Merge pull request #1620 from matrix-org/erikj/concurrent_room_access

Limit the number of events that can be created on a given room concurrently
This commit is contained in:
Erik Johnston 2016-12-12 10:30:23 +00:00 committed by GitHub
commit d53a80af25
3 changed files with 159 additions and 25 deletions

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@ -24,7 +24,7 @@ from synapse.push.action_generator import ActionGenerator
from synapse.types import (
UserID, RoomAlias, RoomStreamToken,
)
from synapse.util.async import run_on_reactor, ReadWriteLock
from synapse.util.async import run_on_reactor, ReadWriteLock, Limiter
from synapse.util.logcontext import preserve_fn
from synapse.util.metrics import measure_func
from synapse.visibility import filter_events_for_client
@ -50,6 +50,10 @@ class MessageHandler(BaseHandler):
self.pagination_lock = ReadWriteLock()
# We arbitrarily limit concurrent event creation for a room to 5.
# This is to stop us from diverging history *too* much.
self.limiter = Limiter(max_count=5)
@defer.inlineCallbacks
def purge_history(self, room_id, event_id):
event = yield self.store.get_event(event_id)
@ -191,6 +195,7 @@ class MessageHandler(BaseHandler):
"""
builder = self.event_builder_factory.new(event_dict)
with (yield self.limiter.queue(builder.room_id)):
self.validator.validate_new(builder)
if builder.type == EventTypes.Member:
@ -221,6 +226,7 @@ class MessageHandler(BaseHandler):
builder=builder,
prev_event_ids=prev_event_ids,
)
defer.returnValue((event, context))
@defer.inlineCallbacks

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@ -197,6 +197,64 @@ class Linearizer(object):
defer.returnValue(_ctx_manager())
class Limiter(object):
"""Limits concurrent access to resources based on a key. Useful to ensure
only a few thing happen at a time on a given resource.
Example:
with (yield limiter.queue("test_key")):
# do some work.
"""
def __init__(self, max_count):
"""
Args:
max_count(int): The maximum number of concurrent access
"""
self.max_count = max_count
# key_to_defer is a map from the key to a 2 element list where
# the first element is the number of things executing
# the second element is a list of deferreds for the things blocked from
# executing.
self.key_to_defer = {}
@defer.inlineCallbacks
def queue(self, key):
entry = self.key_to_defer.setdefault(key, [0, []])
# If the number of things executing is greater than the maximum
# then add a deferred to the list of blocked items
# When on of the things currently executing finishes it will callback
# this item so that it can continue executing.
if entry[0] >= self.max_count:
new_defer = defer.Deferred()
entry[1].append(new_defer)
with PreserveLoggingContext():
yield new_defer
entry[0] += 1
@contextmanager
def _ctx_manager():
try:
yield
finally:
# We've finished executing so check if there are any things
# blocked waiting to execute and start one of them
entry[0] -= 1
try:
entry[1].pop(0).callback(None)
except IndexError:
# If nothing else is executing for this key then remove it
# from the map
if entry[0] == 0:
self.key_to_defer.pop(key, None)
defer.returnValue(_ctx_manager())
class ReadWriteLock(object):
"""A deferred style read write lock.

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@ -0,0 +1,70 @@
# -*- coding: utf-8 -*-
# Copyright 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 tests import unittest
from twisted.internet import defer
from synapse.util.async import Limiter
class LimiterTestCase(unittest.TestCase):
@defer.inlineCallbacks
def test_limiter(self):
limiter = Limiter(3)
key = object()
d1 = limiter.queue(key)
cm1 = yield d1
d2 = limiter.queue(key)
cm2 = yield d2
d3 = limiter.queue(key)
cm3 = yield d3
d4 = limiter.queue(key)
self.assertFalse(d4.called)
d5 = limiter.queue(key)
self.assertFalse(d5.called)
with cm1:
self.assertFalse(d4.called)
self.assertFalse(d5.called)
self.assertTrue(d4.called)
self.assertFalse(d5.called)
with cm3:
self.assertFalse(d5.called)
self.assertTrue(d5.called)
with cm2:
pass
with (yield d4):
pass
with (yield d5):
pass
d6 = limiter.queue(key)
with (yield d6):
pass