Combine Limiter and Linearizer
Linearizer was effectively a Limiter with max_count=1, so rather than maintaining two sets of code, let's combine them.
This commit is contained in:
Richard van der Hoff
parent
8462c26485
commit
7c712f95bb
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@ -33,7 +33,7 @@ from synapse.events.utils import serialize_event
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from synapse.events.validator import EventValidator
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from synapse.replication.http.send_event import send_event_to_master
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from synapse.types import RoomAlias, RoomStreamToken, UserID
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from synapse.util.async import Limiter, ReadWriteLock
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from synapse.util.async import Linearizer, ReadWriteLock
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from synapse.util.frozenutils import frozendict_json_encoder
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from synapse.util.logcontext import run_in_background
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from synapse.util.metrics import measure_func
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@ -427,7 +427,7 @@ class EventCreationHandler(object):
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# We arbitrarily limit concurrent event creation for a room to 5.
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# This is to stop us from diverging history *too* much.
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self.limiter = Limiter(max_count=5, name="room_event_creation_limit")
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self.limiter = Linearizer(max_count=5, name="room_event_creation_limit")
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self.action_generator = hs.get_action_generator()
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@ -157,91 +157,8 @@ def concurrently_execute(func, args, limit):
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class Linearizer(object):
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"""Linearizes access to resources based on a key. Useful to ensure only one
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thing is happening at a time on a given resource.
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Example:
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with (yield linearizer.queue("test_key")):
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# do some work.
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"""
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def __init__(self, name=None, clock=None):
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if name is None:
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self.name = id(self)
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else:
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self.name = name
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self.key_to_defer = {}
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if not clock:
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from twisted.internet import reactor
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clock = Clock(reactor)
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self._clock = clock
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@defer.inlineCallbacks
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def queue(self, key):
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# If there is already a deferred in the queue, we pull it out so that
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# we can wait on it later.
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# Then we replace it with a deferred that we resolve *after* the
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# context manager has exited.
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# We only return the context manager after the previous deferred has
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# resolved.
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# This all has the net effect of creating a chain of deferreds that
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# wait for the previous deferred before starting their work.
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current_defer = self.key_to_defer.get(key)
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new_defer = defer.Deferred()
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self.key_to_defer[key] = new_defer
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if current_defer:
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logger.info(
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"Waiting to acquire linearizer lock %r for key %r", self.name, key
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)
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try:
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with PreserveLoggingContext():
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yield current_defer
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except Exception:
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logger.exception("Unexpected exception in Linearizer")
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logger.info("Acquired linearizer lock %r for key %r", self.name,
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key)
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# if the code holding the lock completes synchronously, then it
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# will recursively run the next claimant on the list. That can
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# relatively rapidly lead to stack exhaustion. This is essentially
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# the same problem as http://twistedmatrix.com/trac/ticket/9304.
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#
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# In order to break the cycle, we add a cheeky sleep(0) here to
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# ensure that we fall back to the reactor between each iteration.
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#
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# (There's no particular need for it to happen before we return
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# the context manager, but it needs to happen while we hold the
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# lock, and the context manager's exit code must be synchronous,
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# so actually this is the only sensible place.
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yield self._clock.sleep(0)
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else:
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logger.info("Acquired uncontended linearizer lock %r for key %r",
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self.name, key)
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@contextmanager
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def _ctx_manager():
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try:
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yield
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finally:
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logger.info("Releasing linearizer lock %r for key %r", self.name, key)
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with PreserveLoggingContext():
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new_defer.callback(None)
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current_d = self.key_to_defer.get(key)
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if current_d is new_defer:
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self.key_to_defer.pop(key, None)
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defer.returnValue(_ctx_manager())
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class Limiter(object):
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"""Limits concurrent access to resources based on a key. Useful to ensure
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only a few thing happen at a time on a given resource.
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only a few things happen at a time on a given resource.
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Example:
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@ -249,7 +166,7 @@ class Limiter(object):
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# do some work.
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"""
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def __init__(self, max_count=1, name=None, clock=None):
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def __init__(self, name=None, max_count=1, clock=None):
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"""
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Args:
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max_count(int): The maximum number of concurrent accesses
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@ -283,10 +200,12 @@ class Limiter(object):
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new_defer = defer.Deferred()
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entry[1].append(new_defer)
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logger.info("Waiting to acquire limiter lock %r for key %r", self.name, key)
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logger.info(
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"Waiting to acquire linearizer lock %r for key %r", self.name, key,
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)
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yield make_deferred_yieldable(new_defer)
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logger.info("Acquired limiter lock %r for key %r", self.name, key)
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logger.info("Acquired linearizer lock %r for key %r", self.name, key)
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entry[0] += 1
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# if the code holding the lock completes synchronously, then it
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@ -302,7 +221,9 @@ class Limiter(object):
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yield self._clock.sleep(0)
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else:
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logger.info("Acquired uncontended limiter lock %r for key %r", self.name, key)
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logger.info(
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"Acquired uncontended linearizer lock %r for key %r", self.name, key,
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)
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entry[0] += 1
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@contextmanager
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@ -310,7 +231,7 @@ class Limiter(object):
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try:
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yield
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finally:
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logger.info("Releasing limiter lock %r for key %r", self.name, key)
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logger.info("Releasing linearizer lock %r for key %r", self.name, key)
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# We've finished executing so check if there are any things
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# blocked waiting to execute and start one of them
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@ -1,70 +0,0 @@
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# -*- coding: utf-8 -*-
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# Copyright 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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from twisted.internet import defer
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from synapse.util.async import Limiter
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from tests import unittest
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class LimiterTestCase(unittest.TestCase):
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@defer.inlineCallbacks
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def test_limiter(self):
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limiter = Limiter(3)
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key = object()
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d1 = limiter.queue(key)
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cm1 = yield d1
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d2 = limiter.queue(key)
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cm2 = yield d2
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d3 = limiter.queue(key)
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cm3 = yield d3
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d4 = limiter.queue(key)
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self.assertFalse(d4.called)
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d5 = limiter.queue(key)
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self.assertFalse(d5.called)
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with cm1:
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self.assertFalse(d4.called)
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self.assertFalse(d5.called)
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cm4 = yield d4
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self.assertFalse(d5.called)
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with cm3:
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self.assertFalse(d5.called)
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cm5 = yield d5
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with cm2:
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pass
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with cm4:
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pass
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with cm5:
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pass
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d6 = limiter.queue(key)
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with (yield d6):
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pass
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@ -1,5 +1,6 @@
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# -*- coding: utf-8 -*-
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# Copyright 2016 OpenMarket Ltd
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# Copyright 2018 New Vector 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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@ -65,3 +66,49 @@ class LinearizerTestCase(unittest.TestCase):
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func(i)
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return func(1000)
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@defer.inlineCallbacks
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def test_multiple_entries(self):
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limiter = Linearizer(max_count=3)
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key = object()
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d1 = limiter.queue(key)
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cm1 = yield d1
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d2 = limiter.queue(key)
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cm2 = yield d2
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d3 = limiter.queue(key)
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cm3 = yield d3
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d4 = limiter.queue(key)
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self.assertFalse(d4.called)
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d5 = limiter.queue(key)
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self.assertFalse(d5.called)
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with cm1:
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self.assertFalse(d4.called)
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self.assertFalse(d5.called)
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cm4 = yield d4
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self.assertFalse(d5.called)
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with cm3:
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self.assertFalse(d5.called)
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cm5 = yield d5
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with cm2:
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pass
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with cm4:
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pass
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with cm5:
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pass
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d6 = limiter.queue(key)
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with (yield d6):
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pass
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