diff options
| -rw-r--r-- | changelog.d/3570.bugfix | 1 | ||||
| -rw-r--r-- | changelog.d/3571.misc | 1 | ||||
| -rw-r--r-- | synapse/handlers/message.py | 4 | ||||
| -rw-r--r-- | synapse/util/async.py | 129 | ||||
| -rw-r--r-- | tests/util/test_limiter.py | 70 | ||||
| -rw-r--r-- | tests/util/test_linearizer.py | 47 |
6 files changed, 88 insertions, 164 deletions
diff --git a/changelog.d/3570.bugfix b/changelog.d/3570.bugfix new file mode 100644 index 0000000000..cec5158a99 --- /dev/null +++ b/changelog.d/3570.bugfix @@ -0,0 +1 @@ +Fix potential stack overflow and deadlock under heavy load \ No newline at end of file diff --git a/changelog.d/3571.misc b/changelog.d/3571.misc new file mode 100644 index 0000000000..8908324e68 --- /dev/null +++ b/changelog.d/3571.misc @@ -0,0 +1 @@ +Merge Linearizer and Limiter diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py index a39b852ceb..abc07ea87c 100644 --- a/synapse/handlers/message.py +++ b/synapse/handlers/message.py @@ -33,7 +33,7 @@ from synapse.events.utils import serialize_event from synapse.events.validator import EventValidator from synapse.replication.http.send_event import send_event_to_master from synapse.types import RoomAlias, RoomStreamToken, UserID -from synapse.util.async import Limiter, ReadWriteLock +from synapse.util.async import Linearizer, ReadWriteLock from synapse.util.frozenutils import frozendict_json_encoder from synapse.util.logcontext import run_in_background from synapse.util.metrics import measure_func @@ -427,7 +427,7 @@ class EventCreationHandler(object): # 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) + self.limiter = Linearizer(max_count=5, name="room_event_creation_limit") self.action_generator = hs.get_action_generator() diff --git a/synapse/util/async.py b/synapse/util/async.py index 5d0fb39130..5a50d9700f 100644 --- a/synapse/util/async.py +++ b/synapse/util/async.py @@ -1,5 +1,6 @@ # -*- coding: utf-8 -*- # Copyright 2014-2016 OpenMarket Ltd +# Copyright 2018 New Vector Ltd. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. @@ -12,7 +13,7 @@ # 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 import logging from contextlib import contextmanager @@ -156,54 +157,56 @@ def concurrently_execute(func, args, limit): class Linearizer(object): - """Linearizes access to resources based on a key. Useful to ensure only one - thing is happening at a time on a given resource. + """Limits concurrent access to resources based on a key. Useful to ensure + only a few things happen at a time on a given resource. Example: - with (yield linearizer.queue("test_key")): + with (yield limiter.queue("test_key")): # do some work. """ - def __init__(self, name=None, clock=None): + def __init__(self, name=None, max_count=1, clock=None): + """ + Args: + max_count(int): The maximum number of concurrent accesses + """ if name is None: self.name = id(self) else: self.name = name - self.key_to_defer = {} if not clock: from twisted.internet import reactor clock = Clock(reactor) self._clock = clock + 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, and + # the second element is a deque of deferreds for the things blocked from + # executing. + self.key_to_defer = {} @defer.inlineCallbacks def queue(self, key): - # If there is already a deferred in the queue, we pull it out so that - # we can wait on it later. - # Then we replace it with a deferred that we resolve *after* the - # context manager has exited. - # We only return the context manager after the previous deferred has - # resolved. - # This all has the net effect of creating a chain of deferreds that - # wait for the previous deferred before starting their work. - current_defer = self.key_to_defer.get(key) + entry = self.key_to_defer.setdefault(key, [0, collections.deque()]) - new_defer = defer.Deferred() - self.key_to_defer[key] = new_defer + # 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) - if current_defer: logger.info( - "Waiting to acquire linearizer lock %r for key %r", self.name, key + "Waiting to acquire linearizer lock %r for key %r", self.name, key, ) - try: - with PreserveLoggingContext(): - yield current_defer - except Exception: - logger.exception("Unexpected exception in Linearizer") + yield make_deferred_yieldable(new_defer) - logger.info("Acquired linearizer lock %r for key %r", self.name, - key) + logger.info("Acquired linearizer lock %r for key %r", self.name, key) + entry[0] += 1 # if the code holding the lock completes synchronously, then it # will recursively run the next claimant on the list. That can @@ -213,15 +216,15 @@ class Linearizer(object): # In order to break the cycle, we add a cheeky sleep(0) here to # ensure that we fall back to the reactor between each iteration. # - # (There's no particular need for it to happen before we return - # the context manager, but it needs to happen while we hold the - # lock, and the context manager's exit code must be synchronous, - # so actually this is the only sensible place. + # (This needs to happen while we hold the lock, and the context manager's exit + # code must be synchronous, so this is the only sensible place.) yield self._clock.sleep(0) else: - logger.info("Acquired uncontended linearizer lock %r for key %r", - self.name, key) + logger.info( + "Acquired uncontended linearizer lock %r for key %r", self.name, key, + ) + entry[0] += 1 @contextmanager def _ctx_manager(): @@ -229,73 +232,15 @@ class Linearizer(object): yield finally: logger.info("Releasing linearizer lock %r for key %r", self.name, key) - with PreserveLoggingContext(): - new_defer.callback(None) - current_d = self.key_to_defer.get(key) - if current_d is new_defer: - self.key_to_defer.pop(key, None) - - 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) - - logger.info("Waiting to acquire limiter lock for key %r", key) - with PreserveLoggingContext(): - yield new_defer - logger.info("Acquired limiter lock for key %r", key) - else: - logger.info("Acquired uncontended limiter lock for key %r", key) - - entry[0] += 1 - - @contextmanager - def _ctx_manager(): - try: - yield - finally: - logger.info("Releasing limiter lock for key %r", key) # We've finished executing so check if there are any things # blocked waiting to execute and start one of them entry[0] -= 1 if entry[1]: - next_def = entry[1].pop(0) + next_def = entry[1].popleft() + # we need to run the next thing in the sentinel context. with PreserveLoggingContext(): next_def.callback(None) elif entry[0] == 0: diff --git a/tests/util/test_limiter.py b/tests/util/test_limiter.py deleted file mode 100644 index a5a767b1ff..0000000000 --- a/tests/util/test_limiter.py +++ /dev/null @@ -1,70 +0,0 @@ -# -*- 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 twisted.internet import defer - -from synapse.util.async import Limiter - -from tests import unittest - - -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 diff --git a/tests/util/test_linearizer.py b/tests/util/test_linearizer.py index c95907b32c..c9563124f9 100644 --- a/tests/util/test_linearizer.py +++ b/tests/util/test_linearizer.py @@ -1,5 +1,6 @@ # -*- coding: utf-8 -*- # Copyright 2016 OpenMarket Ltd +# Copyright 2018 New Vector Ltd. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. @@ -65,3 +66,49 @@ class LinearizerTestCase(unittest.TestCase): func(i) return func(1000) + + @defer.inlineCallbacks + def test_multiple_entries(self): + limiter = Linearizer(max_count=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) + + cm4 = yield d4 + self.assertFalse(d5.called) + + with cm3: + self.assertFalse(d5.called) + + cm5 = yield d5 + + with cm2: + pass + + with cm4: + pass + + with cm5: + pass + + d6 = limiter.queue(key) + with (yield d6): + pass |