window_size, sleep_limit, sleep_msec,
reject_limit, concurrent_requests):
self.clock = clock
self.window_size = window_size
self.sleep_limit = sleep_limit
self.sleep_msec = sleep_msec
self.reject_limit = reject_limit
self.concurrent_requests = concurrent_requests
self.sleeping_requests = set()
self.ready_request_queue = collections.OrderedDict()
self.current_processing = set()
self.request_times = []
def is_empty(self):
time_now = self.clock.time_msec()
self.request_times[:] = [
r for r in self.request_times
if time_now - r < self.window_size
]
return not (
self.ready_request_queue
or self.sleeping_requests
or self.current_processing
or self.request_times
)
@contextlib.contextmanager
def ratelimit(self):
# `contextlib.contextmanager` takes a generator and turns it into a
# context manager. The generator should only yield once with a value
# to be returned by manager.
# Exceptions will be reraised at the yield.
request_id = object()
ret = self._on_enter(request_id)
try:
yield ret
finally:
self._on_exit(request_id)
def _on_enter(self, request_id):
time_now = self.clock.time_msec()
self.request_times[:] = [
r for r in self.request_times
if time_now - r < self.window_size
]
queue_size = len(self.ready_request_queue) + len(self.sleeping_requests)
if queue_size > self.reject_limit:
raise LimitExceededError(
retry_after_ms=int(
self.window_size / self.sleep_limit
),
)
self.request_times.append(time_now)
def queue_request():
if len(self.current_processing) > self.concurrent_requests:
logger.debug("Ratelimit [%s]: Queue req", id(request_id))
queue_defer = defer.Deferred()
self.ready_request_queue[request_id] = queue_defer
return queue_defer
else:
return defer.succeed(None)
logger.debug(
"Ratelimit [%s]: len(self.request_times)=%d",
id(request_id), len(self.request_times),
)
if len(self.request_times) > self.sleep_limit:
logger.debug(
"Ratelimit [%s]: sleeping req",
id(request_id),
)
ret_defer = sleep(self.sleep_msec/1000.0)
self.sleeping_requests.add(request_id)
def on_wait_finished(_):
logger.debug(
"Ratelimit [%s]: Finished sleeping",
id(request_id),
)
self.sleeping_requests.discard(request_id)
queue_defer = queue_request()
return queue_defer
ret_defer.addBoth(on_wait_finished)
else:
ret_defer = queue_request()
def on_start(r):
logger.debug(
"Ratelimit [%s]: Processing req",
id(request_id),
)
self.current_processing.add(request_id)
return r
def on_err(r):
self.current_processing.discard(request_id)
return r
def on_both(r):
# Ensure that we've properly cleaned up.
self.sleeping_requests.discard(request_id)
self.ready_request_queue.pop(request_id, None)
return r
ret_defer.addCallbacks(on_start, on_err)
ret_defer.addBoth(on_both)
return ret_defer
def _on_exit(self, request_id):
logger.debug(
"Ratelimit [%s]: Processed req",
id(request_id),
)
self.current_processing.discard(request_id)
try:
request_id, deferred = self.ready_request_queue.popitem()
self.current_processing.add(request_id)
deferred.callback(None)
except KeyError:
pass
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