2014-08-12 10:10:52 -04:00
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# -*- coding: utf-8 -*-
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2016-01-06 23:26:29 -05:00
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# Copyright 2014-2016 OpenMarket Ltd
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2019-04-11 12:08:13 -04:00
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# Copyright 2018 New Vector Ltd
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2014-08-12 10:10:52 -04:00
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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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2019-10-02 08:29:01 -04:00
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2018-07-20 07:43:23 -04:00
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import collections
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import logging
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from contextlib import contextmanager
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from typing import Dict, Sequence, Set, Union
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from six.moves import range
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2019-10-11 10:26:09 -04:00
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import attr
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2018-06-22 04:37:10 -04:00
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from twisted.internet import defer
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2018-04-27 07:52:30 -04:00
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from twisted.internet.defer import CancelledError
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from twisted.python import failure
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2014-08-12 10:10:52 -04:00
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2019-07-03 10:07:04 -04:00
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from synapse.logging.context 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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from synapse.util import Clock, unwrapFirstError
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2018-04-28 07:57:00 -04:00
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2016-12-30 15:00:44 -05:00
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logger = logging.getLogger(__name__)
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2014-11-20 12:26:36 -05:00
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2015-05-08 11:27:36 -04:00
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class ObservableDeferred(object):
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"""Wraps a deferred object so that we can add observer deferreds. These
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observer deferreds do not affect the callback chain of the original
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deferred.
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If consumeErrors is true errors will be captured from the origin deferred.
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Cancelling or otherwise resolving an observer will not affect the original
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ObservableDeferred.
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2017-10-17 05:59:30 -04:00
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NB that it does not attempt to do anything with logcontexts; in general
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you should probably make_deferred_yieldable the deferreds
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returned by `observe`, and ensure that the original deferred runs its
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callbacks in the sentinel logcontext.
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"""
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__slots__ = ["_deferred", "_observers", "_result"]
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def __init__(self, deferred, consumeErrors=False):
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object.__setattr__(self, "_deferred", deferred)
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object.__setattr__(self, "_result", None)
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object.__setattr__(self, "_observers", set())
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def callback(r):
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object.__setattr__(self, "_result", (True, r))
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while self._observers:
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try:
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# TODO: Handle errors here.
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self._observers.pop().callback(r)
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except Exception:
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pass
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return r
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def errback(f):
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object.__setattr__(self, "_result", (False, f))
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while self._observers:
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try:
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# TODO: Handle errors here.
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self._observers.pop().errback(f)
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except Exception:
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pass
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if consumeErrors:
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return None
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else:
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return f
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deferred.addCallbacks(callback, errback)
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def observe(self):
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"""Observe the underlying deferred.
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Can return either a deferred if the underlying deferred is still pending
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(or has failed), or the actual value. Callers may need to use maybeDeferred.
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"""
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if not self._result:
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d = defer.Deferred()
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def remove(r):
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self._observers.discard(d)
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return r
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d.addBoth(remove)
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self._observers.add(d)
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return d
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else:
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success, res = self._result
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return res if success else defer.fail(res)
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def observers(self):
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return self._observers
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2016-06-02 06:52:32 -04:00
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def has_called(self):
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return self._result is not None
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def has_succeeded(self):
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return self._result is not None and self._result[0] is True
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def get_result(self):
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return self._result[1]
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def __getattr__(self, name):
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return getattr(self._deferred, name)
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def __setattr__(self, name, value):
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setattr(self._deferred, name, value)
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def __repr__(self):
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return "<ObservableDeferred object at %s, result=%r, _deferred=%r>" % (
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id(self),
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self._result,
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self._deferred,
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)
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def concurrently_execute(func, args, limit):
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"""Executes the function with each argument conncurrently while limiting
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the number of concurrent executions.
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Args:
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func (func): Function to execute, should return a deferred or coroutine.
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args (list): List of arguments to pass to func, each invocation of func
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gets a signle argument.
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limit (int): Maximum number of conccurent executions.
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Returns:
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deferred: Resolved when all function invocations have finished.
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"""
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it = iter(args)
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async def _concurrently_execute_inner():
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try:
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while True:
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await maybe_awaitable(func(next(it)))
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except StopIteration:
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pass
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2019-07-03 10:07:04 -04:00
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return make_deferred_yieldable(
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defer.gatherResults(
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[run_in_background(_concurrently_execute_inner) for _ in range(limit)],
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consumeErrors=True,
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)
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).addErrback(unwrapFirstError)
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def yieldable_gather_results(func, iter, *args, **kwargs):
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"""Executes the function with each argument concurrently.
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Args:
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func (func): Function to execute that returns a Deferred
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iter (iter): An iterable that yields items that get passed as the first
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argument to the function
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*args: Arguments to be passed to each call to func
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Returns
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Deferred[list]: Resolved when all functions have been invoked, or errors if
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one of the function calls fails.
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"""
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return make_deferred_yieldable(
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defer.gatherResults(
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[run_in_background(func, item, *args, **kwargs) for item in iter],
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consumeErrors=True,
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)
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).addErrback(unwrapFirstError)
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class Linearizer(object):
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"""Limits concurrent access to resources based on a key. Useful to ensure
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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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with (yield limiter.queue("test_key")):
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# do some work.
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"""
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2018-07-20 08:11:43 -04:00
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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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"""
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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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2018-07-20 07:37:12 -04:00
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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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self.max_count = max_count
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# key_to_defer is a map from the key to a 2 element list where
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# the first element is the number of things executing, and
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# the second element is an OrderedDict, where the keys are deferreds for the
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# things blocked from executing.
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self.key_to_defer = (
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{}
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) # type: Dict[str, Sequence[Union[int, Dict[defer.Deferred, int]]]]
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def queue(self, key):
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# we avoid doing defer.inlineCallbacks here, so that cancellation works correctly.
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# (https://twistedmatrix.com/trac/ticket/4632 meant that cancellations were not
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# propagated inside inlineCallbacks until Twisted 18.7)
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entry = self.key_to_defer.setdefault(key, [0, collections.OrderedDict()])
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2016-11-11 05:42:08 -05:00
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# If the number of things executing is greater than the maximum
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# then add a deferred to the list of blocked items
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# When one of the things currently executing finishes it will callback
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# this item so that it can continue executing.
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if entry[0] >= self.max_count:
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res = self._await_lock(key)
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else:
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logger.debug(
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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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res = defer.succeed(None)
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# once we successfully get the lock, we need to return a context manager which
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# will release the lock.
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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.debug("Releasing linearizer lock %r for key %r", self.name, key)
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2016-11-11 05:42:08 -05:00
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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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entry[0] -= 1
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if entry[1]:
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(next_def, _) = entry[1].popitem(last=False)
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2018-07-20 07:43:23 -04:00
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# we need to run the next thing in the sentinel context.
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2017-11-06 19:48:57 -05:00
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with PreserveLoggingContext():
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next_def.callback(None)
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elif entry[0] == 0:
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# We were the last thing for this key: remove it from the
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# map.
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del self.key_to_defer[key]
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2018-08-10 05:59:09 -04:00
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res.addCallback(_ctx_manager)
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return res
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def _await_lock(self, key):
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"""Helper for queue: adds a deferred to the queue
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Assumes that we've already checked that we've reached the limit of the number
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of lock-holders we allow. Creates a new deferred which is added to the list, and
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adds some management around cancellations.
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Returns the deferred, which will callback once we have secured the lock.
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"""
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entry = self.key_to_defer[key]
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2019-06-20 05:32:02 -04:00
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logger.debug("Waiting to acquire linearizer lock %r for key %r", self.name, key)
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2018-08-10 05:59:09 -04:00
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new_defer = make_deferred_yieldable(defer.Deferred())
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entry[1][new_defer] = 1
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def cb(_r):
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logger.debug("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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# 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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# (This needs to happen while we hold the lock, and the context manager's exit
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# code must be synchronous, so this is the only sensible place.)
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return self._clock.sleep(0)
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|
|
|
|
|
|
def eb(e):
|
|
|
|
logger.info("defer %r got err %r", new_defer, e)
|
|
|
|
if isinstance(e, CancelledError):
|
2019-01-29 06:05:31 -05:00
|
|
|
logger.debug(
|
2019-06-20 05:32:02 -04:00
|
|
|
"Cancelling wait for linearizer lock %r for key %r", self.name, key
|
2018-08-10 05:59:09 -04:00
|
|
|
)
|
|
|
|
|
|
|
|
else:
|
|
|
|
logger.warn(
|
|
|
|
"Unexpected exception waiting for linearizer lock %r for key %r",
|
2019-06-20 05:32:02 -04:00
|
|
|
self.name,
|
|
|
|
key,
|
2018-08-10 05:59:09 -04:00
|
|
|
)
|
|
|
|
|
|
|
|
# we just have to take ourselves back out of the queue.
|
|
|
|
del entry[1][new_defer]
|
|
|
|
return e
|
|
|
|
|
|
|
|
new_defer.addCallbacks(cb, eb)
|
|
|
|
return new_defer
|
2016-11-10 11:29:51 -05:00
|
|
|
|
|
|
|
|
2016-07-05 09:44:25 -04:00
|
|
|
class ReadWriteLock(object):
|
|
|
|
"""A deferred style read write lock.
|
|
|
|
|
|
|
|
Example:
|
|
|
|
|
|
|
|
with (yield read_write_lock.read("test_key")):
|
|
|
|
# do some work
|
|
|
|
"""
|
|
|
|
|
|
|
|
# IMPLEMENTATION NOTES
|
|
|
|
#
|
|
|
|
# We track the most recent queued reader and writer deferreds (which get
|
|
|
|
# resolved when they release the lock).
|
|
|
|
#
|
|
|
|
# Read: We know its safe to acquire a read lock when the latest writer has
|
|
|
|
# been resolved. The new reader is appeneded to the list of latest readers.
|
|
|
|
#
|
|
|
|
# Write: We know its safe to acquire the write lock when both the latest
|
|
|
|
# writers and readers have been resolved. The new writer replaces the latest
|
|
|
|
# writer.
|
|
|
|
|
|
|
|
def __init__(self):
|
|
|
|
# Latest readers queued
|
2019-10-02 08:29:01 -04:00
|
|
|
self.key_to_current_readers = {} # type: Dict[str, Set[defer.Deferred]]
|
2016-07-05 09:44:25 -04:00
|
|
|
|
|
|
|
# Latest writer queued
|
2019-10-02 08:29:01 -04:00
|
|
|
self.key_to_current_writer = {} # type: Dict[str, defer.Deferred]
|
2016-07-05 09:44:25 -04:00
|
|
|
|
|
|
|
@defer.inlineCallbacks
|
|
|
|
def read(self, key):
|
|
|
|
new_defer = defer.Deferred()
|
|
|
|
|
|
|
|
curr_readers = self.key_to_current_readers.setdefault(key, set())
|
|
|
|
curr_writer = self.key_to_current_writer.get(key, None)
|
|
|
|
|
|
|
|
curr_readers.add(new_defer)
|
|
|
|
|
|
|
|
# We wait for the latest writer to finish writing. We can safely ignore
|
|
|
|
# any existing readers... as they're readers.
|
2017-11-14 06:22:42 -05:00
|
|
|
yield make_deferred_yieldable(curr_writer)
|
2016-07-05 09:44:25 -04:00
|
|
|
|
|
|
|
@contextmanager
|
|
|
|
def _ctx_manager():
|
|
|
|
try:
|
|
|
|
yield
|
|
|
|
finally:
|
|
|
|
new_defer.callback(None)
|
|
|
|
self.key_to_current_readers.get(key, set()).discard(new_defer)
|
|
|
|
|
2019-07-23 09:00:55 -04:00
|
|
|
return _ctx_manager()
|
2016-07-05 09:44:25 -04:00
|
|
|
|
|
|
|
@defer.inlineCallbacks
|
|
|
|
def write(self, key):
|
|
|
|
new_defer = defer.Deferred()
|
|
|
|
|
|
|
|
curr_readers = self.key_to_current_readers.get(key, set())
|
|
|
|
curr_writer = self.key_to_current_writer.get(key, None)
|
|
|
|
|
|
|
|
# We wait on all latest readers and writer.
|
|
|
|
to_wait_on = list(curr_readers)
|
|
|
|
if curr_writer:
|
|
|
|
to_wait_on.append(curr_writer)
|
|
|
|
|
|
|
|
# We can clear the list of current readers since the new writer waits
|
|
|
|
# for them to finish.
|
|
|
|
curr_readers.clear()
|
|
|
|
self.key_to_current_writer[key] = new_defer
|
|
|
|
|
2017-11-14 06:22:42 -05:00
|
|
|
yield make_deferred_yieldable(defer.gatherResults(to_wait_on))
|
2016-07-05 09:44:25 -04:00
|
|
|
|
|
|
|
@contextmanager
|
|
|
|
def _ctx_manager():
|
|
|
|
try:
|
|
|
|
yield
|
|
|
|
finally:
|
|
|
|
new_defer.callback(None)
|
|
|
|
if self.key_to_current_writer[key] == new_defer:
|
|
|
|
self.key_to_current_writer.pop(key)
|
|
|
|
|
2019-07-23 09:00:55 -04:00
|
|
|
return _ctx_manager()
|
2018-04-27 07:52:30 -04:00
|
|
|
|
|
|
|
|
2018-09-19 05:39:40 -04:00
|
|
|
def _cancelled_to_timed_out_error(value, timeout):
|
|
|
|
if isinstance(value, failure.Failure):
|
|
|
|
value.trap(CancelledError)
|
2018-09-19 06:05:21 -04:00
|
|
|
raise defer.TimeoutError(timeout, "Deferred")
|
2018-09-19 05:39:40 -04:00
|
|
|
return value
|
2018-04-27 07:52:30 -04:00
|
|
|
|
|
|
|
|
2018-09-19 05:39:40 -04:00
|
|
|
def timeout_deferred(deferred, timeout, reactor, on_timeout_cancel=None):
|
|
|
|
"""The in built twisted `Deferred.addTimeout` fails to time out deferreds
|
|
|
|
that have a canceller that throws exceptions. This method creates a new
|
|
|
|
deferred that wraps and times out the given deferred, correctly handling
|
|
|
|
the case where the given deferred's canceller throws.
|
2018-04-27 07:52:30 -04:00
|
|
|
|
2019-01-17 09:00:23 -05:00
|
|
|
(See https://twistedmatrix.com/trac/ticket/9534)
|
|
|
|
|
2018-09-19 05:39:40 -04:00
|
|
|
NOTE: Unlike `Deferred.addTimeout`, this function returns a new deferred
|
2018-04-27 07:52:30 -04:00
|
|
|
|
2018-09-19 05:39:40 -04:00
|
|
|
Args:
|
|
|
|
deferred (Deferred)
|
|
|
|
timeout (float): Timeout in seconds
|
2019-01-17 09:00:23 -05:00
|
|
|
reactor (twisted.interfaces.IReactorTime): The twisted reactor to use
|
2018-04-27 07:52:30 -04:00
|
|
|
on_timeout_cancel (callable): A callable which is called immediately
|
|
|
|
after the deferred times out, and not if this deferred is
|
|
|
|
otherwise cancelled before the timeout.
|
|
|
|
|
|
|
|
It takes an arbitrary value, which is the value of the deferred at
|
|
|
|
that exact point in time (probably a CancelledError Failure), and
|
|
|
|
the timeout.
|
|
|
|
|
|
|
|
The default callable (if none is provided) will translate a
|
2018-09-19 06:05:21 -04:00
|
|
|
CancelledError Failure into a defer.TimeoutError.
|
2018-04-27 07:52:30 -04:00
|
|
|
|
2018-09-19 05:39:40 -04:00
|
|
|
Returns:
|
|
|
|
Deferred
|
2018-09-14 14:23:07 -04:00
|
|
|
"""
|
|
|
|
|
|
|
|
new_d = defer.Deferred()
|
|
|
|
|
|
|
|
timed_out = [False]
|
|
|
|
|
|
|
|
def time_it_out():
|
|
|
|
timed_out[0] = True
|
|
|
|
|
2018-09-19 06:04:42 -04:00
|
|
|
try:
|
|
|
|
deferred.cancel()
|
2019-06-20 05:32:02 -04:00
|
|
|
except: # noqa: E722, if we throw any exception it'll break time outs
|
2018-09-19 06:04:42 -04:00
|
|
|
logger.exception("Canceller failed during timeout")
|
|
|
|
|
2018-09-14 14:23:07 -04:00
|
|
|
if not new_d.called:
|
2018-09-19 06:05:21 -04:00
|
|
|
new_d.errback(defer.TimeoutError(timeout, "Deferred"))
|
2018-09-14 14:23:07 -04:00
|
|
|
|
|
|
|
delayed_call = reactor.callLater(timeout, time_it_out)
|
|
|
|
|
|
|
|
def convert_cancelled(value):
|
|
|
|
if timed_out[0]:
|
2018-09-19 05:39:40 -04:00
|
|
|
to_call = on_timeout_cancel or _cancelled_to_timed_out_error
|
|
|
|
return to_call(value, timeout)
|
2018-09-14 14:23:07 -04:00
|
|
|
return value
|
|
|
|
|
|
|
|
deferred.addBoth(convert_cancelled)
|
|
|
|
|
|
|
|
def cancel_timeout(result):
|
|
|
|
# stop the pending call to cancel the deferred if it's been fired
|
|
|
|
if delayed_call.active():
|
|
|
|
delayed_call.cancel()
|
|
|
|
return result
|
|
|
|
|
|
|
|
deferred.addBoth(cancel_timeout)
|
|
|
|
|
|
|
|
def success_cb(val):
|
|
|
|
if not new_d.called:
|
|
|
|
new_d.callback(val)
|
|
|
|
|
|
|
|
def failure_cb(val):
|
|
|
|
if not new_d.called:
|
|
|
|
new_d.errback(val)
|
|
|
|
|
|
|
|
deferred.addCallbacks(success_cb, failure_cb)
|
|
|
|
|
|
|
|
return new_d
|
2019-10-11 10:26:09 -04:00
|
|
|
|
|
|
|
|
|
|
|
@attr.s(slots=True, frozen=True)
|
|
|
|
class DoneAwaitable(object):
|
|
|
|
"""Simple awaitable that returns the provided value.
|
|
|
|
"""
|
|
|
|
|
|
|
|
value = attr.ib()
|
|
|
|
|
|
|
|
def __await__(self):
|
|
|
|
return self
|
|
|
|
|
|
|
|
def __iter__(self):
|
|
|
|
return self
|
|
|
|
|
|
|
|
def __next__(self):
|
|
|
|
raise StopIteration(self.value)
|
|
|
|
|
|
|
|
|
|
|
|
def maybe_awaitable(value):
|
|
|
|
"""Convert a value to an awaitable if not already an awaitable.
|
|
|
|
"""
|
|
|
|
|
|
|
|
if hasattr(value, "__await__"):
|
|
|
|
return value
|
|
|
|
|
|
|
|
return DoneAwaitable(value)
|