226 lines
7.5 KiB
Python
226 lines
7.5 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2015, 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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import contextlib
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import logging
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from twisted.internet import defer
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from synapse.api.errors import LimitExceededError
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from synapse.util.logcontext import (
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PreserveLoggingContext,
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make_deferred_yieldable,
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run_in_background,
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)
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logger = logging.getLogger(__name__)
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class FederationRateLimiter(object):
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def __init__(self, clock, window_size, sleep_limit, sleep_msec,
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reject_limit, concurrent_requests):
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"""
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Args:
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clock (Clock)
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window_size (int): The window size in milliseconds.
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sleep_limit (int): The number of requests received in the last
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`window_size` milliseconds before we artificially start
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delaying processing of requests.
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sleep_msec (int): The number of milliseconds to delay processing
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of incoming requests by.
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reject_limit (int): The maximum number of requests that are can be
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queued for processing before we start rejecting requests with
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a 429 Too Many Requests response.
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concurrent_requests (int): The number of concurrent requests to
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process.
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"""
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self.clock = clock
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self.window_size = window_size
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self.sleep_limit = sleep_limit
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self.sleep_msec = sleep_msec
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self.reject_limit = reject_limit
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self.concurrent_requests = concurrent_requests
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self.ratelimiters = {}
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def ratelimit(self, host):
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"""Used to ratelimit an incoming request from given host
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Example usage:
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with rate_limiter.ratelimit(origin) as wait_deferred:
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yield wait_deferred
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# Handle request ...
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Args:
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host (str): Origin of incoming request.
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Returns:
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_PerHostRatelimiter
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"""
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return self.ratelimiters.setdefault(
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host,
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_PerHostRatelimiter(
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clock=self.clock,
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window_size=self.window_size,
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sleep_limit=self.sleep_limit,
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sleep_msec=self.sleep_msec,
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reject_limit=self.reject_limit,
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concurrent_requests=self.concurrent_requests,
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)
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).ratelimit()
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class _PerHostRatelimiter(object):
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def __init__(self, clock, window_size, sleep_limit, sleep_msec,
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reject_limit, concurrent_requests):
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self.clock = clock
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self.window_size = window_size
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self.sleep_limit = sleep_limit
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self.sleep_sec = sleep_msec / 1000.0
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self.reject_limit = reject_limit
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self.concurrent_requests = concurrent_requests
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# request_id objects for requests which have been slept
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self.sleeping_requests = set()
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# map from request_id object to Deferred for requests which are ready
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# for processing but have been queued
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self.ready_request_queue = collections.OrderedDict()
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# request id objects for requests which are in progress
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self.current_processing = set()
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# times at which we have recently (within the last window_size ms)
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# received requests.
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self.request_times = []
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@contextlib.contextmanager
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def ratelimit(self):
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# `contextlib.contextmanager` takes a generator and turns it into a
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# context manager. The generator should only yield once with a value
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# to be returned by manager.
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# Exceptions will be reraised at the yield.
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request_id = object()
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ret = self._on_enter(request_id)
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try:
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yield ret
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finally:
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self._on_exit(request_id)
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def _on_enter(self, request_id):
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time_now = self.clock.time_msec()
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# remove any entries from request_times which aren't within the window
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self.request_times[:] = [
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r for r in self.request_times
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if time_now - r < self.window_size
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]
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# reject the request if we already have too many queued up (either
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# sleeping or in the ready queue).
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queue_size = len(self.ready_request_queue) + len(self.sleeping_requests)
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if queue_size > self.reject_limit:
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raise LimitExceededError(
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retry_after_ms=int(
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self.window_size / self.sleep_limit
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),
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)
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self.request_times.append(time_now)
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def queue_request():
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if len(self.current_processing) > self.concurrent_requests:
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queue_defer = defer.Deferred()
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self.ready_request_queue[request_id] = queue_defer
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logger.info(
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"Ratelimiter: queueing request (queue now %i items)",
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len(self.ready_request_queue),
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)
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return queue_defer
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else:
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return defer.succeed(None)
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logger.debug(
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"Ratelimit [%s]: len(self.request_times)=%d",
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id(request_id), len(self.request_times),
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)
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if len(self.request_times) > self.sleep_limit:
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logger.debug(
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"Ratelimiter: sleeping request for %f sec", self.sleep_sec,
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)
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ret_defer = run_in_background(self.clock.sleep, self.sleep_sec)
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self.sleeping_requests.add(request_id)
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def on_wait_finished(_):
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logger.debug(
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"Ratelimit [%s]: Finished sleeping",
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id(request_id),
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)
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self.sleeping_requests.discard(request_id)
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queue_defer = queue_request()
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return queue_defer
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ret_defer.addBoth(on_wait_finished)
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else:
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ret_defer = queue_request()
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def on_start(r):
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logger.debug(
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"Ratelimit [%s]: Processing req",
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id(request_id),
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)
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self.current_processing.add(request_id)
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return r
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def on_err(r):
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# XXX: why is this necessary? this is called before we start
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# processing the request so why would the request be in
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# current_processing?
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self.current_processing.discard(request_id)
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return r
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def on_both(r):
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# Ensure that we've properly cleaned up.
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self.sleeping_requests.discard(request_id)
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self.ready_request_queue.pop(request_id, None)
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return r
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ret_defer.addCallbacks(on_start, on_err)
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ret_defer.addBoth(on_both)
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return make_deferred_yieldable(ret_defer)
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def _on_exit(self, request_id):
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logger.debug(
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"Ratelimit [%s]: Processed req",
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id(request_id),
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)
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self.current_processing.discard(request_id)
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try:
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# start processing the next item on the queue.
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_, deferred = self.ready_request_queue.popitem(last=False)
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with PreserveLoggingContext():
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deferred.callback(None)
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except KeyError:
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pass
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